Table of Contents
Have you ever pondered what the basic elements of life are? The answer lies within the cells! Animal cells are intricate structures that play a vital role in sustaining life and ensuring the proper functioning of organisms. This article will explore the structure, function, diagram, and labelled models of animal cells, as well as their structure and diagram.
Every living entity, from the smallest insect to the greatest mammal, is composed of cells. Among these cells, animal cells are among the most intricate and interesting structures in nature.
Cells are the fundamental unit of life and are present in all organisms. Animal cells are among the most sophisticated and well-studied types of cells, despite their variety of sizes and shapes. Understanding the biology and physiology of live things, as well as devising therapies for diseases and injuries, requires the study of animal cells.
Definition of animal cell
Animal cell are considered to be the fundamental living species belonging to the kingdom Animalia. They are eukaryotic cells which means they possess an actual nucleus as well as organelles, which are special structures which perform various functions. Animal cells don’t have specific organelles for plants, such as cell walls that support the plant cell or the chloroplasts, an organelle that is responsible for photosynthesis.
Animals are a huge collection of living creatures which comprise three quarters of all species of earth. They are able to move, react to stimulus, react to changes in the environment, and adapt to various forms of defense mechanisms for food and reproductive processes, each of of these processes are enhanced by the components in the body. But, animals are not able to make their own food, as do plants and , therefore, they rely on plants in a way or another.
Every living thing is composed of cells that form your body’s structures. Certain living creatures are unicellular (unicellular) as well as other species that comprise multiple cells (Multicellular). A cell is the smallest (microscopic) structural-functional unit of life of an organism. The cells of animals are referred to as Animal cells, and the ones which make up plants are referred to as plant cells.
The majority of cells are covered with a membrane of protection called the cell wall. It helps shape the cells and stiffness. Because animal cells do not have an unsteady cell wall, they are able to grow the widest range of tissues, cell types and organs. The muscles and nerves are made of specific cells that plant cells are unable to develop into, thus providing these muscle and nerve cells an ability of moving.
Overview of Animal Cells
Plants, animals, fungi and protists are comprised of at the very minimum one eukaryotic cells. However archaea and bacteria comprise one prokaryotic cell.
Every cell is surrounded by cells that are surrounded by a membrane (also known as plasma membrane). The cell membrane forms the boundary that divides the cell’s interior and the exterior of the cells. The plasma membrane covers all cell components which are suspended within an emulsion-like fluid known as the cytoplasm. The cytoplasm is the place of organelles.
Eukaryotic cells differ from prokaryotic cells due to their presence in a distinct nucleus, as well as other membrane-bound organelles like mitochondria, endoplasmic-reticulum and the Golgi apparatus. Prokaryotic cells don’t have an identified nucleus (instead there is a space in the cytoplasm, known as the nucleotide holds all the DNA). They also do not have membrane-bound organelles.
Animals are multicellular and multicellular, which means that many cells are collaborating to create the entire organism. In multicellular organisms, like humans the cells may be extremely specialized to carry out various tasks. Therefore, they can behave and look very different from each other, even though they’re the same human cells.
Animal cell size and shape
Animal cells are found in a variety of shapes and sizes with sizes ranging in size from millimeters all the way to micrometers. Largest animal cells are an ostrich egg with a diameter of 5 inches that weighs 1.2-1.4 kg. The tiniest cell in the animal kingdom is a neuron that measure around 100 microns in size.
The animal cells have a smaller size than plant cells , and they tend to be irregular in their shape and take on various shapesdue to the absence of cell walls. Certain cells are oval, round rod-shaped, flattened, or concave, spherical or rectangular. The reason for this is the absence of an outer cell wall. Be aware that most cells are microscopic, which means they are only visible under a microscope to observe their anatomy.
Animal cells also share organelles of the cell with plants because both evolved from cells that are eukaryotic. As we have mentioned the animal cell is an eukaryotic cells that have a nucleus bound to membrane. They also have its genetic materials in DNA contained within the nucleus. They also have various organelles structurally located in the plasma membrane, which serve a variety of specific roles for normal cell function and to keep the body functioning normally. processes.
Animal Cell Types
There are a variety of cells from animals, all created to perform a specific function. The most popular kinds comprise:
- Skin Cells: Melanocytes, keratinocytes, Merkel cells and Langerhans cells
- Muscle Cells: Myocyte, Myosatellite cells, Tendon cells, Cardiac muscle cells
- Blood Cells: Leukocytes, erythrocytes, platelet
- Nerve Cells: Schwann cell, glial cells etc
- Fat Cells: Adipocytes
- The primary purpose of skin cells is to safeguard the animal.
- As humans, our skin protects us from the cold, pathogens, ultraviolet rays, and more! In addition to regulating our body temperature and allowing us to perceive feelings such as heat and discomfort, the nervous system protects us by sending us warning messages.
- There are three skin layers. The epidermis is the outermost layer, the dermis is the middle layer, and the hypodermis is the deepest layer. The epidermis is composed of numerous types of skin cells, the bulk of which being keratinocytes.
- Red blood cells and white blood cells are the two distinct types of blood cells. Red blood cells comprise the majority of the body’s blood cells.
- Red blood cells are responsible for transporting oxygen from the lungs to the rest of the body and collecting carbon dioxide. Red blood cells that have reached maturity are the only animal cells without nuclei. This allows the cells to transport more haemoglobin and oxygen.
- The function of white blood cells is to aid in the fight against infections. They are essential components of the immune system!
- Neurons, commonly known as nerve cells, are the fundamental cells of the neurological system. The purpose of these cells is to use chemical and electrical impulses to transmit and receive messages from the brain. These neurons are the primary components of the brain, spinal cord, and peripheral nervous system of vertebrate animals, such as humans.
- Neurons influence the state of our internal organs (consider how our heart rate increases in response to fear), assist us decide how to act and move, and enable us to think and remember what’s happening.
- We have around 86 billion neurons in our brains, according to estimates.
- Myocytes, often known as muscle cells, have one basic function, contraction. Muscle cells use motor proteins to shorten (or contract) in response to instructions from neurons. When no signal is received from the neurons, the muscle cell is in a relaxed condition.
- The three types of muscles in the human body consist of muscle cells: skeletal, cardiac, and smooth. They aid in the motion of our limbs and organs.
- Adipose cells, often known as fat cells, play a crucial role in the human body. These cells store fats and lipids, which are then used to provide energy to the body as needed. This source of energy is triglycerides.
- In addition to storing energy, fat cells also assist detect and respond to fluctuations in energy levels. They have the ability to influence processes such as insulin sensitivity and protect against hypothermia and diabetes.
Animal Cell Diagram and Structure (cross section of an animal cell)
The cell of the animal is composed of a variety of structural organelles that are enclosed within the plasma membrane. These organelles allow it to function effectively by triggering mechanisms that are beneficial to those who are the hosts (animal). The interaction of all cells provides an animal the capacity to move, reproduce as well as respond to stimuli in a way, take in and digest food, etc. In general, the effort put forth of all animal cells is what provides the regular working of the human body.
List of Animal cell organelles
- Plasma membrane (Cell membrane): The animal cell membrane is a lipid bilayer with embedded proteins. The structure of the cell membrane allows for selective permeability. Not every substance can enter the cell. Small, nonpolar molecules can easily flow through. However, polar compounds cannot, necessitating transporters such as membrane-associated proteins. The only structure that surrounds an animal cell is the cell membrane. Despite lacking a cell wall, the animal cell membrane contains cholesterol, which offers structural stability and support. In addition, the presence of cholesterol and the absence of cell walls in animal cells renders them fluid as opposed to rigid, so granting them the ability to move.
- Nucleus: It is an organelle containing multiple sub-organelles, including nucleolus, nucleosomes, and chromatins. Additionally, it includes DNA and other genetic material.
- Cytoplasm: A gelatinous substance containing all cell organelles and surrounded by the cell membrane. Nucleoplasm is the substance present within the cell nucleus and confined by the nuclear membrane.
- Mitochondria: They are organelles that are spherical or rod-shaped with a double membrane. They play a significant part in the release of energy, making them the cell’s powerhouse.
- Ribosomes: They are comprised of RNA-rich cytoplasmic granules and serve as the sites of protein production.
- Endoplasmic Reticulum (ER): The endoplasmic reticulum is a network of sacs that generates, processes, and transports chemical substances for intracellular and extracellular usage. It is attached to the double-layered nuclear envelope and functions as a conduit between the nucleus and cytoplasm.
- Golgi apparatus (Golgi bodies/Golgi complex): A flat, smooth, sac-like organelle found near the nucleus and responsible for the production, storage, packaging, and transit of particles throughout the cell.
- Lysosomes: They are spherical organelles surrounded by a membrane that contain digestive enzymes that aid in digestion, excretion, and the process of cell renewal.
- Cytoskeleton: The cytoskeleton is the cellular’s internal framework. The cytoskeleton is composed of actin filaments, intermediate filaments, and microtubules. Their primary function is to regulate cell shape, maintain intracellular order, and facilitate cell mobility.
- Microtubules: These straight, hollow cylinders are present in the cytoplasm of all eukaryotic cells (but not prokaryotes) and provide a number of tasks, including transport and structural support.
- Centrioles: Centrioles are self-replicating organelles composed of nine microtubule bundles and are exclusive to animal cells. They appear to aid in the organisation of cell division, although they are not necessary for the process.
- Peroxisomes: Microbodies are an assortment of cytoplasmic organelles that are generally spherical and surrounded by a single membrane. There are numerous forms of microbodies, with peroxisomes being the most prevalent.
- Cilia and Flagella: Cilia and flagella are required for the motility of single-celled eukaryotic organisms. In multicellular animals, cilia serve to transport fluids or materials past an immobile cell as well as to move a cell or group of cells.
- Endosomes and Endocytosis: The fundamental mechanism of endocytosis is the opposite of exocytosis or cellular secretion. It involves the invagination (folding inward) of the plasma membrane of a cell to enclose macromolecules or other substances flowing in the extracellular fluid.
- Vacuoles: Within a cell, a membrane-bound organelle responsible for maintaining shape and storing water, food, waste, etc.
- Microvilli: Microvilli are tiny, finger-like projections on the surface of specific cells, such as the epithelial cells of the small intestine and certain types of sensory cells. Microvilli are composed of an actin-based cytoskeleton and a plasma membrane comparable to the cell membrane. They increase the cell’s surface area, which is advantageous for multiple tasks, such as the absorption of nutrients and the detection of stimuli. For instance, microvilli in the small intestine increase the surface area for absorption of nutrients, but microvilli in sensory cells improve the cell’s ability to detect stimuli such as light, sound, and touch. Microvilli are dynamic structures that can change length and shape rapidly, allowing the cell to respond to its surroundings and perform specialised functions.
1. Plasma membrane (Cell membrane)
Definition of Plasma membrane (Cell membrane)
The plasma membrane, also known as the cell membrane, is a thin, semi-permeable barrier that separates a cell’s internal environment from its exterior environment. It regulates the passage of ions, molecules, and other substances into and out of the cell. Maintaining the integrity and function of the cell is dependent on the plasma membrane.
Structure of Plasma membrane (Cell membrane)
- The plasma membrane is made up of a lipid bilayer composed of two layers of phospholipid molecules.
- The phospholipids have a hydrophobic (repellent to water) tail and a hydrophilic (attractive to water) head.
- The hydrophobic tails constitute the inside of the bilayer and face each other, while the hydrophilic heads face the outside and inside of the cell, forming a barrier that divides the cell from its surroundings.
- A variety of proteins are embedded inside the lipid bilayer, including transmembrane proteins, which span the entire membrane and act as channels, pumps, and receptors for the transit of ions, molecules, and other substances into and out of the cell.
- The arrangement of these proteins confers distinct features and activities on the plasma membrane, such as selective permeability, cell-cell recognition, and signal transmission.
Functions of Plasma membrane (Cell membrane)
The plasma membrane (cell membrane) performs a number of critical activities, including:
- Selective permeability: The plasma membrane regulates the transport of ions, molecules, and other substances into and out of the cell, allowing only certain substances to pass through while preventing others from doing so.
- Cell-cell recognition: The plasma membrane contains proteins involved in cell-cell recognition and communication, which is essential for tissue organisation and coordinating cellular activity.
- Signal transduction: The plasma membrane contains receptors that receive signals from outside the cell and transfer them into the cell, prompting a variety of cellular responses such as cell division, differentiation, and stimulus response.
- Cell form maintenance: The plasma membrane serves to maintain cell shape and offers mechanical strength, protecting the cell from injury.
- Protection: The plasma membrane acts as a barrier between the cell and its external environment, helping to keep the cell’s internal environment stable.
Definition of Nucleus
The nucleus is an organelle found in eukaryotic cells that is surrounded by a membrane. It is commonly referred to as the “control centre” of the cell because it contains the genetic material (DNA) and plays a crucial role in regulating the cell’s activity. The nucleus is responsible for coordinating cellular functions such as growth, division, and reactions to external signals, as well as regulating gene expression and DNA replication. The nuclear envelope separates the genetic material from the cytoplasm and regulates the exchange of materials between the nucleus and cytoplasm.
Structure of Nucleus
The nucleus is a membrane-bound organelle found in eukaryotic cells. It is composed of several structural components, including:
- Nuclear envelope: The nuclear envelope is a double membrane that surrounds the nucleus and separates the genetic material from the cytoplasm. The envelope is composed of two lipid bilayers, with embedded proteins, that regulate the exchange of materials between the nucleus and cytoplasm.
- Nuclear pores: The nuclear envelope contains nuclear pores, which are large protein complexes that control the movement of molecules and ions in and out of the nucleus.
- Chromatin: The nucleus contains chromatin, which is a complex of DNA and proteins that make up the cell’s genetic material. Chromatin is highly organized and packaged, making it easier to control gene expression and DNA replication.
- Nucleolus: The nucleolus is a dense region of the nucleus that is involved in the production of ribosomes, the cellular structures responsible for protein synthesis.
- Nuclear lamina: The nuclear lamina is a network of intermediate filaments that provides mechanical support for the nucleus and helps to maintain its shape.
These components work together to regulate the activities of the nucleus and to protect the cell’s genetic material.
Functions of Nucleus
- The main function for the nucleus’s role is to regulate and regulate the activities of cells during growth and to maintain metabolism of cells.
- It also contains genes that carry the hereditary information in the cell.
- The chromosomal DNA as well as genetic materials that are composed of genetic coded end up making the amino acid sequences, which are utilized by cells.
- The nucleus, therefore, is the information center.
- It is the place where Transcription takes place (formation of mRNA out of DNA) and the mRNA gets transported into within the nucleus.
It’s a gel-like compound that houses all cell organelles, which are enclosed in cells’ membranes. Organelles that are included include: Mitochondria endoplasmic Golgi apparatus, reticulum microfilaments, intermediate filaments of lysosomes microtubules and Vesicles.
Definition of Cytoplasm
The cytoplasm is the gel-like substance that fills the interior of a cell, excluding the nucleus. It is composed of a complex mixture of water, salts, sugars, and other organic and inorganic substances. The cytoplasm is also home to various cellular structures and organelles, including mitochondria, ribosomes, and the endoplasmic reticulum, which are involved in important cellular functions such as energy production, protein synthesis, and lipid metabolism. The cytoplasm provides a physical support for the cell and helps to maintain the stability of the internal environment, allowing for optimal cellular function.
Structure of Cytoplasm
The cytoplasm is a complex and dynamic gel-like substance that fills the interior of a cell. The structure of the cytoplasm includes:
- Cytosol: The cytosol is the liquid component of the cytoplasm, consisting of water and various dissolved substances, including ions, sugars, and metabolic products.
- Organelles: The cytoplasm contains various organelles, including mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, and peroxisomes, which carry out specific cellular functions.
- Cytoskeleton: The cytoplasm contains a network of protein fibers, called the cytoskeleton, which provides structural support for the cell and helps to maintain its shape. The cytoskeleton is also involved in cell movement and division.
- Microfilaments: Microfilaments are thin, rod-like structures made up of actin proteins, which are involved in cell movement and division.
- Intermediate filaments: Intermediate filaments are thicker protein fibers that provide support for the cell and help to maintain its shape.
- Microtubules: Microtubules are hollow, tube-like structures composed of tubulin proteins, which are involved in cell division and the transport of organelles and other cellular components.
These components work together to maintain the structure and stability of the cytoplasm, and to support the various cellular processes that take place within the cell.
Functions of Cytoplasm
The cytoplasm is a crucial component of a cell and has several key functions, including:
- Physical support: The cytoplasm provides a physical support for the cell, helping to maintain its shape and stability.
- Metabolic activities: The cytoplasm is the site of various metabolic activities, including the breakdown of nutrients and the production of energy.
- Transport: The cytoplasm helps to transport materials within the cell, allowing for the efficient distribution of nutrients and waste products.
- Enzyme and metabolic regulation: The cytoplasm contains a variety of enzymes and metabolic pathways that are involved in cellular processes such as respiration, protein synthesis, and DNA replication.
- Cell movement: The cytoplasm is involved in cell movement, including the movement of organelles and the overall movement of the cell.
- Signal transduction: The cytoplasm is involved in the transduction of signals within the cell, allowing for communication between different parts of the cell.
- Maintenance of cellular environment: The cytoplasm helps to maintain the internal environment of the cell, providing a stable and supportive environment for cellular processes to take place.
Definition of Mitochondria
They are membrane-bound organelles found within the cell cytoplasm in all eukaryotic cells. The amount of mitochondria present in every cell is different according to the purpose of the cell that it serves. For instance, erythrocytes may not contain mitochondria, whereas the muscles and liver cells contain hundreds of mitochondria.
Structure of Mitochondria
They can be rod-shaped, oval or spherically formed and have a diameter that ranges from 0.5 to 10 millimeters. Mitochondria are composed of two distinct membranes, the outer and the inner membrane. They also have a mitochondrial gel-matric within the middle mass. The membranes are bent into folds, referred to as the cristae.
Mitochondria are complex organelles found in eukaryotic cells, and their structure can be divided into several key components:
- Outer membrane: The outer membrane is a lipid bilayer that surrounds the mitochondrion and separates it from the cytoplasm. This membrane is permeable to small molecules, but impermeable to larger proteins.
- Intermembrane space: The intermembrane space is a narrow region between the outer and inner membranes of the mitochondrion.
- Inner membrane: The inner membrane is a highly folded, lipid bilayer that contains a large number of integral proteins, including enzymes involved in cellular respiration.
- Cristae: The inner membrane is folded into a series of invaginations called cristae, which increase the surface area of the inner membrane and provide a larger area for the oxidative reactions of cellular respiration to occur.
- Matrix: The matrix is the interior of the mitochondrion, which contains enzymes involved in cellular respiration and the citric acid cycle, as well as DNA, RNA, and ribosomes.
- Mitochondrial DNA: Mitochondria contain their own DNA, which is separate from the DNA found in the nucleus of the cell. This DNA is used to synthesize a few of the proteins that are necessary for the proper functioning of the mitochondria.
These various components work together to allow the mitochondria to carry out cellular respiration, generate energy in the form of ATP, and regulate the cellular environment.
Functions of Mitochondria
- They produce energy in the form of Adenosine Triphosphate (ATP) by turning nutrients and oxygen into energy, so allowing the cell to execute its function and releasing surplus energy from the cell.
- In addition to storing calcium, mitochondria participate in cell signalling, generate cellular and mechanical heat, and regulate cellular development and death.
- The outer membrane is permeable, enabling small molecules to pass through while a specialised channel transports big molecules.
- The inner mitochondrial membrane is less permeable, allowing very small molecules to enter the gel-matrix of the centre mass of mitochondria. The gel matrix is made of mitochondrial DNA and Tricarboxylic Acid (TCA) cycle or Kreb’s Cycle enzymes.
- The TCA cycle converts nutrients into byproducts that mitochondria use to generate energy. These actions occur in the inner membrane because the membrane is folded into cristae, where the protein components of the Electron Transport Chain, the main energy generation mechanism of cells, are located (ETC). ETC is the body’s primary source of ATP production.
- The ETC involves many sequences of oxidation-reduction reactions to move electrons from one protein component to another, so generating energy for the phosphorylation of ADP to ATP. The chemiosmotic coupling of oxidative phosphorylation describes this mechanism. This system provides energy for the majority of cellular operations, including muscle movement, as well as the overall function of the brain.
- If not all, proteins and chemicals that comprise mitochondria are derived from the cell nucleus. The mitochondrial nucleus genome has 37 genes, 13 of which create the majority of ETC components. However, mitochondrial DNA is extremely susceptible to mutations due to the absence of a major DNA repair machinery, a common feature of nuclear DNAs.
- In addition, Reactive Oxygen Species (ROS), also known as free radicals, are generated in the mitochondrion due to the aberrant creation of free electrons. These electrons are neutralised by mitochondrion antioxidant proteins. Nevertheless, some free radicals can harm mitochondrial DNA (mtDNA).
- Similarly, alcohol consumption can damage mtDNA because excess ethanol in the body causes saturation of the detoxifying enzymes, resulting in the production and leakage of highly reactive electrons into the cytoplasmic membrane and into the mitochondrial matrix, where they combine with other cellular molecules to form numerous radicals that significantly damage cells.
- The vast majority of organisms inherit mtDNA from their mother. The maternal egg gives the majority of cytoplasm to the embryo, whereas the mitochondria inherited from the father’s sperm are destroyed. This is due to mutations passed into the embryo from the maternal and paternal DNA or maternal mtDNA. As a result, inherited and acquired mitochondrial disorders arise. Alzheimer’s disease and Parkinson’s disease are examples of such conditions. The accumulation of altered mtDNA over time has been associated with ageing and the onset of various malignancies and illnesses.
- Mitochondria play a significant part in programmed cell death (apoptosis) and mutations in mtDNA can prevent cell death, resulting in the development of cancer.
Definition of Ribosomes
Ribosomes are small, non-membranous organelles found in cells that play a crucial role in protein synthesis. They are composed of RNA and protein components and are responsible for assembling amino acids into proteins through a process called translation. During translation, ribosomes read the genetic information encoded in messenger RNA (mRNA) and use it to synthesize a protein by linking individual amino acids together. Ribosomes can be found free in the cytoplasm or attached to the endoplasmic reticulum (ER), where they participate in the synthesis of proteins destined for secretion from the cell or insertion into the plasma membrane. In this way, ribosomes play a critical role in the growth, maintenance, and function of cells and organisms.
Structure of Ribosomes
Ribosomes consist of ribosomal proteins as well as an RNA molecule called ribosomal (rRNA). In eukaryotic cells, they are half ribosomal DNA in addition to half ribosomal proteins. The ribosome is composed of two parts i.e. one large subunit as well as a small subunit , each with its distinctive forms. The subunits are referred to by the 1940s as well as the 60s in the cell of an animal.
Ribosomes are small, non-membranous organelles found in cells that play a crucial role in protein synthesis. The structure of ribosomes can be divided into two main parts:
- Subunits: Ribosomes are composed of two subunits, a large subunit (50S in prokaryotes and 60S in eukaryotes) and a small subunit (30S in prokaryotes and 40S in eukaryotes). These subunits come together during protein synthesis and then separate after synthesis is complete.
- RNA and protein components: Each ribosomal subunit is composed of both RNA and protein components. The RNA component of the ribosome, called ribosomal RNA (rRNA), is responsible for catalyzing the peptide bond formation during protein synthesis. The protein component of the ribosome helps to stabilize the structure and maintain the proper orientation of the rRNA and the growing polypeptide chain.
- Active sites: Ribosomes contain active sites where the peptide bonds are formed between amino acids during protein synthesis. These active sites are composed of specific regions of the rRNA and protein components of the ribosome.
Overall, the structure of ribosomes allows them to carry out their key role in protein synthesis by catalyzing the formation of peptide bonds and stabilizing the growing polypeptide chain.
Functions of Ribosomes
The primary function of ribosomes is to carry out protein synthesis, which is the process of assembling amino acids into proteins. The main steps of protein synthesis include:
- Transcription: The first step in protein synthesis is the transcription of genetic information from DNA into messenger RNA (mRNA) through the process of transcription.
- Translation: The second step in protein synthesis is the translation of the genetic information encoded in the mRNA into a protein. This is accomplished by ribosomes, which read the sequence of codons in the mRNA and use this information to assemble a chain of amino acids.
- Peptide bond formation: During translation, ribosomes catalyze the formation of peptide bonds between adjacent amino acids, which are the chemical bonds that hold the amino acids together to form a protein.
- Protein folding: Once the ribosome has assembled the protein, the newly formed protein must fold into its correct three-dimensional structure. This is necessary for the protein to be functional.
By carrying out these key steps in protein synthesis, ribosomes play a critical role in the growth, maintenance, and function of cells and organisms. They help to ensure that cells have the necessary proteins to carry out their various functions, and they also play a role in regulating gene expression by controlling the synthesis of specific proteins.
6. Endoplasmic Reticulum (ER)
Definition of Endoplasmic Reticulum (ER)
The endoplasmic reticulum (ER) is an extensive network of flattened, membranous sacs and tubules that is found in eukaryotic cells. It functions as a site of protein synthesis and lipid metabolism, and is also involved in the folding and modification of proteins.
There are two main types of ER in eukaryotic cells: the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER). The RER is characterized by its rough appearance due to the presence of ribosomes on its outer surface, which are involved in the synthesis of secreted and membrane-bound proteins. The SER, on the other hand, lacks ribosomes and is involved in the synthesis and storage of lipids and other small molecules.
The ER is connected to the Golgi apparatus, where proteins are further modified, and to the nuclear envelope, which surrounds the cell’s nucleus. The ER also plays a role in calcium homeostasis and the regulation of cell signaling pathways, and it is involved in the processing of toxic and misfolded proteins. Overall, the endoplasmic reticulum is an important cellular structure that is involved in a wide range of cellular processes.
Structure of Endoplasmic Reticulum (ER)
The endoplasmic reticulum (ER) is an extensive network of flattened, membranous sacs and tubules that form a complex, interconnected system within eukaryotic cells. The ER is composed of a continuous lipid bilayer membrane that encloses a large, internal space called the lumen.
There are two main types of ER: the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER). The RER is characterized by its rough appearance due to the presence of ribosomes on its outer surface, which are involved in the synthesis of secreted and membrane-bound proteins. The SER, on the other hand, lacks ribosomes and is involved in the synthesis and storage of lipids and other small molecules.
The ER is connected to other cellular organelles, such as the Golgi apparatus and the nuclear envelope, through a series of narrow channels called cisternae. Transport vesicles form at the RER and move secretory and membrane proteins to the Golgi apparatus for further processing. The ER is also connected to the cytoplasm through small openings in the ER membrane, which allow for the exchange of materials between the ER and the cytoplasm.
The ER membrane is studded with a variety of proteins that perform specific functions, such as enzymes involved in lipid metabolism, channels that regulate the flow of ions and other small molecules, and chaperones that help to fold and modify proteins. The lumen of the ER also contains a variety of enzymes and other proteins involved in cellular metabolism and protein synthesis. Overall, the endoplasmic reticulum is a complex and dynamic organelle that plays a key role in many cellular processes.
Functions of Endoplasmic Reticulum (ER)
- Manufacturing, processing , and transporting proteins that are essential for the utilization of cells within and out of cells. This is due to the fact that it is directly linked with the nucleus, allowing an avenue between the nucleus as well as the cell cytoplasm.
- The ER contains more than half of the membranous cells, which means it has a huge surface area on which chemical reactions occur. They also have the enzymes that are responsible for the majority of cell lipid synthesis , and therefore are the main site for the synthesis of lipids.
The differences in functional and physical features differentiates those who have ER into two kinds i.e rough endoplasmic reticulum as well as smooth endoplasmic-reticulum.
Types of Endoplasmic Reticulum
- Rough Endoplasmic Reticulum (Rough ER) – The ER that is rough is referred to as “rough” because its the surface is covered by the ribosomes that give rough appearance. The purpose of the Ribosomes that reside on the their rough ER is to synthesize proteins. They are equipped with a signaling pathway, sending them to the reticulum of the endoplasmic ring to process. The rough ER transports proteins and lipids throughout cells into the cristae. They then go to the Golgi bodies or placed inside the cell membrane.
- Smooth Endoplasmic Reticulum (Smooth ER) – Smooth ER is not connected with ribosomes. Their function differs from that of the endoplasmic reticulum although it is located close to the endoplasmic reticulum. It’s role is to produce of lipids (cholesterol as well as phospholipids) which are used for creating new cell membranes. They also play a role in the production of steroid hormones made from cholesterol in certain cell types. They also aid in the liver’s detoxification following the consumption of toxic chemicals and drugs.
Additionally, there is a specific kind of smooth ER, known as the sarcoplasmic retina. Its role is to control the level of Calcium ions within the muscle cell’s cells’ cytoplasm.
7. Golgi apparatus (Golgi bodies/Golgi complex)
The Golgi apparatus, also known as the Golgi complex or Golgi bodies, is a stack of flattened, membranous sacs that is found in eukaryotic cells. The Golgi apparatus is involved in the modification, sorting, and trafficking of proteins and lipids that are synthesized in the endoplasmic reticulum (ER) and destined for secretion, membrane insertion, or use within the cell.
The Golgi apparatus is organized into multiple cisternae, or flattened, stacked sacs, that are organized in a series of progressively more mature cisternae, from the cis-Golgi to the trans-Golgi. Proteins and lipids enter the Golgi at the cis-Golgi and are modified and sorted as they move through the stack of cisternae to the trans-Golgi.
The Golgi apparatus modifies proteins by adding carbohydrate and lipid modifications, such as glycosylation and phosphorylation, which play important roles in determining the final function of the protein. The Golgi also sorts proteins into transport vesicles that are destined for different locations, including the plasma membrane, lysosomes, or secretion outside the cell.
In addition to its role in protein and lipid trafficking, the Golgi is also involved in the synthesis of complex carbohydrates, such as mucins and glycosaminoglycans, and in the production of lysosomal enzymes. Overall, the Golgi apparatus is a critical cellular organelle that plays a key role in many cellular processes.
Structure of Golgi apparatus (Golgi bodies)
They are cell organelles that are bound to membranes. They can be that are found in the cytoplasm an eukaryotic cell. They are located next to the endoplasmic retina and close to the nucleus. Golgi bodies are surrounded by microtubules in the cytoplasm and held by a protein matrix . It is composed of flattened pouches that are referred to as cisternae.
These cisternae can range from 4-10 in size for Golgi cells of animal cells but some single-celled organisms can have around 60 cisternae. They are comprised of three main compartments referred to as the cis (Cisternae closest to to the Endoplasmic Reticulum) and medial (central layers of cisternae) and trans (cisternae further away from the endoplasmic Reticulum). Animal cells possess a few (1-2) Golgi bodies , whereas plants have around a hundred.
Functions of Golgi apparatus (Golgi bodies)
- They are primarily used to transport protein, modify it and then pack it and lipids in the Golgi vesicles, which then transport them to their intended locations. Animal cells have several Golgi bodies, while plants have only a few hundred.
- Cis as well as the trans Golgi network form the upper layer of cisternae that lies between the trans and cis faces and are responsible for sorting proteins as well as fats that are received by the cis face , and released from the trans face, and by the Golgi bodies.
- The cis surface collects the lipids and proteins of the vesicles fused in clusters. The vesicles fused are able to are transported along microtubules to the specialized area known as the vesicular tubular cluster. This is a space between the endoplasmic as well as the Golgi apparatus.
- The vesicle clusters join the trans Golgi network, which carries proteins and lipids into Cisternae on the cis side. As they shift from the face of the cis to the faces of trans, they are transformed into functional units. These functional units are then transported to extracellular and intracellular cells.
- Modification mechanisms comprise:
- Cleaving of chains of oligosaccharides
- Sugar moieties are attached to various side chains
- The addition of fatty acids or groups of phosphates by phosphorylation or removing monosaccharides e.g. the removal of mannose moieties is done in the cis as well as the medial cisternae, while the addition of galactose is done inside the trans-cisternae.
- Sorting of modified proteins , lipids and proteins is carried out within the trans-Golgi system and is packed into trans vesicles. The vesicles then sends them to the Lysosomes, or occasionally into the cell membrane to allow exocytosis. Facilitated by ligands attached to receptors, causing an fusion reaction and the secretion of proteins.
It’s also called cell vesicles. Lysosomes were first discovered through Christian Rene de Duve, an Belgian Cytologist in the 1950s.
Lysosomes are membrane-bound organelles found in eukaryotic cells that contain a variety of hydrolytic enzymes that can break down a wide range of biomolecules, including proteins, carbohydrates, lipids, and nucleic acids.
Lysosomes are formed from the Golgi apparatus and are essentially waste-disposal units for the cell. They function to degrade and recycle cellular waste, foreign invaders, and cellular debris, as well as play a role in cellular growth, development, and homeostasis.
Lysosomes have a single, lipid bilayer membrane that protects the cellular contents from the hydrolytic enzymes inside. The membrane also controls the flow of substances in and out of the lysosome, ensuring that the enzymes remain inside the organelle and do not damage other cellular structures.
Lysosomal enzymes are highly specific and are able to degrade complex biological molecules into their component parts, which can then be reused by the cell. In addition, lysosomes play a role in the regulation of intracellular pH and are involved in the regulation of cell growth and division.
Overall, lysosomes are critical cellular organelles that play important roles in many cellular processes and are essential for the proper functioning and survival of eukaryotic cells.
Structure of Lysosomes
Lysosomes are spherical or ovoid-shaped organelles with a single lipid bilayer membrane. The membrane encloses an interior space, or lumen, that is filled with a variety of hydrolases, or hydrolytic enzymes, that can break down a range of biomolecules.
The lipid bilayer membrane of the lysosome acts as a barrier that protects the cellular contents from the enzymes inside and also controls the flow of substances in and out of the lysosome. The membrane is studded with transmembrane proteins, such as lysosomal membrane proteins (LMPs), that play important roles in the formation and maintenance of lysosomes, as well as in the regulation of lysosomal enzyme activity.
The lumen of the lysosome contains a variety of hydrolases, including proteases, lipases, nucleases, and phosphatases, that are involved in the degradation and recycling of cellular waste, foreign invaders, and cellular debris. These enzymes are synthesized in the rough endoplasmic reticulum (ER) and are transported to the Golgi apparatus, where they are packaged into transport vesicles that eventually become lysosomes.
Lysosomes also contain a variety of regulatory proteins and other factors that control the activity of the hydrolases and help to maintain the proper pH and ion balance within the lumen of the lysosome.
Overall, the structure of lysosomes is characterized by a single lipid bilayer membrane that encloses an interior space filled with a variety of hydrolytic enzymes and regulatory factors. This combination of membrane and enzymes is essential for the proper functioning of lysosomes as cellular waste-disposal units.
Functions of Lysosomes
- This is where you can find the digestion of cells’ nutrients, excretion and cell renewal.
- Lysosomes break down macromolecules and components that are found outside the cell into smaller components that are then carried to the cytoplasm through an electron pump. This is used to construct new cell materials.
- These macromolecules are composed of parts and cells from the past of cell waste products microorganisms, cell debris.
- The digestive enzymes that are found in lysosomes are known as acid hydrolases or hydrolytic enzymes that break down massive molecules into smaller molecules that are then utilized by cells.
- They also breakdown large molecules, e. carbohydrates, proteins and lipids into smaller molecules e.g. simple sugars and amino acids as well as fatty acids.
- Notice That the enzymes work only inside the acidic lysosome. The acidity prevents cells from being destroyed in the event of lysosomal leakage due to the fact that the pH of cells is between neutral and slightly alkaline.
The cytoskeleton is a complex network of protein fibers that provides mechanical support and shape to cells, as well as plays critical roles in cell division, intracellular transport, and cell movement.
The cytoskeleton is composed of three main types of protein fibers: microfilaments, intermediate filaments, and microtubules. Each type of fiber is composed of different proteins and has distinct structural and functional characteristics.
Microfilaments are thin, flexible fibers made of actin protein that are involved in cell division, cell movement, and the contraction of muscle cells.
Intermediate filaments are thicker, more rigid fibers that provide mechanical support to cells and are involved in the maintenance of cell shape.
Microtubules are long, stiff fibers that are involved in cell division, intracellular transport, and the maintenance of cell shape.
The cytoskeleton is dynamic and constantly changing in response to the needs of the cell. For example, during cell division, the cytoskeleton reorganizes to help separate the chromosomes and divide the cell into two daughter cells.
Overall, the cytoskeleton is a critical component of eukaryotic cells that provides mechanical support, shape, and organization to cells and plays important roles in a variety of cellular processes.
Structure of Cytoskeleton
It’s a fibrous system made up of and by various proteins that form lengthy chains of amino acids. These proteins are located in the in the cytoplasm of eukaryotic cells. They are made up of three kinds of tiny filaments that include The Actin filaments (Microfilaments) Microtubules Intermediate filaments.
Functions of Cytoskeleton
- The cytoskeleton is responsible for creating an organized network of cells components, and also to keep the shape of the cell.
- It also allowed for a consistent motion of the cell as well as its organelles by the filament system that is found in the cell’s cell cytoplasm.
- It also organizes the cell components to maintain the cell’s shape
- It is a key player for the motion of cells and certain organelles of the cell in the cytoplasm.
- The tiny filaments comprise:
- Actin filaments; Actin filaments, also known as microfilaments. It’s an interconnected network of fibers that run parallel to one another. they play a major function in giving cells its shape. They alter continuously, assisting cells to move as well as facilitate certain cell functions such as adhesion ability to substrates as well as cleavage mechanisms during the mitotic cell division
- Microtubules– Microtubules are the long filaments that aid in mitosis, moving daughter chromosomes from the original daughter cells.
- Intermediate filaments– Intermediate filaments are more stable filaments as compared to microtubules and actin. They constitute the real cell skeleton, and they keep the nucleus in its proper place inside the cell.
- It also enhances the cell’s elastic factor to enable it to withstand physical stress.
- Other proteins that can be added to the cytoskeleton of cells comprise septin (assembles the filaments) and spectrin (help to maintain the shape of cells by bringing together the cell membrane and the intracellular membrane of the cell).
Microtubules are long, thin, and stiff protein fibers that are part of the cytoskeleton in eukaryotic cells. They are composed of repeating subunits of a protein called tubulin and are involved in several important cellular processes, including cell division, intracellular transport, and the maintenance of cell shape.
Microtubules are usually arranged in an organized and dynamic pattern, with the ends of the fibers constantly growing and shrinking. This dynamic behavior enables microtubules to assemble and disassemble rapidly, which is essential for many of their functions, such as the separation of chromosomes during cell division.
Microtubules also serve as a scaffold for motor proteins, such as kinesin and dynein, which move along the microtubules and transport cellular cargo, such as organelles and vesicles, from one part of the cell to another.
In addition to their structural and functional roles, microtubules are also involved in several cellular signaling pathways and are important targets for many drugs that are used to treat cancer and other diseases.
Overall, microtubules are critical components of the cytoskeleton in eukaryotic cells that play important roles in cell division, intracellular transport, and the maintenance of cell shape.
Structure of Microtubules
These are straight, long hollow cylinder filaments which consist of 13-15 subfilaments (protofilament) string of a specific tubulin-like globular protein only found in eukaryotic cell. They are present in the cytoplasm within the animal cell.
Microtubules are cylindrical structures composed of repeating subunits of a protein called tubulin. Each microtubule is composed of a row of tubulin dimers arranged in a specific pattern.
The tubulin dimers are composed of two identical subunits, alpha-tubulin and beta-tubulin, that associate in a head-to-tail manner to form the dimer. The dimers then associate end-to-end to form the microtubule.
Microtubules have a distinct polarity, with one end having a different structure than the other end. The “minus” end of the microtubule is referred to as the “catastrophic end” because it is more prone to disassembly, while the “plus” end is more stable and grows more rapidly.
The tubulin dimers are held together by a series of intermolecular bonds, including hydrogen bonds and hydrophobic interactions. This gives microtubules their stiffness and stability, which is essential for their structural and functional roles in cells.
Overall, the structure of microtubules is based on the arrangement of tubulin dimers, which are held together by a series of intermolecular bonds to form stiff and stable cylindrical structures that are critical components of the cytoskeleton in eukaryotic cells.
Functions of Microtubules
- Organelles that transport certain organelles, such as mitochondria and vesicles i.e. transporting vesicles from the cell to tips of the axons, and then back to the cell body.
- Structural support. They provide particular support to Golgi bodies, keeping them in the gel matrix of the celluloid.
- They form the rigid and well-organized component of the cytoskeleton cell, allowing it to assume a certain shape.
- They are the principal components that form the locomotive projections in cells (cilia as well as flagella)
- They also play an important role in the creation of the spindle fibers of chromosomes of the cell when the mitotic cell division.
It is found specifically within the cell of an animal which is able to duplicate or create copies on its own. It’s comprised of 9 microtubule bundles . their main function is to help in coordinating the process of cell division.
Structure of Centrioles
It is a tiny structure made up of nine microtubules that are arranged in groups of three , which is why they are known as triplet microtubules. Because they are triplets, they are extremely solid and are observed within structures like cilia or flagella. The microtubules that make up the triplet are joined by proteins, which gives the centriole shape. They are found inside the centrosome and are responsible for creating and holding microtubules in the cell. The microtubules of the triplet are enclosed by a pericentriolar structure that is populated with molecules that make up microtubules. Each microtubule of the triplet microtubule structure is comprised of tubulin subunits, which connect to form lengthy hollow tubes, which appear as if they are made of straw (microtubules).
Functions of Centrioles
- The centriole microtubules facilitate the transport of compounds that are joined by glycoprotein to any cell. The glycoprotein linkage functions as a signaling device to transport specific proteins.
- The centrioles bind the microtubules which extend out from it and hold the necessary factors to form more tubules.
- Mitosis occurs through reproduction of every centriole that produces duplicates of every centriole (4 centrioles). Centrioles that have been formed break up into two centrosomes, with each centriole angled to the other centriole. The microtubules that connect the centrosomes push the centrioles’ pairs apart and to opposite ends within the cell. When the centrioles have been put in place, the microtubules stretch to the cell’s cytoplasm in search of the chromosome. Microtubules are then bound to the chromosome in the centromere. The microtubules then break away from the centriole, tearing the chromosomes away.
Peroxisomes are membrane-bound organelles found in the cytoplasm of eukaryotic cells. They are similar in size and shape to lysosomes and are involved in several metabolic processes, including the breakdown of fatty acids and the detoxification of harmful substances.
Peroxisomes contain a variety of enzymes, including those involved in the breakdown of fatty acids, the detoxification of harmful substances such as alcohol, and the production of hydrogen peroxide. The hydrogen peroxide produced by peroxisomes is then converted into water by the enzyme catalase, which is also present in peroxisomes.
Peroxisomes are formed from the endoplasmic reticulum and are similar in structure to lysosomes, with a single membrane surrounding the inner space of the organelle. The membrane of peroxisomes is distinct from the endoplasmic reticulum and the lysosomal membrane and is not connected to the Golgi apparatus.
Overall, peroxisomes are important organelles in eukaryotic cells that play a critical role in several metabolic processes, including the breakdown of fatty acids and the detoxification of harmful substances.
Structure of Peroxisomes
They have a spherical form and are bound by a membrane , and are the most frequent micro-bodies that reside in cells’ the cytoplasm.
Peroxisomes are small, spherical organelles found in the cytoplasm of eukaryotic cells. They have a single membrane surrounding the inner space of the organelle, which contains a variety of metabolic enzymes.
The peroxisomal membrane is composed of a lipid bilayer and is similar in structure to the plasma membrane, with phospholipids, cholesterol, and proteins forming the membrane components. The membrane encloses the inner space of the peroxisome and separates its metabolic enzymes from the rest of the cytoplasm.
Peroxisomes contain a variety of metabolic enzymes, including those involved in the breakdown of fatty acids, the detoxification of harmful substances such as alcohol, and the production of hydrogen peroxide. The enzymes are dispersed throughout the inner space of the peroxisome and are not organized into any specific structures within the organelle.
Overall, the structure of peroxisomes is composed of a single membrane surrounding the inner space of the organelle, which contains a variety of metabolic enzymes involved in several important metabolic processes.
Functions of Peroxisomes
Peroxisomes are responsible for:
- Lipid metabolism
- Chemical detoxification is the process of the removal of hydrogen atoms from different oxygen molecules to create hydrogen peroxide. This neutralizes the effects of alcohol on the body.
- The mechanism it uses in the Reactive Oxygen is important.
13. Cilia and Flagella
Cilia and flagella are hair-like appendages that protrude from the surface of eukaryotic cells and are used for motility and movement. They are composed of microtubules and are covered by an extension of the plasma membrane.
Cilia are short, numerous, and uniform in length, while flagella are longer, fewer, and more variable in length. Cilia are found on the surface of cells in various tissues and organs, such as the respiratory tract and fallopian tubes, and they move in a synchronized, coordinated manner. Flagella are found on cells such as sperm and are used for propulsion.
The movement of cilia and flagella is generated by the sliding of microtubules relative to each other. The microtubules are organized into a 9 + 2 array, with 9 microtubules surrounding a central pair, and dynein proteins are responsible for generating the sliding movement.
Overall, cilia and flagella play an important role in cell motility and movement and are found on cells in a variety of tissues and organs.
Structure of Cilia and flagella
They are composed of of filaments. These filaments are made up of partially and fully formed microtubules that prolong the projections. Microtubules that are partially extended don’t reach the edge of the cilium while the full microtubules reach the top of the cilium. They also have motor proteins called Dynein that form a bridge between partial microtubules and entire microtubules. The entire collection is joined as extensions of the plasma membrane of cells.
Cilia and flagella are hair-like appendages that protrude from the surface of eukaryotic cells and are composed of microtubules, which are cylindrical protein structures that form part of the cytoskeleton. The microtubules are organized into a 9 + 2 array in cilia and flagella, with 9 outer microtubules surrounding a central pair of microtubules.
The microtubules are covered by an extension of the plasma membrane, which is composed of a lipid bilayer containing phospholipids, cholesterol, and proteins. The membrane encloses the inner space of the cilia or flagella and separates the microtubules from the rest of the cytoplasm.
The movement of cilia and flagella is generated by the sliding of microtubules relative to each other. Dynein proteins are responsible for generating the sliding movement and power the beating of the cilia or the swimming of the flagellum.
Overall, the structure of cilia and flagella is composed of microtubules organized into a 9 + 2 array and covered by an extension of the plasma membrane, which encloses the inner space of the appendage and separates it from the rest of the cytoplasm. The microtubules and the membrane work together to generate movement and allow for cell motility and movement.
Functions of Cilia and flagella
- Sperm cells are equipped with flagella, which allows them to swim to egg for fertilization. For individual cells, like Sperm, this permits they to swim.
- Cilia inside the animal cell help move fluids away from and through cells that are immobile.
- Cilia aid in moving surface particles , particularly in the epithelial linings of the nostrils. They also move mucus on the cell’s surface.
They are vesicles that are bound to membranes and created by the process of endocytosis. They can be found within the cell’s the cytoplasm.
Endosome is a membrane-bound compartment found within eukaryotic cells that plays a crucial role in intracellular trafficking and the sorting of proteins and other biomolecules. It is formed from the inward budding of the plasma membrane, and it can be thought of as an intermediary compartment between the plasma membrane and lysosomes, where lysosomal enzymes degrade internalized material.
Endosomes are highly dynamic and can undergo several transformations and maturation stages, depending on their content and destination. Early endosomes receive material from clathrin-coated pits, which are specialized regions of the plasma membrane that internalize and sort material for transport. Early endosomes then mature into late endosomes, which are larger, have a lower pH, and are the site of final sorting of material destined for the lysosome.
The contents of endosomes are sorted and directed to their final destination, which can be either the lysosome for degradation or the Golgi apparatus for further processing. The sorting of material in endosomes is regulated by a variety of mechanisms, including the presence of specific receptors, the pH of the endosomal lumen, and the activity of GTP-binding proteins.
In summary, endosomes are important compartments in eukaryotic cells that play a crucial role in intracellular trafficking and the sorting of proteins and other biomolecules. They are highly dynamic and undergo several transformations and maturation stages, and they are responsible for directing material to its final destination.
Structure of Endosome
Endosomes are spherical or tubular membrane-bound compartments within eukaryotic cells. They are formed from the inward budding of the plasma membrane, and they consist of a single lipid bilayer composed of phospholipids, cholesterol, and proteins.
The endosomal membrane is studded with specific receptors and other proteins that play a role in endosomal function and material sorting. Endosomes also contain a lumen, or internal space, which is separated from the cytoplasm by the endosomal membrane. The lumen of endosomes is acidified, with a lower pH than the cytoplasm, and this acidic environment is important for the sorting and maturation of endosomal contents.
The size and shape of endosomes can vary, depending on their stage of maturation and the type of material they contain. Early endosomes are small and spherical, while late endosomes are larger and more elongated. Additionally, endosomes can be further divided into different subtypes, depending on the presence of specific markers and their function.
In summary, the structure of endosomes is that of spherical or tubular membrane-bound compartments, composed of a single lipid bilayer with specific receptors and other proteins, and containing an acidified lumen that is separated from the cytoplasm by the endosomal membrane. The size and shape of endosomes can vary depending on their stage of maturation and the type of material they contain.
Functions of Endosome
- Its primary purpose is to fold within the plasma membrane. It allows the diffusion of molecules through extracellular fluids.
- Their main purpose is to eliminate waste material from cells through endocytosis and the process of phagocytosis
A vacuole is a membrane-bound compartment within eukaryotic cells that stores and transports various materials, such as water, salts, enzymes, waste products, and other cellular components. Vacuoles are found in the cytoplasm of cells and can vary in size and shape, depending on the cell type and the materials they contain.
Vacuoles are formed from the fusion of smaller vesicles with the plasma membrane, and they are composed of a single lipid bilayer surrounded by a cytoplasmic membrane called the tonoplast. The tonoplast is selectively permeable, meaning that it regulates the movement of material in and out of the vacuole.
Vacuoles play important roles in cell physiology and function, including maintaining turgor pressure and regulating the internal environment of the cell, helping to protect the cell from damage, and facilitating the degradation and recycling of cellular components.
In summary, a vacuole is a membrane-bound compartment within eukaryotic cells that stores and transports various materials, such as water, salts, enzymes, waste products, and other cellular components. Vacuoles play important roles in cell physiology and function.
Structure of Vacuoles
They are membrane-bound sacs that reside within the cell’s in the cytoplasm. Vacuoles have only one membrane around it that is known as a tonoplast. This membrane is similar to its plasma membrane.
A vacuole is a large, membrane-bound compartment within eukaryotic cells that stores and transports various materials. The structure of vacuoles consists of the following components:
- Tonoplast: The tonoplast is the cytoplasmic membrane surrounding the vacuole. It is selectively permeable, meaning that it regulates the movement of material in and out of the vacuole.
- Lumen: The lumen of the vacuole is the internal space of the vacuole, where the materials being stored or transported are located.
- Contents: The contents of the vacuole can vary greatly, depending on the cell type and the function of the vacuole. Vacuoles can store water, salts, enzymes, waste products, and other cellular components.
In summary, the structure of a vacuole consists of a tonoplast, which is the cytoplasmic membrane surrounding the vacuole, a lumen, which is the internal space of the vacuole, and contents, which can vary greatly depending on the cell type and function of the vacuole.
Functions of Vacuoles
- Their primary purpose is to store water, food as well as carbohydrate in the form sugars, and the waste material.
- Tonoplast can be described as an regulating device that controls the flow and outflow of proteins that are small across the pump
- is the guardian for the kinds of things that can be accessed out of vacuoles
- They also remove harmful substances and waste material from the cells as security measures.
- They also eliminate weakly folded proteins from cells.
- Vacuoles can also be used modify their function to fulfill the roles to the cell by changing the shape and size.
They are protrusions that appear on the surface within the intestinal lining on the egg cell’s surface, as well as on white blood cells.
Microvilli are small, finger-like projections that extend from the surface of many eukaryotic cells. They are found on the apical surface of many epithelial cells and help to increase the surface area of the cell, allowing for greater absorption or secretion of material.
The structure of microvilli consists of an actin filament core that provides the structural stability, and a brush border, which is composed of numerous membrane proteins and glycoproteins. These proteins and glycoproteins are involved in various functions, such as nutrient uptake and signal transduction.
In addition to increasing surface area, microvilli also play important roles in cell physiology and function, including the regulation of cell adhesion, signaling, and the control of ion channels. They are also involved in the maintenance of cell polarity, which is important for proper cell function and tissue organization.
In summary, microvilli are small, finger-like projections that extend from the surface of many eukaryotic cells, increasing the surface area of the cell and playing important roles in cell physiology and function. They consist of an actin filament core and a brush border composed of membrane proteins and glycoproteins.
Structure of Microvilli
They are surface protrusions that are formed by the accessory proteins of filaments of actin. The accessory proteins join to form microvilli that are located on the surface of the cell membrane.
The structure of microvilli is composed of two main components: an actin filament core and a brush border.
- Actin filament core: The actin filament core is composed of actin filaments, which are long, fibrous proteins that provide structural support to the microvilli. The actin filaments are organized in a bundled, parallel arrangement, and are anchored at the base of the microvillus to the underlying cytoskeleton.
- Brush border: The brush border is the apical surface of the microvillus, and is composed of a dense layer of membrane proteins and glycoproteins. The brush border is involved in various functions, such as nutrient uptake and signal transduction. Proteins in the brush border also play a role in maintaining the stability of the microvilli and the proper alignment of the actin filaments.
In summary, the structure of microvilli consists of an actin filament core, which provides structural support, and a brush border, which is composed of a dense layer of membrane proteins and glycoproteins that are involved in various functions. The microvilli are anchored at the base to the underlying cytoskeleton.
Functions of Microvilli
- Within the small intestines they enhance the surface to allow the absorption of digested foods and water. There are microvilli in the ear to detect of sound. They transmit sounds to the brain using an electrical signal.
- They also aid in anchoring the egg’s sperm to facilitate fertilization.
White blood cells serve as anchors that allow the white blood cells circulate throughout the system, allowing them to connect to pathogens.
Animal Cell Summary Tables
Locations of Different Organelles within the Animal Cell
|Location within the cell
|Plasma membrane (Cell membrane)
|Outermost boundary of the cell, surrounds the cytoplasm
|Central, usually spherical organelle that contains the cell’s genetic material (DNA)
|Semi-fluid matrix that contains all the cell’s organelles and is bounded by the plasma membrane
|Scattered throughout the cytoplasm, the powerhouses of the cell, involved in cellular respiration
|Found free in the cytoplasm or attached to the endoplasmic reticulum (ER), involved in protein synthesis
|Endoplasmic Reticulum (ER)
|Network of flattened, interconnected sacs that run throughout the cytoplasm, involved in protein synthesis and lipid metabolism
|Golgi apparatus (Golgi bodies/Golgi complex)
|Usually found near the nucleus, involved in the modification, sorting and packaging of proteins and lipids
|Small, membrane-bound organelles scattered throughout the cytoplasm, involved in the degradation and recycling of cellular waste and nutrients
|Network of protein filaments that provides shape, structure, and support to the cell
|Composed of protein tubulin, found throughout the cytoplasm, involved in cell division, maintenance of cell shape and movement of organelles
|Found near the nucleus, involved in cell division and the formation of cilia and flagella
|Small, membrane-bound organelles scattered throughout the cytoplasm, involved in fatty acid oxidation and the breakdown of harmful substances
|Cilia and Flagella
|Thin, hair-like projections from the cell surface, involved in movement and sensory reception
|Vesicles formed from the Golgi apparatus, involved in the internalization of materials from the cell surface
|Large, fluid-filled organelles found in plant and some fungal cells, involved in storage and waste management
|Tiny, finger-like projections from the surface of some cells, involved in increased surface area for absorption or secretion.
Functions of Different Organelles within the Animal Cell
|Plasma membrane (Cell membrane)
|Controls the exchange of substances between the cell and its surroundings, regulates the passage of materials in and out of the cell.
|Control center of the cell, contains genetic material (DNA) and coordinates the functions of the cell.
|Jelly-like substance that surrounds the nucleus and contains other organelles.
|Powerhouses of the cell, responsible for producing energy.
|Site of protein synthesis.
|Endoplasmic Reticulum (ER)
|Network of tubes and flattened sacs involved in the synthesis, modification and transport of proteins and lipids.
|Golgi apparatus (Golgi bodies/Golgi complex)
|Modifies, sorts and packages proteins and lipids for storage and transport.
|Contain digestive enzymes, break down waste and cellular debris.
|Provides structural support to the cell and helps maintain its shape.
|Form part of the cytoskeleton, involved in cell division and maintenance of cell shape.
|Involved in the formation of cilia and flagella and play a role in cell division.
|Contain enzymes that detoxify harmful substances and break down fatty acids.
|Cilia and Flagella
|Hair-like structures that help the cell move or move substances over its surface.
|Vesicles that carry substances internalized from the plasma membrane for further processing.
|Storage compartments for food, waste and other materials.
|Tiny finger-like projections on the surface of a cell, increase surface area for the absorption of nutrients.
Important Points to Note About Animal Cell / Facts About Animal Cells
- Animal cells are eukaryotic cells that form the basic unit of life in multicellular animals.
- Animal cells are different from plant cells in several ways, including their lack of a cell wall, their smaller size, and their more spherical shape.
- Animal cells contain various organelles, including a nucleus, cytoplasm, mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, cytoskeleton, microtubules, centrioles, peroxisomes, cilia, flagella, endosomes, vacuoles, and microvilli.
- The plasma membrane or cell membrane acts as a barrier, regulating the exchange of materials between the cell and its environment.
- The nucleus is the control center of the cell, housing the cell’s genetic material in the form of DNA.
- The cytoplasm is a gel-like substance that contains all the cell’s organelles and other cellular structures.
- Mitochondria are the powerhouses of the cell, producing energy through cellular respiration.
- Ribosomes are responsible for protein synthesis.
- The endoplasmic reticulum is involved in protein synthesis, lipid metabolism, and calcium storage.
- The Golgi apparatus is involved in protein modification, sorting, and transport.
- Lysosomes function as the cell’s waste disposal system, breaking down cellular waste and foreign substances.
- The cytoskeleton provides structural support to the cell and plays a role in cell division and movement.
- Microtubules help maintain the cell’s shape, support organelle movement, and are involved in cell division.
- Centrioles are involved in cell division and the formation of cilia and flagella.
- Peroxisomes are involved in breaking down fatty acids and eliminating toxic waste products.
- Cilia and flagella help the cell move and are involved in transporting materials along cell surfaces.
- Endosomes are involved in endocytosis, the process by which cells take in material from their surroundings.
- Vacuoles are fluid-filled sacs that store materials such as water, salts, and waste products.
- Microvilli are tiny projections from the plasma membrane that increase the surface area of the cell, allowing for increased absorption of nutrients.
What are the differences between animal and plant cells?
Differences between Animal and Plant Cells:
|No cell wall
|Cell wall present
|Mostly irregular shape
|Usually rectangular or square shape
|Small, multiple vacuoles
|Large, single central vacuole
|Rough and smooth ER present
|Rough ER present
|Typically larger Golgi complex
|Typically smaller Golgi complex
|One central, rounded nucleus
|One central, rounded nucleus
|Microfilament and microtubule-based cytoskeleton
Animal and plant cell diagram
Animal Cell Animation Video Lecture
FAQ on Animal Cell
What is an animal cell?
Animal cells, as their name suggests, are a type of cell found exclusively in animal tissues. It is characterised by the lack of a cell wall and the encapsulation of cell organelles within the cell membrane.
Which cell organelle is responsible for the generation of energy for cellular activities?
Mitochondria is responsible for the generation of energy for cellular activities
Name the double-layered membrane responsible for enveloping the nucleus.
Nuclear envelope is the double-layered membrane responsible for enveloping the nucleus.
Name the cell organelle that contains the genetic material of the cell.
Nucleus contains the genetic material of the cell
What is the role of lysosomes?
Lysosomes help in digestion, excretion and cell renewal process.
State the various types of animal cells.
Explain how an animal cell varies from a plant cell.
Typically, an animal cell is irregular and spherical in shape. This is mostly attributable to the absence of the cell wall, a characteristic of plant cells. Additionally, animal cells lack plastids since animals are not autotrophs.
Name the selectively permeable structure that envelopes the entire cell.
Cell membrane is the selectively permeable structure that envelopes the entire cell.
Which cell organelle is responsible for packing?
Golgi apparatus is responsible for packing
What are animal cells called?
What is animal cell and function?
Animal cells are the fundamental components of all Animalia kingdom living beings. They provide structure, absorb nutrients for energy conversion, and facilitate movement. They also contain all of an organism’s genetic material and can replicate themselves.
What shape is an animal cell?
Animal cells are predominantly spherical and variable in shape, whereas plant cells are rectangular and fixed. As eukaryotic cells, plant and animal cells have key characteristics, including the presence of a cell membrane and organelles such as the nucleus, mitochondria, and endoplasmic reticulum.
What does a animal cell look like?
The majority of animal cells are spherical and variable in shape, whereas plant cells are rectangular and stable. Plant and animal cells are both eukaryotic, meaning they share characteristics such as the presence of a cell membrane and organelles such as the nucleus, mitochondria, and endoplasmic reticulum.
What does the nucleolus do in an animal cell?
The nucleolus is a spherical structure found in the nucleus of a cell that is responsible for producing and assembling ribosomes. Additionally, ribosomal RNA genes are transcribed in the nucleolus.
How does the shape of a plant cell differ from that of an animal cell?
Plant cells have a defined shape, often rectangular or square with rounded corners, due to the presence of a rigid cell wall. Animal cells lack this cell wall and tend to have a more amorphous, irregular shape.
Animal Cell Worksheet
Cell Membrane (Plasma Membrane) Worksheet
Nucleus & Endoplasmic Reticulum Structure 3D Worksheet
Mitochondria Structure Animal Cell worksheet
Ribosome Structure Worksheet
Cytoskeleton Components (Fluorescent) Worksheet