What is the primary function of HDL cholesterol in the body?
Answer: B
HDL (High-Density Lipoprotein) is known as 'good cholesterol' because it transports cholesterol from peripheral tissues back to the liver for degradation and excretion.
Q.202Easy
Omega-3 fatty acids are beneficial for human health because they:
Answer: C
Omega-3 polyunsaturated fatty acids (found in fish, flaxseed) have anti-inflammatory properties and support heart health by reducing triglycerides and blood pressure.
Q.203Easy
Which lipid type is essential for maintaining the structural integrity of cell membranes?
Answer: A
Cell membranes are composed of a phospholipid bilayer with embedded cholesterol molecules that regulate membrane fluidity and maintain structural integrity.
Q.204Easy
What is the difference between saturated and unsaturated fatty acids in terms of their chemical structure?
Answer: B
Saturated fatty acids have all single bonds between carbon atoms (straight chain), while unsaturated fatty acids have one or more C=C double bonds (kinked structure).
Q.205Medium
In the context of lipid metabolism, what does beta-oxidation primarily accomplish?
Answer: B
Beta-oxidation is the catabolic pathway that breaks down fatty acids in the mitochondria, producing acetyl-CoA which enters the Krebs cycle for ATP production.
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Q.206Medium
Which of the following is a consequence of excessive cholesterol accumulation in arteries?
Answer: B
High cholesterol, particularly LDL cholesterol, can accumulate in artery walls forming atherosclerotic plaques, leading to arterial narrowing (atherosclerosis) and increased risk of heart disease.
Q.207Medium
A patient with familial hypercholesterolemia shows extremely high cholesterol levels. What is the most likely defect?
Answer: B
Familial hypercholesterolemia is caused by mutations in the LDL receptor gene, preventing cells from taking up LDL particles, resulting in elevated blood cholesterol levels.
Q.208Medium
Which enzyme catalyzes the rate-limiting step of cholesterol synthesis?
Answer: B
HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate, the rate-limiting and key regulatory step in cholesterol biosynthesis. It is targeted by statin drugs.
Q.209Medium
Phospholipids differ from triglycerides in that they contain:
Answer: B
Phospholipids have a glycerol backbone with two fatty acids and a phosphate group, making them amphipathic. This structure is crucial for membrane formation.
Q.210Medium
A person consumes excessive saturated fats. Which lipoprotein level is most likely to increase?
Answer: B
Excessive dietary saturated fat increases liver production of VLDL, which carries triglycerides and cholesterol. VLDL is converted to LDL in circulation, raising LDL levels.
Q.211Medium
Which steroid hormone is synthesized from cholesterol in the adrenal cortex?
Answer: B
Cortisol and other corticosteroids are synthesized from cholesterol in the adrenal cortex through a series of enzymatic reactions involving cytochrome P450 enzymes.
Q.212Medium
The process of lipogenesis primarily occurs in which tissue during fed state?
Answer: C
The liver is the primary site of lipogenesis, where excess carbohydrates and amino acids are converted to fatty acids and triglycerides for storage and export via VLDL.
Q.213Hard
A clinical test shows high triglycerides and low HDL cholesterol. What metabolic condition might be indicated?
Answer: B
High triglycerides with low HDL is characteristic of metabolic syndrome, often associated with insulin resistance, obesity, and increased cardiovascular risk.
Q.214Hard
In the mobilization of fatty acids from adipose tissue, which hormone plays the primary regulatory role?
Answer: B
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.
Q.215Hard
Which of the following conditions results from deficiency of lipoprotein lipase?
Answer: A
Lipoprotein lipase deficiency causes Type I hyperlipoproteinemia with severe accumulation of chylomicrons and triglycerides (>1000 mg/dL), risk of acute pancreatitis.
Q.216Hard
What is the net ATP yield from complete oxidation of one molecule of a 16-carbon saturated fatty acid (palmitate)?
Answer: B
Palmitate (C16) undergoes 7 cycles of beta-oxidation producing 8 acetyl-CoA molecules, 7 FADH2, and 7 NADH. Total ATP yield is approximately 129 ATP (accounting for initial activation cost).
Q.217Hard
Apolipoproteins serve multiple functions in lipid transport. Which apolipoprotein is most important for HDL maturation and cholesterol efflux?
Answer: B
ApoA-I is the major apolipoprotein of HDL, essential for LCAT activation and cholesterol esterification, promoting reverse cholesterol transport and HDL maturation.
Q.218Hard
In the synthesis of eicosanoids, what is the first critical step?
Answer: B
Eicosanoid synthesis begins with phospholipase A2-mediated release of arachidonic acid (C20 polyunsaturated fatty acid) from membrane phospholipids, which then serves as substrate for COX and LOX pathways.
Q.219Hard
A 45-year-old patient presents with xanthomas and corneal arcus. Which lipid abnormality is most consistent with these clinical signs?
Answer: B
Xanthomas (lipid deposits in skin and tendons) and corneal arcus (lipid deposition in cornea) are hallmark signs of severe hypercholesterolemia, typically with very high LDL cholesterol levels.
Q.220Easy
Which of the following lipids is NOT a structural component of cell membranes?
Answer: D
Triacylglycerols are storage lipids found primarily in adipose tissue. Phosphatidylcholine, cholesterol, and sphingomyelin are major components of cell membranes.
