Govt. Exams
Entrance Exams
Classical galactosemia results from galactose-1-phosphate uridyltransferase (GALT) deficiency, causing accumulation of galactose-1-phosphate and galactosylated proteins.
Glucose-1-phosphate is converted to UDP-glucose by UDP-glucose pyrophosphorylase, which is the activated form used by glycogen synthase for glycogen synthesis.
Von Gierke disease (GSD Type I) involves glucose-6-phosphatase deficiency, leading to impaired glucose release. However, alternative glucose production through gluconeogenesis and pentose phosphate pathway increases.
Glycogen has more frequent α-1,6 branch points (approximately every 8-12 glucose units) compared to starch, increasing its solubility and accessibility for enzyme action.
NADP+ is reduced to NADPH in the oxidative phase of the pentose phosphate pathway, primarily in the G6PD and 6-PGD reactions.
Pompe disease results from deficiency of acid α-glucosidase (lysosomal α-1,4-glucosidase), leading to accumulation of glycogen in lysosomes, especially in muscles and heart.
Under anaerobic conditions, pyruvate is reduced to lactate by lactate dehydrogenase (LDH) to regenerate NAD+ for continued glycolysis.
During exercise, epinephrine increases and ATP/AMP ratio decreases, both of which activate phosphorylase kinase and promote glycogenolysis.
Acetyl-CoA condenses with oxaloacetate to form citrate, which enters the citric acid cycle. Citrate synthase catalyzes this reaction.
Glycogen's highly branched structure with α-1,6-branch points every 8-12 glucose residues increases its solubility, provides multiple substrate sites for glycogen phosphorylase simultaneously, and enables rapid glucose mobilization during energy demands. This is metabolically superior to linear polymers.
