Biological Molecules
CHAPTER 01
BIOLOGICAL MOLECULES
TOPICS
& SUBTOPICS
1.1 INTRODUCTION Page: 05
· Biochemistry
· Chemical Composition
of the Cell
· Fundamental types of
Biomolecules
· Synthesis &
Breakdown of Macromolecules
a)
Condensation
b)
Hydrolysis
1.2 IMPORTANCE OF WATER Page: 07
· Hydrogen Bond
a)
Cohesive Force
b)
Adhesive Force
· High Specific Heat
· Hydrophobic Exclusion
· Ionization of Water
· Anomalous Behavior of
Water
1.3 CARBOHYDRATES Page: 10
· Classification of
Carbohydrates
a)
Monosaccharides
b)
Oligosaccharides
i.
Starch
ii.
Glycogen
iii.
Cellulose
iv.
Chitin
· Stereoisomers in
Carbohydrates
1.4 PROTEINS Page: 15
· Amino Acid
a)
Formation & Breakdown of Peptide Linkage
b)
Sequence of Amino Acids
· Classification of
Proteins
a)
Fibrous Protein
b)
Globular Protein
· Structural Proteins
· Functional Proteins
1.5 LIPIDS Page: 21
· Acylglycerol
a)
Saturated Acylglycerol (Fats)
b)
Unsaturated Acylglycerol (Oils)
· Phospholipids
· Waxes
a)
Natural Waxes
b)
Synthetic Waxes
· Terpenoids
b)
Steroids
c)
Carotenoids
d)
Prostaglandins
1.6 NUCLEIC ACIDS Page: 26
· Composition of
Nucleotide
· Mononucleotide
·
Dinucleotide
a)
Formation of Phosphodiester Bond
· Polynucleotide
· Structure of DNA
· Gene
a)
Transcription
b)
Translation
· Ribonucleic Acid (RNA)
a)
Messenger RNA (mRNA)
b)
Transfer RNA (tRNA)
c)
Ribosomal RNA (rRNA)
1.7 CONJUGATED MOLECULES Page: 32
· Glycolipids
· Glycoproteins
· Lipoprotein
· Nucleoprotein
1.1 INRODUCTION
Biochemistry: It is the branch of biology that studies the chemical processes
and substances that occur (ہوتا ہے/ ٿيڻ) within living organisms.
It is the most important branch of biology due to:
·
It provides information about all the processes
caried out in the living organisms from construction of body structures to flow
of information from nucleus, especially DNA for enzyme/protein synthesis
and control of all mechanisms.
·
It provides information about abnormal mechanisms
which lead to diseases.
·
It ultimately opens the door of development of
medicines and medical equipment to elucidate these abnormalities.
·
It enables us to investigate and understand the
most challenging and fundamental problems of biology and medicine e.g.
i. How do cells find each other to form a complex organ?
ii. How does the growth of cells control?
iii. What are the causes of cancer?
iv. What is the mechanism of memory?
Biochemistry is a multidisciplinary (کثیر الشعبہ) field that bridges the gap between biology
and chemistry, providing a molecular-level understanding of life processes. It
has significant implications (اهم اثر) for various areas of science, medicine, and technology, and continues
to contribute to our understanding of the fundamental principles that govern
life.
The cell, which is the basic unit of life, is
a complex structure composed of various chemical components. These components
can be broadly categorized into two main types, Inorganic and Organic
molecules.
Water is the most abundant molecule in cells,
accounting for 70% to 90%, if the water is evaporated, the remaining mass of
the cell is called Dry Weight of the cell, consists of many carbons
containing long chain molecules called Biomolecules which are the type
of organic molecules.
So, the compounds produced by living
organisms are called biomolecules.
·
Inorganic: Inorganic substances in living organisms are water, carbon
dioxide, acids, bases, and salts.
·
Organic: Organic substances in living organisms are carbohydrates,
proteins, lipids, and nucleic acids.
Fundamental Types of
Biomolecules:
Biomolecules can be
divided into following types:
1. Carbohydrates 2. Proteins 3. Lipids
4. Nucleic Acids 5.
Conjugated Molecules
These five types of
biomolecules are considered fundamental because they are essential for the
structure, function, and regulation of living organisms, and they form the
basis of biochemistry and molecular biology.
|
Biomolecules |
Units\Monomers |
Bonds\Linkages |
|
Carbohydrates Oligo. & Poly Saccharides |
Monosaccharides |
Glycosidic |
|
Proteins |
Amino
Acids |
Peptide |
|
Lipids Fats & Oils Phospholipids Terpenoids |
Glycerol & Fatty Acids Glycerol, Fatty Acids, Phosphate, &
Choline Isoprenoids Units |
Ester Ester & C-C C-C |
|
Nucleic
Acids DNA RNA |
Deoxyribonucleotides Ribonucleotides |
Phosphodiester Phosphodiester |
|
Conjugates
Molecules |
Different |
Different |
Synthesis & Breakdown of Macromolecules: Synthesis and breakdown of macromolecules are fundamental
processes that occur in living organisms. Macromolecules are large molecules
made up of smaller subunits, and they include carbohydrates, proteins, nucleic
acids, and lipids. Let's briefly explore how synthesis and breakdown occur.
a) Condensation:
Condensation reactions are a key mechanism in
the synthesis of macromolecules or polymers, which are large molecules
made up of repeating units called monomers. When monomers join together
through condensation reactions, they form covalent bonds
and release a small molecule, usually water, as a byproduct. This
process is also known as dehydration synthesis because water is
removed during the formation of the covalent bond. Water
is released during condensation reactions through the elimination
of a hydroxyl (OH) group from one molecule and a hydrogen (H)
atom from another molecule. The hydroxyl group and hydrogen atom combine
to form a water molecule (H2O), which is released as a
byproduct of the condensation reaction.
Ø This reaction needs energy.
Ø This is anabolic process.
b)
Hydrolysis: Hydrolysis is the opposite of condensation,
and it is a chemical reaction in which a larger molecule is broken
down into smaller molecules or monomers through the addition
of water. In hydrolysis, a covalent bond is cleaved,
and a water molecule is used to break the bond,
resulting in the formation of two or more smaller
molecules. During hydrolysis, water molecules are added to
the reactants, and the water molecule is split into a hydroxyl
group (-OH) and a hydrogen ion (H+). The
hydroxyl group and hydrogen ion are added to the atoms or groups of atoms that
were originally joined by the covalent bond, causing the bond to
break.
Ø This reaction releases energy.
Ø This is catabolic process.
Synthesis
and breakdown processes in cells, known as anabolism and catabolism,
respectively, are essential for maintaining cellular functions. Anabolism
involves the synthesis of complex molecules from simpler molecules, requiring
energy, and examples include glucose synthesis, protein synthesis, and lipid
synthesis. On the other hand, catabolism involves the breakdown of complex
molecules into simpler molecules, releasing energy, and examples include
glucose breakdown, protein degradation, and lipid breakdown. These processes
are interconnected and work together to regulate cellular metabolism and
maintain cellular health.
1.2 IMPORTANCE OF
WATER
a)
b)
Adhesive Force (Adhesion): Adhesive force refers to
the attractive force between molecules of different substances, allowing them
to adhere or stick together. In the case of water,
adhesive forces arise when water molecules form hydrogen bonds with other polar
or charged molecules or surfaces. Water molecules can form hydrogen bonds with
materials such as glass, paper, and plant cell walls, among others, due to
their polar nature. This adhesive force allows water to "wet" or
cling to surfaces, promoting capillary action, which is the ability of water to
move against gravity in narrow spaces, such as in plant roots or small blood
vessels. Adhesive forces, combined with cohesive forces, contribute to the
unique properties of water and its importance in various biological processes,
such as plant water uptake, transport of nutrients in organisms, and
maintenance of cell structure and function.
High Specific Heat: High specific heat refers to the amount
of heat energy required to raise the temperature of a substance by a certain
amount. Water has a high specific heat compared to many other
substances, which means that it can absorb or release a relatively large amount
of heat energy without experiencing a significant change in temperature.
·
Its value is 1.0 for water
·
Water has great ability to absorb
heat with minimum change in its temperature.
·
Water works as temperature/thermal
stabilizer for the organisms and protects living material
from sudden thermal changes.
·
Water has high heat of vaporization i.e., 574 kcal/kg
·
High heat of vaporization of water enables evaporative cooling,
a crucial mechanism for temperature regulation in living
organisms.
·
Water absorbs much heat when it changes from liquid
to gas.
·
Evaporation of only two ml out of one liter
of water lowers the temperature of the remaining 998 ml by 1oC.
·
It provides cooling effect to plants when water is transpired.
·
Similarly, it provides cooling effect to the animals
when water is perspired (پسینہ).
·
It plays an important role in the regulation of heat produced
by the oxidation.
Ionization of Water: Ionization of water refers to the process by
which water molecules dissociate or break apart into positively charged
hydrogen ions (H+) and negatively charged hydroxide ions (OH-)
in an aqueous solution. This process occurs due to the inherent tendency of
water molecules to undergo a self-ionization reaction, where a small fraction
of water molecules spontaneously dissociates into ions:
·
It behaves as acid or base i.e., Amphoteric.
·
At 25-degree Casius the concentration of each of H+
and OH- ions in pure water is about 10-7 moles/liter.
Anomalous Behavior of Water: The anomalous behavior of water refers to its
unique and unusual properties that deviate from the normal behavior expected of
a typical liquid. Some of the key anomalous properties of water include:
·
After reaches its maximum density at 4 degrees Celsius. As water
cools further below 4 degrees Celsius, it expands and becomes less
dense, which is why ice floats on water.
·
At 0 oC water expands maximumly in ice conditions
·
It makes the life possible under frozen water.
Carbohydrates are polyhydroxy aldehydes or ketones, or complex substances which on hydrolysis produce polyhydroxy
aldehydes or ketone subunits.
·
They are organic
compounds made up of carbon, hydrogen, and oxygen
in a specific ratio, typically with the formula (CH2O)n,
where ‘n’ represents the number of carbon atoms in the carbohydrate
molecule.
·
Carbohydrates
serve as an important source of energy for living organisms,
playing a crucial role in cellular respiration, metabolism,
and various physiological processes.
Main sources of
carbohydrates are plants because the synthesize carbohydrate molecules as
primary product during photosynthesis.
·
The word
carbohydrate means hydrated carbon (پانی ملا کاربن).
·
The ratio
of hydrogen and oxygen is the same as in water.
·
Carbohydrates
are abundant in living organisms.
·
They are found
in all organisms & almost all parts of cell.
·
Carbohydrates can be classified into different types,
including monosaccharides (simple sugars), disaccharides (double
sugars), and polysaccharides (complex carbohydrates).
·
They are sweet
in taste. (The sweetness of carbohydrates can vary depending on the type
and structure of the carbohydrate. For example, monosaccharides like glucose
and fructose are generally sweeter than disaccharides like sucrose (table
sugar) or lactose (milk sugar). This is because the simpler structure of
monosaccharides allows for a more direct interaction with the sweet taste
receptors, resulting in a sweeter taste.)
Classification of Carbohydrates: Carbohydrates
can be classified into several categories based on their chemical structure and
complexity.
a)
Monosaccharides: Monosaccharides are the simplest form of carbohydrates, often referred
to as "simple sugars." They are composed of a single
sugar unit, which is a small molecule made up of carbon,
hydrogen, and oxygen atoms. Monosaccharides are the building
blocks of more complex carbohydrates and are widely
found in nature, including in many foods we eat.
·
Monosaccharides are classified based on the number of carbon
atoms they contain, with the most common ones being trioses (3
carbons), tetroses (4 carbons), pentoses (5 carbons), hexoses (6 carbons), and heptoses
(7 carbons).
·
Examples of monosaccharides include glucose, fructose,
and galactose.
·
Glucose is the primary
source of energy for many living organisms, including humans.
It is commonly found in fruits, vegetables, and other
foods, and is an important fuel for our bodies. Glucose
can be used directly by cells for energy production
through a process called cellular respiration, or it can be converted
into other forms of carbohydrates for storage, such as glycogen
in animals or starch in plants.
·
Fructose is a naturally
occurring sugar found in many fruits and vegetables,
and it is also used as a sweetener in various foods and beverages (مشروب).
It is sweeter than glucose and is often used as a sweetening ingredient in
processed foods and soft drinks.
·
Galactose is less
commonly found in nature, but it is an important component of lactose, which is
the sugar found in milk. Lactose is a disaccharide composed of one molecule of
galactose and one molecule of glucose, and it is the main carbohydrate in
mammalian milk, providing energy for infants.
·
Trioses contain three
carbon atoms in their molecular structure, along with hydrogen
and oxygen atoms. Trioses are important intermediates in various
metabolic pathways, including glycolysis, which is the process by which cells
break down glucose to produce energy.
·
Tetroses contain four
carbon atoms in their molecular structure, along with hydrogen
and oxygen atoms. Tetroses are relatively rare in nature
compared to other types of monosaccharides, and they are not
as commonly found in biological system.
·
Pentoses contain five
carbon atoms in their molecular structure, along with hydrogen
and oxygen atoms. Pentoses are important molecules in
various biological processes, as they are key components of nucleic
acids (DNA and RNA) and other important biomolecules.
There are two types of pentoses: ribose and deoxyribose.
Ribose is a component of RNA (ribonucleic acid),
which is a nucleic acid that plays a crucial role in the synthesis
of proteins. Ribose also forms the backbone of ATP
(adenosine triphosphate), which is the primary energy
currency of cells.
·
Hexoses contain six
carbon atoms in their molecular structure, along with hydrogen
and oxygen atoms. Hexoses are important molecules in various
biological processes, as they serve as a source of energy
and are used in the synthesis of other biomolecules. There
are several types of hexoses, including glucose, fructose,
and galactose, which are commonly found in nature.
·
Heptose is a type
of monosaccharide that contains seven carbon atoms in its molecular
structure, along with hydrogen and oxygen atoms. Heptoses
are less common than hexoses and are typically found in specific
types of bacteria and other microorganisms.
b)
Oligosaccharides: Oligosaccharides are a type of carbohydrate that consist
of a small number of sugar units (typically 2 to 10),
linked together by glycosidic bonds. They are intermediate
in size between monosaccharides (which are single sugar units)
and polysaccharides (which are large, complex carbohydrates composed of
many sugar units). Oligosaccharides are found in various forms
in nature and play important roles in biological processes.
Sucrose is one of the most well-known disaccharides,
also known as table sugar. Sucrose is composed of one glucose
unit and one fructose unit linked together. It is the primary form
in which carbohydrates are transported in plants, serving
as a source of energy during plant growth and development.
Sucrose is also a major sweetening agent in many foods
and beverages.
·
On hydrolysis gives a glucose and fructose.
·
Chemical formula: C12H22O11
·
The name “sucrose” comes from the
French “sucre”, which is derived from the Latin saccharum
(meaning “sugar”).
·
Sucrose is non-reducing sugar.
·
Non-reducing sugar
refers to a type of sugar that has not free aldehyde or ketone
group in its molecular structure and it is unable of being oxidized
and don’t cause the reduction of other substances.
Lactose is another
important disaccharide, which is found in milk and milk
products. Lactose is composed of one glucose unit and one galactose
unit linked together. It serves as a source of energy for infants
and is an essential component of human milk.
However, some individuals may be lactose intolerant, meaning they are unable to digest lactose properly due
to a deficiency in the enzyme lactase, which breaks down lactose
into its component sugars.
·
On hydrolysis gives a glucose and galactose.
·
Chemical formula: C12H22O11
·
The name “lactose” comes from the word
lac or lactis (meaning “milk”) and the suffix -ose
to indicate it is a sugar.
·
Lactose is a reducing sugar.
·
Reducing sugar refers to a type of sugar
that has free aldehyde or ketone group in its
molecular structure and it is capable of being oxidized and
causes the reduction of other substances without being
hydrolyzed.
Maltose is another common disaccharide, which is formed from
the breakdown of starch in plants and glycogen in animals.
Maltose is composed of two glucose units linked together and serves as an
intermediate in the digestion of starch and glycogen into smaller, more readily
absorbed sugars. It is commonly referred to as malt sugar
and is found in germinating grains, such as malted barley,
as well as in other foods.
·
On hydrolysis gives two glucose
molecules.
·
Chemical formula: C12H22O11
·
The name “maltose” comes from the word
malt (i.e., germinated grain, for use in brewing, distilling,
etc.) and the suffix -ose that indicates it is a sugar.
·
Maltose is a reducing sugar.
·
Reducing sugar
refers to a type of sugar that has free aldehyde or ketone group
in its molecular structure and it is capable of being oxidized
and causes the reduction of other substances without being
hydrolyzed.
c) Polysaccharides: Polysaccharides are complex carbohydrates
composed of many monosaccharide units joined together by glycosidic
bonds. They are generally insoluble in water and
can have a structural or storage role in organisms.
One important structural polysaccharide is cellulose,
which is found in the cell walls of plants and
some bacteria. It is composed of long chains
of glucose molecules linked by beta-1,4-glycosidic
bonds, forming a rigid, fibrous structure.
·
The term polysaccharide etymologically means multi saccharides.
·
A saccharide refers to the unit structure of carbohydrates.
·
Thus, a polysaccharide is a carbohydrate comprised of many saccharides,
particularly, more than ten monosaccharide units.
·
Not sweet
in taste
·
Many of which are insoluble in water
·
Do not form crystals when desiccated.
·
General chemical formula of Cx(H2O)y
i.
Starch:
ii.
Glycogen is a highly branched polysaccharide
that serves as a form of energy storage in animals,
including humans. It is made up of glucose monomers linked
together by alpha-1,4 glycosidic bonds with alpha-1,6
glycosidic bonds forming branch points.
It is stored mainly in liver and muscle cells
and can be broken down into glucose to provide energy
when needed. The highly branched structure of glycogen
allows for a rapid release of glucose when energy demand
is high, making it an important energy source during
exercise or other forms of physical activity.
iii.
Cellulose:
However, some animals,
such as cows and termites, can digest cellulose
with the help of specialized microorganisms in their digestive
tracts. Cellulose is an important source of dietary
fiber for humans and plays a crucial role in maintaining a healthy
digestive system. It is also used in the production of various
products, such as paper, textiles, and plastics. Cellulose
is biodegradable, odorless, and has no taste. It is
a straight-chain polymer of carbohydrates. It is an organic
compound just like the other carbohydrates. It is made up of a linear
chain of multiple glucose residues (e.g., 300 to 1000
or more units) linked by β(1→4) glycosidic bond.
The hydroxyl groups
on the glucose from one chain connect (via hydrogen
bonds) with the oxygen atoms on the glucose on another
or the same chain. No glycosidic bonds occur
in between the chains. Hydrogen bonds are the ones holding the
chains together, side-by-side. Thus, cellulose appears as a microfibril.
It renders tensile strength to the cell wall where
it serves as the plant’s “cytoskeleton”. The other properties of
cellulose depend on the length of the chain or on the degree of polymerization.
iv.
Chitin: (C8H13O5N)n
1.4 PROTEINS
Proteins are biomolecules
comprised of amino acid residues joined together by
peptide bonds. Proteins are one of the major biomolecules.
The components of proteins include carbon, hydrogen, oxygen,
nitrogen, and sometimes sulfur. Due to presence of nitrogen in
large proportion they are called nitrogenous compounds. They
are essential to life and perform a wide range of functions in the
body, such as catalyzing chemical reactions, transporting
molecules, providing structural support, and regulating
gene expression. The structure of a protein is determined by the
sequence of amino acids that make it up. There are 20 different amino acids
that can be arranged in different ways to create a variety
of proteins. The order of amino acids is specified by the genetic
code encoded in DNA. Proteins are synthesized in cells by ribosomes,
which read the genetic code in DNA and use it to build
a protein chain from amino acids. The newly
synthesized protein may undergo additional modifications such as folding,
cleavage, and chemical modification to become fully functional.
· The term protein came
from French protéine, from Late Greek prōteios, of the first quality,
from Greek prōtos, meaning “first rank”.
· Proteins can be denatured
or unfolded by changes in pH, temperature, or exposure to chemicals,
which can lead to loss of function.
· Protein deficiencies
can lead to a variety of health problems, and many diseases
are caused by defects in specific proteins.
· Protein sources
include both animal and plant-based foods, with different sources containing
different amino acid profiles.
· Recommended protein
intake varies depending on factors such as age, sex, weight, and physical
activity level.
·
The 20 types of amino acids
based on the variability of R group.
·
As shown in following simple amino acids.
Glycine:
Glycine is one of the 20 amino acids that are the building
blocks of proteins. In the case of glycine, the R group is just a
hydrogen atom, which makes it the smallest and simplest
amino acid.
Alanine is another one of the 20 amino
acids that are the building blocks of proteins. In the
case of alanine, the R group is a simple methyl (-CH3)
group, which makes it a nonpolar, neutral amino acid.
Serine:
Serine is one of the 20 standard
amino acids that are the building blocks of proteins. Its side chain contains a
hydroxyl (-OH) group, which makes it a polar, uncharged amino
acid. The polar nature of serine's side chain makes
it hydrophilic, meaning that it has an affinity for water molecules and
can form hydrogen bonds with other polar molecules
a)
b)
Insulin: Insulin is a peptide hormone that is produced by the pancreas
and plays a critical role in regulating blood glucose levels.
It is a small protein consisting of two polypeptide
chains, an alpha chain and a beta chain, that are linked
together by disulfide bonds. The alpha chain of insulin
contains 21 amino acids, while the beta
chain contains 30 amino acids. These chains are synthesized
as larger precursor molecules, called proinsulin,
which are then cleaved by specific enzymes to produce the active
insulin hormone.
The globin
protein chains in hemoglobin are of two types:
alpha and beta. Each hemoglobin molecule contains two alpha
chains and two beta chains, each of which is bound to a heme
group. The heme group contains an iron ion
that can bind to oxygen molecules, allowing hemoglobin
to transport oxygen through the bloodstream.
Each alpha chain has 141 amino acids, while the beta
chain has 146 amino acids. The sequence of amino
acids in each chain is unique and plays a critical role in determining the structure
and function of the hemoglobin molecule.
a)
Fibrous Protein: Fibrous proteins are a class of proteins
that have a long and narrow shape, typically composed
of repeating units of secondary structures such as alpha-helices
or beta-sheets.
·
They are insoluble in water.
·
Play a structural role in cells
and tissues.
·
They are non-crystalline and Elastic in nature.
·
Examples of fibrous
proteins: Spidroin (proteins in spider silk), Collagen, Myosin,
and Keratin etc.
b)
·
They are soluble in salt, acid or
base containing aqueous medium or alcohol.
·
They are crystalline in nature.
·
These are either Tertiary or Quaternary
structures.
·
Examples of globular
proteins: Enzymes, Antibodies, and Transport Proteins
(such as hemoglobin).
·
Structural Proteins: Structural
proteins are a class of proteins that play a crucial role in providing physical
support and shape to cells and tissues. Some examples of structural proteins
include:
·
Actin: A globular protein that plays a key role in
cell movement and contraction, as well as in maintaining the shape and
structure of cells.
· Amyloid: A group of fibrous proteins that accumulate
in tissues and organs, leading to various diseases such as Alzheimer's and
Parkinson's disease.
· Fibroin (Caddisfly Silk): Caddisfly silk is a structural protein that
is used by the larvae of caddisflies to construct their protective cases. It is
a fibrous protein that is similar to silk produced by spiders and silkworms,
but has unique properties that make it suitable for the caddisfly larvae's
specific needs.
· Chondrocalcin: A protein found in cartilage that plays a
role in maintaining the strength and elasticity of cartilage tissue.
·
· Elastin: A fibrous protein that provides elasticity
and resilience to tissues such as skin, lungs, and blood vessels.
· Fibrillin: A glycoprotein that forms microfibrils in
connective tissue and plays a key role in elastic fiber formation and
maintenance.
· Gelatin: A protein derived from collagen, gelatin is
commonly used in food and pharmaceutical industries as a gelling agent.
· Sclera Protein: A collagen-like protein found in the sclera,
or the white outer layer of the eyeball, that provides strength and support to
the eye.
· Titin:
The largest known protein, titin provides elasticity and
resilience to muscle fibers and helps maintain their structural integrity.
· Tubulin: A protein that forms microtubules, which play
a key role in maintaining cell shape and structure, as well as in cell
division.
· Keratin: A fibrous protein found in hair, nails,
horns, and feathers, keratin provides strength and protection to these
structures.
Functional Proteins: Functional proteins are a class of proteins that perform specific
functions in living organisms, often related to their structure
and shape. These proteins can have a wide range
of functions, including catalyzing chemical reactions,
transporting molecules across membranes, signaling within
cells and between cells, and providing mechanical
support or movement.
Examples of functional
proteins include:
Enzymes: Proteins that catalyze chemical
reactions in the body, such as digestive enzymes, which break
down food in the digestive system, and metabolic enzymes,
which help to synthesize and break down molecules
within cells. e.g., amylase, lipase, pepsin, and trypsin.
Hormones: Signaling molecules
that regulate physiological processes in the body, such as
insulin, which regulates glucose metabolism, and growth
hormone, which regulates growth and development.
Transport proteins: Proteins that transport molecules across cell
membranes and within the body, such as hemoglobin,
which transports oxygen in the blood, and transferrin,
which transports iron.
Structural proteins: Proteins that provide support and structure to cells
and tissues, such as collagen, which is found in connective
tissues, and keratin, which makes up hair, nails,
and skin.
Contractile proteins: Proteins that enable muscle contraction, such as actin
and myosin.
Immunoglobulins: Antibodies that help to defend the body against
foreign substances and pathogens.
1.5 LIPIDS
Lipids are a diverse group of
biomolecules that include fats, oils, waxes, sterols,
and phospholipids. They are composed of carbon, hydrogen,
and oxygen atoms, and are characterized by their insolubility in water
(hydrophobic nature). Lipids are essential components
of cell membranes, where they provide structural support
and regulate cell permeability. They are also important
for energy storage, as they are highly concentrated
sources of energy, and play a role in the production of
hormones and other signaling molecules. Lipids can be classified into several
subcategories, including triglycerides, phospholipids, and steroids.
·
Lipids are organic compounds.
·
They contain almost double amount
of energy than carbohydrates (due to high amount of
Carbon & Hydrogen).
·
They dissolve easily in a nonpolar
solvent (e.g., ether) but do not in a
polar solvent (e.g., water).
·
It is usually made up of glycerol or fatty
acid units, with or without other types of biomolecules.
·
Many lipids are amphiphilic or amphipathic,
meaning they have both hydrophobic and hydrophilic components.
Acylglycerol (Fats & Oils): Acylglycerols, also known as fats and oils, are a type of
lipid that are essential for many biological processes. They are esters that
are formed when glycerol reacts with three fatty acids.
Fatty acids can be either saturated or unsaturated. The
fatty acid chains in acylglycerols are attached to the glycerol backbone via ester
linkages, which are formed through a condensation reaction
between the carboxylic acid group of the fatty acid
and the hydroxyl group of the glycerol.
·
Fats and oils
are examples of acylglycerols that differ in their physical properties
due to differences in their fatty acid composition
and degree of saturation.
a)
Saturated Acylglycerol (Fats): Saturated
acylglycerols, also known as saturated fats, are a type of
acylglycerol molecule that contains only saturated fatty acid
chains. These fatty acids are typically solid at room
temperature and are commonly found in animal products such
as meat, dairy, and eggs, as well as in some plant-based
sources such as coconut and palm oil.
·
b)
Unsaturated Acylglycerol (Oils): Unsaturated acylglycerol, commonly referred to as oils,
are lipids composed of a glycerol molecule bonded with three
fatty acids, where one or more of the fatty acids
contain one or more double bonds between
their carbon atoms. The double bonds cause a link in the fatty
acid chain, which makes it difficult for the fatty acids to pack together
tightly. This results in oils being liquid at room
temperature, unlike fats, which are usually solid.
·
Unsaturated acylglycerols can be further
classified as monounsaturated, if there is only one double
bond, or polyunsaturated, if there are two or more double
bonds in the fatty acids.
·
Examples of unsaturated acylglycerols include
olive oil, canola oil, and fish oil, all of which are sources
of essential fatty acids that the human body cannot
synthesize on its own.
·
A person of average sizes contains approximately
16kg of fat which contains 1.44x105 kcal of energy.
a)
b)
Terpenoids: Terpenoids are natural compounds found in plants
and some animals. They are responsible for the smells and flavors
of many plants and fruits. Terpenoids also help plants defend against
pests and diseases. They are used in perfumes, essential
oils, and flavorings, and some have medicinal properties.
Examples of terpenoids include the cooling sensation of menthol
in peppermint and the citrusy smell of limonene in citrus
fruits.
·
They are made up of isoprenoids units
(C5H8).
·
Terpenoids, Steroids,
Carotenoids, and Prostaglandins are types of Terpenoids.
a) Terpenes:
Terpenes are special
compounds found in plants that have a strong smell. They are made up of smaller
parts called isoprene units. Some examples of terpenes are diterpenes and
triterpenes. These terpenes have a nice fragrance and can be found in different
plants.
Diterpenes, which are made up of two isoprene units, give pine trees their fresh,
woody smell. When you walk through a forest and smell that wonderful pine
scent, you can thank diterpenes for it!
Triterpenes, on the other hand, have six isoprene units
and are found in many plants, like flowers and herbs. They are responsible for
the pleasant smells you might experience in a garden or when you rub certain
plants between your fingers.
·
Terpenes not only smell great, but they can
also have some health benefits.
·
Some terpenes have anti-inflammatory
properties, which means they can help reduce swelling and pain.
·
Others have antimicrobial effects, which
means they can fight against harmful bacteria.
·
Scientists are even studying terpenes to see
if they can be used to treat diseases like cancer.
b)
Steroids are a type of organic
compounds that have a special structure consisting of four
interconnected rings of carbon atoms. They are
found in both plants and animals.
·
Steroids have a unique structure called a
steroid nucleus.
·
This nucleus is made up of four
interconnected rings of carbon atoms.
·
|
Steroid Skeleton |
·
·
·
Cholesterol is a well-known example of a
steroid. It is found in animal cell membranes and has important functions in
the body.
·
c) Carotenoids:
Carotenoids are a group of
organic compounds that belong to the class of polyterpenes. They are composed
of a long chain of isoprenoid units and typically contain isoprenoid rings at
one or both ends of the chain. Carotenoids are responsible for producing red,
orange, yellow, and brown colors in plants, and they serve as important
pigments.
·
Carotenoids play a vital role in
photosynthesis, where they work alongside chlorophyll to capture light energy
and convert it into chemical energy.
·
They also act as antioxidants, helping to
protect plants from damage caused by sunlight and other environmental factors.
·
Some well-known carotenoids include beta-carotene,
lycopene, and lutein, which are found in various fruits,
vegetables, and plant-based foods.
d) Prostaglandins:
Prostaglandins are a
special group of lipids that are produced by our body's tissues when there is
damage or infection. They act like messengers and help the body deal with
injuries and illnesses. Prostaglandins have important roles in controlling
different processes in our body.
·
They play a role in inflammation.
·
When there is inflammation, prostaglandins
are released to help regulate the process and control the body's response. They
can either promote or reduce inflammation, depending on what is needed.
·
Prostaglandins also affect the intensity of
pain sensation. They can make us feel more pain or help to decrease it,
depending on the situation.
·
Additionally, they have an impact on blood
flow and can affect the formation of blood clots, which is important for wound
healing and preventing excessive bleeding.
·
Prostaglandins are involved in our immune
system's response, helping to regulate the body's defense mechanisms against
infections and diseases.
·
They also play a role in the induction of
labor, helping to trigger the process of childbirth.
1.6 NUCLEIC ACIDS
Nucleic acids are essential biomolecules found in
all living organisms. They play a fundamental role in storing, transmitting,
and expressing genetic information. Nucleic acids are made up of building
blocks called nucleotides, which are composed of a sugar molecule, a phosphate
group, and a nitrogenous base. The two main types of nucleic acids are
deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA carries the genetic
instructions for the development and functioning of an organism, while RNA is
involved in translating and expressing those instructions.
·
Lipids Nucleic acids are involved in the
preservation, replication, and expression of hereditary information in every
living cell.
Phosphate group: Nucleotides also contain a phosphate group, which is attached at 5th
carbon of the sugar molecule. The phosphate group plays a crucial role in the
linkage between nucleotides, forming the backbone of the nucleic acid chain.
Sugar molecule: Nucleotides contain a sugar molecule, which is a pentose sugar. In DNA,
the sugar is deoxyribose (C5H10O4),
while in RNA, the sugar is ribose (C5H10O5).
The sugar molecule provides the backbone structure for the nucleotide.
Nitrogenous base: Nucleotides have a nitrogenous base attached to the sugar molecule.
There are four different nitrogenous bases found in DNA: adenine (A), cytosine
(C), guanine (G), and thymine (T). In RNA, thymine is replaced by uracil (U).
The specific arrangement of these bases along the nucleic acid chain encodes
the genetic information.
a) Formation of
Phosphodiester Bond:
Phosphodiester bonds are
formed due to the reaction in between the hydroxyl groups of two sugar groups
and a phosphate group and thus, oligonucleotide polymers are formed as the
result of a combination of the diester bond in the phosphoric acid and the sugar
molecules present in the DNA and RNA backbone.
Polynucleotide: A
polynucleotide is a long chain or polymer made up of nucleotides. Nucleotides
are the building blocks of nucleic acids like DNA and RNA. In a polynucleotide,
nucleotides are joined together in a specific sequence to form a continuous
chain. Polynucleotides,
such as DNA and RNA, play crucial roles in living organisms. DNA carries
genetic information and is responsible for the transmission of hereditary
traits from one generation to another. It serves as a blueprint for the
synthesis of proteins and other molecules necessary for life.
Structure of DNA: DNA, or
deoxyribonucleic acid, is a double helical structure that carries genetic
information in living organisms. Let's
study its structure:
·
Double Helix: DNA is made up of two strands that twist
around each other, forming a shape similar to a twisted ladder or a spiral
staircase. This shape is called a double helix.
·
Nucleotides: Each strand of the DNA helix is made up of
smaller units called nucleotides. There are four types of nucleotides in DNA:
adenine (A), thymine (T), cytosine (C), and guanine (G). These nucleotides act
like the "letters" of the genetic code.
·
Complementary
Base Pairing: The two
strands of DNA are complementary to each other, meaning they fit together like
puzzle pieces. Adenine always pairs with thymine, and cytosine always pairs
with guanine. This pairing is held together by hydrogen bonds, which are like
tiny "glue" bonds between the nucleotides.
·
Structure of
Each Strand: Each
strand of the DNA helix has two parts. The upright part is made up of
deoxyribose sugars and phosphate molecules, forming a backbone that provides
stability to the DNA molecule. The rungs of the helix are made up of the
nitrogenous bases (A, T, C, G), which form the "steps" of the ladder.
These nitrogenous bases interact with each other through hydrogen bonds.
·
Opposite
Directions: The two
strands of the DNA helix run in opposite directions. One strand runs from the
5' end to the 3' end (downward), while the other strand runs from the 3' end to
the 5' end (upward). This arrangement is called antiparallel.
·
Distance and
Stability: The distance
between the two strands of the DNA helix remains consistent throughout the
molecule, measuring about 20 angstroms. Each turn of the duplex consists of 10
base pairs, meaning there are 10 pairs of nucleotides in one complete twist of
the double helix. This stable distance and base pairing provide structural
stability to the DNA molecule.
The flow of genetic information within a cell occurs
through two main steps: Transcription and Translation.
a)
b) Translation: Translation is the process of converting mRNA into proteins at the
ribosomes. It involves reading the genetic code and assembling amino acids to
form a protein.
v The ribosomes read the mRNA codons, which are three-letter sequences of
nucleotides, and match them with the corresponding transfer RNA (tRNA)
molecules carrying specific amino acids. The ribosomes catalyze the formation
of peptide bonds between the amino acids, ultimately creating a chain of amino
acids called a polypeptide or protein.
v DNA is a heredity material, while RNA helps in protein synthesis.
There are three types of RNA.
a)
b)
c)
1.7 CONJUGATED MOLECULES
Conjugated molecules are formed when different
types of biomolecules join together chemically to create a single unit. They
include compounds like glycolipids, glycoproteins, lipoproteins, and
nucleoproteins. These molecules have unique properties and functions that arise
from the combination of their constituent biomolecules.
Glycolipids (Cerebrosides): Glycolipids,
also known as cerebrosides, are molecules formed by the combination of lipids
and carbohydrates. They are called cerebrosides because they are found in the
white matter of the brain and the myelin sheath of nerve fibers. They are also
present in the inner membrane of chloroplasts. Glycolipids play important roles
in cell recognition, cell signaling, and maintaining the integrity of cell
membranes.
Lipoproteins: Lipoproteins
are molecules that combine lipids (fats) and proteins. They play a key role in
carrying lipids in the bloodstream and are also found in various cellular
membranes. They help transport lipids and are important components of
structures like mitochondria, endoplasmic reticulum, nucleus, egg yolk, and
chloroplast membranes.