Carbohydrates

Chapter # 21
XII FDC
Prepared by: Sidra Javed

 The branch of science concerned with the
chemical and physico-chemical
processes and substances which occur
within living organisms.
 It attempts to describe in molecular terms
the structure, mechanisms and Chemical
processes shared by all organism.

MACROMOLECULES
 A molecule of high relative molecular mass,
the structure of which essentially
comprises the multiple repetition of units
derived, actually or conceptually, from
molecules of low relative molecular mass.
 The most common macromolecules
in biochemistry are biopolymers (nucleic
acids, proteins, carbohydrates and
polyphenols) and large non-polymeric
molecules (such as lipids and macrocycles).

CARBOHYDRATES
 A carbohydrate is a biological
molecule consisting
of carbon (C), hydrogen(H)
and oxygen (O) atoms, usually with a
hydrogen–oxygen atom ratio of 2:1 (as in
water); in other words, with the empirical
formula Cm(H2O)n (where m could be
different from n).

 All organic compound containing
hydrogen and oxygen in the
proportion of 2:1 are not
carbohydrates. For example:
i) Formaldehyde -HCHO =C(H2O)
ii) Acetic acid -CH3 COOH
=C2(H2O)2
 Carbohydrates are Polyhydroxy
compounds of aldehydes and
ketones.

ROLE OF CARBOHYDRATE
Energy stores, fuels and
metabolic intermediaries.
Ribose and deoxyribose
sugars are part of the
structural framework of RNA
and DNA.

ROLE OF CARBOHYDRATE
Formation of bacterial and plant
cell wall.
Linked with proteins and lipids
and involved in many
interactions.

CLASSIFICATION

MONOSACCHARIDES
 Monosaccharides; also called simple
sugars, are the most basic units of
carbohydrates.
 They are fundamental units of
carbohydrates and cannot be further
hydrolyzed to simpler compounds.
 The general formula is CnH2nOn.

 Glucose is a major source of energy for
cell.
 Glucose is naturally in honey and corns.

STRUCTURE OF GLUCOSE

 Fructose is found mostly in vegetables
and fruits such as grapes.

STRUCTURE OF FRUCTOSE

 Galactose can be found most readily in
milk and dairy products

 Monosaccharides can be further classified
by the number of carbon atoms.
NUMBER OF CARBON ATOMS
Six = Hexose Five = Pentose Three = Triose
Glucose Ribose Glyceraldehydes
Galactose
Fructose

DISACCHARIDES
 Two monosaccharide molecules are
bounded together to form
Disaccharide.

Sucrose is found in sugarcane, pineapples,
mangoes, beet root, apricots and many other
fruits & vegetables

Lactose is found in milk, yogurt & cheese.

Maltose is a component of malt. It is found in
beverages, beer, cereal, pasta, potatoes etc.

HOW THE MONOSACCHARIDES
COMBINE TOGETHER?
 The OH group of monsaccharides act
as alcohol.
 It forms a glycosidic linkage with the
Hemiacetal group of second
monosaccharide molecule.
 In this way a glucoside is produced
which is called a Disaccharide.

 Disaccharides are the acetals which are
formed from two monosaccharides by the
elimination of one molecule of water.

POLYSACCHARIDES
 The carbohydrates producing large
number of monosaccharide on
hydrolysis are called Polysaccharides.

 A polysaccharide is a chain of two
monosaccharides.
 The chain may be branched or
unbranched.
 Polysachharides chains are made up
of hundreds or thousands of
monosaccharides.
 A polysaccharide is a polymer and a
monosaccharide is a monomer.

Starch is found mainly in corn, bread,
potatoes, cereals etc.

Glycogen is the stored form of excess blood
glucose in humans and other animals.

Cellulose is found in cell wall of all plants.

GLYCEMIC INDEX
“The glycemic index ranks foods on how
they affect blood sugar level by measuring
how much the blood sugar increases after
one eats.”

FUNCTIONS OF CARBOHYDRATES
1. They spare protein so that protein can
concentrate on building, repairing and
maintaining body tissue instead of being
used up as an energy source.
2. For fat to be metabolized properly,
carbohydrates must be present. If there are
not enough carbohydrates, then large
amounts of fat are used for energy. The
body is not able to handle this large amount
so quickly so it accumulates Ketone Bodies
which make the body acidic. This causes a
condition called ketosis. Prepared by: Sidra Javed

3. Carbohydrate is necessary for the
regulation of nerve tissue and is the only
source of energy for the brain.
4. Certain types of Carbohydrates support
the growth of healthy bacteria in the
intestine for digestion.
5. Some carbohydrates are high in fiber,
which helps prevent constipation and
lowers the risk for certain diseases such
as cancer, heart diseases and diabetes.

ROLE OF POLYSACCHARIDES
 Polysaccharides act as food stores in
plants in the form of starch, or in
humans and other animals in the form
of Glycogen.
 Polysaccharides also have structural
roles in the plant cell wall in the form
of Cellulose or Pectin, and the tough
outer skeleton of insects in the form of
Chitin.

(a) STORAGE POLYSACCHARIDES
 Glycogen – A polysaccharide that humans
and animals store in the liver and muscles.

(a) STORAGE POLYSACCHARIDES
 Starch – These are glucose polymers
made up of Amylose (10-20%) and
amylopectin (80-90%). Humans and
animals digest them by hydrolysis; our
bodies have amylases which break
them down.

(b) STRUCTURAL POLYSACCHARIDES
 Cellulose – The structural constituents of
plants are made mainly from cellulose.
Wood is mostly made of cellulose, while
paper and cotton are almost pure
cellulose.

(b) STRUCTURAL POLYSACCHARIDES
 Chitin – It is the main component of fungi
cell walls, the exoskeletons of arthropods
such as crabs, lobsters, ants, beetles and
butterflies.

(c) BACTERIAL POLYSACCHARIDES
 Found in Bacterial
capsule.
 Pathogenic bacteria
produce a thick layer
of mucous-like
Polysaccharide
which protects the
bacteria from the
host’s immune
system.

NUTRITIONAL
IMPORTANCE OF
CARBOHYDRATESPrepared by: Sidra Javed

(a) BODY WEIGHT REGULATION
 Eating a carbohydrate rich diet leads to less
fat accumulation in body.
 High carbohydrate diets have lower energy
density.
 Fiber rich foods are tends to be bulky and
physically filling.
 Carbohydrate works quickly to aid satiety
therefore over eating is unlikely.
 Diets high in carbohydrate reduce the
likelihood of developing obesity.

(b) DIABETES
 There is no evidence of link between
sugar consumption and development of
diabetes but obesity and physical inactivity
increases the risk of developing insulin
independent diabetes (Type II).
 Weight reduction is necessary for people
with Type II Diabetes.
 Low Glycemic Index foods are beneficial
as they help to regulate blood glucose
level.

(c) DENTAL HEALTH
 Tooth decay is influenced by following
factors:
◦ Degree of oral hygiene and plaque
removal carried out
◦ Availability of fluoride
◦ Type of food eaten
◦ Frequency of consumption of any
fermentable carbohydrate
◦ Genetic fators

(c) DENTAL HEALTH
 Sugar or starchy foods can be broken
down by bacteria in mouth to produce acid
which attack the enamel of the teeth.
 After an acid challenge, saliva provides a
natural repair process which rebuilds the
enamel.
 When such foods are consumed too
frequently , the natural repair process is
overwhelmed and the risk of tooth decay
is increased.

(d) GETTING ACTIVE
 Carbohydrates improve the performance of
athletes.
 During high intensity exercises, carbohydrate
are the main fuel for the muscles.
 Well stocked glycogen helps the athlete to
perform for longer and help their bodies
sustain the effort.
 Physical activity reduce the risk of diseases
such as heart attacks and diabetes.
 A well balanced high carbohydrate diet is
recommended to be fit and active.

Carbohydrates

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