SECTION A

Mannose is an important component of the oligosaccharides that are found in glyco-proteins. As it is a minor component in the diet, mannose enters the glycolytic pathway as fructose-6-phosphate.

The galactose and glucose have similar structures; that is, they are epimerase. Several reactions are required for this sugar to enter the glycolytic pathway. Galactose is initially converted to galactose-1-phosphate by galactokinase. The galactose-1-phosphate is transformed into the nucleotide derivative UDP galactose. During fetal development and childhood, the first step in this conversion is catalysed…

Dietary sources of fructose include fruit, honey, and the disaccharide sucrose. Fructose is a significant source of carbohydrate in the human diet. It can enter the glycolytic pathway by two routes. In liver, fructose is converted to fructose-1-phosphate by fructose kinase. When fructose-1-phosphate enters the flycolytic pathway, it is first split into dihydroxyacetone phosphate (DHAP)…

Many other sugars are consumed by human beings. They are fructose, galactose, and mannose. Beside glucose, fructose, galactose, and mannose are the most common sugars found in oligosaccharides and polysaccharides. They are also energy sources. The reactions by which these sugars are converted into glycolytic intermediates are shown in the following pathways.

In the liver, glucose is converted to glucuronic acid and ascorbic acid (except in human beings and other species in which ascorbate and pentose are produced) through uronic acid pathway. It is also considered as an alternative pathway that does not lead to the formation of ATP. Glucose 6-phosphate reacts with uridine triose phosphate to…

Fructose 2,6-bisphosphate plays a unique role in regulation of gluconeogenesis in liver. The concentration of the blood glucose is regulated within narrow limits. Since glycolysis and gluconeogenesis share the same pathway but operate in opposite directions, their activities are regulated reciprocally. The pathway of gluconeogenesis in liver and kidney utilises those reactions in glycolysis, which…

There is a continuous transport of amino acids from muscle to liver, which predominantly occurs during starvation. Alanine dominates among the amino acids. It is postulated that pyruvate in skeletal muscle undergoes transamination to produce alanine. Alanine is transported to liver and used for gluconeogenesis. This cycle is referred to as Glucose Alanine Cycle (Figure…