Biological Molecules
All Biological Molecules are Organic!
A biological or organic molecule is:
● Carbon (C) based
● Made from living matter.
All organisms are made up of organic
molecules that contain Carbon (C), Hydrogen
(H) and Oxygen (O).
Organisms need organic molecules to:
● Provide energy for life processes
(energy is obtained from carbohydrates
and lipids in food).
● Provide raw materials for tissue growth
and repair (proteins in food molecules
contain these raw materials).
This means that Carbohydrates, Fats and
Proteins are all Organic.
Understanding Hydrolysis and
Condensation!
Carbon atoms bond strongly with each other,
forming chains or rings which are complex
molecules.
What all are present in Organic
Molecules?
Your Notes
Carbohydrate Molecules are: keratin (present in skin and
Carbohydrates are either: hair) is long and thin and
● Complex (polysaccharides): haemoglobin (present in RBCs and
insoluble in water, stores of energy, can carry oxygen) is biconcave
formed from many monosaccharides shaped).
(examples include starch, cellulose
and glycogen). Amino acids build up proteins by
condensation, and are formed by the
● or Simple (monosaccharides): breakdown of proteins hydrolysis.
soluble in water (dissolve in the Your Notes
cytoplasm of cells), main source of
energy in cells, can easily be
transported by blood (examples
include glucose).
Monosaccharides
are formed by the
hydrolysis of
polysaccharides,
and polysaccharides
are formed by the
condensation of
monosaccharides.
Lipid/Fat Molecules
Lipids are broken down
into:
● Fatty acids
● and Glycerol
Lipids are formed by the
condensation of 3
molecules of fatty
acids and 1 molecule
of glycerol.
The diagram of C, H
and O is shown on the right-hand side.
Notice that water (H2O) breaks down
the fats.
Protein Molecules
Amino acids are the subunits that are put
together in different combinations to form
chains called proteins.
● They are soluble which allows easy
transport because they are used in
several reactions.
● Sequences of amino acids determine
the shape of a protein (examples
Nucleic Acid Molecules The combinations of bases repeat to
Nucleic Acids are present in form a DNA molecule.
deoxyribonucleic acid (DNA) and
ribonucleic acid (RNA). The The genome (all genes that make up
subunits of these acids are known an organism) pattern in each
as nucleotides. This means that organism is what makes each
nucleic acids are chains of organism (plant, animal even
nucleotides. bacterium) different and unique.
Each nucleotide is made up of a This ladder forms a twisted shape
sugar, phosphate and a called a double helix when nucleic
nitrogenous base. Each chains are coiled around one
nucleotide differs based on its another.
base.
Your Notes
There are 4 nucleotides, suggesting that
there are 4 bases (In all nucleic substances
other than RNA):
● A – Adenine
● T – Thymine
● G – Guanine
● C – Cytosine
● U – Uracil (Replaces Thymine in
RNA).
A-T are
complimentary
and G-C are
complementary
(in RNA A-U is
complementary).
These
combinations
form ladders in
different
combinations of
A-T, T-A, G-C and
C-G:
● The wall of
these ladders are
made up of the
sugar and
phosphates in
each nucleotide.
● The rungs or the steps of the ladder
are made up of the nitrogenous
bases
Water, An Important Solvent!
Water is important for all living organisms as many substances are able to dissolve in it (it is a
solvent). This makes it incredibly useful and essential for all life on Earth.
Water is important as a solvent in the following situations within organisms:
● Dissolved substances can be easily transported around organisms
● Digested food molecules are in the alimentary canal but need to be moved to cells all
over the body
● Toxic substances such as urea and substances in excess of requirements such as salts
can dissolve in water which makes them easy to remove from the body in urine
● Water is also an important part of the cytoplasm and plays a role in ensuring metabolic
reactions can happen as necessary in cells
Protein Shape! – Continued
There are thousands of different proteins in the human body and other organisms. Many of
these proteins are different shapes and the shape often has an important effect on the
function of the protein.
For example:
● Enzymes have an area in them known as the active site – this is important as this is the place
where another molecule fits into the enzyme in order for a reaction to take place.
● If the shape of the active site does not match the shape of the molecule that fits into it, the
reaction will not take place.
● Antibodies are proteins produced by certain types of white blood cell to attach to antigens on
the surface of pathogens.
● The shape of the antibody must match the shape of the antigen so that it can attach to it and
signal it for destruction.
The different sequences of amino acids cause the polypeptide chains to fold in different ways
and this gives rise to the different shapes of proteins. In this way every protein has a unique 3D
shape that enables it to carry out its function.
