What are Biomolecules?

Biomolecules are the most essential organic molecules, which are involved in the
maintenance and metabolic processes of living organisms. These non-living molecules
are the actual foot-soldiers of the battle of sustenance of life. They range from small
molecules such as primary and secondary metabolites and hormones to large
macromolecules like proteins, nucleic acids, carbohydrates, lipids etc.

Let us study them in brief.

Also, read – Biomolecules in Living Organisms

Types of Biomolecules

here are four major classes of Biomolecules – Carbohydrates, Proteins, Nucleic acids
and Lipids. Each of them is discussed below.

Carbohydrates
Carbohydrates are chemically defined as polyhydroxy aldehydes or ketones or
compounds which produce them on hydrolysis. In layman’s terms, we acknowledge
carbohydrates as sugars or substances that taste sweet. They are collectively called as
saccharides (Greek: sakcharon = sugar). Depending on the number of constituting
sugar units obtained upon hydrolysis, they are classified as monosaccharides (1 unit),
oligosaccharides (2-10 units) and polysaccharides (more than 10 units). They have
multiple functions’ viz. they’re the most abundant dietary source of energy; they are
structurally very important for many living organisms as they form a major structural
component, e.g. cellulose is an important structural fibre for plants.

Explore more about Carbohydrates

Proteins
Proteins are another class of indispensable biomolecules, which make up around 50per
cent of the cellular dry weight. Proteins are polymers of amino acids arranged in the
form of polypeptide chains. The structure of proteins is classified as primary, secondary,
tertiary and quaternary in some cases. These structures are based on the level of
complexity of the folding of a polypeptide chain. Proteins play both structural and
dynamic roles. Myosin is the protein that allows movement by contraction of muscles.
Most enzymes are proteinaceous in nature.

Explore more about Proteins

Nucleic Acids
Nucleic acids refer to the genetic material found in the cell that carries all the hereditary
information from parents to progeny. There are two types of nucleic acids namely,
deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The main function of nucleic
acid is the transfer of genetic information and synthesis of proteins by processes known
as translation and transcription. The monomeric unit of nucleic acids is known as
nucleotide and is composed of a nitrogenous base, pentose sugar, and phosphate. The
nucleotides are linked by a 3’ and 5’ phosphodiester bond. The nitrogen base attached
to the pentose sugar makes the nucleotide distinct. There are 4 major nitrogenous
bases found in DNA: adenine, guanine, cytosine, and thymine. In RNA, thymine is
replaced by uracil. The DNA structure is described as a double-helix or double-helical
structure which is formed by hydrogen bonding between the bases of two antiparallel
polynucleotide chains. Overall, the DNA structure looks similar to a twisted ladder.

Explore more- Difference Between DNA and RNA

Lipids
Lipids are organic substances that are insoluble in water, soluble in organic solvents,
are related to fatty acids and are utilized by the living cell. They include fats, waxes,
sterols, fat-soluble vitamins, mono-, di- or triglycerides, phospholipids, etc. Unlike
carbohydrates, proteins, and nucleic acids, lipids are not polymeric molecules. Lipids
play a great role in the cellular structure and are the chief source of energy.

Explore more about Lipids

Learn more in detail about the Biomolecules, different types, their structure, functions,
importance and other related topics a BYJU’S Biology

Table of Contents
 Protein Structure
 Protein Synthesis
 Types of Proteins and Their Functions
 Functions of Proteins
 Frequently Asked Questions

We often see bodybuilders and physical trainer drinking whey protein along with milk to
build-up metabolism and strength.When it comes to our body, our hair and nails are
mostly made of proteins. Basically, proteins are the fundamental building blocks of our
body. They are large and complex macromolecules or bio-molecules which perform a
major role in the functioning and regulating of our body cells, tissues and other organs
in the human body. They are also used in providing strength to our body in producing
hormones, enzymes, and other metabolic chemicals. They are also involved in
functioning and regulating of our body cells, tissues and organs.

Proteins are composed of amino acids, arranged into different groups. These
fundamental amino acids sequences are specific and its arrangements are controlled by
the DNA. Since our body cannot synthesize these essential amino acids by its own, we
should have plenty of protein foods in our everyday diet to keep our
body metabolisms stable.
unctions of Proteins
1. Enzymes: Enzymes mostly carry out all numerous chemical reactions which take place
within a cell. They also help in regenerating and creating DNA molecules and carry out
complex processes.
2. Hormones: Proteins are involved in the creation of various types of hormones which help in
balancing the components of the body. For example hormones like insulin, which helps in
regulating blood sugar and secretin. It is also involved in the digestion process and formation
of digestive juices.
3. Antibody: Antibody also known as an immunoglobulin. It is a type of protein which is majorly
used by the immune system to repair and heal the body from foreign bacteria. They often
work together with other immune cells to identify and separate the antigens from increasing
until the white blood cells destroy them completely.
4. Energy: Proteins are the major source of energy that helps in the movements of our body. It
is important to have the right amount of protein in order to convert it into energy. Protein,
when consumed in excess amounts, gets used to create fat and becomes part of the fat
cells.

Listed below are few functions of Proteins.

Aspect Functions of Proteins in Human Body Examples

Storage Legume Storage, albumin, and proteins. Supplies food during the early stage
of the seedling or embryo.

Hormone Counterpart activities of different body parts. Glucagon and Insulin.

Signalling

Transport It transport substances throughout the body through Hemoglobin.

lump or blood cells.

Contraction To carry out muscle contraction. Myosin.

Digestive Breaks down nutrients present in the food into Pepsin, Amylase, and Lipase
Enzyme smaller portions so that it can be easily absorbed

Carbohydrates are macronutrients and are one of the three main ways by which our
body obtains its energy. They are called carbohydrates as they
comprise carbon, hydrogen and oxygen at their chemical level. Carbohydrates are
essential nutrients which include sugars, fibers and starches. They are found in grains,
vegetables, fruits and in milk and other dairy products. They are the basic food groups
which play an important role in a healthy life.

The food containing carbohydrates are converted into glucose or blood sugar during the
process of digestion by the digestive system.

Functions of Carbohydrates
The main function of carbohydrates is to provide energy and food to the body and to
the nervous system.

Carbohydrates are known as one of the basic components of food, including sugars,
starch, and fibre which are abundantly found in grains, fruits and milk products.
Carbohydrates are also known as starch, simple sugars, complex carbohydrates and so
on.

It is also involved in fat metabolism and prevents ketosis.

Inhibits the breakdown of proteins for energy as they are the primary source of energy.

An enzyme by name amylase assists in the breakdown of starch into glucose, finally to
produce energy for metabolism.

Sources of Carbohydrates
1. Simple sugars are found in the form of fructose in many fruits.
2. Galactose is present in all dairy products.
3. Lactose is abundantly found in milk and other dairy products.
4. Maltose is present in cereal, beer, potatoes, processed cheese, pasta, etc.
5. Sucrose is naturally obtained from sugar and honey containing small amounts of vitamins
and minerals.

These simple sugars that consist of minerals and vitamins exist commonly in milk, fruits,
and vegetables. Many refined and other processed foods like white flour, white rice, and
sugar, lack important nutrients and hence, they are labelled “enriched.” It is quite
healthy to use vitamins, carbohydrates and all other organic nutrients in their normal
forms.

Carbohydrate Foods
Eating too much sugar results in an abnormal increase in calories, which finally leads to
obesity and in turn low calories leads to malnutrition. Therefore, a well-balanced diet
needs to be maintained to have a healthy life. That is the reason a balanced diet is
stressed so much by dietitians.

Let us look into the differences between the good and bad carbohydrates.

Good Carbohydrates Bad Carbohydrates

High in Nutrients Low in nutrients

Moderate in calories High in calories

Low in sodium and saturated fats High in sodium and saturated fats
 Low in trans-fat and cholesterol High in trans-fat and cholesterol

They are complex carbs. For instance: Foods considered bad carbs rarely have any nutritional value.
Legumes, vegetables, whole grains, fruits, Some of the foods include white flour, rice, pastries, sodas and
and beans. processed foods.

Examples of Carbohydrates
Following are the important examples of carbohydrates:

 Glucose
 Galactose
 Maltose
 Fructose
 Sucrose
 Lactose
 Starch

Nucleic Acids
Nucleic acids refer to the genetic material found in the cell that carries all the hereditary
information from parents to progeny. There are two types of nucleic acids namely,
deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The main function of nucleic
acid is the transfer of genetic information and synthesis of proteins by processes known
as translation and transcription. The monomeric unit of nucleic acids is known as
nucleotide and is composed of a nitrogenous base, pentose sugar, and phosphate. The
nucleotides are linked by a 3’ and 5’ phosphodiester bond. The nitrogen base attached
to the pentose sugar makes the nucleotide distinct. There are 4 major nitrogenous
bases found in DNA: adenine, guanine, cytosine, and thymine. In RNA, thymine is
replaced by uracil. The DNA structure is described as a double-helix or double-helical
structure which is formed by hydrogen bonding between the bases of two antiparallel
polynucleotide chains. Overall, the DNA structure looks similar to a twisted ladder.

Explore more- Difference Between DNA and RNA

NA: Structure, Function and Discovery
Nucleic acids are the organic materials present in all organisms in the form of DNA or RNA.
These nucleic acids are formed by the combination of nitrogenous bases, sugar molecules and
phosphate groups that are linked by different bonds in a series of sequences. The DNA structure
defines the basic genetic makeup of our body. In fact, it defines the genetic makeup of nearly all
life on earth.

Table of Contents

 What is DNA?
 Discovery
 Diagram
 DNA Structure
 Chargaff’s Rule
 DNA Replication
 Function of DNA
 Why DNA is called a Polynucleotide Molecule?
Read on to explore DNA meaning, structure, function, DNA discovery and diagram in complete
detail.

What is DNA?
“DNA is a group of molecules that is responsible for carrying and transmitting the hereditary
materials or the genetic instructions from parents to offsprings.”
This is also true for viruses, as most of these entities have either RNA or DNA as their genetic
material. For instance, some viruses may have RNA as their genetic material, while others have
DNA as the genetic material. The Human Immunodeficiency Virus (HIV) contains RNA, which
is then converted into DNA after attaching itself to the host cell.

Apart from being responsible for the inheritance of genetic information in all living beings, DNA
also plays a crucial role in the production of proteins. Nuclear DNA is the DNA contained within
the nucleus of every cell in a eukaryotic organism. It codes for the majority of the organism’s
genomes while the mitochondrial DNA and plastid DNA handles the rest.

The DNA present in the mitochondria of the cell is termed mitochondrial DNA. It is inherited
from the mother to the child. In humans, there are approximately 16,000 base pairs of
mitochondrial DNA. Similarly, plastids have their own DNA, and they play an essential role in
photosynthesis.

Also Read: Difference between gene and DNA

Full-Form of DNA
DNA is known as Deoxyribonucleic Acid. It is an organic compound that has a unique molecular
structure. It is found in all prokaryotic cells and eukaryotic cells.

DNA Types
There are three different DNA types:

 A-DNA: It is a right-handed double helix similar to the B-DNA form. Dehydrated DNA takes an A
form that protects the DNA during extreme conditions such as desiccation. Protein binding also
removes the solvent from DNA, and the DNA takes an A form.
 B-DNA: This is the most common DNA conformation and is a right-handed helix. The majority of
DNA has a B type conformation under normal physiological conditions.
 Z-DNA: Z-DNA is a left-handed DNA where the double helix winds to the left in a zig-zag pattern.
It was discovered by Andres Wang and Alexander Rich. It is found ahead of the start site of a
gene and hence, is believed to play some role in gene regulation.

Who Discovered DNA?

DNA was first recognized and identified by the Swiss biologist Johannes Friedrich
Miescher in 1869 during his research on white blood cells.

The double helix structure of a DNA molecule was later discovered through the experimental
data by James Watson and Francis Crick. Finally, it was proved that DNA is responsible for
storing genetic information in living organisms.

Also Read: Difference between deoxyribose and ribose

DNA Diagram
The following diagram explains the DNA structure representing the different parts of the DNA.
DNA comprises a sugar-phosphate backbone and the nucleotide bases (guanine, cytosine,
adenine and thymine).
 DNA Diagram representing the DNA Structure
Read more: Properties of DNA

DNA Structure
The DNA structure can be thought of as a twisted ladder. This structure is described as a double-
helix, as illustrated in the figure above. It is a nucleic acid, and all nucleic acids are made up of
nucleotides. The DNA molecule is composed of units called nucleotides, and each nucleotide is
composed of three different components such as sugar, phosphate groups and nitrogen bases.

The basic building blocks of DNA are nucleotides, which are composed of a sugar group, a
phosphate group, and a nitrogen base. The sugar and phosphate groups link the nucleotides
together to form each strand of DNA. Adenine (A), Thymine (T), Guanine (G) and Cytosine (C)
are four types of nitrogen bases.

These 4 Nitrogenous bases pair together in the following way: A with T, and C with G. These
base pairs are essential for the DNA’s double helix structure, which resembles a twisted ladder.

The order of the nitrogenous bases determines the genetic code or the DNA’s instructions.
ifference Between DNA and RNA
Life on earth is very diverse, from single-celled protozoans to complex multicellular plants and
animals. But at the molecular level, all life is fundamentally made up of the same building blocks
– DNA and RNA. One of the primary differences between DNA and RNA is that DNA is
double-stranded while RNA is single-stranded.

Table of Contents

 Difference
 DNA

 Structure
 Types
 RNA


 RNA Types
 Proteins
 Frequently Asked Questions
Read on to explore the DNA and RNA differences in detail.

Differences Between DNA and RNA

Following are the important differences between DNA and RNA:
 

NA and RNA Difference

DNA (Deoxyribonucleic acid) RNA (Ribonucleic acid)

Definition

It is a long polymer. It has a deoxyribose and phosphate Is a polymer with a ribose and phosphate
backbone having four distinct bases: thymine, adenine, backbone with four varying bases: uracil,
cytosine and guanine. cytosine, adenine and guanine.

Location

It is located in the nucleus of a cell and in the It is found in the cytoplasm, nucleus and in the
mitochondria. ribosome.

Sugar portion
 It has 2-deoxyribose. It has Ribose.

Function

RNA is critical for the transmission of the genetic

The function of DNA is the transmission of genetic
code that is necessary for protein creation from
information. It acts as a medium for long-term storage.
the nucleus to the ribosome.

Predominant Structure

DNA is a double-stranded molecule that has a long chain RNA is a single-stranded molecule which has a
of nucleotides. shorter chain of nucleotides.

Propagation

RNA does not replicate on its own. It is

DNA replicates on its own, it is self-replicating.
synthesized from DNA when required.

Nitrogenous Bases and Pairing

The base pairing is as follows: GC (Guanine pairs with The base pairing is as follows: GC (Guanine pairs
Cytosine) A-T (Adenine pairs with Thymine). with Cytosine) A-U (Adenine pairs with Uracil).

DNA
In cells, DNA (Deoxyribonucleic acid) is the nucleic acid that functions as the original
blueprint for the synthesis of proteins. DNA contains the sugar deoxyribose, phosphates
and a unique sequence of the nitrogenous bases adenine (A), guanine (G), cytosine (C)
and thymine (T).

Brief Insight into the Structure and Composition of

DNA
The DNA molecules contain instructions a living entity requires to grow, develop and
reproduce. These instructions are present inside each cell and are inherited from the
parents to their offspring.
It is made up of nucleotides which contain a nitrogenous group, a phosphate group, and
a sugar group. The order of the nitrogenous bases – thymine(T), guanine(G),
cytosine(C), and adenine(A), is crucial in determining the genetic code.

Genes are formed by the order of the nitrogenous bases present in the DNA which is
crucial for protein synthesis. RNA is another nucleic acid that translates genetic
information into proteins from DNA.

The nucleotides are linked together for the formation of two long strands which spiral to
produce a structure known as the double-helix which resembles that of a ladder wherein
the sugar and phosphate molecules form the sides while the rungs are formed by the
bases.

The bases located on one strand pair up with the bases on the other strand, as in
– guanine pairs with cytosine and adenine pairs with thymine.

The DNA molecules are extremely long and hence without the right packaging, they
cannot fit into cells. Thus, DNA is tightly coiled to produce formations referred to
as chromosomes. Every chromosome has a single DNA molecule. In humans, there
are 23 pairs of chromosomes that are present within the nucleus of the cells.

Main article: DNA Structure

Types Of DNA
 A-DNA: It is found at a relative humidity of 75%. In an environment where there is a higher
salt concentration or ionic concentrations, such as K+, Na+, Cs+ or in a state of dehydration
it endures in a form that contains 11 nucleotide pairs with a rise of 2.56Å vertically per base
pair. It has the broadest helical diameter amongst all DNA forms – 23Å DNA which is a
typical helix that is right-handed with a rotation of 32.70 per base pair.
 B-DNA: The most common form, present in most DNA at neutral pH and physiological salt
concentrations, is B-form. It has 10 base pairs per turn from the helix axis. There is a
distance of 3.4Å with a helical diameter of 20Å. Watson-Crick’s double helix model is
defined as a B-form of DNA.
 C-DNA: It is observed at a relative humidity of 66% and in the occupancy of a few ions such
as Lithium(Li+). It closely has 9.33 base pairs for every turn. The diameter of the helix is
about 19Å and the vertical rise for every base pair for the right-handed helix is 3.320.
 D-DNA: It is observed rarely as an extreme variant. The 8 base pairs are titled negatively
from the helix axis with an axial rise of about 3.03Å
 Z-DNA: It is found in an environment with a very high salt concentration. Unlike the A, B, and
C types of DNA, it is a left-handed helical structure. The backbone is arranged in a zig-zag
 pattern formed by the sugar-phosphate linkage wherein the recurrent monomer is the
dinucleotide in contrast to the mononucleotide, which is observed in alternate forms.

RNA
Ribonucleic acid (RNA) is a nucleic acid which is directly involved in protein synthesis.
Ribonucleic acid is an important nucleotide with long chains of nucleic acid present in all
living cells. Its main role is to act as a messenger conveying instructions from DNA for
controlling protein synthesis.

RNA contains the sugar ribose, phosphates, and the nitrogenous bases adenine (A),
guanine (G), cytosine (C), and uracil (U). DNA and RNA share the nitrogenous bases
A, G, and C. Thymine is usually only present in DNA and uracil is usually only present in
RNA.

Types Of RNA
Only some of the genes in cells are expressed into RNA. The following are the types of
RNA wherein each type is encoded by its own type of gene:

 tRNA– The transfer RNA or the tRNA carries amino acids to ribosomes while translation
 mRNA – The messenger RNA or the mRNA encodes amino acid sequences of a
polypeptide
 rRNA – The ribosomal RNA or the rRNA produces ribosomes with the ribosomal proteins
that are organelles responsible for the translation of the mRNA.
 snRNA – The small nuclear RNA forms the complexes along with proteins which are utilized
in RNA processing in the eukaryotes.

Explore More: Structure of RNA

Role Of Protein
To place these ideas in the proper context, remember that some proteins are enzymes
that aid cells by catalyzing chemical reactions. These chemical reactions occur after the
enzyme binds its substrate at the enzyme’s active site. The enzyme’s active site
matches the substrate molecule in size, shape and chemical properties.

The size, shape, and chemical properties of an enzyme’s active site are due to the
combination of the enzyme’s amino acids, which are the individual subunits of the
enzyme. For the cell to reliably make an enzyme, the cell must be able to control the
placement of amino acids in a protein during the synthesis of enzymes.
Proteins play a critical role in how cells successfully meet the challenges of living. Cells
use proteins to maintain their shape and to speed up important chemical reactions such
as photosynthesis and respiration.

A cell will not live long if it cannot reliably create the proteins that it needs for survival.

More to Read: Proteins

To learn more about the difference between DNA and RNA, visit BYJU’S Biology.

Further Reading

 The Polynucleotide Molecule

Lipids Definition
“Lipids are organic compounds that contain hydrogen, carbon, and oxygen
atoms, which form the framework for the structure and function of living
cells.”

What are Lipids?

These organic compounds are nonpolar molecules, which are soluble only in nonpolar
solvents and insoluble in water because water is a polar molecule. In the human body,
these molecules can be synthesized in the liver and are found in oil, butter, whole milk,
cheese, fried foods and also in some red meats.

Let us have a detailed look at the lipid structure, properties, types and classification of
lipids.

Also read: Biomolecules

Properties of Lipids
Lipids are a family of organic compounds, composed of fats and oils. These molecules
yield high energy and are responsible for different functions within the human body.
Listed below are some important characteristics of Lipids.

1. Lipids are oily or greasy nonpolar molecules, stored in the adipose tissue of the body.
2. Lipids are a heterogeneous group of compounds, mainly composed of hydrocarbon chains.
3. Lipids are energy-rich organic molecules, which provide energy for different life processes.
4. Lipids are a class of compounds characterised by their solubility in nonpolar solvents and
insolubility in water.
5. Lipids are significant in biological systems as they form a mechanical barrier dividing a cell
from the external environment known as the cell membrane.

Also Read: Digestion and Absorption of Lipids

Lipid Structure
Lipids are the polymers of fatty acids that contain a long, non-polar hydrocarbon chain
with a small polar region containing oxygen. The lipid structure is explained in the
diagram below:
 Lipid Structure – Saturated and Unsaturated Fatty Acids

Classification of Lipids
Lipids can be classified into two main classes:

 Nonsaponifiable lipids
 Saponifiable lipids

Nonsaponifiable Lipids
A nonsaponifiable lipid cannot be disintegrated into smaller molecules through
hydrolysis. Nonsaponifiable lipids include cholesterol, prostaglandins, etc

Saponifiable Lipids
A saponifiable lipid comprises one or more ester groups, enabling it to undergo
hydrolysis in the presence of a base, acid, or enzymes, including waxes,
triglycerides, sphingolipids and phospholipids.

Further, these categories can be divided into non-polar and polar lipids.

Nonpolar lipids, namely triglycerides, are utilized as fuel and to store energy.
Polar lipids, that could form a barrier with an external water environment, are utilized in
membranes. Polar lipids comprise sphingolipids and glycerophospholipids.

Fatty acids are pivotal components of all these lipids.

Types of Lipids
Within these two major classes of lipids, there are numerous specific types of lipids,
which are important to life, including fatty acids, triglycerides, glycerophospholipids,
sphingolipids and steroids. These are broadly classified as simple lipids and complex
lipids.

Also read: Biomolecules in Living Organisms

Simple Lipids
Esters of fatty acids with various alcohols.

1. Fats: Esters of fatty acids with glycerol. Oils are fats in the liquid state

2. Waxes: Esters of fatty acids with higher molecular weight monohydric alcohols

Complex Lipids
Esters of fatty acids containing groups in addition to alcohol and fatty acid.

1. Phospholipids: These are lipids containing, in addition to fatty acids and alcohol, phosphate
group. They frequently have nitrogen-containing bases and other substituents, eg, in
glycerophospholipids the alcohol is glycerol and in sphingophospholipids the alcohol is
sphingosine.

2. Glycolipids (glycosphingolipids): Lipids containing a fatty acid, sphingosine and

carbohydrate.

3. Other complex lipids: Lipids such as sulfolipids and amino lipids. Lipoproteins may also be
placed in this category.

Precursor and Derived Lipids

These include fatty acids, glycerol, steroids, other alcohols, fatty aldehydes, and ketone
bodies, hydrocarbons, lipid-soluble vitamins, and hormones. Because they are
uncharged, acylglycerols (glycerides), cholesterol, and cholesteryl esters are termed
neutral lipids. These compounds are produced by the hydrolysis of simple and
complex lipids.

Some of the different types of lipids are described below in detail.

Fatty Acids
Fatty acids are carboxylic acids (or organic acid), usually with long aliphatic tails (long
chains), either unsaturated or saturated.

 Saturated fatty acids

Lack of carbon-carbon double bonds indicate that the fatty acid is saturated. The
saturated fatty acids have higher melting points compared to unsaturated acids of the
corresponding size due to their ability to pack their molecules together thus leading to a
straight rod-like shape.

 Unsaturated fatty acids

Unsaturated fatty acid is indicated when a fatty acid has more than one double bond.

“Often, naturally occurring fatty acids possesses an even number of carbon atoms and
are unbranched.”

On the other hand, unsaturated fatty acids contain a cis-double bond(s) which create a
structural kink that disables them to group their molecules in straight rod-like shape.

Role of Fats
Fats play several major roles in our body. Some of the important roles of fats are
mentioned below:

 Fats in the correct amounts are necessary for the proper functioning of our body.
 Many fat-soluble vitamins need to be associated with fats in order to be effectively absorbed
by the body.
 They also provide insulation to the body.
 They are an efficient way to store energy for longer periods.

Also Read: Fats

Examples of Lipids
There are different types of lipids. Some examples of lipids include butter, ghee,
vegetable oil, cheese, cholesterol and other steroids, waxes, phospholipids, and fat-
soluble vitamins. All these compounds have similar features, i.e. insoluble in water and
soluble in organic solvents, etc.

Waxes
Waxes are “esters” (an organic compound made by replacing the hydrogen with acid by
an alkyl or another organic group) formed from long-alcohols and long-chain carboxylic
acids.

Waxes are found almost everywhere. The fruits and leaves of many plants possess
waxy coatings, that can safeguard them from small predators and dehydration.

Fur of a few animals and the feathers of birds possess the same coatings serving as
water repellants.

Carnauba wax is known for its water resistance and toughness (significant for car wax).

Phospholipids

Membranes are primarily composed of phospholipids that are Phosphoacylglycerols.

Triacylglycerols and phosphoacylglycerols are the same, but, the terminal OH group of
the phosphoacylglycerol is esterified with phosphoric acid in place of fatty acid which
results in the formation of phosphatidic acid.

The name phospholipid is derived from the fact that phosphoacylglycerols are lipids
containing a phosphate group.
Steroids
Our bodies possess chemical messengers known as hormones, which are basically
organic compounds synthesized in glands and transported by the bloodstream to
various tissues in order to trigger or hinder the desired process.

Steroids are a kind of hormone that is typically recognized by their tetracyclic skeleton,
composed of three fused six-membered and one five-membered ring, as seen above.
The four rings are assigned as A, B, C & D as observed in the shade blue, while the
numbers in red indicate the carbons.

Cholesterol
 Cholesterol is a wax-like substance, found only in animal source foods. Triglycerides, LDL,
HDL, VLDL are different types of cholesterol found in the blood cells.
 Cholesterol is an important lipid found in the cell membrane. It is a sterol, which means that
cholesterol is a combination of steroid and alcohol. In the human body, cholesterol is
synthesized in the liver.
 These compounds are biosynthesized by all living cells and are essential for the structural
component of the cell membrane.