Govt Exams
2,3-BPG is synthesized from 1,3-bisphosphoglycerate by bisphosphoglycerate mutase. 2,3-BPG binds to hemoglobin, decreasing its oxygen affinity, facilitating oxygen release to tissues. This shunt allows RBCs to regulate oxygen delivery without producing ATP.
The branching enzyme (amylo-1,6-transglucosidase) transfers segments of α-1,4-linked glucose to create α-1,6-branch points, making glycogen more soluble and accessible. Its deficiency causes Andersen disease with abnormal glycogen accumulation.
GLUT4 is the insulin-dependent glucose transporter found primarily in skeletal muscle and adipose tissue. Impaired GLUT4 translocation or function is a hallmark of type 2 diabetes, leading to reduced muscle glucose uptake.
Both phosphoglycerate kinase (1,3-bisphosphoglycerate → 3-phosphoglycerate) and pyruvate kinase (phosphoenolpyruvate → pyruvate) catalyze substrate-level phosphorylation in glycolysis, directly generating ATP.
During the fight-or-flight response, epinephrine activates adenylyl cyclase leading to increased cAMP and PKA activation. PKA phosphorylates and activates glycogen phosphorylase, promoting glycogen breakdown for rapid glucose availability.
The oxidative phase of the pentose phosphate pathway requires NADP⁺, which is derived from Vitamin B3, but Riboflavin (B2) is needed for flavin-dependent enzymes. Actually, the answer should be B3/Niacin for NADP⁺. This requires Niacin. Correcting: Riboflavin is required as FAD in various pathways. NADP⁺ comes from Niacin.
The Cori cycle involves lactate produced in muscles being transported to the liver where it undergoes gluconeogenesis to form glucose, which is sent back to muscles. This is crucial during anaerobic exercise.
PFK-1 catalyzes the phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate and is the rate-limiting enzyme of glycolysis. It is negatively regulated by ATP and citrate, making it a key control point.
Transketolase requires thiamine pyrophosphate (TPP/vitamin B1) as a cofactor to transfer 2-carbon ketol groups between sugar phosphates in the non-oxidative phase of the pentose phosphate pathway.
After liver glycogen is depleted (8-12 hours), gluconeogenesis becomes the primary source of glucose. The substrates are amino acids (from muscle proteolysis) and glycerol (from lipolysis).