JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Pharmacy II Year BIOCHEMISTRY Previous Question Paper (December-2019 - R17)

The citric acid cycle (Krebs cycle) yields a total of 12 ATP molecules per acetyl-CoA molecule oxidized. This is derived from 3 NADH (9 ATP), 1 FADH₂ (2 ATP), and 1 GTP/ATP produced via substrate-level phosphorylation (1 ATP). The cycle is significant as it serves as the final common pathway for the oxidation of carbohydrates, lipids, and proteins, provides essential precursors for the biosynthesis of amino acids and porphyrins, and acts as the primary source of reducing equivalents for the electron transport chain.

Diabetes mellitus is primarily regulated by the antagonistic actions of insulin and glucagon, which maintain blood glucose homeostasis. In a healthy state, insulin is secreted by the beta cells of the pancreas in response to high blood glucose, promoting glucose uptake into cells and glycogenesis, thereby lowering blood sugar. Glucagon is secreted by alpha cells during hypoglycemia to stimulate glycogenolysis and gluconeogenesis, raising blood glucose levels.

In Type 1 Diabetes Mellitus, the autoimmune destruction of beta cells leads to an absolute deficiency of insulin, preventing glucose entry into peripheral tissues and resulting in hyperglycemia. In Type 2 Diabetes Mellitus, the hormonal regulation is disrupted by peripheral insulin resistance, where target cells fail to respond to insulin despite its presence. This leads to a compensatory but insufficient increase in insulin secretion, eventually causing pancreatic beta-cell exhaustion and chronic hyperglycemia.