Entrance Exams
Govt. Exams
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.
Maltose consists of two glucose units linked by an α-1,4-glycosidic bond. Sucrose contains glucose and fructose, lactose contains glucose and galactose, and trehalose has an α-1,1-glycosidic linkage.
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.
Fructose is a ketohexose (6-carbon ketone sugar) with the molecular formula C₆H₁₂O₆, making it a structural isomer of glucose. Galactose and mannose are aldohexoses (epimers of glucose), while ribose is a pentose.
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.
In Pompe disease, acid α-glucosidase deficiency prevents lysosomal glycogen hydrolysis. Normally structured glycogen accumulates in lysosomes (unlike the abnormal structures seen in Type IV GSD), causing lysosomal dysfunction and cellular damage.