In Gaucher disease, the accumulation of glucocerebroside occurs due to deficiency of which enzyme?
Answer: A
Gaucher disease is caused by deficiency of glucocerebrosidase (beta-glucosidase), leading to accumulation of glucocerebroside in macrophages of the reticuloendothelial system. Type 1 is the non-neuronopathic form with hepatosplenomegaly; Type 2 and 3 involve CNS involvement.
Q.122Medium
Which of the following correctly describes the composition of lipoproteins?
Answer: C
Lipoproteins are organized with a hydrophobic lipid core (cholesterol esters and triglycerides) surrounded by a hydrophilic shell of proteins, free cholesterol, and phospholipids.
Q.123Medium
Familial hypercholesterolemia is primarily caused by defects in:
Answer: A
Familial hypercholesterolemia results from mutations in the LDL receptor gene, leading to impaired LDL uptake and elevated plasma LDL cholesterol levels.
Q.124Medium
During fasting state, which lipoprotein level increases significantly?
Answer: B
During fasting, the liver increases synthesis and secretion of VLDL to transport endogenous triglycerides produced from gluconeogenesis and fatty acid oxidation.
Q.125Medium
Which enzyme is responsible for the esterification of cholesterol in the bloodstream?
Answer: B
LCAT esterifies free cholesterol on lipoprotein surfaces, forming cholesterol esters that move to the hydrophobic core. This process is essential for lipoprotein maturation.
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Q.126Medium
What is the primary function of apolipoprotein E in lipid metabolism?
Answer: B
ApoE acts as a ligand recognized by hepatic receptors (LDL receptor and LDL receptor-related protein), mediating the uptake of chylomicron remnants and VLDL remnants.
Q.127Medium
Niemann-Pick disease is characterized by accumulation of which lipid?
Answer: B
Niemann-Pick disease results from deficiency of sphingomyelinase, leading to accumulation of sphingomyelin in lysosomes, particularly affecting the nervous system and liver.
Q.128Medium
What is the approximate percentage of cholesterol that is synthesized de novo in the liver?
Answer: C
Approximately 70-80% of body cholesterol is synthesized de novo, primarily in the liver. The remaining 20-30% comes from dietary sources.
Q.129Medium
Which of the following best explains the inverse relationship between LDL and HDL cholesterol in atherogenesis?
Answer: A
LDL carries cholesterol into arterial walls and can be oxidized, promoting atherosclerosis. HDL mediates reverse cholesterol transport, removing cholesterol from tissues and delivering it to the liver.
Q.130Medium
Which lipid is most abundant in myelin sheath?
Answer: B
Myelin contains approximately 80% lipid by weight, with cholesterol being the most abundant lipid (27% of total myelin mass), followed by galactocerebroside.
Q.131Medium
What is the primary product of the initial step of ketogenesis?
Answer: A
Acetoacetate is the first ketone body formed from two molecules of Acetyl-CoA via HMG-CoA synthase. It can be reduced to beta-hydroxybutyrate or decarboxylated to acetone.
Q.132Medium
Which of the following correctly describes the role of carnitine in fatty acid metabolism?
Answer: B
Carnitine, via carnitine palmitoyltransferase (CPT), transfers long-chain fatty acyl groups across the inner mitochondrial membrane, enabling their oxidation in the matrix.
