carbohydrates

2. INTRODUCTION
• Carbohydrates are the most abundant organic molecules in nature and the
major functional constituents of living cells.
• carbohydrates have the empirical formula (CHO)n.
•Carbohydrates, along with lipids, proteins, nucleic acids, and other compounds
are known as biomolecules because they are closely associated with living
organisms.
•Carbohydrates, or saccharides(saccharo is Greek for “sugar”) are polyhydroxy
aldehydes or ketones, or substances that yield such compounds on hydrolysis.
•The term “carbohydrate” comes from the observation that when you heat
sugars, you get carbon and water (hence, hydrate of carbon).
• They are primarily produced by plants and form a very large group of naturally
occurring organic substances.

3. General properties of carbohydrates
• Carbohydrates act as energy reserves, also stores fuels, and metabolic
intermediates.
• Ribose and deoxyribose sugars forms the structural frame of the genetic material,
RNA and DNA.
• Polysaccharides like cellulose are the structural elements in the cell walls of
bacteria and plants.
• Carbohydrates are linked to proteins and lipids that play important roles in cell
interactions.
• Carbohydrates are organic compounds, they are aldehydes or ketones with many
hydroxyl groups.

5. Physical Properties of Carbohydrates
• Stero isomerism - Compound shaving same structural formula but they
differ in spatial configuration. Example: Glucose has two isomers. They
are D-glucose and L-glucose.
• Optical Activity - It is the rotation of plane polarized light forming (+)
glucose and (-) glucose.
• Diastereoisomeers - It the configurational changes with regard to C2,
C3, or C4 in glucose. Example: Mannose, galactose.
• Anomerism - It is the spatial configuration with respect to the first
carbon atom in aldoses and second carbon atom in ketoses.

7. Biological 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.

8. Biological Importance
• 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 fiber content help to prevent constipation.
• Also they help in modulation of immune system.

9. CLASSIFICATION OF CHARBOHYDRATES

10. Monosaccharides
• The word “Monosaccharides” derived from the Greek word “Mono” means
Single and “saccharide” means sugar.
• Monosaccharides are polyhydroxy aldehydes or ketones which cannot be further
hydrolyzed to simple sugar.
• Monosaccharides are simple sugars. They are sweet in taste. They are soluble in
water. They are crystalline in nature.
• They contain 3 to 10 carbon atoms, 2 or more hydroxyl (OH) groups and one
aldehyde (CHO) or one ketone (CO) group.

11. Classification of Monosaccharides
Monosaccharides are classified in two ways.
• (a) First of all, based on the number of carbon atoms present in them
and
• (b) secondly based on the presence of carbonyl group.

12. Disaccharides
• Disaccharides are produced from the condensation of 2 monosaccharide
molecules.
• Lactose [milk sugar] is formed in the mammary gland. It is composed of
galactose and glucose.
• Maltose (Malt sugar) is composed of 2 molecules of glucose.
• Sucrose (Table sugar, Cane sugar, Beet sugar) is composed of glucose and
fructose-Sucrose: the most widely occurring disaccharide of ordinary table
sugar.

14. Oligosaccharides
• Oligosaccharides consist of short chains of monosaccharide units, or
residues, joined by characteristic linkages called glycosidic bonds.
• 3- 9 sugar molecules.
• Are not commonly found free floating in cells, but are instead attached
to lipids or proteins, especially those bound in the plasma membrane.
• Major source of energy used by brain.
• Regulate normal sugar level- hypoglycemia
• Maintain bowel functions.
• Regulates blood pressure .
• Glycoprotein and lipoproteins maintain shape of body.

16. Polysaccharides
• Polysaccharides contain hundreds or thousands of carbohydrate units.
• Polysaccharides are not reducing sugars, since the anomeric carbons
are connected through glycosidic linkages.
• Homopolysaccharide- a polysaccharide is made up of one type of
monosaccharide unit
• Heteropolysaccharide- a polysaccharide is made up of more than one
type of monosaccharide unit

18. Homopolysaccharide
• A polysaccharide that contains the same type of monosaccharides is known as a
homopolysaccharide. Some of the important homopolysaccharides are:
• Glycogen: It is made up of a large chain of molecules. It is found in animals and
fungi.
• Cellulose: The cell wall of the plants is made up of cellulose. It comprises long
chains of ꞵ-glycosides.
• Starch: It is formed by the condensation of amylose and amylopectin. It is found
largely in plants, fruits, seeds, etc.
• Inulin: It is made up of a number of fructo-furanose molecules linked together in
chains. It is found in the tubers of dahlia, artichoke, etc.
• Dextrin: These are partially hydrolyzed product of starch.

19. Starch
•Starch is a polymer consisting of D-glucose units.
•Starches (and other glucose polymers) are usually insoluble in water because of
the high molecular weight.Because they contain large numbers of OH groups,
some starches can form thick colloidal dispersions when heated in water(e.g., flour
or starch used as a thickening agent in gravies or sauces).
•There are two forms of starch: amylose and amylopectin.
• Starches(plants)
• Amylose –unbranched
• Amylopectin –branched

20. • Amylose consists of long, unbranched chains of glucose (from 1000 to
2000 molecules) connected by a(1-4) glycosidic linkages.
•10%-20% of the starch in plants is in this form.
•The amylose chain is flexible enough to allow the molecules to twist
into the shape of a helix. Because it packs more tightly, it is slower to
digest than other starches.
• Amylose helices can trap molecules of iodine, forming a characteristic
deep blue-purple color. (Iodine is often used as a test for the presence
of starch.)

21. Starch —Amylopectin
• Amylopectin consists of long chains of glucose (up to 105molecules)
connected by a(1-4) glycosidic linkages, with a(1-6) branches every 24
to 30 glucose units along the chain.
•80%-90% of the starch in plants is in this form.

22. Glycogen
• Glycogen, also known as animal starch, is structurally similar to amylopectin,
containing both a(1-4) glycosidic linkages and a(1-6) branch points. Glycogen is
even more highly branched, with branches occurring every 8 to 12 glucose units.
•Glycogen is abundant in the liver and muscles; on hydrolysis it forms D-glucose,
which maintains normal blood sugar level and provides energy.
• Glycogen (animals) –highly branched

23. Cellulose
• Cellulose is a polymer consisting of long, unbranched chains of D-glucose
connected by b(1-4) glycosidic linkages; it may contain from 300 to 3000 glucose
units in one molecule.
• Because of the b-linkages, cellulose has a different overall shape from amylose,
forming extended straight chains which hydrogen bond to each other, resulting in
a very rigid structure.
•Cellulose is the most important structural polysaccharide, and is the single most
abundant organic compound on earth. It is the material in plant cell walls that
provides strength and rigidity; wood is 50% cellulose.

24. Cellulose
• Most animals lack the enzymes needed to digest cellulose, but it does provide
roughage (dietary fiber) to stimulate contraction of the intestines and help pass
food through the digestive system.
• Some animals, such as cows, sheep, and goats (ruminants), process cellulose
using colonies of bacteria in the digestive system which are capable of breaking
down cellulose, and a series of stomachs to give cellulose a longer time to digest.
• Some other animals have a longer intestinal tract (e.g., horses), and others
reprocess digested food (e.g., rabbits) to allow more time for the breakdown of
cellulose to occur.
•Cellulose is important industrially, from its presence in wood, paper, cotton,
cellophane, rayon, linen, nitrocellulose (guncotton), photographic films (cellulose
acetate), etc.

25. Hetero-polysaccharide
• polysaccharide that contains different types of monosaccharides is known as a
heteropolysaccharide. Some of the important heteropolysaccharides are:
• Hyaluronic Acid: It is made up of D-glucuronic acid and N-acetyl-glucosamine. It
is found in connective tissues and skin.
• Heparin: It is made up of D-glucuronic acid, L-iduronic acid, N-sulfo-D-
glucosamine and is largely distributed in mast cells and blood.
• Chondroitin-4-sulfate: Its component sugars are D-glucuronic acid and N-acetyl-
D-galactosamine-4-O-sulfate. It is present in the cartilages.
• Gamma globulin: N-acetyl-hexosamine, D-mannose, D-galactose are the
component sugars of this polysaccharide. It is found in the blood.
• Keratin sulfate: glycose amino glycans, found in cornea, cartilage and bone
• Dermatan sulfate: glycose amino glycans, found in skin

26. Functions Of Polysaccharides
• The polysaccharides serve as a structural organization in animals and plants.
Other functions of polysaccharides include:
• 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.

27. FUNCTIONS OF CHO
• Provide energy: - each gram of CHO provides 4 calories
- body needs a constant energy
-stored in the liver and muscle for use as needed
- stored form is called glycogen
• protein sparing action:
• Normal fat metabolism
• Provide fiber

28. Sources of CHO
• Diary and diary products: Milk, yogurt, ice creams, etc.
• Fruits: whole fruits, fruit juices
• Grains : Rice, breads, cereals, etc.
• Legumes: Beans
• Starchy vegetables : potatoes, corn
• Sweets and Added sugars: high-fructose corn syrup or another form
of sugar for added flavor.
• Beverages: Wine, beer and liqueurs

29. Recommended Dietary Allowances
• RDA of CHO for an individual is 45-60% of daily total calories.
• If an individual takes 2000 calories a day b/w 900-1300 should be
from CHO. That translates to b/w 225-335g of carbohydrates a day