Bke2 Biochemistry Lectures

Lecture 12: Carbohydrates, vitamins, glycolysis
Reading material: Horton, Chapters (7, 8), 12

Abstract:
Carbohydrates
Carbohydrates are the most abundant biomolecules on earth. Certain carbohydrates are staple of the human and animal diet, and the oxidation of carbohydrates is the central energy-yielding pathway in most nonphotosyntetic cells.
There are three major classes of carbohydrates: 1) monosaccharides, or simple sugars, consist of a singel polyhydroxy aldehyd or ketone unit. 2) Oligosaccharides consist of short chains of monosaccharide units joined together with glycosid linkages. The most abundant oligosaccharides are the disaccharides, with two monosaccharide units. 3) Polysaccharides consist of long chains having hundreds or more of monosaccharides units. Some polysaccharides, such as e.g. cellulose, have linear chains of monosaccharides , whereas others, glycogen for example, have branched chains.

Glycolysis
Glycolysis is a universal metabolic pathway for the catabolic conversion of glucose to pyruvate accompanied by the formation of ATP. The process is catalysed by ten cytosolic enzymes, and all of the intermediates are phosphorylated compounds. There is a net gain of two ATP and 2 NADH per oxidised glucose. Under aerobic conditions, electrons pass from NADH to O₂ through the respiratory chain. The NADH formed in glycolysis must be recycled to regenerate NAD⁺, which is required as electron acceptor. Under anaerobic conditions, many organisms regenerate NAD⁺ by transferring electrons from NADH to pyruvate to form lactate. A variety of hexsoses, including fructose and galactose can be funneled into glycolysis.
Phosphofructokinase is the most important enzyme for control of glycolysis. The most important factor in the regulation of glycolysis is the concentration of ATP.

Vitamins
Vitamins are small biomolecules that are needed in small amounts in the diet of higher animals. The vitamins are classified in two major groups: water soluble and fat soluble. B-vitamins comprise a large group of vitamins which are involved in several different biochemical reactions. One example is the enzyme complex named pyruvate dehydrogenase where four different vitamins are involved in the conversion of pyruvate to acetyl CoA .

Key concepts:

Links:
The MIT hypertext book: Glycolysis

Lecture index

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