Biomolecules

LEARNING OUTCOMES
As a result of the lesson you will be able to:
• summarize the structural properties of biomolecules - simple
carbohydrates, lipids, amino acids, nucleotides - and their polymers;
• explain the information function of proteins and nucleic acids;
• describe the structure of DNA and RNA;
• explain what base pair complementarity means and list Chargaff's rules;
• identify carbohydrates depending on their structure and functions;
• give examples of monosaccharides, disaccharides, polysaccharides;
• identify fats and oils depending on their structure and functions; explain
the differences between them;
• identify the differences between animal and vegetable fats;
• give examples of saturated, unsaturated and polyunsaturated fatty acids;
• identify amino acids and their functions
Cells are composed of water, inorganic ions and organic components.
Organic molecules are unique constituents of cells. The main classes of this
molecules are

✔ Carbohydrates
✔ Lipids
✔ Proteins Constitute 80-90% of the dry weight of most
cell
✔ Nucleic acids

Macromolecules are polymers consisting of small molecules called monomers.

 Carbohydrates
• Carbohydrates are formed by green plants from carbon
dioxide and water during the process of photosynthesis.

Cn(H2O)n –general
formula of
carbohydrates
•Sugars
•Source of energy

•Starting material for synthesis

•Markers in cell recognition processes
•Take part in processes of cell adhesion

•Take part in transport of some biomolecules

Chemically, carbohydrates are defined as “optically active polyhydroxy aldehydes or
ketones or the compounds which produce units of such type on hydrolysis”.
 Monosacharides
• General formula (CH2O)n
• n –number of carbons – 3, 4 , 5 or 6
• Monosacharides contain an aldehyde group (aldose) or ketone group
(ketose)
 Features of monosacharides
• In aqueous solution, the aldehyde or ketone group of a sugar
molecule tends to react with a hydroxyl group of the same
molecule, thereby closing the molecule into a ring.

https://www.khanacademy.org/test-prep/mca
t/biomolecules/carbohydrates/v/carbohydrate
s-cyclic-structures-and-anomers-1
 Isomers
• Many monosaccharides differ only in the spatial arrangement of
atoms—that is, they are isomers. These small differences make only minor
changes in the chemical properties of the sugars. But the differences are
recognized by enzymes and other proteins and therefore can have major
biological effects.
 The hydroxyl groups of a simple monosaccharide, such as glucose, can be
replaced by other groups

• The hydroxyl group on the carbon that carries the aldehyde or ketone can
rapidly change from one position to the other. These two positions are
called α and β. As soon as one sugar is linked to another, the α orβ form is
frozen
The carbon that carries the aldehyde or the ketone can react with any hydroxyl
group on a second sugar molecule to form a disaccharide, oligosacharide
and polysacharide

Monosaccharides can be linked by covalent bonds—called glycosidic bonds—to form

larger carbohydrates. A bond is formed between an –OH group on one sugar and an –OH
group on another by a condensation reaction, in which a molecule of water is expelled as
the bond is formed. The subunits in other biological polymers, including nucleic acids
and proteins, are also linked by condensation reactions in which water is expelled.
 • Monosaccharides are the simplest form of carbohydrate and cannot be
further hydrolyzed to smaller subunits. The most nutritionally important
monosaccharides are the pentoses ( ribose), and the hexoses (glucose).
• https://www.sciencedirect.com/science/article/pii/S0304416521000568

Class Species Significance Role of sugars in pathology

Hexoses d-glucose Major cell fuel, unbound in body fluids diabetes mellitus, hyper – and
and tissues, building block of several hypoglycemia
polysaccharides
d-fructose Cell fuel, constituent of sucrose can synthesize at metabolic
syndrome, renal disorders
d-galactose Cell fuel, constituent of lactose, congenital metabolic disorders
alternative carbon source in glycan galactosemia, galactose-related
synthesis, precursor in protein lysosomal disorders
glycosylation processes in some tissues
d-mannose Constituent of plant cell wall Can be used in treatment of
polysaccharides and gums, take part in carbohydrate-deficient
protein glycosylation processes glycoprotein syndrome type 1b,
urinary tract infections,
disbacteriosis
Class Species Significance Role of sugars in pathology
Pentoses d-ribose RNA and ATP constituent Used to treat
many pathological conditions,
such as chronic fatigue
syndrome, fibromyalgia, and
myocardial dysfunction.
Uronic acids d-glucuronic, d- Constituent of plant cell wall mucopolysaccharidoses
galacturonic polysaccharides, (MPS) and hereditary
glycosaminoglycans (GAGs), inclusion body myopathy
proteoglycans, and other
(HIBM)
physiologically relevant
compounds in human body
Deoxysugars d-deoxyribose DNA constituent
Aminosugars d-glucosamine, Constituent of arthritis, skin aging, thrombosis
d-galactosamine aminosaminoglycans, cartilage,
hormones
Olygosacharides and polysacharides (glycans)
are long linear or branched chains of carbohydrate molecules, composed of several
smaller monosaccharides.
 Polysaccharides have the following properties:
They are not sweet
in taste.
Many are insoluble
in water.
They are
hydrophobic in
nature.
They do not form
crystals on
desiccation.
Can be extracted to
form a white
powder.
They are high
molecular weight
carbohydrates.
Inside the cells, they are
compact and osmotically
inactive.
They consist of
hydrogen, carbon, and
oxygen. The hydrogen to
oxygen ratio being 2:1.
 Functions of glycans
✔ They store energy in organisms.
✔ Due to the presence of multiple hydrogen bonds, the water
cannot invade the molecules making them hydrophobic.
✔ They allow for changes in the concentration gradient which
influences the uptake of nutrients and water by the cells.
✔ Many polysaccharides become covalently bonded with lipids
and proteins to form glycolipids and glycoproteins. These
glycolipids and glycoproteins are used to send messages or
signals between and within the cells.
✔ They provide support to the cells. The cell wall of plants is
made up of polysaccharide cellulose, which provides support
to the cell wall of the plant. In insects and fungi, chitin plays
an important role in providing support to the extracellular
matrix around the cells.
 Lipids
• Lipids are a class of organic molecules that are fatty acids or their
derivatives.
• Lipids are loosely defined as molecules that are insoluble in water but
soluble in fat and organic solvents such as benzene.
• Lipid, any of a diverse group of organic compounds including fats, oils,
hormones, and certain components of membranes
• They typically contain long hydrocarbon chains, as in the fatty acids, or
multiple linked aromatic rings, as in the steroids
A fatty acid molecule, which has two chemically distinct regions:
- hydrocarbon chain is hydrophobic and not very reactive chemically.
- carboxyl (–COOH) group, which behaves as an acid (carboxylic acid): in
an aqueous solution, it is ionized (–COO–), extremely hydrophilic, and
chemically reactive. Almost all the fatty acid molecules in a cell are
covalently linked to other molecules by their carboxylic acid group.

P.S. Molecules that possess both hydrophobic and hydrophilic regions are termed
amphipathic
Fatty acid chains may differ in length, as well as in their degree
of unsaturation.
Examples of fatty acids
 Physical Properties of Fatty Acid:

• Saturated fatty acids are solid at room temperature.

• Unsaturated fatty acids are liquid at room temperature.

• The long chain length of fatty acid has a high melting point than short-chain fatty acids.
• The solubility of fatty acids decrease due to increase in no. of the methylene group

• Presence of double bond increases the solubility of fatty acids.

• Fatty acids form salts with alkali and alkaline earth metal.

• Salts of sodium, potassium, calcium, and magnesium are formed when fatty acids react with these salts.

• Fats have the specific gravity less than 1 and, also lower than water, therefore, they float on water.

• The melting point of fats depends upon their constituent fatty acids.

• Freshly prepared fats are colorless, odorless and tasteless..

The double bonds in unsaturated fatty acids, like other types of double bonds, can
exist in either a cis or a trans configuration. In the cis configuration, the two
hydrogens associated with the bond are on the same side, while in
a trans configuration, they are on opposite sides. A cis double bond generates a
kink or bend in the fatty acid, a feature that has important consequences for the
behavior of fats.
 Essential fatty acids
• The term essential fatty acids (EFA) refers to those polyunsaturated fatty
acids (PUFA) that must be provided by foods because these cannot be
synthesized in the body yet are necessary for health.
• Lipids may consist of fatty acids alone, or they may contain other
molecules as well.
 Triglycerides

Solid at room temperature

Liquid at room temperature
Saturated and trans are its
types Unsaturated fats like
monounsaturated and
Mostly derived from animal polyunsaturated are its types

Mostly derived from plants

Increases cholesterol levels
Improves cholesterol levels
Mainly comes from animal
food but also through
Mainly comes from plants or
vegetable oil by process
fish
called hydrogenation
Example:Vegetable oil, fish
Example: Butter, beef fat
oil
• Triglycerides are a common type of fat that accounts for about 95 % of all
dietary fats. Both animal and vegetable fats contain triglycerides. Once
digested, triglycerides circulate in the bloodstream to be used as energy by
the cells. Any leftovers are stored in body fat to fuel the body between
meals.
 Phospholipids
• are the main component of the cell membrane, bile and lipoproteins
• are made up of two fatty acids, a phosphate group, and a glycerol molecule.
• are able to form cell membranes because the phosphate group head is
hydrophilic (water-loving) while the fatty acid tails are hydrophobic
(water-hating).
• are ubiquitous molecules that participate in innumerous cellular events.
 Phospholipids
✔ It regulates the permeability of the membrane.
✔ It is also involved in the absorption of fat from the intestine.
✔ It helps in ETC- Electron Transport Chain in the mitochondria.
✔ Phospholipids help by preventing the accumulation of fats in the liver.
✔ It plays a major role in the transportation and removal of cholesterol from
the cells.
✔ It forms the structural components of the cell membrane with the
association of proteins.
✔ They act as surfactants in the respiratory system and are also involved in
the coagulation of blood cells.
✔ It helps in the synthesis of different lipoproteins, prostacyclins,
prostaglandins and thromboxanes.
✔ Lipid composition of membranes depends on their function
 Cause of phospholipid
disorders

• Alteration of phospholipid
metabolism -Barth syndrome,
Senger syndrome, obesity,
cancer
• Alteration of phospholipid
transport - insulin resistance,
glucose intolerance,
non-alcoholic steatohepatitis
• Alteration of phospholipid
oxidation – atheroslerosis ,
cancer, inflamation
 Steroids
• Steroids are lipids because they are hydrophobic and insoluble in water, but
they do not resemble lipids since they have a structure composed of four
fused rings.
• Sex hormones, cholesterol are main compounds related to steroids
Cholesterol

• is mainly synthesized in the liver

• is the precursor to vitamin D
• is precursor to many important steroid hormones like estrogen,
testosterone, and progesterone, which are secreted by the gonads and
endocrine glands.
• is component of cell membrane
• hypercholesterinemia increases the risk of atherosclerosis, cardiovascular
diseases, cholesterol gallsones

Steroid hormones
• synthetized in special glands, spread in the body by bloodstream
• regulates a lot of functions in body
• participate in cell signalling
• alteration of hormone level in body leads to different pathologies of
reproductive system, stress, bloo pressure, etc
 Amino acids and proteins
• Cells use amino acids to build proteins—polymers made of amino acids,
which are joined head-to-tail in a long chain that folds up into a
three-dimensional structure that is unique to each type of protein
There are approximately 20,000
unique protein encoding genes
responsible for more than 100,000
unique proteins in the human body.
Although there are hundreds of amino
acids found in nature, only about 20
amino acids are needed to make all the
proteins found in the human body and
most other forms of life. These 20
amino acids are all L-isomer,
alpha-amino acids.
Formation of α-helix and β-sheets
Types of bonds in tertiary structure of
protein
• Amino acids are used efficiently by the body by multiple
mechanisms such as recycling, transamination, or energy
production, building of proteins and enzymes. Alterations in
amino acid metabolism and transport processes result in severe
consequences for organisms. Amino acid metabolism disorders
are hereditary metabolic disorders.

✔Phenylketonuria
✔ Tyrosinemia
✔ Homocystinuria
✔ Non-ketotic hyperglycinemia
✔Maple syrup urine disease.
 Nucleic acids, nucleotides
• The nucleic acids-DNA and RNA-are the principal informational molecules of the cell.
DNA and RNA are polymers of nucleotides, which consist of purine and pyrimidine
bases linked to phosphorylated sugars
Components of nucleotide
The polymerization of nucleotides
Nucleotides are building blocks of nucleic acids.

Direction of polymerization is 5’ to3’

• The information in DNA and RNA is conveyed by the order of the bases in
the polynucleotide chain

The bases are on the inside of the molecule, and

the two chains are joined by hydrogen bonds
between complementary base pairs-adenine
pairing with thymine and guanine with cytosine
In the mid-to-late 1940s, Chargaff, through numerous experiments with DNA
from various species, came to the following conclusions:
Purines and pyrimidines are essential building blocks of DNA, RNA, and compounds
involved in cellular energy transfer and biosynthetic reactions (e.g., adenosine
triphosphate, ATP).
Purine and pyrimidine disorders have a wide spectrum of signs and symptoms,
including autism, kidney stones, susceptibility to infections, and severe intellectual
disability. Symptoms may present from infancy to old age.
 Proteins and nucleic acids and are known as the
informational macromolecules.

Proteins produced in a similar two-step process in all organisms –

DNA is first transcribed into RNA, then RNA is translated into
protein
We have just 4 types of nucleotides to encode more than 20,000 genes and 20 types of amino acids to
synthesize more than 1,000,000 types of proteins. So, the order of nucleotides in NA and amino acids
in protein determines the huge diversity of genes and proteins in the body.

Example: The blood disease Sickle-cell anemia is caused by a simple substitution mutation. In the mutation,
a single nucleotide is replaced in the portion of DNA which codes for a unit of hemoglobin. The
substitution mutation causes a glutamic acid in the protein to be changed to a valine amino acid.
• Thanks for your attention!