Carbohydrates are macronutrients and are one of the three main ways by which our body obtains its energy. They are called carbohydrates as they comprise carbon, hydrogen and oxygen at their chemical level. Carbohydrates are essential nutrients which include sugars, fibers and starches. They are found in grains, vegetables, fruits and in milk and other dairy products. They are the basic food groups which play an important role in a healthy life.
The food containing carbohydrates are converted into glucose or blood sugar during the process of digestion by the digestive system.
Our body utilizes this sugar as a source of energy for the cells, organs and tissues. The extra amount of energy or sugar is stored in our muscles and liver for further requirement. The term ‘carbohydrate’ is derived from a French term ‘hydrate de carbone‘ meaning ‘hydrate of carbon‘. The general formula of this class of organic compounds is Cn(H2O)n.
he carbohydrates are further classified into simple and complex which is mainly based on their chemical structure and degree of polymerization.
Complex Carbohydrates (Polysaccharides)
Complex carbohydrates have two or more sugar molecules, hence they are referred to as starchy foods. In complex carbohydrates, molecules are digested and converted slowly compared to simple carbohydrates.
Functions of Carbohydrates
The main function of carbohydrates is to provide energy and food to the body and to the nervous system.
Carbohydrates are known as one of the basic components of food, including sugars, starch, and fibre which are abundantly found in grains, fruits and milk products.
Carbohydrates are also known as starch, simple sugars, complex carbohydrates and so on.
It is also involved in fat metabolism and prevents ketosis.
Inhibits the breakdown of proteins for energy as they are the primary source of energy.
An enzyme by name amylase assists in the breakdown of starch into glucose, finally to produce energy for metabolism.
Sources of Carbohydrates
Simple sugars are found in the form of fructose in many fruits.
Galactose is present in all dairy products.
Lactose is abundantly found in milk and other dairy products.
Maltose is present in cereal, beer, potatoes, processed cheese, pasta, etc.
Sucrose is naturally obtained from sugar and honey containing small amounts of vitamins and minerals.
Examples of Carbohydrates
Following are the important examples of carbohydrates:
Glucose
Galactose
Maltose
Fructose
Sucrose
Lactose
Starch
Cellulose
Chitin
Carbohydrate Foods
Eating too much sugar results in an abnormal increase in calories, which finally leads to obesity and in turn low calories leads to malnutrition. Therefore, a well-balanced diet needs to be maintained to have a healthy life. That is the reason a balanced diet is stressed so much by dietitians.
These simple sugars that consist of minerals and vitamins exist commonly in milk, fruits, and vegetables. Many refined and other processed foods like white flour.
2. CARBOHYDRATE
Definition:
Carbohydrates are polyhydroxy aldehydes or
ketones, or substances that yield such compounds
on hydrolysis.
• carbohydrates have the empirical formula
(CH O)n.
2
ALDEHYDE
GROUP
KETO
GROUP
GLUCOSE
C 6H12O6
FRUCTOSE
C6H12O6
4. MONOSACCHARIDES:
• These are simplest carbohydrate and cannot be
hydrolyzed further into smaller carbohydrate
molecules
• Some monosaccharide have general formula C H O
n 2n n
GLUCOSE
C 6H12O6
FRUCTOSE
C6H12O6
RIBOSE
C5H10O5
SEDOHEPTULOSE
C7H14O7
GLYCERALDEHYDE
C3H6O3
6. ISOMERISM
ALDOSE – KETOSE ISOMERISM
• ALDOSE SUGAR
Aldose are monosaccharide
bearing an aldehyde (CHO) group.
Example
GLUCOSE,GALACTOSE,MANNOSE
• KETOSE SUGAR
Ketose are monosaccharide
bearing an keto(C=O) group.
EXAMPLE- FRUCTOSE,RIBULOSE
GLUCOSE
C 6H12O6
FRUCTOSE
C6H12O6
7. D&L STEREOISOMER
• D- ISOMER
D isomer is right side
orientation of OH group on
asymmetric carbon i.e.
farthest from aldehyde or
kenyl group and nearest to
terminal carbon
• L- ISOMER
L isomer is left side
orientation of OH group on
asymmetric carbon. Mirror
image of D isomer.
9. PYRANOSE AND FURANOSE RING
• Monosaccharide forms 6 member ring (5 carbon
and1 oxygen) and 5 member ring (4 carbon and 1
oxygen) that is called respectively pyranose and
furanose ring
10. ANOMERISM
• Isomer that differ on position of OH group
around anomeric carbon when ring is formed.
11. MUTAROTATION
• When pure alpha and beta anomers are dissolved in
a solvent their measured specific rotation will change
over time untill converging on an intermediate value.
this is called mutarotation and it is occur only on
reducing sugar.
+52.7
12. DISACCHARIDES
• Disaccharides are made up of two monosaccharides
joined together by a condensation reaction.
2.1
glycoside
bond
.1,4
glycoside
bond
1,4
glycoside
bond
14. Polysaccharides
• Polysaccharides contain hundreds or thousands of
carbohydrate units connected through glycosidic linkages.
• Nomenclature:
• Homopolysaccharide- a polysaccharide is made up of one
type of monosaccharide unit. Starch , glycogen etc
• Heteropolysaccharide- a polysaccharide is made up of
more than one type of monosaccharide unit. Heparin
15. • STARCH made up of long chains of α-glucose (Amylose and Amylopectin).
DEXTRIN is pertially hydrolyzed product of starch.GLYCOGEN is made of α-
glucose linked together by glycosidic bonds. Cellulose is also made of
many β-glucose molecules linked by glycosidic bonds between carbon 1
and carbon 4.
Starch is the main energy storage materials in plants. Glycogen is the main
energy storage materials in animals. Cellulose is the major component of
cell walls in plants.
.1,4
glycoside
bond
1,4 and 1,6
glycoside bond
1,4 and 1,6
glycoside bond
16. Reaction of Carbohydrate
REDUCING PROPERTY
• Sugar is classified as reducing sugar and non reducing
sugar because reducinfg property is attributed to
free aldehyde and keto group. The test is used for
that property is BENEDICT TEST, FEHLING’S TEST
etc.
20. IMPORTANCE
• Carbohydrates are chief energy source, in many animals, they are instant
source of energy. Glucose is broken down by glycolysis/ kreb's cycle to yield
ATP.
• Glucose is the source of storage of energy. It is stored as glycogen in animals
and starch in plants.
• Stored carbohydrates acts as energy source instead of proteins.
• Carbohydrates are intermediates in biosynthesis of fats and proteins.
• Carbohydrates aid in regulation of nerve tissue and is the energy source for
brain.
• Carbohydrates gets associated with lipids and proteins to form surface
antigens, receptor molecules, vitamins and antibiotics.
• They form structural and protective components, like in cell wall of plants and
microorganisms.
• In animals they are important constituent of connective tissues.
• They participate in biological transport, cell-cell communication and activation
of growth factors.
• Carbohydrates that are rich in fibre content help to prevent constipation.
• Also they help in modulation of immune system
