Lipids Definition, Structure, Properties, Types, Examples, and Functions

MN Editors

It is common to discuss fat as if it was a villainous substance that is bent to destroy our diets. However, they are beautiful tiny molecules composed of three hydrocarbon tails that are attached to a small coathanger-like molecule known as Glycerol. Similar to the other big organic molecules they perform crucial functions in the biology of both humans and other living things. (Also numerous recent diet studies suggest that sugar can cause many more health issues that fat!)

Fats are one of the types of lipid, a class of molecules that are bonded due to their ability not mix with water. Lipids are generally nonpolar, hydrophobic, and comprised of hydrocarbon chains, however there are variations to this that we’ll discuss in the next section. Different kinds of lipids have distinct designs, and consequently, different functions in living organisms. They, for instance, store energy, act as insulation and cell membranes, make layers of water-resistant leaves and are the building blocks of hormones such as testosterone.

What are lipids? / Lipids definition

Lipids (Greek term: lipos-fat) are extremely important for the body because they are the most concentrated form of energy, in addition to their importance in the structure of cells and different biochemical processes. Lipids are a diverse group of substances and, as such it is challenging to pinpoint them accurately. Lipids can be described as organic compounds that are insoluble in water, and soluble with organic solvents (alcohol and ether. ) and possibly connected to fatty acids and used by living cells. Contrary to polysaccharides, proteins or nucleic acid, lipids do not constitute polymers. In addition, lipids are small molecules.

Types of lipids

Lipids broadly categorize (modified to Bloor) as simple complex, complex, derived and miscellaneous lipids. They further subdivided into various categories.

1. Simple lipids

Ester of fatty acids containing alcohols. They are mostly of two kinds

a. Fats and oils (triacylglycerols)

They are fatty acid esters that contain glycerol. The distinction between oil and fat is purely physical. So the oils are liquids whereas fat is solid at room temperature.

b. Waxes

Esters of fat acid (usually lengthy chains) with alcohols that are not Glycerol. These alcohols could be either aliphatic or the alicyclic. Cetyl alcohol is typically present in the waxes. These are the ingredients used to make candles, lubricants and cosmotics polishes, ointments and polishes.

2. Complex (or compound) lipids

These are esters of fatty acids that contain alcohols that have other groups like nitrogenous base, phosphate, carbohydrate, protein , etc. They are further classified according to the following order

(a) Phospholipids

They are a source of phosphoric acid, and often nitrogenous bases. It is also a source of alcohol and the fatty acids.

(i) Glycerophospholipids: These phospholipids contain glycerol as the alcohol e.g., lecithin, cephalin.

(ii) Sphingophospholipids: Sphingosine is the alcohol in this group of phospholipids e.g., sphingomyelin.

(b) Glycolipids

These lipids are made up of the fatty acid, carbohydrate, and nitrogenous base. Alcohol is called sphingosine so they are referred to as glycosphingolipids. Glycerol and Phosphate aren’t present e.g. cerebrosides Gangliosides.

(c) Lipoproteins

Macromolecular complexes of lipids that contain proteins.

(d) Other complex lipids

Lipopolysaccharides, aminolipids, and Sulfolipids are just a few of the complex lipids.

3. Derived lipids

They are the derivatives derived from the hydrolysis of groups 1 and 2 lipids that have the properties of lipids. They include glycerol, as well as various alcohols as well as fatty acids diacylglycerols and mono-glycerols, the lipid (fat) liquid vitamins, steroids, ketones and hydrocarbons.

4. Miscellaneous lipids

They include a variety of compounds with the properties of oils e.g. carotenoids hydrocarbons like pentacosane (in honey bees’ wax) as well as terpenes and others.

NEUTRAL LIPIDS: Lipids that are free of charge are known as neutral Lipids. These include monodi-, tri- and triacylglycerols. They are cholesterol as well as cholesteryl esters.

Properties of Lipids

  • Lipids could be liquids or solids that are not crystallized at the temperature of room.
  • The pure fats are colorless and odorless and in tasteless.
  • They are organic molecules that have a lot of energy.
  • Insoluble in water
  • Solutable in organic solvents such as alcohol and chloroform as well as acetone, the benzene and others.
  • There are no Ionic charges
  • Solid Triglycerols (Fats) have high percentages of saturated fat acids.
  • Liquid Triglycerols (Oils) contain high levels of unsaturated fatty acids.

1. Hydrolysis of triglycerols

Triglycerols are similar to other esters. They interact with water and create their carboxylic acid as well as alcohol- a process that is known as hydrolysis.

2. Saponification:

Triacylglycerols can be hydrolyzed using different methods, but the most well-known one is using an alkali solution or enzymes known as lipases. Saponification is the term used for alkaline hydrolysis since one of the results from the process is a soap, typically sodium or potassium salts of fatty acids.

3. Hydrogenation

Double bonds between carbon and carbon of unsaturated fatty acids could be hydrogenated through the reaction of hydrogen to make saturated fat acids.

4. Halogenation

Unsaturated fatty acids (whether they are free or mixed as esters in fats or oils react with halogens via an addition to their dual bond(s). The reaction causes discoloration of the solution of halogens.

5. Rancidity:

The term”rancid” is used to refer to any oil or fat that has a sour smell. Oxidation and hydrolysis can cause rancidity. The oxidative runcidity is common in triacylglycerols with unsaturated fat acids.

Lipids structure

  • Lipids are composed of the elements Carbon Oxygen, Hydrogen and Carbon however, they have a smaller proportion of water than other molecules like carbohydrates.
  • In contrast to proteins and polysaccharides, the lipids aren’t polymers, they are monomeric and do not repeat.
  • They are made of two compounds: Glycerol and Fatty Acids.
  • A glycerol-containing molecule is made from three carbon atoms, with an”hydroxyl” group attached and hydrogen atoms taking up the other positions.
  • Fatty acids are made up of an acid group located at one other end, and the hydrocarbon chain that is typically identified by the letter ‘R’..
  • They could either be unsaturated or saturated.
  • A saturated fatty acid occurs when every possible bond is formed by the Hydrogen atom in the sense that there aren’t any C=C bonds.
  • Unsaturated fatty acids however contain C=C bonds. Monounsaturated fatty acids contain one C=C bond. Polyunsaturated fatty acids polyunsaturated contain several C=C bonds.

Structure of Triglycerides

  • Triglycerides are lipids that consist of a single glycerol molecule that is bonded to 3 fatty acid molecules.
  • The bonds that connect the molecules are covalent. They are known as Ester bonds.
  • They form by a condensation reaction.
  • They are equally distributed across the molecule, allowing hydrogen bonds are not formed with water molecules, which makes them insoluble in water.

Lipids function

It is well-known that lipids play a crucial role in the regular functioning of cells. They not only function as extremely low storage forms of energy, they also play an integral part to the structure and function of the cell membranes as well as organellar membranes. Lipids play a number of roles like:

  • They are the most concentrated fuel reserves in our human body (triacylglycerols).
  • Lipids form the basis of membrane structure. They regulate membrane permeability (phospholipids and cholesterol).
  • They provide a source of fat-soluble Vitamins (A, D, E and K).
  • Lipids are essential as cellular regulatory agents of metabolism (steroid hormones, prostaglandins).
  • Lipids shield organs within the body, act as insulation materials and provide form and a smooth appearance to the human body.
  • Buoyancy
  • They functions as hormones.
  • They function as the structural component of the body. It also provides the hydrophobic barrier which allows partitioning of the aqueous content of the cell as well as subcellular structures.
  • Lipids are a major source of energy for animals, as are the seeds that are high in lipids.
  • The enzymes that are activated, for example. glucose-6-phosphatase, stearyl CoA desaturase and o-monooxygenase, and b-hydroxybutyric dehydrogenase (a mitochondrial enzyme) require phosphatidylcholine micelles for activation.

Lipids monomer

Glycerol as well as fatty acids form monomers of the lipids. Lipids comprise waxes, oil and fats. Some are used to aid in energy storage. Other types of cushion bony regions of the body.


  • A sugar alcohol composed of two polyols that result from saponification of fats as well as oils. It is used principally as a metabolic intermediary and an essential structural component of the main types of biological lipids, triglycerides and phosphatidylphospholipids.
  • Sugar alcohols are the polyol class that is distinguished by being water-soluble, white organic compounds having general chemical formulas of (CHOH)nH2. Sugar alcohols can be made through the hydrogenation process of sugars.
  • Glycerol is a colorless flavorless, odorless, viscous sweet-tasting polyol having the chemical formula C3H8O3.
  • This is known as a trihydric alcohol because it is composed from three carbon atoms. every one of two ends carbon atoms are bound by two hydrogen atoms as well as an hydroxyl group. The central carbon atom is linked with a hydrogen atom as well as an group of hydroxyl. This is what makes glycerol water-soluble (readily draws moisture) and is soluble in water and alcohol.
  • The melting temperature is 18degC.
  • Their boiling point is 290°C.
  • It is sweeter than sucrose i.e. 75% sweeter than sucrose.

Fatty acid

  • A fatty acid is a subunit of fats, oils and waxes.
  • It is a reference to any long chain of hydrocarbons that has one carboxylic group, and an the aliphatic tail.
  • It is created through the degrading of fats (usually phospholipids or triglycerides) in a process called hydrolysis.
  • Fatty acids form a subset of the lipids. The other major kinds of lipids include Glycerol, Glycerophospholipid, Sphingolipid, sterol lipid, as well as prenol lipid. They are organic molecules that happen to be easily and easily soluble in nonpolar solvents (e.g. ether) however not in polar solvents (e.g. water).
  • A fatty acid can be represented as R-COOH in which R is the absorptive moiety, and COOH is an carboxylic group (making the molecules one of acid).
  • The formula for the general formulation is as follows: CnH2n+1COOH. Nearly all natural fatty acids possess an even amount of carbons. This is due to the fact that they are made using two carbons at a every time malonyl CoA is added to.
  • The fatty acids are classified in two main categories based on the type of the covalent bond: (1) unsaturated fat acid as well as (2) saturated acid fatty.

Saturated and unsaturated fatty acids

  • If there are just single bonds between carbons that are adjacent to each other within the hydrocarbon chain, it is considered to be saturated. (The factor that fat acids are saturated is hydrogen. In saturated fats the atoms of hydrogen as numerous as are possible are bound to carbon skeleton.)
  • If the hydrocarbon chain contains two bonds and a double bond, the fatty acid can be classified as unsaturated since it is now containing fewer hydrogens. If there’s just one double bond within a fatty acid it’s monounsaturated. However, if there are several double bonds it’s polyunsaturated.
  • Double bonds in unsaturated fatty acids, as with other double bonds, may exist in either a trans or trans configuration. In the cis configuration the two hydrogens that form bonds are on the same side, whereas in a trans configuration they are located on opposing side (see the section below). A double bond in cis causes an elongation or kink in the fat acid, an aspect which has significant implications for the behaviour of fats.
  • Tails of saturated fatty acids are straight, meaning that fat molecules that are saturated tails are able to pack tight against one another. This packing tightness results in fats that remain solid at the temperature of room (have an extremely high melting temperature). In particular, the majority of the butter’s fat is saturated fat.
  • Contrary to this, cis-unsaturated fat acid tails bend because of the cis double bond. This makes it difficult for fat molecules that have at least one or more cis-unsaturated acid tails to pack tight. Therefore, fats that have unsaturated tails are typically liquid at temperatures of room temperature (have relatively low melting point) They are often referred to as oils. For example, olive oil is mostly composed of unsaturated fats.

Examples of lipids

A variety of lipids can be included in your daily food routine. Other kinds of lipids develop naturally within the body. However they are made the lipids are a vital element of our lives and our overall health. There are various kinds of lipids. Examples of lipids are butter, ghee and cheese, vegetable oil cholesterol, and various steroids, waxesand phospholipids along with fat-soluble vitamins. These compounds share similar properties, i.e. insoluble in water, and soluble within organic solvents, for instance.

Here are a few examples of lipids that you could find within your body, and where they can be found in a balanced diet.


Fats are the most significant category of lipids. They are also known as triacylglycerols, triacylglycerols, and Glycerolipids. There are a variety of fats. Certain kinds of fats are unhealthy when consumed in large amounts including saturated fats, whereas others are best avoided such as trans fats. Omega-3 fats in foods, however, may reduce the risk of having heart attacks.

Type of Fat Basic Information Where to Find It
Saturated Fats Solid substance when it is at room temperature Animal foods (butter, meat, cheese, milk, etc.)Tropical oils (palm oil, cocoa butter, coconut oil)
Unsaturated Fats (monounsaturated) Liquid when it is at room temperature Vegetable oils (olive, peanut, canola oils)

Unsaturated Fats (polyunsaturated) Two types of fats: Omega-6 and Omega-3 Plant-based oils (Omega-6: sunflower, sesame, corn, soybean, and safflower oils)
Seafood (Omega-3: shellfish, salmon, herring, sardines, anchovies, and trout)
Nuts and seeds: (Omega-3: walnuts, flaxseed, soybeans)
Trans Fats (trans polyunsaturated fatty acids) Hydrogenated fats make foods crispy
Processed foods (potato chips, crackers, cookies)
Dressings and spreads (salad dressing, margarine)


There are a variety of lipids that naturally occur in your body , as the steroid cholesterols. Although they appear different from other lipids they are insoluble when in water. Here are a few examples of steroid lipids

Type of Steroid Function in the Body
Cholesterol Assists with digestion
Estrogen Female hormone
Testosterone Male hormone
Bile Salts Lipids found in human intestinal bile
Cortisol Produced in response to stress


Waxes are a different kind of naturally occurring lipids. They have melting points of high (40 ° Celsius) and are useful as candles or sealants. Certain waxes are found inside the human body as well as those produced by animals, insects, and even plants.

Type of Wax Where to Find It Function
Beeswax Beehives Forms honeycombs and protects larvae
Earwax Human ears Protects insides of ears
Cutin Surfaces of plant leaves Stops water from evaporating from the leaves; protects and seals the plant.
Preen wax Feathers of birds Prevents water from penetrating feathers; keeps bacteria from growing


Lipids are fat-soluble vitamins. It’s essential to maintain an equilibrium of these kinds of lipids to maintain the body in good working order. Individuals with low levels or imbalanced levels of vitamins may supplement the body’s functions.

Examples of fat-soluble vitamins are:

Type of Vitamin Function in the Body Vitamin-Rich Foods
Vitamin A Assists immune function, vision, and reproduction Colorful fruits and vegetables
Whole milk
Liver and organ meat
Vitamin D Enhance how intestines absorb calcium, zinc, phosphate, iron, and magnesium Fatty fish (tuna, salmon)
Egg yolks
Sunlight exposure
Vitamin E Protects the human heart and helps protect the body from free radicals (keeps cells healthy) Nuts, seeds, vegetable oils
Vitamin K Allows blood to clot; may aid with bone strength in elderly people Leafy vegetables (kale, spinach, collards, romaine, green leaf lettuce, brussels sprouts, broccoli, cauliflower, cabbage)


The final class of lipids is the phospholipids. They are present in many cell membranes, and they provide a protective layer that covers cells and their outer membrane. The foods that contain phospholipids are:

Type of Phospholipid Function in the Body Vitamin-Rich Foods
Phosphatidylcholine Aids neural processes (learning and reasoning) Red meat
Phosphatidylserine Regulates heartbeat and bone repair PoultryCarrots
Phosphatidylethanolamine Maintains neural tissue (cognition and memory) Dairy productsChocolate

Frequently Asked Questions

Q1. What are lipids made of?

Lipids consist of a glycerol molecule which is linked by three different fatty acid molecules. This lipid is known as triglyceride.

Q2. What are the functions of lipids?

Lipids play a crucial function in the body. They’re the primary structural element that makes up the membrane of cells. They aid in creating energy and hormones that are produced by our body. They assist in proper digestion and digestion of food. They can be a beneficial component of our diet when taken in the right quantities. They also play a significant function in the process of signalling.

Q3. Are fatty acids lipids?

Fatty acids are a common component of complex Lipids

Q4. Are steroids lipids?

Steroids are lipids as they are insoluble and hydrophobic within water. However, they are not similar to the lipids because they have a structure that is composed of four rings that are fused.

Q5. What elements makeup lipids?

Lipids are made up of hydrogen, carbon and oxygen atoms. They also occasionally, they also include nitrogen, phosphorus, sulfur, and other elements.

Q6. What are examples of lipids?

Examples of lipids are waxes, oils, fats and specific Vitamins (such like A D K, E or A) hormones, as well as the majority of the cell membrane which isn’t composed of proteins.

Q7. What are the building blocks of lipids?

Glycerol and fatty acids are the basic building blocks of fats (lipids).

Q8. Where are lipids made in the cell?

In the case of excess carbohydrates, they are transformed into triglycerides which are the result of the creation of fatty acids by the acetyl-CoA molecule in a process known as lipogenesis. The process occurs in the endoplasmic retina. In both fungi and animals one protein that is multi-functional handles all of these processes while bacteria make use of multiple distinct enzymes. Certain kinds of unsaturated fat acids are not able to be produced in mammalian cells, consequently, they should be consumed as a component of the daily diet for example, omega-3.

Acetyl-CoA also plays a role in the mevalonate process, that is responsible for the production of a diverse assortment of isoprenoids. These comprise important lipids like cholesterol and steroids.

Q9. How are carbohydrates and lipids similar?

Both are composed from carbon, hydrogen and oxygen. Both are broken down to provide fuel sources Both have structure-related functions. For example, carbohydrates are sugars and starches. Likewise, oily lipids are comprised of oils, fats, and waxes.

Q10. In which form are most dietary lipids found?

Triglycerides. Triglycerides account for over 95 percent the lipids found in the diet. They are typically found in foods that are fried including butter milk, cheese and a few meats. Triacylglycerols naturally occur in a variety of foods, including olives, avocados, corn and nuts.

We hope you've enjoyed reading our latest blog article! We're thrilled to see the positive response it's been receiving so far. We understand that sometimes, after going through an interesting piece of content, you might have questions or want to delve deeper into the topic.

To facilitate meaningful discussions and encourage knowledge sharing, we've set up a dedicated QNA Forum page related to this specific article. If you have any questions, comments, or thoughts you'd like to share, we invite you to visit the QNA Forum.

QNA Forum Page

Feel free to ask your questions or participate in ongoing discussions. Our team of experts, as well as fellow readers, will be active on the forum to engage with you and provide insightful answers. Remember, sharing your thoughts not only helps you gain a deeper understanding but also contributes to the community's growth and learning. We look forward to hearing from you and fostering an enriching discussion. Thank you for being a part of our journey!

Leave a Comment