• Proteins are also a group of biomolecule alongside
carbohydrates, lipids and nucleic acid. A protein is an
organic compound composed of chains of amino acids.
• Proteins, which make up 20% of our bodies, have
various functions. They can serve as structural
components, transport molecules, enzymes and cell
• All proteins are macromolecules which are synthesized
by polymerizing or stringing together specific
combinations of amino acids. Unlike carbohydrate and
lipid monomers, amino acid monomers are composed
of carbon, oxygen, hydrogen, and nitrogen atoms.
3. An amino group
is the nitrogen-
A carboxyl group
is the portion with a
A hydrogen atom
is bonded to the a-
carbon via single bond
An R group
which is also called the
radical group or side
chain, is the variable
group that is unique in
every amino acid.
• Each amino acid consists a central carbon (also called a-carbon) bonded
to four covalent groups. These four attachments are common to all amino
acids, which are follows.
4. standard code for
synthesizing proteins in
our cells uses 20 kinds of
amino acids. Each amino
acid has a unique side
group, which gives
amino acid its special
• Almost 500 types of
amino acids exist in
nature. However, the
5. Based on Nutritional Requirements
Essential amino Semi-essential amino Non-essential amino
acids acids acids
Isoleucine Arginine Alanine, Aspargine
Leucine Histidine Tyrosine, Aspartic acid
Lysine, Methionine Cysteine, Glutamic acid
Phenylalanine Glycine, Proline
Threonine Serine, Hydrosxylysine
Tryptophan, Valine Glutamine, Hydroxyproline
Based on Chemical Properties
Non Polar Polar Aromatic Positively Negatively
Amino acids Charged Charged
Glycine Serine Phenylalanine Lysine Aspartic Acid
Alanine Threonine Tyrosine Arginine Glutamatic Acid
Valine Cysteine Tryptophan Histidine
• Cells link amino acid monomers together by dehydration reactions. This
means that combining two amino acids together yields a water molecule.
This bond between adjacent amino acids is called a peptide bond.
The quaternary structure
refers to proteins with
multiple protein subunits.
The secondary structure
refers to the formation of
sheets or helices of amino
The primary structure
refers to the amino acid
sequence of proteins.
The tertiary structure
refers to the three
dimensional structure of
• Protein shape is sensitive to the surrounding environment. Any unfavorable change
in temperature, pH, salinity, or some other conditions can cause a protein to unravel
and lose its normal shape. This phenomenon is called denaturation of a protein.
• Our body has thousands of different kinds of proteins. It is possible to make such a
variety of proteins from just 20 kinds of amino acids because of the diversity of their
arrangements and combinations. Ultimately, proteins can be classified into their
structures as follows
7. The urea cycle refers to a set
of biochemical reactions
that produces urea from
ammonium ions in order to
prevent toxic levels in the
body. This cycle occurs in
the liver and, to a lesser
extent, in the kidneys.
Ammonium ions are
produced from the
breakdown of amino acids,
wherein an amine group, or
ammonium ion, from the
amino acid, is exchanged
with keto group on another
• Urea Cycle
8. The term nucleic in these
biomolecules comes from the
fact that they are found in the
nuclei of eukaryotic cells or
nucleoid in prokaryotic cells.
Their primary functions is to
store and transmit genetic
information in every cell of
Two groups of nucleic
acids exist ---the
(DNA) and ribonucleic
9. • General Nucleotide Structure:
Nucleic Acids are also biological
polymers that consist of repeating
subunits. Their monomers are called
nucleotides, which are small organic
molecules that may functions as
energy carriers, enzyme helpers,
chemical messengers, and
10. 1. adenine which is abbreviated as A;
2. thymine which is abbreviated as T;
3. cytosine which is abbreviated as C;
4. guanine which is abbreviated as G
• In DNA, each nucleotide has one of four different bases:
11. DNA is a doubled-stranded molecule. It is a double helix that resembles a spiral staircase or
twisted ladder, consisting of two polynucleotide chains that are connected through the pairing of
bases. During base pairing, adenine always pairs with thymine, while cytosine always pairs with
RNA is usually a single polynucleotide strand, as opposed to the DNA helix, which is composed of
two polynucleotide strands.
The other two differences between DNA and RNA include the ribose sugar in RNA (instead of
deoxyribose in DNA) and the uracil base in place of the thymine in DNA.
In terms of function, RNA is essential in expressing the information contained in the DNA molecule.
Roles of DNA Molecules: 1.) Storage of genetic information, 2.) Expression of genetic information,
3.) Ability to be replicated, 4.) Variation through mutation
One of the functions of RNA is to enable cells to use the protein-encoding information in DNA. The
cell uses the order of nucleotides in DNA to guide the production of RNA and proteins.
Three classes of RNA: 1.) Messenger RNA (mRNA), 2.) Transfer RNA (tRNA), 3.) Ribosomal RNA
12. Difference between DNA and RNA are
It is double stranded nucleic
It is single stranded nucleic acid.
It contains deoxyribose sugar. It contains ribose sugar.
It contains Thymine (T) as a
It contains Uracil (U) instead of
It is the genetic and hereditary
material of the cells.
It is involved in synthesis of
It is the present in the nucleus of
It is present in both nucleus and