Carbohydrates презентация

BIOMEDICAL IMPORTANCE
Carbohydrates are widely distributed in plants and animals; they have important structural and metabolic roles.
In plants, glucose is synthesized from carbon dioxide and water by photosynthesis and stored as starch or used to synthesize the cellulose of the plant cell walls.
Animals can synthesize carbohydrates from amino acids, but most are derived ultimately from plants.

Glucose is the most important carbohydrate; most dietary carbohydrate is absorbed into the bloodstream as glucose formed by hydrolysis of dietary starch and disaccharides, and other sugars are converted to glucose in the liver.

Function of glucose
Glucose is the major metabolic fuel of mammals (except ruminants).
a universal fuel of the fetus.
It is the precursor for synthesis of all the other carbohydrates in the body, including glycogen for storage; ribose and deoxyribose in nucleic acids; galactose in lactose of milk, in glycolipids, and in combination with protein in glycoproteins and proteoglycans.

Diseases associated with CHO

Carbohydrates (CHO)
also called as saccharides, are most abundant biological molecules containing C, H and O, which are combined as (CH2O)n, where n is 3 or more. These may be defined as aldehyde or ketone derivatives of polyhydric alcohols.

Classification of Carbohydrates
Depending upon the number of monomeric units present in a molecule, carbohydrates are classified as :
1- Monosaccharides :
are those sugars that cannot be hydrolyzed into simpler carbohydrates.
They may be classified as trioses, tetroses, pentoses , hexoses, or heptoses, depending upon the number of carbon atoms, and as aldoses or ketoses, depending upon whether they have an aldehyde or ketone group.
2- Disaccharides are condensation products of two monosaccharide units; examples are maltose, lactose and sucrose.

3-Oligosaccharides are condensation products of three to ten monosaccharides. Most are not digested by human enzymes.
4-Polysaccharides are condensation products of more than ten monosaccharide units; examples are the starches and dextrins, which may be linear or branched polymers. Polysaccharides are sometimes classified as hexosans or pentosans, depending on the identity of the constituent monosaccharides (hexoses and pentoses, respectively). foods contain a wide variety of other polysaccharides that are collectively known as non starch polysaccharides; they are not digested by human enzymes, and are the major component of dietary fiber .Examples are cellulose from plant cell walls (a glucose polymer) and inulin, the storage carbohydrate in some plants (a fructose polymer).

Classification of Important Sugars
Trioses (C3 H6 O3 ): Trioses are smallest monosaccharides with three carbon atoms, e.g.
Glycerose (glyceraldehyde) (an aldotriose)
Dihydroxyacetone(a ketotriose)
Tetroses(C4 H8 O4 ):Tetroses have foure carbon atoms e.g.
Erythrose (aldotetrose)
Erythrulose (ketotetrose)

Pentoses (C5 H10 O5 ):Pentoses are sugars containing five carbon atoms, such as Ribose (an aldopentose)
Ribulose (a ketopentose),both of these are intermediates of the HMP
Hexoses (C6 H12 O6 ):Hexoses contain six carbon atoms, e.g.
Glucose, commonly known as dextrose, is used as source of energy in the body.
Fructose, is constituent of the common sugar, sucrose.
Galactose, is a constituent of milk sugar lactose.
Heptoses (C7 H14 O7 )
—
Sedoheptulose

Example of aldoses of physiologic significance

Example of ketoses

Structure of Glucose
The structure of glucose can be represented in three ways: straight-chain (Fischer form)
cyclic structure (Haworth projection)widely used
(a hemiacetal formed by reaction between the aldehyde group and a hydroxyl group)
Chair form

Structure of D-Glucose