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CELL AND MOLECULAR BIOLOGY

TOPIC 1: Cell, Basic Structure of All Living Creatures

The Cell Theory

1. All organisms are made of one or more cells.

2. The cell is the basic unit of all living things
3. All cells come from existing cells.
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Name Memorable phase Description

Plasma membrane Cell’s fortification Separates the interior of the
cell from the outside
environment

Cytoplasm Cell’s environment Fluid part enclosed by the

membrane, contains
organelles

Nucleus Cell’s brain Contains most of the genetic

material , in the form of DNA

Endoplasmic reticulum Cell’s pipe system Smooth ER- System of

metabolic processes
Rough ER- Protein
manufacturing ribosomes

Golgi apparatus Cell’s delivery center It tags vesicles and proteins to

help them get carried to their
destinations

Centrosome Cell’s anchor Organizes and produces the

microtubules of the cell’s
cytoskeleton

Mitochondria Cell’s powerplant Produce energy for the cell,

break down carbohydrates
and some durations lipids to
form molecule ATP

Ribosome Cell’s factories Translate RNA into proteins

Lysosome Cell’s stomach Vesicles filled with digestive

proteins can absorb
something and break it down
into recyclable pieces

Peroxisome Cell’s firemen Vesicles that defend (or

neutralize) the cell from free
radicals
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Cytoskeleton Cell’s shapeshifter It modifies the cell’s shape

and ensures mechanical
resistance

Vacuole Cell’s compartments Enclosed storage vessels

which are filled with water
containing inorganic and
organic molecules

Anatomy of Human Cells

 Red Blood cells

 Ovum Cell
 Nerve cell
 Columnar epithelial cell
 Smooth muscle cell
 Bone cell
 Sperm Cell

Kinds of cells: - Eukaryota, whose members are known as

eukaryotes, is a device domain of organisms
A. Eukaryotic cell
whose cells have a nuclues.
- All animals, plants, fungi and many
unicellular organisms, are eukaryotes. they
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belong to the group of organisms Structure of Eukaryotic Cell

eukaryota or eukarya, which is one of the
Plasma Membrane
three domains of life.
- defined as cells containing organized • The plasma membrane separates the cell
nucleus and organelles which are enveloped from the outside environment.
by membrane-bound organelles. • It comprises specific embedded proteins,
- Examples of eukaryotic cells are plants, which help in the exchange of substances in
animals, protists, fungi. Their genetic and out of the cell.
material is organized in chromosomes.
- Eukaryotic cells have a nucleus enclosed
within the nuclear membrane and form
large and complex organisms. Protozoa,
fungi, plants, and animals all have
eukaryotic cells. They are classified under
Cell Wall
the kingdom Eukaryota.
- They can maintain different environments in • A cell wall is a rigid structure present
a single cell that allows them to carry out outside the plant cell. It is, however,
various metabolic reactions. This helps them absent in animal cells.
grow many times larger than the • It provides shape to the cell and helps in
prokaryotic cells. cell-to-cell interaction.
• It is a protective layer that protects the
cell from any injury or pathogen attacks.
• It is composed of cellulose,
hemicellulose, pectins, proteins, etc.
Characteristics of Eukaryotic Cells

Cytoskeleton
 The features of eukaryotic cells are as
follows: • The cytoskeleton is present inside the
 Eukaryotic cells have the nucleus enclosed cytoplasm, which consists of
within the nuclear membrane. microfilaments, microtubules, and fibres
 The cell has mitochondria. to provide perfect shape to the cell,
 Flagella and cilia are the locomotory organs anchor the organelles, and stimulate the
in a eukaryotic cell. cell movement.
 A cell wall is the outermost layer of the
Endoplasmic Reticulum
eukaryotic cells.
 The cells divide by a process called mitosis. • It is a network of small, tubular
 The eukaryotic cells contain a cytoskeletal structures that divides the cell surface
structure. into two parts: luminal and extraluminal.
 The nucleus contains a single, linear DNA, Endoplasmic Reticulum is of two types:
which carries all the genetic information. • Rough Endoplasmic Reticulum contains
ribosomes.
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• Smooth Endoplasmic Reticulum that • They are known as “suicidal bags”

lacks ribosomes and is therefore smooth because they possess hydrolytic
enzymes to digest protein, lipids,
carbohydrates, and nucleic acids.

Nucleus Plastids
• These are double-membraned structures
• The nucleoplasm enclosed within the
and are found only in plant cells. These
nucleus contains DNA and proteins.
are of three types:
• The nuclear envelop consists of two
• Chloroplast that contains chlorophyll
layers- the outer membrane and the
and is involved in photosynthesis.
inner membrane. Both the membranes
• Chromoplast that contains a pigment
are permeable to ions, molecules, and
called carotene that provides the plants
RNA material.
yellow, red, or orange colours.
Ribosome production also takes place
• Leucoplasts that are colourless and store
inside the nucleus.
oil, fats, carbohydrates, or proteins.

Golgi Apparatus
Examples of Eukaryotic Cells
• It is made up of flat disc-shaped
structures called cisternae. • Eukaryotic cells are exclusively found in
• It is absent in red blood cells of humans plants, animals, fungi, protozoa, and
and sieve cells of plants. other complex organisms. The examples
• They are arranged parallel and of eukaryotic cells are
concentrically near the nucleus.
• It is an important site for the formation
of glycoproteins and glycolipids.

Plant Cells
Ribosomes
• The cell wall is made up of cellulose,
These are the main site for protein
which provides support to the plant. It
synthesis and are composed of proteins
has a large vacuole which maintains the
and ribonucleic acids.
turgor pressure. The plant cell contains
Mitochondria chloroplast, which aids in the process of
photosynthesis.
• These are also known as “powerhouse
of cells” because they produce energy. Fungal Cells
• It consists of an outer membrane and an
• The cell wall is made of chitin. Some
inner membrane. The inner membrane is
fungi have holes known as septa which
divided into folds called cristae.
allow the organelles and cytoplasm to
• They help in the regulation of cell
pass through them.
metabolism.
Animal Cells
Lysosomes
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• These do not have cell walls. Instead, 4. The histone proteins, the important
they have a cell membrane. That is why constituents of eukaryotic
animals have varied shapes. They have chromosomes, are lacking in them.
the ability to perform phagocytosis and 5. The cell wall is made up of
pinocytosis. carbohydrates and amino acids.
6. The plasma membrane acts as the
Protozoa
mitochondrial membrane carrying
• Protozoans are unicellular organisms. respiratory enzymes.
Some protozoa have cilia for 7. They divide asexually by binary fission.
locomotion. A thin layer called pellicle The sexual mode of reproduction
provides supports to the cell. involves conjugation.

Prokaryotic Cell Structure

A prokaryotic cell does not have a nuclear

membrane. However, the genetic material is
present in a region in the cytoplasm known
as the nucleoid. They may be spherical, rod-
shaped, or spiral. A prokaryotic cell
B. Prokaryotic cell
structure is as follows:
- lack both, a well-defined nuclues and
membrane- bound cell organelles. Examples • Capsule– It is an outer protective
of prokaryotes are blue-green algae, covering found in the bacterial cells, in
bacteria and mycoplasma, among addition to the cell wall. It helps in
prokaryotes, bacteria are the most common moisture retention, protects the cell
and multiply very fast. when engulfed, and helps in the
attachment of cells to nutrients and
- is a type of cell that does not have a true
surfaces.
nucleus or membrane-bound organelles.
Organisms within the domains Bacteria and • Cell Wall– It is the outermost layer of
Archaea are based on the prokaryotic cell. the cell which gives shape to the cell.

- A prokaryotic cell consists of a single • Cytoplasm– The cytoplasm is mainly

membrane and therefore, all the reactions composed of enzymes, salts, cell
occur within the cytoplasm. They can be organelles and is a gel-like component.
free-living or parasites.
• Cell Membrane– This layer surrounds
Characteristics of Prokaryotic Cell the cytoplasm and regulates the entry
and exit of substances in the cells.
1. They lack a nuclear membrane.
2. Mitochondria, Golgi bodies, chloroplast, • Pili– These are hair-like outgrowths that
and lysosomes are absent. attach to the surface of other bacterial
3. The genetic material is present on a cells.
single chromosome.
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• Flagella– These are long structures in • Plasmids– Plasmids are non-

the form of a whip, that help in the chromosomal DNA structures. These are
locomotion of a cell. not involved in reproduction.

• Ribosomes– These are involved in • Nucleoid Region– It is the region in the

protein synthesis. cytoplasm where the genetic material is
present.

Components of Prokaryotic Cells

The prokaryotic cells have four main

components

1. Plasma Membrane - It is an outer

protective covering of phospholipid
molecules which separates the cell
from the surrounding environment. Reproduction in Prokaryotes
2. Cytoplasm- It is a jelly-like substance
present inside the cell. All the cell A. Asexually by binary fission
organelles are suspended in it. Binary Fission
3. DNA- It is the genetic material of the • The DNA of an organism
cell. All the prokaryotes possess a replicates and the new copies
circular DNA. It directs what proteins attach to the cell membrane.
the cell creates. It also regulates the • The cell wall starts increasing in
actions of the cell. size and starts moving inwards.
4. Ribosomes- Protein synthesis occurs • A cell wall is then formed
here. between each DNA, dividing the
cell into two daughter cells.
B. Sexually by conjugation
NOTE: Some prokaryotic cells possess cilia and
flagella which helps in locomotion.
A prokaryotic cell lacks certain
Examples of Prokaryotic Cells
organelles like mitochondria, endoplasmic
reticulum, and Golgi bodies. A. Bacterial Cells
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• These are unicellular organisms The prokaryotic cell structure is

found everywhere on earth from soil composed of:
to the human body.
• Cell wall
• They have different shapes and
• Cell membrane
structures.
• Capsule
• The cell wall is composed of
• Pili
peptidoglycan that provides
• Flagella
structure to the cell wall.
• Ribosomes
• Bacteria have some unique structures
• Plasmids
such as pili, flagella and capsule.
How is the prokaryotic cell structure
• They also possess extrachromosomal
different from that of the eukaryotic cell?
DNA known as plasmids.
• They have the ability to form tough, Prokaryotic cells lack a true nucleus. The
dormant structures known as nucleus is devoid of the nuclear membrane. On
endospores that helps them to the contrary, the nucleus of the eukaryotic cells
survive under unfavourable is enclosed by a nuclear membrane. A
conditions. The endospores become prokaryotic cell also lacks mitochondria and
active when the conditions are chloroplast, unlike a eukaryotic cell.
favourable again.
How does a prokaryotic cell divide?

Prokaryotic cells undergo asexual reproduction.

B. Archaeal Cells Most prokaryotic cells divide by binary fission,
• Archaebacteria are unicellular where the cells divide into two daughter cells.
organisms similar to bacteria in
Why is the process of cell division in
shape and size.
prokaryotic cells different from that in
• They are found in extreme
eukaryotes?
environments such as hot springs
and other places such as soil, Prokaryotic cells are simpler than eukaryotic
marshes, and even inside humans. cells. They do not have a nuclear membrane
• They have a cell wall and flagella. surrounding their DNA, therefore, cell division
The cell wall of archaea does not is different than that in eukaryotes.
contain peptidoglycan.
When did the prokaryotic cells evolve?
• The membranes of the archaea
have different lipids with a The first prokaryotic cells evolved around 3.5
completely different billion years ago. The eukaryotic cells were
stereochemistry. formed after the prokaryotic cells and are
• Just like bacteria, archaea have believed to have evolved from them.
one circular chromosome. They
What are the difference between
also possess plasmids.
EUKARYOTIC AND PROKARYOTIC CELLS?

Prokaryotic cell:
What are the structural features of
prokaryotic cells?
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1. The cell which lacks a well-defined Eukaryotic cell:

nucleus is called prokaryotic cells. 1. The cell having a well-defined
2. These cells have a primitive nucleus is called a eukaryotic cell.
organization of genetic material. 2. It lacks respiratory enzymes.

Prokaryotic cell Eukaryotic cell

- The nucleus is not well defined and - The nuclear region well-defined
is called the nucleoid. nucleus with a nuclear membrane
- A single length of only - Several lengths of genetic material
deoxyribonucleic acid (DNA) (chromosomes) containing DNA
are wound around certain proteins.
- Small ribosomes - Larger ribosomes
- No other cell organelles - Several organelles like
mitochondria, endoplasmic
reticulum, chloroplasts, etc
Examples: Bacteria, Blue- green
algae (Cyanobacteria) Examples: Euglena, Amoeba, and
all plants and animals

When did the first eukaryotic cell evolve? Endosymbiotic theory: - Prokaryotes existed
first. Eukaryotes evolved from prokaryotes that
• The first eukaryotic cells evolved about 2
begin to live within one another.
billion years ago. This is explained by the
endosymbiotic theory that explains the Proof: Mitochondria & Chloroplasts have their
origin of eukaryotic cells by the own DNA, so they existed independently as
prokaryotic organisms. Mitochondria bacteria at one time; this is how eukaryotes
and chloroplasts are believed to have evolved from prokaryote ancestors
evolved from symbiotic bacteria.
Mitochondria and chloroplast originated as
bacterial cells that came to live inside larger
cells
Cell Evolution
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Most membrane-enclosed organelles including Alongside the three-domain system, there

the nucleus, ER and golgi probably originated exists a six kingdom system of life, i.e.
from deep folds in the plasma membrane Archaebacteria (comprising ancient bacteria),
Eubacteria (comprising true bacteria), Protista
(comprising one-celled organisms), Fungi,
Evolution of the Eukaryotic Cell Plantae, and Animalia. While Archaebacteria
and Eubacteria constitute the Archaea and
ENDOSYMBIOSIS:
Bacteria domains respectively, Protista, Fungi,
1. Start with two independent bacteria Plantae and Animalia together form the
2. One bacterium engulf the other Eukaryote domain of life.
3. One bacterium now lives inside the other
4. Both bacteria benefit from the arrangement
5. The internal bacteria are passed on from • BACTERIA
generation to generation - A member of a large group of unicellular
microorganisms which have cell walls but
• Endosymbiosis theory was proposed by lack of organelles and an organized nuclues,
Lynn Margulis including some that can cause disease.
• Endosymbiosis theory states that larger - Are single-celled organisms that are pretty
bacterial cells lost their cell walls and much everywhere: inn the ground, in the
engulfed smaller bacterial cells ocean, on your hand and in your gut. While
• Eukaryotes come from prokaryotes some are harmful, most are not - and some
• Symbiosis means “living together’” are even beneficial to human health. In
many cases, humans live in symbiosis with
bacteria, maintaining a mutually beneficial
THREE DOMAINS OF LIFE AND THEIR relationship without even knowing it.
CHARACTERISTICS - are ubiquitous, mostly free-living organisms
often consisting of one biological cell. They
The three-domain system biological
constitute a large domain of prokaryotic
classification of life, which classifies life on the
microorganisms. Typically a few
planet into three different domains – Archaea,
micrometres in length, bacteria were among
Bacteria and Eukaryote, was put forth by
the first life forms appear on earth, and are
American microbiologist and physicist Carl
present in most of its habits.
Woese in 1990.
- Even though bacteria are prokaryotic cells
just like Archaea, their membranes are
made of unbranched fatty acid chains
attached to glycerol by ester linkages.
Cyanobacteria and mycoplasmas are the
best examples of bacteria.
- As they don’t have ether containing
linkages like Archaea, they are grouped into
a different category – and hence a different
domain. There is a great deal of diversity in
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this domain, such that it is next to Kingdom Fungi (yeast, mold, etc.), Kingdom
impossible to determine how many species Plantae (flowering plants, ferns, etc.) and
of bacteria exist on the planet. Kingdom Animalia (insects, vertebrates,
etc.).
• ARCHAEA
- Archaea are prokaryotic cells which are - Not all Eukaryotes have a cell wall, and even
typically characterized by membranes that if they do they don’t contain
are branched hydrocarbon chains attached peptidoglycan as bacteria do. While cells
to glycerol by ether linkages. The presence are organized into tissues in case of
of this ether containing linkages in Archaea kingdom Plantae as well as kingdom
adds to their ability of withstanding extreme Animalia, the presence of cell walls is only
temperature and highly acidic conditions. restricted to the members of kingdom
Plantae.
Examples of Archaea

- Extreme halophiles – organisms which

thrive in highly salty environment Each of these three domains recognized by
- Hyperthermophiles – organisms which biologists today contain rRNA which is unique
thrive in extremely hot environment to them, and this fact in itself forms the basis of
three-domain system. While the presence of
• EUKARYA nuclear membrane differentiates the Eukarya
- As the name suggests, the Eukaryote are domain from Archaea domain and Bacteria
eukaryotic cells which have membranes that domain – both of which lack nuclear
are pretty similar to that of bacteria. membrane, the distinct biochemistry and RNA
Eukaryote are further grouped into markers differentiate Archaea and Bacteria
Kingdom Protista (algae, protozoans, etc.), domains from each other.

Topic 2:

MOLECULAR BIOLOGY

- is the branch of biology that seeks to

understand the molecular basis of
biological activity in and between cells,
including molecular synthesis,
modification, mechanisms, and
interactions.
- The study of chemical and physical
structure of biological macromolecules
- coined by an American scientist, Warren
Weaver in the year 1938.

BIOMOLECULES
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- also called biological molecule - Form membranes, which separate cells

- any of numerous substances that are from their environments and
produced by cells and living organisms. compartmentalize the cell interior,
- Have a wide range of sizes and giving rise to organelles, such as
structures and perform a vast array of the nucleus and the mitochondrion, in
functions. higher (more complex) organisms.

The 4 major types of biomolecules   All biomolecules share in common a

fundamental relationship between structure
 carbohydrates 
and function, which is influenced by factors
 lipids 
such as the environment in which a given
 nucleic acids
biomolecule occurs.
 proteins
 Lipids, for example, are hydrophobic
(“water-fearing”); in water, many
 Nucleic acids, namely DNA and RNA spontaneously arrange themselves in
Function: Storing an such a way that the hydrophobic ends
organism’s genetic code— of the molecules are protected from the
Genetic code is the the sequence water, while the hydrophilic ends are
of nucleotides that determines exposed to the water. This arrangement
the amino acid sequence of proteins gives rise to lipid bilayers, or two layers
of phospholipid molecules, which form
 Protein has 20 different amino acids; the membranes of cells and organelles.
the order in which they occur plays a
In another example, DNA, which is a very long
fundamental role in
molecule—in humans the combined length of
determining protein structure and
all the DNA molecules in a single cell stretched
function
end to end would be about 1.8 metres (6 feet),
Function:
whereas the cell nucleus is about 6 μm (6 10-
- Transporters, moving nutrients and
6 metre) in diameter—has a highly flexible
other molecules in and out of cells
helical structure that allows the molecule to
- Acts as enzymes and catalysts for the
become tightly coiled and looped
vast majority of chemical reactions that
take place in living organisms This structural feature plays a key role in
- Form antibodies and hormones enabling DNA to fit in the cell nucleus, where it
- influence gene activity. carries out its function in coding genetic traits.

 Carbohydrates are built from four types

of sugar units—monosaccharides, disac MOLECULAR BASIS OF HEREDITY
charides, oligosaccharides (2-10),
 DNA consists of long chains of
and polysaccharides(10 or more).
nucleotides lying parallel to one another.
Function:
 Each nucleotide has a backbone of
- source of stored energy
sugar and phosphate linked to a base.
- acting as chemical messengers
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 There are four complementary bases in

DNA: adenine and thymine, which
What is the structure of DNA?
always bond together, as do cytosine
and guanine. A collection of nucleotides makes a DNA
molecule. Each nucleotide contains three
Molecular basis of inheritance is the study of components:
genes, hereditary and genetic
variations which explains how an offspring • a sugar
looks similar to its maternal or paternal • a phosphate group
features. DNA, RNA and genetic code are the • a nitrogen base
fundamental parts of the molecular basis of
inheritance and are responsible to transmit The sugar in DNA is called 2-deoxyribose.
genes from parents to offspring. These sugar molecules alternate with the
DNA (Deoxyribonucleic acid) phosphate groups, making up the
“backbone” of the DNA strand.
- a self-replicating material that is present in
nearly all living organisms as the main Each sugar in a nucleotide has a nitrogen base
constituent of chromosomes. It is the carrier attached to it. There are four different types of
of genetic information. nitrogen bases in DNA
- the fundamental and distinctive • adenine (A)
characteristics or qualities of someone or • thymine (T)
something, especially when regarded as • cytosine (C)
unchangeable • guanine (G)
- It contains units of biological building
blocks called nucleotides.
- DNA is a vitally important molecule for not
only humans but also most other
organisms. DNA contains our hereditary
material and our genes, the things that
make us unique.
-

The two strands of DNA form a 3-D structure

called a double helix. When illustrated, DNA
looks like a spiral ladder in which the base
pairs are the rungs, and the sugar-phosphate
backbones are the legs.

Additionally, it’s worth noting that the DNA in

the nucleus of eukaryotic cells is linear,
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meaning that the ends of each strand are free.

In a prokaryotic cell, the DNA forms a circular How do you get from the DNA code to a
structure. protein?
First, the two DNA strands split apart. Then,
DNA Structure special proteins within the nucleus read the
base pairs on a DNA strand to create an
- DNA is a long polymer made up of many intermediate messenger molecule.
smaller units called nucleotides
- A nucleotide consists of a phosphate This process creates the messenger molecule
group, 5 carbon sugar and nitrogenous RNA (mRNA). mRNA is another type of nucleic
base acid. It travels outside the nucleus, serving as a
- DNA contains 4 nitrogenous bases message to the cellular machinery that builds
proteins.
What does DNA do?
DNA contains the instructions that are In the second step, specialized components of
necessary for an organism to grow, develop, the cell read the mRNA’s message three base
and reproduce. These instructions exist within pairs at a time and work to assemble a protein,
the sequence of nucleotide base pairs. amino acid by amino acid. This process is called
translation.
DNA helps your body grow
Your cells read this code three bases at a time DNA damage and mutations
to generate proteins that are essential for The DNA code is prone to damage. According
growth and survival. The DNA sequence that to estimates, tens of thousands of DNA
houses the information to make a protein is damage events occur every day in each of our
called a gene. cells. Damage can occur due to errors in DNA
replication, free radicals, and exposure to UV
Each group of three bases corresponds to radiation.
specific amino acids, which are the building
blocks of proteins. For example, the base pairs Your cells have specialized proteins that can
T-G-G specify the amino acid tryptophan, detect and repair many cases of DNA damage.
while the base pairs G-G-C specify the amino There are at least five major DNA repair
acid glycine. pathways.

Some combinations, like T-A-A, T-A-G, and T- Mutations are permanent changes in the DNA
G-A, also indicate the end of a protein sequence. Changes in the DNA code can
sequence. This tells the cell not to add more negatively impact how the body produces
amino acids to the protein. proteins.

Proteins contain different combinations of If the protein doesn’t work properly, diseases
amino acids. When placed together in the can develop. Some diseases that occur due to
correct order, each protein has a unique mutations in a single gene include cystic
structure and function within your body. fibrosis and sickle cell anemia.
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damage, but they also shorten with each round

Mutations can also lead to the development of DNA replication.
of cancer. For example, if genes coding for
proteins involved in cellular growth mutate, Studies associate telomere shortening with the
cells may grow and divide out of control. Some aging process. Some lifestyle factors such as
cancer-causing mutations are heritable, while obesity, exposure to cigarette smoke, and
others develop through exposure to psychological stress can also contribute to
carcinogens like UV radiation, chemicals, or telomere shortening.
cigarette smoke.
Where is DNA found?
But not all mutations are bad. Some are DNA is present in our cells. The exact location
harmless, while others contribute to our of it depends on the type of cell.
diversity as a species.
Eukaryotic cells
Changes that occur in at least or more than 1 In a eukaryotic cell, DNA is within the
of the population are called polymorphisms. nucleus.
Examples of some polymorphisms are hair and Prokaryotic cells
eye color. In prokaryotic cells, DNA resides in the
middle of the cell, called a nucleoid, coiled
DNA and aging tightly.
Unrepaired DNA damage can accumulate as we
age, helping to drive the aging process. RNA
Something that may play a large role in the (Ribonucleic Acid)
DNA damage associated with aging is damage is a nucleic acid present in all living cells that
due to free radicals. However, this one has structural similarities to DNA. Unlike DNA,
mechanism of damage may not be sufficient to however, RNA is most often single-stranded.
explain the aging process. Several factors may An RNA molecule has a backbone made of
also be involved. alternating phosphate groups and the sugar
ribose, rather than the deoxyribose found in
One theory as to why DNA damage DNA
accumulates as we age concerns evolution.
It’s thought that DNA damage is repaired Attached to each sugar is one of four bases:
more faithfully when we’re of reproductive adenine (A), uracil (U), cytosine (C) or
age and having children. After we’ve passed guanine (G).
our peak reproductive years, the repair process Different types of RNA exist in cells: messenger
naturally declines. RNA (mRNA), ribosomal RNA (rRNA) and
transfer RNA (tRNA). In addition, some RNAs
Another part of DNA that may be involved in are involved in regulating gene expression.
aging is telomeres. Telomeres are stretches of Certain viruses use RNA as their genomic
repetitive DNA sequences at the ends of your material.
chromosomes. They help protect DNA from
Different types of RNA exist in cells:
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• messenger RNA (mRNA), The importance of proteins was recognized by

• ribosomal RNA (rRNA) chemists in the early 19th century, including
• transfer RNA (tRNA). Swedish chemist Jöns Jacob Berzelius, who in
In addition, some RNAs are involved in 1838 coined the term protein, a word derived
regulating gene expression. Certain viruses use from the Greek prōteios, meaning “holding
RNA as their genomic material. first place.”
messenger RNA (mRNA)
A protein molecule is very large compared with
molecule in cells that carries codes from molecules of sugar or salt and consists of
the DNA in the nucleus to the sites many amino acids joined together to form long
of protein synthesis in chains, much as beads are arranged on a string.
the cytoplasm (the ribosomes).
There are about 20 different amino acids that
The molecule that would eventually become occur naturally in proteins. Proteins of similar
known as mRNA was first described in 1956 by function have similar amino
scientists Elliot Volkin and Lazarus Astrachan acid composition and sequence.

ribosomal RNA (rRNA) Basic players in molecular biology: DNA, RNA

and proteins
molecule in cells that forms part of the protein-
synthesizing organelle known as What they do is this:
a ribosome and that is exported to
the cytoplasm to help translate the information WHAT IS THE IMPORTANCE OF
in messenger RNA (mRNA) into protein BIOCHEMISTRY IN AN ORGANISM

transfer RNA (tRNA) Biochemistry combines biology and chemistry

to study living matter. It powers scientific and
small molecule in cells that carries amino medical discovery in fields such as
acids to organelles called ribosomes, where pharmaceuticals, forensics and nutrition.
they are linked into proteins. With biochemistry, you will study chemical
reactions at a molecular level to better
PROTEIN understand the world and develop new ways to
highly complex substance that is present in all harness these.
living organisms. Proteins are of great
nutritional value and are directly involved in the Biochemistry leads us to an understanding of
chemical processes essential for life. structures and functions of DNA which is the
genetic carrier in all living organisms.
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