Govt Exams
NADPH from the oxidative pentose phosphate pathway is essential for reductive biosynthesis of fatty acids and cholesterol, which occur predominantly in the fed state.
HFI results from aldolase B deficiency, preventing cleavage of fructose-1-phosphate into DHAP and glyceraldehyde, leading to accumulation and hepatotoxicity.
Von Gierke disease (GSD Type I) results from glucose-6-phosphatase deficiency, preventing final step of both gluconeogenesis and glycogenolysis, causing severe hypoglycemia.
Liver glycogen maintains blood glucose but cannot directly supply glucose-6-phosphate to other tissues as glucose-6-phosphate cannot cross cell membranes.
Muscle glycogen is the primary energy source during high-intensity exercise because muscle lacks glucose-6-phosphatase and retains glucose-6-phosphate for glycolysis.
Branching enzyme (amylo-1,6-transglucosidase) transfers segments of α-1,4-linked glucose chains to create α-1,6 branch points in glycogen.
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.