Table of Contents
- Many of the molecules that make up cells, tissues, and organs are identical to those found in nonliving stuff, while others are exclusive to living species.
- Biochemistry is the study of chemical molecules found in biological systems and the reactions in which they participate.
- Molecular biology is the study of the structure and behaviour of individual molecules. If the “secret of life” exists elsewhere, it exists within these molecules.
- In reality, all living and nonliving systems are subject to the same physical and chemical principles.
- Within the cells of any organism, the living substance, or protoplasm, is composed of a variety of non-living components, including proteins, nucleic acids, fats (lipids), carbohydrates, vitamins, minerals, waste metabolites, crystalline aggregates, and pigments, all of which are composed of molecules and their constituent atoms.
- The protoplasm is alive due to the extraordinarily intricate arrangement and interaction of various nonliving elements. This is similar to a watch, which is only a timepiece when all of its gears, springs, and bearings are arranged in a particular way and interact.
- According to universal physical principles, neither the gears of a watch nor the molecules of protoplasm may interact in any way that defies these rules.
- The greater our understanding of the functioning of protoplasm and its elements on the basis of chemical principles, the greater our comprehension of the phenomena of life.
- Outside of the organelles, the cytoplasmic matrix or cytosol is the fluid and soluble component of the cytoplasm. This chapter will cover the physical and chemical properties of cytosol.
Physical Nature of Cytosol (Or Cytoplasmic Matrix)
The cytosol (cytoplasmic matrix) is a colloidal substance that is colourless or greyish, transparent, viscous, gelatinous, or jelly-like. It is more dense than water and may flow. In the past, there has been considerable debate on the physical nature of the matrix. Regarding the physical properties of the matrix, diverse workers offered divergent hypotheses. Their theories can be represented in the following manner:
- Reticular theory: According to the reticular theory, the matrix is made up of a reticulum of fibres or particles in the ground material.
- Alveolar theory: Butschili proposed the Alveolar theory in 1892. According to this idea, the matrix consists of several suspended droplets or alveoli or minute bubbles resembling emulsion foams.
- Granular theory: The granular theory was first proposed by Altmann in 1893. This hypothesis supports the notion that the matrix is composed of several granules of various sizes and configurations. These particles were referred to as bioplasts.
- Fibrillar theory: Fleming suggested the fibrillar theory, which asserts that the matrix has a fibrillar structure.
- Colloidal theory: After the electron microscopy studies of the matrix, the colloidal theory has been proposed fairly recently. In accordance with the most recent theory, the matrix is partially a real solution and partially a colloidal system.
A solution is a mixture of a liquid called the solvent and any solid or liquid chemical component called the solute. In a solution, the solute particles should have a diameter of less than 1/10,000 millimetre. In the solution portion of the matrix, biologically significant solutes such as glucose, amino acids, fatty acids, electrolytes, minerals, vitamins, hormones, and enzymes are dissolved in water.
A colloidal system is described as a system containing a liquid medium in which particles with diameters ranging from approximately 1/1,000,000 to 1/10,000 millimetres remain distributed. Therefore, the colloidal state is a condition in which one substance, such as a protein or other macromolecule, is dispersed in another substance to produce several tiny phases suspended in a single continuous phase. Every colloidal system comprises two phases: a discontinuous or dispersion phase and a continuous or dispersion phase. Total protoplasm (cytoplasm + nucleoplasm) is a colloidal solution because the protoplasm’s primary molecular components, proteins, exhibit all the properties of a colloidal state. Proteins form stable colloids because, first, they are charged ions in solution that repel each other and, second, each protein molecule attracts water molecules in distinct layers around it.
- The cytosol (cytoplasmic matrix), like numerous colloidal systems, exhibits phase reversal. For instance, gelatin particles (discontinuous phase) are spread across water (continuous phase) in a thin, shakable consistency.
- This condition is known as a sol. As the solution cools, gelatin transforms into the continuous phase and water becomes the discontinuous phase.
- In addition, the solution has now turned semisolid and is known as a gel. In the gel state, the molecules of a colloidal substance are bound together by a variety of chemical linkages, including H—H, C—H, and C—N interactions.
- Chemical linkages determine the nature and strength of gel’s stability. Heating the gel solution will transform it back into a liquid, reversing the phases.
- Under normal conditions, the phase reversal of the cytosol (cytoplasmic matrix) is dependent on the cell’s physiological, mechanical, and biochemical processes.
Chemical Organization of Cytosol (Or Cytoplasmic Matrix)
As atoms, ions, and molecules, the cytoplasmic matrix consists of several chemical components.
- Approximately 46 of the 92 naturally occurring elements are found in the cytosol (cytoplasmic matrix).
- Twenty-four of these are regarded essential for life (termed essential elements), whereas others are only present in the cytosol due to their presence in the organism’s surroundings.
- Six of the twenty-four fundamental components play crucial roles in biological systems. These are the primary elements: carbon (20%), hydrogen (10%), nitrogen (3%), oxygen (62%), phosphorus (1.14%), and sulphur (S, 0.14 per cent).
- The majority of organic molecules are composed of these six components. The remaining five important elements found in less quantity in living systems are calcium (Ca, 2.5%), potassium (K, 0.11%), sodium (Na, 0.10%), chlorine (Cl, 0.16%), and magnesium (Mg, 0.16%). (Mg, 0.07 per cent).
- Other elements, known as trace elements, are also present in minute quantities in animals and plants, yet are vital to existence.
- These include iron (0.10 %), iodine (0.014 %), molybdenum (Mo), manganese (Mn), cobalt (Co), zinc (Zn), selenium (Se), copper (Cu), chromium (Cr), tin (Sn), vanadium (V), silicon (Si), nickel (Ni), fluorine (F), and boron (B).
- The cytoplasmic matrix is composed of a variety of ions. The ions are essential for the maintenance of osmotic pressure and acid-base equilibrium in the cells.
- The retention of ions in the matrix results in a rise in osmotic pressure and, consequently, the entry of water into the cell.
- The intracellular fluid (matrix) contains a different concentration of ions than the interstitial fluid. K+ and Mg++ concentrations can be high inside the cell, but Na+ and Cl— concentrations can be high outside the cell.
- There is a large discrepancy between intracellular K+ and external Na+ in muscle and nerve cells.
- Free calcium ions (Ca++) may be present in cells or blood. Grasses contain silicon ions in their epithelial cells. Phosphate’s free ions (primary, H2PO4, and secondary, HPO4) are found in the matrix and blood.
- These ions serve as buffers and stabilise the pH of blood and cellular fluids. Aside from sulphate (SO4 —), carbonate (CO3 —), bicarbonate (HCO3 —), magnesium (Mg++), and amino acids, the ions of various cells also include carbonate (CO3 —), bicarbonate (HCO3 —), and carbonate (CO3 —).
Electrolytes and Non-electrolytes
Electrolytes and non-electrolytes make up the matrix.
- Electrolytes are essential for maintaining osmotic pressure and acid-base equilibrium in the matrix.
- Mg2+ ions, phosphate, and other substances are examples of electrolytes.
- Some minerals in the matrix exist in a non-ionizing condition.
- The matrix’s non-electrolytes include Na, K, Ca, Mg, Cu, I, Fe, Mn, Fl, Mo, Cl, Zn, Co, and Ni, among others.
- Iron (Fe) is present in haemoglobin, ferritin, cytochromes, and some enzymes, including catalase and cytochrome oxidase. Calcium (Ca) can be found in the blood, matrix, and bones.
- Copper (Cu), manganese (Mn), molybdenum (Mo), and zinc (Zn) serve as cofactors for enzyme processes.
- Iodine and fluorine are necessary for thyroid and enamel metabolisms, respectively.
Inorganic Compounds of Cytosol
Inorganic compounds include elements, metals, non-metals, and their compounds, such as water, salts, and a wide range of electrolytes and non-electrolytes. In the previous part, we explored inorganic substances extensively, with the exception of water, which will be covered in the following paragraph.
- Water is the most abundant inorganic component of the cytosol (the notable exceptions are seeds, bone and enamel).
- Water comprises between 65 and 80 percent of the matrix. There are two forms of water in the matrix: free water and bound water.
- Free water refers to the 95 percent of the total cellular water utilised by the matrix as a solvent for various inorganic and organic molecules.
- The remaining 5% of total cellular water is weakly connected to protein molecules by hydrogen bonds or other factors and is referred to as bound water.
- The water content of an organism’s cellular matrix is directly dependent on its age, environment, and metabolic activity.
- For instance, the cells of the embryo contain 90 to 95% water, whereas the cells of the adult organism contain gradually less water.
- Comparatively, the cells of lower aquatic creatures contain a greater proportion of water than the cells of higher terrestrial animals.
- Moreover, the proportion of water in the matrix fluctuates from cell to cell based on the metabolic rate.
Molecular structure of water
- Water’s unique physical qualities are reflected in its molecular structure. Hydrogen and oxygen combine to make water through the production of covalent bonds, in which atoms share pairs of electrons to form chemical bonds.
- Covalent bonds are strong chemical bonds between atoms that carry a significant quantity of chemical energy (110,6 kilocalories/mole or 462 kilojoules/mole).
- Hydrogen is depicted in Figure with its single electron, which it may share with an oxygen atom. Each oxygen atom can share two electrons with two hydrogen atoms.
- The special physical properties of water are found in its molecular structure. Water is formed by the combination of hydrogen and oxygen through the formation of covalent bonds, in which atoms by sharing pairs of electrons, become linked together.
- Covalent bonds are strong chemical bonds between atoms and contain a relatively large amount of chemical energy (110.6 kilocalories/Mole or 462 kilojoules/Mole).
- In Figure hydrogen is shown with its one electron which it may share with an oxygen atom. Each oxygen atom has two electrons which it may share with two hydrogen atoms.
Unique physical properties of water and their biological utility
a number of exceptional features of water make it ideally suited for its crucial role in protoplasmic systems (i.e., cytosol or matrix). Among the distinctive characteristics of water are the following:There are several extraordinary properties of water that make it especially fit for its essential role in the protoplasmic systems (i.e., cytosol or matrix). Some of the unique properties of water are the following :
1. Water as a solvent
- The most stable and flexible solvent is water. The dipole nature of water determines its properties as a solvent for inorganic things such as mineral ions, solids, etc., and organic compounds such as carbohydrates and proteins.
- Due to its polarity, water can electrostatically connect to both positively and negatively charged protein groups.
- Therefore, each amino group in a protein molecule can bind 2.60 water molecules. All cellular chemical reactions take occur in aqueous solution, hence the solubility is of enormous biological significance.
- The water also serves as an effective dispersion medium for the matrix’s colloidal structure.
2. Water’s thermal properties
- Water is the only substance that occurs in the three states of solid, liquid, and gas within the normal temperature range of the earth.
- It takes 1 calorie (4.185 joules) to raise the temperature of 1 gramme of water by 1 degree Celsius (such as from 15 to 16 degrees Celsius).
- Such a large thermal capacity of water has a considerable moderating influence on temperature variations in the environment and is an excellent life-saving agent. Additionally, water has a high vaporisation heat.
- More than 540 calories (2,259 joules) are required to transform 1 gramme of liquid water into water vapour.
- Consequently, for a substance with such a low relative molecular mass, water’s boiling temperature (100o C) is surprisingly high.
- It seems conceivable that liquid water would never have existed on Earth and would have been lost to space if not for this fortunate event.
- In addition, for terrestrial plants and animals, the cooling caused by water evaporation is an essential technique of removing excess heat.
- Furthermore, at the opposite temperature extreme, enormous amounts of energy (335 joules or 80 calories per gramme) must be wasted in order for water to go from liquid to solid. This is known as fusion heat.
- 0 degrees Celsius is the temperature of melting for water. The peculiar behaviour of water’s density as a function of temperature change is an additional biologically significant feature.
- Most liquids become increasingly denser as they cool. However, water reaches its greatest density at 4 degrees Celsius and then becomes lighter as the temperature is lowered.
- Consequently, ice floats instead of sinking to the bottom of lakes and ponds. This prevents the freezing of aquatic life.
3. Surface tension
- Water’s surface tension is high. This feature, which is a result of the high cohesion of water molecules, is essential for the maintenance of protoplasmic shape and motion.
- Water’s low viscosity, despite its high surface tension, facilitates the passage of blood through minute capillaries and cytoplasm within cellular borders.
- Molecules dissolved in water tend to accumulate at the interface between its liquid phase and other phases, lowering the surface tension of water.
- This may have played a key part in the formation of the plasma membrane, and it plays a crucial role in the transport of molecules across it.
- Transparent to light, the water enables the specialised photosynthetic organelles, chloroplasts, within the plant cell to absorb sunlight for photosynthesis.
Organic Compounds of Cytosol
- Organic compounds are substances containing carbon (C) in conjunction with one or more additional elements, such as hydrogen (H), nitrogen (N), or sulphur (S).
- Organic compounds typically consist of big molecules produced by monomers with similar or distinct unit structures.
- A monomer (Greek: ; mono=one; ; meros=part) is the smallest unit of an organic molecule that may exist alone.
- Some organic molecules, such as carbohydrates, serve as monomers in the matrix. Typically, the monomers bond with other monomers to form oligomers (Greek: oligo=few or small) and polymers (Greek: poly=many)
- Oligomers are composed of a small number of monomers, whereas polymers are composed of a large number of monomers. Oligomers and polymers are composed of big molecules or macromolecules.
- When a polymer’s macromolecule is comprised of identical types of monomers, it is referred to as homopolymer, but when it is composed of various types of monomers, it is referred to as heteropolymer.
- Carbohydrates, lipids, proteins, vitamins, hormones, and nucleotides make up the matrix’s primary organic constituents.
- The carbohydrates (L., carbo=carbon or coal, Gr., hydro=water) are carbon, hydrogen, and oxygen-based molecules.
- They constitute the primary source of energy for all living things.
- Only the green portions of plants and a few microorganisms are capable of generating carbohydrates from water, carbon dioxide, and chlorophyll in the presence of light and chlorophyll via photosynthesis.
- All animals, non-green plant parts (e.g., stem, root), non-green plants (e.g., fungi), bacteria, and viruses depend on green plant parts for their glucose needs.
- Carbohydrates are chemically polyhydroxy aldehydes or ketones and are categorised as follows: A. Monosaccharides (Monomers), B. Oligosaccharides (Oligomers), and C. Polysaccharides (Polymers).
- With the empirical formula Cn (H2O)n, monosaccharides are the simple sugars.
- According to the number of carbon atoms in their molecules, they are classified and named as follows:
- Trioses have molecules with three carbon atoms, such as glyceraldehyde and dihydroxy acetone.
- Tetrose molecules contain four carbon atoms, as in erythrulose and erythrose.
- The molecules of pentoses, which include ribose, ribulose, deoxyribose, arabinose, and xylulose, contain five carbon atoms.
- Glucose, mannose, fructose, and galactose are examples of hexoses with six carbon atoms in their molecules.
- Heptoses, such as sedoheptulose, contain seven carbon atoms in their molecules.
- Typically, monosaccharides occur as isomers. For instance, three hexose sugars—glucose, fructose, and galactose—contain the same number of carbon, hydrogen, and oxygen atoms (i.e., C6H12O6), but they are distinct sugars due to unique atomic configurations inside their molecules. Glucose and galactose are optical and stereo isomers, respectively.
- If a carbon atom is present in a molecule with four separate chemical groups linked to it, the groups can be arranged spatially in two alternative ways around the carbon atom (such a carbon atom is often called asymmetric carbon atom).
- These two distinct configurations are referred to as mirror-images, and a useful illustration of such structures are the two human hands, which are identically formed yet cannot be superimposed.
- The two isomers are denoted as ‘D’ or ‘L’ analogously to aldotrioses D– and L– glyceraldehyde. The majority of monosaccharides are optically active, meaning that their asymmetric carbon (s) causes the plane of polarised light to rotate.
- Molecules that rotate the plane of polarisation to the right, as one faces the light source, are known as dextrorotatory and are denoted by the symbol d or (+), whereas the opposite situation, levorotation, is denoted by the symbol l or (-). (–). It is essential to recall that capital D and L refer to structure, whereas lowercase d and l refer to optical activity created prior to the determination of structure (see Dyson, 1978).
- Consequently, references are made to D (+) -glucose, also known as dextrose, and D (–) -fructose, also known as levulose.
- Additionally, sugars can be expressed in a linear straight chain form for the sake of simplicity. In actuality, the cyclic configuration is the more relevant one; it is an isomer with an oxygen bridge connecting two of the carbons.
- At position one, ring creation creates a new asymetric carbon. Due to the stereochemistry of monosaccharides, the ring produced has either five or six members; a ring with seven members would be too strained.
- In pentose (five-carbon) sugars such as ribose, a furanose ring with five members is generated. In hexoses such as fructose and glucose, a pyranose ring with six members is generated. Haworth proposed an effective method of depicting the ring structures of sugars (1927).
- Therefore, in gluco-pyranose, carbon atoms 2 and 3 are in front of the plane of the paper, whereas carbon atom 5 and the ring oxygen are behind the plane of the paper. The substitution groups are either located above or below the ring’s plane.
- The monosaccharides, which are the monomers, cannot be further divided or hydrolyzed into simpler molecules. Pentoses and hexoses are the most abundant monosaccharides found in the matrix.
- RNA and certain coenzymes, such as nicotinamide adenine dinucleotide (NAD), nicotinamide adenine dinucleotide phosphate (NADP), adenosine triphosphate (ATP), and coenzyme A, include ribose, a pentose sugar (CoA).
- Deoxyribose, a pentose sugar, is an essential component of deoxyribonucleic acid (DNA).
- Ribulose is a pentose sugar that is required for the photosynthetic process. The glucose, a hexose sugar, is the cell’s principal source of energy. Fructose and galactose are two other essential hexose sugars of the matrix.
The molecules of oligosaccharides include between two and ten monosaccharides (monomers). The monomers remain connected to one another via glycosidic connections or links. Important oligosaccharides include the following:
- Disaccharides include two monomers, e.g., sucrose, maltose, lactose, etc.
- Trisaccharides comprise three monomers, e.g.,reffinose, mannotriose, rabinose, rhaminose, gentianose and melezitose.
- Tetrasaccharides, such as stachyose and scordose, are composed of four monomers.
- Pentasaccharides include five monomers, e.g., verbascose.
Disaccharides such as sucrose, maltose, and lactose are the most prevalent oligosaccharides found in animal and plant cells. Sucrose and maltose are predominantly found in the matrix of plant cells, whereas lactose is found only in the matrix of animal cells. D-glucose and D-fructose constitute the molecules of sucrose. Maltose molecules are composed of two D-glucose molecules. Lactose molecules consist of two monomers, namely D-glucose and D-galactose. Similar to monosaccharides, disaccharides are all sweet, water-soluble, and crystallizable.
- In their macromolecules, polysaccharides consist of tens to thousands of monosaccharides as monomers.
- They have the empirical formula (C6H10O6)n. The polysaccharide molecules are colloidal in size and have high molecular weights.
- It is possible to hydrolyze polysaccharides into simple sugars. There are two major functional types of polysaccharides: structural polysaccharides and nutritional polysaccharides.
- Primarily, structural polysaccharides function as extracellular or intracellular structural components. Included in this category are cellulose (found in plant cell walls), mannan (a homopolymer of mannose found in yeast cell walls), chitin (in the exoskeleton of arthropods and the cell walls of most fungi and some green algae), hyaluronic acid, keratin sulphate, and chondroitin sulphate (found in cartilage and other connective tissues, respectively), and the peptidoglycans (in bacterial cell wall).
- Polysaccharides function as monosaccharide reserves and undergo continual metabolic turnover. This category includes starch (plant cells and bacteria), glycogen (animal cells), inulin (artichokes and dandelions) and paramylum (an unbranched nutrient and storage homopolymer of glucose found in certain protozoa, e.g., Euglena).
- Some polysaccharide molecules are unbranched (i.e., linear) chains with ribbon-like or helical structures (usually a left-handed spiral).
- Like many proteins, other polysaccharides are branching and assume a globular shape.
- On the basis of their chemical structure, polysaccharides can be classified into two major categories: homopolysaccharides and heteropolysaccharides.
The molecules of homopolysaccharides contain similar types of monosaccharides. The matrix’s most significant homopolysaccharides are starch, glycogen, paramylum, and cellulose.
- Starch is a nutritional, plant-cell storage polymer (e.g., potato tubers). Typically, it appears in cells as grains or granules (they are located inside the spherical plastids).
- Starch granules contain a mixture of two distinct polysaccharides, amylose and amylopectin, the proportions of which vary depending on the starch’s source.
- Amylose is an unbranched glucose 1→4 polymer that can be several thousand glycosyl units in length.
- The polysaccharide chain is a left-handed helix with six glycosyl residues per turn.
- It is believed that the famous blue colour produced when starch is treated with iodine is due to the coordination of iodine ions within the helix. (In actuality, such a colour reaction occurs when the helix has at least six helical turns or 36 glycosyl units.)
- Amylopectin resembles glycogen and is a polysaccharide with many 1→4- and few 1→6-linked glucosyl units.
- Glycogen, often known as animal starch, is a branching, nutrient-storing homopolysaccharide found in all mammal cells, certain protozoa, and algae.
- It is especially prevalent in the liver and muscle cells of humans and other animals. Glycogen is more soluble than starch and resides as minute granules within the cytoplasm.
- The biggest glycogen molecules contain tens of thousands of glucose or glycosyl units (e.g., 30,000).
- Each glycogen molecule is composed of long, abundantly branched chains of -glucose molecules.
- The glycosidic bonds are formed between the carbons 1 and 4 of glucose (i.e., -1→4 linkages), with the exception of the branching sites, which involve -1→6 connections.
- A glycogen molecule is composed of three distinct types of chains: A, B, and C. There is a single C chain that contains several B and A chains and terminates in a free reducing group (i.e., carbon 1 of glucose at the end of C chain bears a hydroxyl or OH group).
- The B chains are directly connected to the C chain and carry at least one A chain. Additionally, the A chain can be joined to the C chain.
- Cellulose is the most prevalent and plentiful biological substance on the planet. It is an essential component of plant cell walls, as well as the cell walls of algae and fungi.
- Cellulose is an unbranched (straight) structural polysaccharide of glucose in which the adjacent monosaccharides are connected via -β-1→4 glycosidic linkages.
- Several hundred to a few thousand glycosyl units comprise the lengths of the chains (e.g., in the algae Valonia, a single molecule of cellulose may contain more than 20,000 glycosyl units).
- In cellulose molecules, successive pyranose rings are rotated 180 degrees relative to one another, giving the sugar chain a “flip-flop” look.
- Due to this, the OH groups of sugar molecules protrude from the chain in all directions, allowing them to make hydrogen bonds with the OH groups of adjacent cellulose chains, thereby forming a three-dimensional lattice.
- Thus, in plant cell walls, 2,000 cellulose molecules are organised into parallel, cross-linked microfibrils (with a diameter of 25 nm) whose long axis is that of the individual glucose chain.
- Chitin is a polymer found in the cell walls of fungal hyphae and the exoskeleton of arthropods.
- Chitin’s chemical structure is similar to that of cellulose, with the exception that the hydroxyl group of each carbon atom at position 2 is substituted by an acetamide group.
- Chitin is therefore an unbranched polymer of N-acetylglucosamine containing thousands of aminosugar units linked by β-1→4 glycosidic linkages.
- In addition to starch and cellulose, plant cells contain other polysaccharides such as xylan, alginic acids (algae), pectic acids, inulin, agar-agar, and hemicellulose.
- Some of these polysaccharides provide mechanical support for the cell, whereas others serve as food reserves.
Heteropolysaccharides are polysaccharides that contain different types of monosaccharides and amino-nitrogen, sulphuric, or phosphoric acids in their molecules. The following are the most important heteropolysaccharides:
i. Hyaluronic acid, keratin sulphate and chondroitin sulphate
- The acidic heteropolysaccharides hyaluronic acid, keratin sulphate, and chondroitin sulphate are found in cartilage tissue.
- Hyaluronic acid is an unbranched heteropolysaccharide composed of N-acetylglucosamine (or D-glucosamine) and glucuronic acid repeating disaccharides.
- Hyaluronic acid is also present in other connective tissues, the synovial fluid of joints, the vitreous humour of the eyes, and bacterial capsules.
- Like hyaluronic acid, keratin sulphate is a repeating disaccharide producing a straight chain. Each disaccharide unit of the polysaccharide is composed of D’Galactose and N-acetylglucosamine that has been sulfated. It is a component of cartilage and cornea.
- Chondroitin sulphate is a disaccharide composed of alternating residues of glucuronic acid and sulphated N-acetyl galactosamine. It exists in cartilage, bone, skin, the notochord, the aorta, and the umbilical cord.
- Heparin is an anticoagulant found in the blood, skin, liver, lung, thymus, and spleen.
- Its molecule consists of D-glucuronic acid and D-glucosamine repeated disaccharide units.
iii. Proteoglycans, glycoproteins and glycolipids
Additionally, polysaccharides combine covalently with proteins and lipids to generate the following three types of molecules:
- Proteoglycans: Proteoglycan molecules are composed primarily of polysaccharides and a minor amount of protein. Additionally known as mucoproteins. Proteoglycans are amorphous and produce gels that are capable of retaining enormous quantities of water. Cartilage and bone include extracellular cartilage proteoglycan. A long, central molecule of hyaluronic acid is surrounded by strands of protein, referred to as core protein. Each core protein strand contains three sections containing carbohydrates. The first section consists primarily of oligosaccharides, the second of keratin sulphate chains, and the third of chondroitin sulphate chains. This configuration confers resilience and tensile strength to cartilage.
- Glycoproteins (or glycosaminoglycans or mucopolysaccharides): Glycoproteins (or glycosaminoglycans or mucopolysaccharides) are polysaccharide-containing proteins. In these compounds, the carbohydrate component consists of significantly shorter, frequently branched chains. Certain enzymes, hormones, blood types, saliva, gastric mucus, ovomucoids, serum, albumins, antibodies, and immunoglobulins are glycoproteins with varied functions in cells and organs.
- Glycolipids: These molecules are composed of carbohydrate and lipid covalent bonds. The carbohydrate component may consist of a monosaccharide or a linear or branched chain. The majority of cell membranes are composed of glycolipids, such as cerebrosides and gangliosides.
2. Lipids (Fats)
- The lipids (Greek:, lipos = fats) are insoluble in water but soluble in non-polar organic solvents like acetone, benzene, chloroform, and ether.
- Caused by the prevalence of long chains of aliphatic hydrocarbons or benzene rings in their molecules, lipids have this general feature. The lipids are hydrophobic and non-polar.
- Examples of common lipids include vegetable oil, butter, ghee, waxes, natural rubber, and cholesterol. Similarly to carbohydrates, lipids serve two primary functions in cells and tissues: 2. They can be kept within cells as reserve energy sources. Similar to starch and glycogen, fat is compact and insoluble and provides a useful structure for storing energy-producing molecules (fatty acids) for utilisation when the need arises.
- Lipids are composed of carbon, hydrogen, and occasionally oxygen. Compared to the quantity of carbon atoms, the number of oxygen atoms in lipid molecules is always negligible. Occasionally, phosphorus, nitrogen, and sulphur are also present in trace levels.
- Natural fats and oils are glycerol (i.e., glycerine or propane1, 2, 3-triol) and fatty acid molecules.
- They are esters that are generated when organic acids combine with alcohols. There is only one type of glycerol; its molecular structure does not vary and is identical in all lipids. Glycerol has the formula C3H8O3 and the following chemical structure:
- Fatty acids: A fatty acid molecule is amphipathic and contains two separate sections or ends: a lengthy hydrocarbon chain that is hydrophobic (water insoluble) and chemically inert, and a carboxylic acid group that is ionised in solution (COO–), extremely hydrophilic (water soluble), and rapidly produces esters and amides. In neutral liquids, salts of fatty acids form small spherical droplets or micelles with dissociated carboxyl groups at the surface and hydrophobic carbon chains extending into the centre. In cells, fatty acids are esterified to other components and produce saponifiable lipids. Fatty acids are rare in their free state; they are esterified to generate saponifiable lipids. A molecule of fatty acid can be either saturated or unsaturated. Long hydrocarbon chains terminating in a carboxyl group characterise saturated fatty acids, which conform to the general formula CH3 – (CH2)n – COOH. Almost all naturally occurring fatty acids have an even number between 2 and 22 for n. In the saturated fatty acids found most frequently in animal tissues, n is either 12 (i.e., myristic acid), 14 (i.e., palmitic acid), or 16 (i.e., palmitic acid) (i.e., stearic acid). In unsaturated fatty acids, at least two but typically no more than six of the carbon atoms of the hydrocarbon chain are connected by double bonds (– C = C –), e.g. oleic acid, linoleic, linolenic, arachidonic, and clupanadonic acids. Double bonds are important because they increase the flexibility of the hydrocarbon chain and, consequently, the fluidity of biological membranes. Unsaturated fatty acids prevail in the lipids of higher plants and cold-adapted animals. Greater amounts of saturated fatty acids can be found in the lipids of animals living in warmer regions.
- Essential fatty acids: Specific creatures, particularly mammals, are incapable of synthesising certain fatty acids and thus require them in their diet. Essential fatty acids are comprised of linoleic acid, linolenic acid, and arachidonic acid. These necessary fatty acids must be derived by the animal from plant matter.
Types of lipids
The lipids are classified into three main types : 1. simple lipids, 2. compound lipids and 3. derived lipids.
1. Simple lipids
The simple lipids are alcohol esters of fatty acids. Simple lipids are also of following two types :
- Neutral fats (Glycerides or triglycerides): Glycerides and triglycerides are triesters of fatty acids and glycerol. The majority of stored lipids are neutral fats, which accumulate in the cytoplasm.
- Waxes: Waxes have a greater melting point than neutral fats and are esters of high-molecular-weight fatty acids with alcohols other than glycerol. Cholesterol is the most major ingredient alcohol of the molecules of waxes, such as beeswax.
2. Compound lipids
In the molecules of lipids are fatty acids, alcohols, and other compounds such as phosphorus, amino-nitrogen carbohydrates, etc. Some chemical lipids are essential structural components of the cell, particularly of the cell membrane. The cell’s compound lipids are of the following types:
(i) Phospholipids (or Glycerophos-phatides)
- Such lipids are the primary component of cell membranes. Two of the —OH or hydroxyl groups in glycerol are linked to fatty acids in a phospholipid molecule, while the third —OH group is linked to phosphoric acid.
- The phosphate is also bonded to a hydrophilic molecule, such as etanolamine, choline, inositol, or serine. Therefore, each phospholipid molecule comprises a hydrophobic or water-insoluble tail made of two fatty acid chains and a hydrophilic or water-soluble polar head group containing the phosphate.
- Consequently, phospholipid molecules are detergents, i.e., when a small amount of phospholipid is spread over the surface of water, a monolayer film of phospholipid molecules forms; in this thin film, the tail regions of the phospholipid molecules are tightly packed against the air, while their head groups are in contact with the water.
- Two of these films can merge end-to-end to form a phospholipid sandwich or self-sealing lipid bilayer, the structural basis of cell membranes. Cell membranes contain the four forms of phospholipids listed below: 4. phosphatidyl inositol
- Other important matrix phospholipids include phosphoinositides, plasmalogens, and isositides. Phosphoinositides are mostly found in liver, brain, muscle, and soyabean cells.
- Plasmalogens are a specialised family of phospholipids that are notably numerous in the membranes of nerve and muscle cells, as well as cancer cells.
- When aqueous phospholipid suspensions are rapidly agitated by ultrasound (i.e., insonation), the lipid disperses in the water and forms liposomes or lipid vesicles.
- Liposomes are small spherical bodies (25 nm to 1 µm in diameter) with a bilayer of phospholipid molecules enclosing a small volume of the surrounding aqueous medium.
- They display many of the permeability characteristics of natural membranes, i.e., water-soluble tiny molecules or ions can be encapsulated by liposomes and can also pass through the lipid bilayer of the latter.
- Recently, it has been shown that liposomes offer significant therapeutic potential since they can be utilised as vectors for the transfer of specific medicines, proteins, hormones, nucleic acids, ions, or any other sort of molecule into certain types of animal cells.
- Two routes allow the liposomes’ contents to access the target cells: Liposomes can bind to the surface of target cells and fuse with the plasma membrane, releasing their contents into the cytosol or cytoplasmic matrix. Liposomes can be endocytosed and destroyed intracellularly in their entirety.
- Sphingolipids are primarily found in brain cells. Instead of glycerol, they include amine alcohol in their molecules (sphingol or sphingosine).
- For instance, the myelin sheaths of nerve fibres include sphingomyelin, a lipid whose molecules comprise sphingosine and phospholipids.
The molecules of glycolipids include both carbohydrates and lipids. The animal cell matrix contains two types of glycolipids: cerebrosides and gangliosides.
- Cerebrosides: The molecules of cerebrosides contain sphingosine, fatty acids, and galactose or glucose. Cerebrosides are essential components of the white matter of brain cells and the myelin sheath of nerves. Kerasin, cerebron, nervon, and oxynervons are crucial cerebrosides.
- Gangliosides: Gangliosides are comprised of sphingosine, fatty acids, and one or more molecules of glucose, lactose, galactosamine, and neuraminic acid. Gangliosides are found in the grey matter of the brain, the membrane of erythrocytes, and spleen cells. Gangliosides have antigenic properties. GM2 ganglioside may accumulate in the lysosomes of brain cells due to a genetic defect that prevents the cells from producing an enzyme that destroys this ganglioside. This disorder, known as Tay-Sachs disease, causes paralysis, blindness, and delayed human development.
3. Derived lipids (or Nonsaponifiable lipids)
Some types of lipids do not contain fatty acids as constituents, and these three types are:
- The terpenes contain certain fat-soluble vitamins (such as vitamins A, E, and K), carotenoids (such as plant photosynthetic pigments), and certain coenzymes (such as coenzyme Q or ubiquinone).
- All terpenes are generated from varying numbers of the isoprene unit, a five-carbon building block. The isoprene units are joined in a head-to-tail arrangement.
- Two isoprene molecules combine to produce a monoterpene, four units combine to form a diterpene, six units combine to form a triterpene, and so on. Monoterpenes are responsible for the distinctive aromas and tastes of plants (e.g., geraniol from geraniums, menthol from mint and limoneme from lemons).
- Dolicol phosphate is utilised to transport activated sugars in the membrane-associated production of glycoproteins and some polysaccharides. Dolicol phosphate is a polyisoprenoid (i.e., a long-chain polymer of isoprene).
- Carotenoids are lipid compounds that make up the pigments of animal and plant cells. There are around 70 carotenoids present in both cell types.
- Important cellular carotenoids include α, β and γ carotenes, retinene, xanthophylls, lactoflavin in milk, riboflavin (vitamin B2), xanthocyanins, coenzyme Q, anthocyanins, flavones, flavonols, and flavonones, among others. Chemically, all carotenoids are isoprenoids with alternating series of double bonds and long chains.
- They are produced by plant tissues and are placed within the chloroplast lamellae to aid in the absorption of light during photosynthesis. In animal cells, carotenoids function as vitamin A precursors.
- Chlorophylls are vital green photosynthetic pigments of chloroplasts. There are a head and a tail on a chlorophyll molecule.
- The head consists of a porphyrin ring or tetrapyrrole nucleus, from which a hydrophobic tail composed of a 20-carbon cluster called the phytol extends.
- Phytol (C20 H39) is a long alcohol with a straight chain and a single double bond. It may be considered a hydrogenated form of carotene (vitamin A).
- The porphyrins (Greek: ; porphyra = purple) are complex carbon-nitrogen molecules that typically surround a metal, i.e., it is composed of four pyrrol rings connected by methane bridges and a metal atom (Mg or Fe) is attached to the pyrrolrings.
- Porphyrin surrounds a magnesium ion in the chlorophyll molecule, but an iron ion in the haeme of haemoglobin. Numerous additional animal cell pigments, such as myoglobin and cytochromes, have porphyrin rings within their molecules.
- A system of fused cyclohexane and cyclopentane rings composes the steroids. All are derivatives of perhydro-cyclopentano-phenanthrene, which is composed of three fused cyclohexane rings and one terminal cyclopentane ring.
- Steroids have vastly distinct physiological properties. Some steroids, for instance, are hormones (e.g., sex hormones such as oestrogen, progesterone, testosterone, and corticosterone) and influence gene expression to change cellular functions.
- Some steroids are vitamins (e.g., vitamin D2) and regulate the activity of specific enzymes within cells.
- Some steroids, such as cholic acid, are bile fat emulsifiers. Sterols are the alcohols of the steroids. Cholesterol present in animals and ergosterol and stigmasterol found in plants are typical examples of sterols.
- Numerous animal cells have cholesterol in their plasma membranes, as well as in their blood, bile, gallstones, brain, spinal cord, and adrenal glands. It is the precursor to the vast majority of steroid sex hormones and cortisones.
- 7-dehydrocholesterol is present in the skin, where it is responsible for vitamin D production in the presence of sunshine. Additionally, ergosterol is a precursor of vitamin D.
- Prostaglandins are hydroxy derivatives of polyunsaturated fatty acids with 20 carbons. Human seminal fluid, testis, kidney, placenta, uterus, stomach, lung, brain, and heart contain them.
- There are at least sixteen distinct prostaglandins, categorised into nine classes (PGA, PGB, PGC …..PGI). Their primary purpose is to attach hormones to the target cell membranes. Prostaglandins are continually formed in membranes from precursors cleaved from membrane phospholipids by phospholipases. Prostaglandins are chemical mediators that are produced locally.
- Initiation of contraction of smooth muscles (thus aiding in birthing), aggregation of platelets, and inflammation are their other essential activities (i.e., arthritis).
- Proteins are the most varied macromolecules in the cell, both chemically and physically.
- More than fifty percent of the dry weight of the cell is comprised of these essential components.
- Protein was coined by the Dutch chemist G.J. Mulder (1802-1880) and is taken from the Greek word proteios, which means “of the highest rank.” Proteins are the primary structural component of protoplasm and play a variety of other crucial roles in biological systems.
- Enzymes are specialised globular proteins that serve as catalysts in practically all biochemical processes within cells.
- Other proteins are antibodies (immunoglobulins), transport proteins, storage proteins, contractile proteins, and several hormones.
- There are thousands of distinct proteins in every living organism, each with a specific structural or functional function.
- A single human cell can have over 10,000 distinct protein molecules. Proteins are chemically polymers of amino acids.
The cytoplasmic matrix and several cellular organelles include the enzymes, which are extremely significant chemical substances. In 1878, Kuhne suggested the term enzyme (Greek:, “in yeast”). Enzymes are specialised proteins that are capable of acting as catalysts in chemical reactions.
Enzymes, like other catalysts in the chemical world, are the catalysts of the biological world; they affect the rate of a chemical reaction while remaining mostly intact at the end of the reaction. The substrate is the substance on which enzymes work. Enzymes play a crucial part in numerous metabolic and biosynthetic cellular processes, including the synthesis (anabolism) of DNA, RNA, and protein molecules and the catabolism (degradation) of carbohydrates, lipids, and other chemical compounds. Matrix and cellular organelles enzymes are classed as follows:
- oxireductases are the enzymes that catalyse the oxidation and reduction reactions of the cell.
- These enzymes, such as hydrogenases or reductases, oxidases, oxygenases, and peroxidases, transfer electrons and hydrogen ions from their respective substrates.
- Transferases are the enzymes that transfer one carbon, aldehydic or ketonic residues, acyl, glycosyl, alkyl, nitrogenous, phosphorus-containing, and sulphur-containing groups from one molecule to another.
- By injecting water across the broken bond, these enzymes hydrolyze a complex molecule into two molecules.
- The following bonds are affected by these enzymes: ester, glycosyl, ether, peptide, other C–N bonds, acid anhydride, C–C, halide, and P–N bonds. Proteases, esterases, phosphatases, nucleases, and phosphorylases are some of the most vital hydrolase enzymes.
- The lysase enzymes add or remove groups from double-bond-containing chemical compounds.
- C–C, C–O, C–N, C–S, and C–halide bonds are affected by the lysases.
- These enzymes catalyse the isomerization or intramolecular rearrangement of substrates, e.g., intramolecular oxidoreductases, intramolecular transferases, intramolecular lysases, cis-trans-isomerases, racemases, and epimerases.
6. Ligases or synthetases
- By breaking a phosphate bond, these enzymes catalyse the bonding of molecules. These enzymes create C–O, C–S, C–N, and C–C bonds.
- Enzymes have also been categorised in accordance with the chemical composition of the substrate: Carbohydrases are ranked first, followed by proteases (endopeptidases and exopeptidases), amylases, esterases, dehydrogenases, oxidases, decarboxylases, hydrases, transferases, and isomerases.
Numerous parameters, including pH, temperature, and substrate concentration, affect the rate of enzyme activity. Enzyme activity is substrate-dependent. Certain enzymes exist in the form of proenzymes or zymogens, which are activated by kinases to conduct catalytic activity. Similarly, trypsinogen from pancreatic cells is activated in the intestine by enterokinase, and pepsinogen from Chief cells of the stomach is activated by hydrochloric acid generated by parietal cells.
5. Prosthetic Groups and Coenzymes
- Certain enzymes, such as cytochromes, are conjugated proteins that contain prosthetic groups like metalloporphyrins in their molecules.
- Certain enzymes cannot function without the presence of coenzyme molecules.
- Apoenzyme refers to the dormant enzyme, which is incapable of functioning alone. Holoenzyme refers to the combination of the apoenzyme and coenzyme.
- For instance, the enzyme hydrogenase is an apoenzyme that can work with either NAD+ or NADP as a coenzyme.
- The following are some essential coenzymes or cofactors: 1. Nicotinamide adenine dinucleotide (NAD) or Diphosphopyridine nucleotide (DPN), 2. Nicotinamide adenine dinucleotide phosphate (NADP) or Triphosphopyridine nucleotide (TPN), 3. Flavin adenine mononucleotide (FAM), 4. Flavin adenine dinucleotide (FAD), 5. Ubiquinone (coenzyme Q or Q), 6. Lipoic acid (LIP or S2) (LIP or S2), Adenosine triphosphate (ATP) and Pyridoxyl phosphate (PALP), Adenosyl methionine, 9. Tetrahydrofolic acid (CoF), 10. Adenosyl methionine 11. Biotin, Coenzyme A (CoA), thiamine pyrophosphate (TPP), and uridine diphosphate (UDP).
- Recent research has revealed that several enzymes share comparable functions and nearly identical chemical structures.
- Isoenzymes are the name given to these enzymes. Isoenzymes have a relationship with inheritance.
- There are around 100 isoenzymes in a cell, such as five identical forms of lactic dehydrogenase (LDH).
- The vitamins are chemically varied organic molecules. They are needed in minute quantities for normal cell development, function, and reproduction.
- The vitamins play a significant role in cellular metabolism and function as enzymes or other biological catalysts in the cell’s many chemical processes.
- Hopkins,Osborne,Mendal, and McCollum have reported on their significance for the animals (1912– 1913).
- Funk (1912) proved the existence of nitrogenous bases in them and gave them the term “vitamins,” which refers to vital amines.
- The animal cell is unable to generate vitamins from regular diet, thus they must be consumed alongside the food. Their lack in cells results in metabolic dysfunction and numerous illnesses.
- For instance, a deficit in ascorbic acid (Vitamin C) impairs the production of procollagen helix. Collagenases, which are unique extracellular enzymes, continuously destroy normal collagens.
- In scurvy, defectively produced pro—chains fail to form a triple helix and are destroyed promptly.
- As a result of the progressive loss of normal collagen in the matrix, blood vessels become exceedingly weak and teeth become dislodged from their sockets.
- This suggests that collagen degradation and replacement are particularly rapid in these tissues.
- In bones, for example, the ‘turnover’ of collagen is exceedingly slow, meaning that collagen molecules persist for around 10 years before being dissolved and replaced.
- Hormones are complex chemical molecules that occur in tiny amounts in the cytoplasm and govern the creation of messenger RNA (mRNA), enzymes, and other intracellular physiological processes.
- The most essential hormones include growth hormones, oestrogen, androgen, insulin, thyroxine, cortisone, etc.
- These hormones are produced by ductless or endocrine glands and delivered to the numerous cells of multicellular animals via blood vessels. In cells, they govern diverse metabolic processes.
- For instance, it has been discovered that the ecdysone hormone forms puffs (Balbiani rings) on the large chromosomes of insects.
- The hormones activate or repress the gene at the specific chromosomal location. Thus, hormones serve to regulate the numerous actions associated with a certain function; for instance, the hormone ecdysone governs insect moulting and metamorphosis.
- -cells of the islets of Langerhans in the pancreas produce the hormone insulin, which regulates the enzymes that turn glucose into glycogen in the liver cells of mammals.
- In addition, the thyroid hormone thyroxine triggers the enzyme phosphorylase to convert glycogen into glucose phosphate.
9. Nucleic Acids
- Nucleic acids are complex macromolecular chemical molecules with enormous biological significance.
- They regulate the essential metabolic processes of the cell and transmit genetic information from generation to generation.
- In living organisms, there are two forms of nucleic acids: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) (DNA). Both forms of nucleic acids are composed of nucleotide polymers.
- The components of a nucleotide are nucleoside and phosphoric acid. Even the nucleoside consists of pentose sugars (Ribose or Deoxyribose) and nitrogen bases (Purines or Pyrimidines).
- Adenine and guanine are purines, while cytosine, thymine, and uracil are pyrimidines. The cytoplasmic matrix is composed solely of RNA, whereas DNA remains exclusively concentrated in the nucleus.
- DNA and RNA have nearly identical chemical makeup, with a few minor variations.
Properties of Cytoplasmic Matrix
The matrix is a living substance and it has following physical and biological properties :
Due to the matrix’s colloidal nature, the majority of its physical properties are as follows:
1. Tyndall’s effect
- When a powerful beam of light is sent into the matrix’s colloidal system at right angles in a dark environment, the light is reflected by the minute colloidal particles that stay suspended in the colloidal system.
- The light’s path looks to be a cone. This light cone is known as Tyndall’s cone since Tyndall (1820–1893) originally described this phenomena in colloids.
2. Brownian movement
- The matrix’s suspended colloidal particles always move in a zigzag pattern. This movement of molecules is created by colliding water molecules that impart motion to the colloidal molecules.
- In 1827, Scottish botanist Robert Brown first discovered this form of movement in a colloidal solution.
- Consequently, these movements are referred to as Brownian movement. The Brownian motion is a characteristic of all colloidal fluids and is dependent on the particle size and temperature.
3. Cyclosis and amoeboid movement
- Due to the cytoplasmic matrix’s phase reversal feature, intracellular streaming or movement of the matrix occurs.
- This characteristic of intracellular matrix mobility is known as cyclosis. Typically, cyclosis occurs in the matrix’s sol phase and is influenced by hydrostatic pressure, temperature, pH, viscosity, etc.
- The intracellular movements of pinosomes, phagosomes, and different cytoplasmic organelles, such as lysosomes, mitochondria, chromosomes, centrioles, etc., are solely the result of matrix cyclosis.
- It has been observed in the majority of animal and plant cells. The mobility of amoebae is directly dependent on cyclosis.
- In protozoans, leucocytes, epithelia, mesenchymal, and other cells, amoeboid movement occurs.
- During amoeboid mobility, the cell actively alters its form and emits pseudopodia, which are cytoplasmic projections. Due to cyclosis, the matrix moves these pseudopodia, which propels the cell forward.
4. Surface tension
- Molecules within a homogeneous liquid are free to move and are pulled in all directions equally by neighbouring molecules.
- At the liquid’s surface, where it comes into contact with air or another liquid, the molecules are pulled downward, laterally, or inward more than upward; as a result, they are subjected to unequal stresses and kept together to create a membrane.
- The force that holds the molecules together is known as the surface tension of the liquid. As a liquid, the cytoplasmic matrix bears the property of surface tension.
- The matrix’s proteins and lipids have low surface tension, thus they are found at the surface and form the membrane, whereas chemical compounds such as NaCl have high surface tension and are found in the matrix’s interior.
- Adsorption is the increase in the concentration of a substance at the surface of a solution (L., ad=to, sorbex=to draw in).
- Adsorption aids the matrix in the formation of protein boundaries.
6. Other mechanical or physical properties of matrix
- In addition to surface tension and adsorption, the matrix possesses a variety of other mechanical qualities, including as elasticity, contractility, stiffness, and viscosity, which offer the matrix with numerous physiological benefits.
7. Polarity of the egg
- Due to the stable phase of the colloidal system, the polarity of the cell matrix cannot be altered by centrifugation or other mechanical means.
8. Buffers and pH
- The matrix has a fixed pH value and cannot sustain considerable shifts in its pH equilibrium. However, numerous metabolic processes produce minute quantities of excess acids or bases.
- To protect itself from such pH fluctuations, the matrix contains buffers such as the carbonate-bicarbonate system, which maintain a steady pH level.
The matrix is a living substance that possesses the following biological characteristics:
- Irritability: The irritability of the matrix is a fundamental and inherent feature. It has sensitivity to stimulation, the ability to transmit excitation, and the ability to respond to stimulus. The contraction of cytoplamic matrix is stimulated by heat, light, chemical compounds, and other causes.
- Conductivity: Conductivity is the process of conduction or transfer of excitement from its source to its reaction zone. The matrix of nerve cells exhibits the conductivity property.
- Movement: Due to cyclosis, the cytoplasmic matrix is capable of mobility. The cyclosis is dependent on age, water content, hereditary variables, and cell makeup.
- Metabolism: The matrix is the site of numerous chemical processes involved in metabolism. These actions can either be constructive or detrimental. Anabolic activities include the creation of proteins, lipids, carbohydrates, and nucleic acids, while catabolic processes include the oxidation of food and other substances. The combined term for the anabolic and catabolic processes is metabolic process.
- Growth: Due to the secretory or anabolic (Gr., anabolism= vomiting up) actions of the cell, the volume of fresh protoplasm continuously rises. The increase in matrix volume results in the expansion of the cell, which ultimately divides into daughter cells by cell division.
- Reproduction: The cytoplasm has the capacity for both asexual and sexual reproduction.