In the mobilization of fatty acids from adipose tissue, which hormone plays the primary regulatory role?
AInsulin
BEpinephrine and glucagon
CThyroxine
DProlactin
Correct Answer:
B. Epinephrine and glucagon
EXPLANATION
Epinephrine and glucagon activate hormone-sensitive lipase via cAMP signaling in adipose tissue, promoting lipolysis and release of free fatty acids during fasting or stress.
A clinical test shows high triglycerides and low HDL cholesterol. What metabolic condition might be indicated?
AIdeal lipid profile
BMetabolic syndrome with insulin resistance
CHypercholesterolemia only
DVitamin D deficiency
Correct Answer:
B. Metabolic syndrome with insulin resistance
EXPLANATION
High triglycerides with low HDL is characteristic of metabolic syndrome, often associated with insulin resistance, obesity, and increased cardiovascular risk.
In the non-oxidative phase of the pentose phosphate pathway, ribulose-5-phosphate is converted to ribose-5-phosphate by the enzyme ribulose-5-phosphate isomerase. Which tissue shows MAXIMUM activity of this pathway and why?
ARed blood cells - for maintaining reducing power via NADPH
BAdipose tissue - for fatty acid synthesis requiring NADPH
CBone marrow - for rapid nucleotide synthesis and cell division
DLiver - for glycogen storage and gluconeogenesis
Correct Answer:
C. Bone marrow - for rapid nucleotide synthesis and cell division
EXPLANATION
Bone marrow shows the highest pentose phosphate pathway activity because rapidly dividing cells require maximum ribose-5-phosphate for nucleotide (DNA/RNA) synthesis during cell division. While adipose tissue needs NADPH for lipogenesis and RBCs need it for antioxidant defense, bone marrow's continuous hematopoiesis demands the most nucleotide precursors. This is clinically relevant in leukemia and chemotherapy patients.
A diabetic patient shows impaired glucose utilization despite high blood glucose. Which enzyme's activity is most likely reduced?
AGlucokinase in beta cells
BPhosphofructokinase in muscle
CGlycogen phosphorylase in liver
DHexokinase in tissues
Correct Answer:
A. Glucokinase in beta cells
EXPLANATION
In diabetes, impaired insulin secretion (due to reduced glucokinase in beta cells) leads to inadequate glucose sensing and utilization by tissues despite hyperglycemia.
A 6-year-old child presents with muscle pain and myoglobinuria after exercise. Muscle biopsy shows normal glycogen structure but elevated content. This is consistent with:
ABranching enzyme deficiency
BMuscle phosphorylase deficiency
CLysosomal acid maltase deficiency
DLiver phosphorylase deficiency
Correct Answer:
B. Muscle phosphorylase deficiency
EXPLANATION
McArdle disease (GSD Type V) results from muscle phosphorylase deficiency. Glycogen accumulates but is structurally normal. Exercise intolerance and myoglobinuria are characteristic.
Which statement best explains the structural basis for the higher energy content of glucose compared to other hexoses?
AGlucose has more hydroxyl groups
BGlucose is more stable and requires less energy for phosphorylation
CAll hexoses have identical energy content; ATP yield depends on metabolic pathway efficiency
DGlucose has a unique aldehyde group arrangement
Correct Answer:
C. All hexoses have identical energy content; ATP yield depends on metabolic pathway efficiency
EXPLANATION
All hexoses yield approximately the same amount of ATP (~32-38 ATP) through complete oxidation. The ATP yield depends on the metabolic pathways utilized, not intrinsic energy differences.
DWarburg effect causes high glucose consumption and lactate production despite oxygen availability
Correct Answer:
D. Warburg effect causes high glucose consumption and lactate production despite oxygen availability
EXPLANATION
The Warburg effect describes the metabolic shift in cancer cells toward anaerobic glycolysis, producing lactate even in the presence of oxygen, resulting in high glucose consumption.
In maple syrup urine disease (MSUD), accumulation of branched-chain amino acids affects carbohydrate metabolism by:
AInhibiting phosphofructokinase
BCompeting with glucose uptake transporters
CInhibiting pyruvate dehydrogenase through altered acetyl-CoA/CoA ratio
DEnhancing glycogen synthase activity
Correct Answer:
C. Inhibiting pyruvate dehydrogenase through altered acetyl-CoA/CoA ratio
EXPLANATION
BCAA metabolism produces acetyl-CoA and increases the acetyl-CoA/CoA ratio, which inhibits pyruvate dehydrogenase, reducing glucose oxidation and affecting carbohydrate metabolism.
