Topic: Biomolecules
Most Essential Learning Competency:
Describe the structure of proteins, nucleic acids, lipids,
and carbohydrates, and relate them to their function
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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.
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4 Major Classes of Biomolecules
Carbohydrates
Proteins
Nucleic Acids
Lipids
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What are carbohydrates?
• The word carbohydrate derives
historically from the fact that
glucose, the rst carbohydrate to
be obtained pure, has the
molecular formula C6H12O6 and
was originally thought to be a
hydrate of carbon C6(H2O)6. This
view was soon abandoned but
the name persisted.
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What are carbohydrates?
• Carbohydrate is used to refer
loosely to the broad class of
polyhydroxylated aldehydes and
ketones commonly called sugars.
• Fischer projection of glucose 9
Carbohydrates
Simple Sugars Complex Sugars
Monosaccharides Disaccharides
Polysaccharides
Aldoses Ketoses
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Carbohydrates
Simple Sugars Complex Sugars
Monosaccharides Disaccharides
Polysaccharides
Aldoses Ketoses The -ose suffix is used as the family name ending for
carbohydrates
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Carbohydrates
Simple Sugars Complex Sugars
Monosaccharides Disaccharides
Polysaccharides
Aldoses Ketoses The keto- and aldo- prefixes identify the nature of the
carbonyl group
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Monosaccharides
• Carbohydrates that cannot be converted
into smaller sugars
• The number of carbon atoms is
indicated by using tri-, tetr-, pent-, hex-,
and so forth
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Monosaccharides
• Glucose • Fructose • Ribose
• Aldohexose • Ketohexose • Aldopentose14
Monosaccharides
• Allose • Xylose • Ribulose
• Aldohexose • Aldopentose • Ketopentose15
Disaccharides
• When two monosaccharides join
together through a condensation
reaction, a disaccharide is produced
along with a molecule of water.
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Disaccharides
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Disaccharides
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Polysaccharides
• Polysaccharides are polymers of
monosaccharides.
• Examples of polysaccharides are starch,
glycogen, and cellulose which are all
polymers of glucose.
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• Starch is found in
plants and used as
source of energy.
Starch consists of
two types of
glucose polymers:
amylose and
amylopectin which
differ from each
other in structure
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Polysaccharides
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• Starch is not found
in animals.
Instead, animals
use glycogen for
energy storage.
Glycogen has
shorter chains than
starch and is more
highly branched.
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• Like amylose, cellulose is a
straight chain polymer consisting
of glucose units. However. In
cellulose. The glycosidic links
between the glucose units in
cellulose alternate in direction.
This produces a long, straight and
rigid molecule. There is no
branching in cellulose. Cellulose
the major structural material
which plants are made of. Wood
is largely cellulose. Humans
cannot digest cellulose. 23
Proteins
• Proteins are natural
polymers. They are very
large molecules that are
critical for the functions of
the human body. They are
made from the linkage of
monomers called amino
acids. 24
Amino Acid
There are 20 kinds of amino
acids depending on the —R
group. The simplest amino
acid is glycine where R is a
hydrogen atom. The body
cannot make all the amino
acids required by the body
and is dependent on protein
taken through food.
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Two amino acids can link together through a condensation
reaction with the removal of a water molecule. The linkage is
called a peptide bond.
When many amino acids are linked together through peptide
bonds, the resulting molecule is called a polypeptide. A very
large number of amino acids linked together results in a
protein. Some proteins are made up of only one polypeptide
while most proteins involve assemblies of two or more
polypeptides.
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The sequence and the
structure of proteins
are important in
determining their
functions. There are
four levels of protein
structures: the primary
structure, secondary
structure, tertiary
structure, and
quaternary structure.
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The primary
structure refers to
the linear
sequence of amino
acids joined by
peptide bonds
such as the
sequence of amino
acids on the left.
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The polypeptide chain can twist and fold in a variety of ways.
These folded structures are referred to as secondary protein
structures. The two essential secondary structures are the alpha
helix and the beta pleated sheets.
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Several secondary
structures come
together forming
tertiary structures.
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When several tertiary structures come together, a quaternary
protein structure is formed.
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For example,
the protein
hemoglobin is a
quaternary
structure formed
by four tertiary
structures.
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Nucleic Acids
• Nucleic acids are natural polymers with very large
molar masses. The two main types of nucleic acids
are deoxyribonucleic acid (DNA) and ribonucleic acid
(RNA). DNA and RNA are polymers made up of
monomers in the form of nucleotides. When these
nucleotides combine, they form polynucleotides. DNA
carries the genetic information passed on from parents
to children. RNA plays an important role in protein
synthesis. 36
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• Nitrogenous base
Purines - adenine (A), and
guanine (G)
Pyrimidines - cytosine (C),
thymine (T), uracil (U)
• A ve-carbon sugar
Deoxyribose
Ribose
• Phosphate group 38
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Features of DNA and RNA
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Lipids
• Lipids are a class of naturally occurring organic
compounds distinguished by their solubility in
an organic solvent (and not in water). Lipids are
hydrophobic, nonpolar, and made up mostly of
hydrocarbon chains. Some of the more
important lipids are: triglycerides (fats),
saturated and unsaturated fatty acids, waxes,
phospholipids, and steroids. 40
• Steroids are chemicals,
often hormones, that your
body makes naturally.
They help your organs,
tissues, and cells do their
jobs. You need a healthy
balance of them to grow
and even to make babies.
"Steroids" can also refer
to man-made medicines.
Corticosteroids ght
in ammation, irritation,
swelling (arthritis,
asthma). Anabolic steroids
help build bigger muscles
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Lipids
• Fatty acids consist of a
long hydrocarbon chain
(typically about 12 – 18
carbons) attached to a
carboxyl group.
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Lipids
• Saturated fatty acid – contains only single C-C bonds
because the carbon atoms are saturated or lled up with
hydrogens. Because their structure is straight, they can
pack well and are solid at room temperature (e.g. fat in
butter)
• Unsaturated fatty acids – contain carbon-carbon double
bonds. When there is only one C-C double bond, it is
called monounsaturated; if there are several C-C double
bonds, they are called polyunsaturated.
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Lipids
• Fats and oils - Fat
molecules have two parts: a
glycerol backbone and three
fatty acid chains. The
resulting molecule is called
a triglyceride. Triglycerides
are the main constituents of
body fat in humans and
other vertebrates, as well as
vegetable fat
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Triglyceride
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