Q.1 Which organ is the primary site of fatty acid β-oxidation?
Liver
Heart
Adipose tissue
Kidney
Explanation - The liver is the major site of fatty acid β-oxidation, although muscle and kidney also contribute significantly.
Correct answer is: Liver
Q.2 What is the first step in fatty acid β-oxidation?
Hydration
Oxidation
Activation of fatty acids
Thiolysis
Explanation - Fatty acids must first be activated to fatty acyl-CoA before entering β-oxidation.
Correct answer is: Activation of fatty acids
Q.3 Which enzyme catalyzes the activation of fatty acids?
Acyl-CoA dehydrogenase
Fatty acyl-CoA synthetase
Carnitine acyltransferase I
Enoyl-CoA hydratase
Explanation - Fatty acyl-CoA synthetase catalyzes the conversion of free fatty acids to fatty acyl-CoA.
Correct answer is: Fatty acyl-CoA synthetase
Q.4 Carnitine plays a key role in:
Transport of fatty acids into mitochondria
Synthesis of triglycerides
Gluconeogenesis
Cholesterol synthesis
Explanation - Carnitine shuttles long-chain fatty acids into the mitochondria for β-oxidation.
Correct answer is: Transport of fatty acids into mitochondria
Q.5 Which enzyme is inhibited by malonyl-CoA?
Acyl-CoA dehydrogenase
Carnitine acyltransferase I
HMG-CoA reductase
Acetyl-CoA carboxylase
Explanation - Malonyl-CoA inhibits carnitine acyltransferase I to prevent simultaneous fatty acid synthesis and degradation.
Correct answer is: Carnitine acyltransferase I
Q.6 Which of the following produces ketone bodies?
Adipose tissue
Liver
Kidneys
Muscles
Explanation - The liver produces ketone bodies during fasting or diabetes, although it cannot use them itself.
Correct answer is: Liver
Q.7 The main ketone bodies include all EXCEPT:
Acetoacetate
β-hydroxybutyrate
Acetone
Succinyl-CoA
Explanation - The three ketone bodies are acetoacetate, β-hydroxybutyrate, and acetone. Succinyl-CoA is a TCA cycle intermediate.
Correct answer is: Succinyl-CoA
Q.8 Which enzyme is the rate-limiting step of cholesterol synthesis?
HMG-CoA reductase
HMG-CoA synthase
Squalene synthase
Mevalonate kinase
Explanation - HMG-CoA reductase is the rate-limiting enzyme in cholesterol biosynthesis, converting HMG-CoA to mevalonate.
Correct answer is: HMG-CoA reductase
Q.9 Which lipoprotein is responsible for reverse cholesterol transport?
VLDL
LDL
HDL
Chylomicrons
Explanation - HDL transports cholesterol from peripheral tissues back to the liver (reverse cholesterol transport).
Correct answer is: HDL
Q.10 The primary storage form of lipids in adipose tissue is:
Phospholipids
Triglycerides
Cholesterol esters
Free fatty acids
Explanation - Adipose tissue stores energy mainly as triglycerides, which can be hydrolyzed into fatty acids when needed.
Correct answer is: Triglycerides
Q.11 What molecule activates acetyl-CoA carboxylase?
Citrate
Malonyl-CoA
Palmitoyl-CoA
AMP
Explanation - Citrate allosterically activates acetyl-CoA carboxylase, linking carbohydrate metabolism to fatty acid synthesis.
Correct answer is: Citrate
Q.12 Which coenzyme is required for fatty acid synthase activity?
NAD+
NADPH
FAD
Coenzyme Q
Explanation - Fatty acid synthesis requires NADPH as a reducing agent, primarily supplied by the pentose phosphate pathway.
Correct answer is: NADPH
Q.13 Which organelle is the site of fatty acid synthesis?
Mitochondria
Cytosol
Peroxisomes
Endoplasmic reticulum
Explanation - Fatty acid synthesis occurs in the cytosol, while β-oxidation occurs in the mitochondria.
Correct answer is: Cytosol
Q.14 Which fatty acid is considered essential in humans?
Palmitic acid
Linoleic acid
Stearic acid
Oleic acid
Explanation - Linoleic acid (omega-6) and alpha-linolenic acid (omega-3) are essential fatty acids required from diet.
Correct answer is: Linoleic acid
Q.15 Which enzyme hydrolyzes triglycerides in adipose tissue during fasting?
Hormone-sensitive lipase
Lipoprotein lipase
Acetyl-CoA carboxylase
HMG-CoA reductase
Explanation - Hormone-sensitive lipase mobilizes stored triglycerides in adipose tissue during fasting.
Correct answer is: Hormone-sensitive lipase
Q.16 Which hormone stimulates lipolysis?
Insulin
Glucagon
Cortisol
Aldosterone
Explanation - Glucagon and epinephrine stimulate lipolysis, whereas insulin inhibits it.
Correct answer is: Glucagon
Q.17 Which fatty acid oxidation occurs in peroxisomes?
Short-chain fatty acid oxidation
Medium-chain fatty acid oxidation
Very-long-chain fatty acid oxidation
Odd-chain fatty acid oxidation
Explanation - Peroxisomes degrade very-long-chain fatty acids before they are transferred to mitochondria.
Correct answer is: Very-long-chain fatty acid oxidation
Q.18 Which ketone body is exhaled in breath and gives fruity odor?
Acetoacetate
β-hydroxybutyrate
Acetone
Pyruvate
Explanation - Acetone is volatile and exhaled in breath, giving fruity odor in ketoacidosis.
Correct answer is: Acetone
Q.19 During fasting, the brain adapts to use:
Glucose only
Ketone bodies
Fatty acids
Lactate
Explanation - In prolonged fasting, the brain shifts to using ketone bodies to spare glucose.
Correct answer is: Ketone bodies
Q.20 Which lipoprotein delivers dietary triglycerides to tissues?
VLDL
HDL
Chylomicrons
LDL
Explanation - Chylomicrons transport dietary triglycerides and cholesterol from the intestine to tissues.
Correct answer is: Chylomicrons
Q.21 What is the role of lipoprotein lipase?
Hydrolyzes triglycerides in lipoproteins
Synthesizes cholesterol
Activates fatty acids
Transports carnitine
Explanation - Lipoprotein lipase hydrolyzes triglycerides in chylomicrons and VLDL, releasing fatty acids.
Correct answer is: Hydrolyzes triglycerides in lipoproteins
Q.22 Which apoprotein activates lipoprotein lipase?
ApoA-I
ApoB-100
ApoC-II
ApoE
Explanation - ApoC-II acts as a cofactor for lipoprotein lipase activity.
Correct answer is: ApoC-II
Q.23 Which fatty acid oxidation yields propionyl-CoA as an intermediate?
Odd-chain fatty acid oxidation
Even-chain fatty acid oxidation
Unsaturated fatty acid oxidation
Branched-chain fatty acid oxidation
Explanation - Odd-chain fatty acids yield propionyl-CoA, which can be converted into succinyl-CoA and enter the TCA cycle.
Correct answer is: Odd-chain fatty acid oxidation
Q.24 Which vitamin is required for carboxylation of propionyl-CoA?
Vitamin B6
Vitamin B12
Vitamin C
Vitamin K
Explanation - Vitamin B12 is essential for the conversion of methylmalonyl-CoA to succinyl-CoA in odd-chain fatty acid metabolism.
Correct answer is: Vitamin B12
Q.25 Which fatty acid is the precursor of prostaglandins?
Stearic acid
Palmitic acid
Arachidonic acid
Oleic acid
Explanation - Prostaglandins and other eicosanoids are synthesized from arachidonic acid, derived from membrane phospholipids.
Correct answer is: Arachidonic acid