The most predominant and versatile element of life. It possesses a unique property to form infinite number of compounds. This is attributed to the ability of carbon to form stable covalent bonds and C—C chains of unlimited length. It is estimated that about 90% of compounds found in living system invariably contain carbon.
The most abundant organic molecules in nature. They are primarily composed of the elements carbon, hydrogen and oxygen. The name carbohydrate literally means 'hydrates of carbon.' Carbohydrates may be defined as polyhydroxy- aldehydes or ketones or compounds which produce them on hydrolysis.
The simplest group of carbohydrates and are often referred to as simple sugars. They have the general formula Cn(H2O)n, and they cannot be further hydrolysed.
An important character of monosaccharides. Stereoisomers are the compounds that have the same structural formulae but differ in their spatial configuration.
The simplest monosaccharide with one asymmetric carbon atom. It exists as two stereoisomers, and has been chosen as the reference carbohydrate to represent the structure of all other carbohydrates.
Mirror images of each other. The special orientation of —H and —OH groups on the carbon atom (C5 for glucose) that is adjacent to the terminal primary alcohol carbon determines whether the sugar is D- or L-isomer.
A characteristic feature of compounds with asymmetric carbon atom. When a beam of polarized light is passed through a solution of an optical isomer, it will be rotated either to the right or left.
Formed when the hemiacetal or hemiketal hydroxyl group (of anomeric carbon) of a carbohydrate reacts with a hydroxyl group of another carbohydrate or a non-carbohydrate (e.g. methyl alcohol, phenol, and glycerol). The bond so formed is known as glycosidic bond and the non- carbohydrate moiety (when present) is referred to as aglycone.
The carbohydrate reserve of plants which is the most important dietary source for higher animals, including man. It is a homopolymer composed of D-glucose units held by α glycosidic bonds. It consists of two polysaccharide components-water soluble amylose (15-20%) and a water insoluble amylopectin (80-85%).
The carbohydrate reserve in animals, hence often referred to as animal starch. It is present in high concentration in liver, followed by muscle, brain etc. The structure of glycogen is similar to that of amylopectin with more number of branches.
Occurs exclusively in plants and it is the most abundant organic substance in plant kingdom. It is a predominant constituent of plant cell wall. Cellulose is composed of β-D-glucose units linked by β (1 → 4) glycosidic bonds. Cellulose cannot be digested by mammals—including man—due to lack of the enzyme that cleaves β-glycosidic bonds.
Heteroglycans made up of repeating units of sugar derivatives, namely amino sugars and uronic acids. They are more commonly known as glycosaminoglycan's (GAG). Acetylated amino groups, besides sulfate and carboxyl groups are generally present in GAG structure.
Organic substances relatively insoluble in water, soluble in organic solvents (alcohol, ether etc.), actually or potentially related to fatty acids and utilized by the living cells