Which of the following statements about HDL (High-Density Lipoprotein) is CORRECT?
AHDL has the highest cholesterol content among all lipoproteins
BHDL facilitates reverse cholesterol transport from tissues to liver
CHDL levels are positively correlated with cardiovascular disease risk
DHDL is synthesized exclusively by the liver
Correct Answer:
B. HDL facilitates reverse cholesterol transport from tissues to liver
EXPLANATION
HDL mediates reverse cholesterol transport, removing excess cholesterol from peripheral tissues and transporting it to the liver for excretion. High HDL levels are protective against cardiovascular disease.
Beta-oxidation of fatty acids occurs primarily in which cellular compartment?
ASmooth endoplasmic reticulum
BRough endoplasmic reticulum
CMitochondrial matrix
DPeroxisomes (for very long chain fatty acids)
Correct Answer:
C. Mitochondrial matrix
EXPLANATION
Most fatty acids undergo beta-oxidation in the mitochondrial matrix. However, very long chain fatty acids (>20 carbons) are initially oxidized in peroxisomes.
The rate-limiting enzyme in de novo fatty acid synthesis is:
AAcetyl-CoA carboxylase
BFatty acid synthase
CCarnitine palmitoyltransferase I
DMalonyl-CoA decarboxylase
Correct Answer:
A. Acetyl-CoA carboxylase
EXPLANATION
Acetyl-CoA carboxylase catalyzes the formation of malonyl-CoA from acetyl-CoA, which is the first committed and rate-limiting step in fatty acid synthesis.
Which of the following lipids is NOT a structural component of cell membranes?
APhosphatidylcholine
BCholesterol
CSphingomyelin
DTriacylglycerol
Correct Answer:
D. Triacylglycerol
EXPLANATION
Triacylglycerols are storage lipids found primarily in adipose tissue. Phosphatidylcholine, cholesterol, and sphingomyelin are major components of cell membranes.
What is the difference between saturated and unsaturated fatty acids in terms of their chemical structure?
ASaturated acids have more carbon atoms
BUnsaturated acids contain one or more double bonds between carbon atoms
CSaturated acids are longer chain molecules
DUnsaturated acids contain oxygen atoms
Correct Answer:
B. Unsaturated acids contain one or more double bonds between carbon atoms
EXPLANATION
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).
Which lipid type is essential for maintaining the structural integrity of cell membranes?
ACholesterol and phospholipids
BTriglycerides and waxes
CSteroids and eicosanoids
DOnly triglycerides
Correct Answer:
A. Cholesterol and phospholipids
EXPLANATION
Cell membranes are composed of a phospholipid bilayer with embedded cholesterol molecules that regulate membrane fluidity and maintain structural integrity.
Omega-3 fatty acids are beneficial for human health because they:
AIncrease LDL cholesterol levels
BAre saturated and stable at high temperatures
CReduce inflammation and support cardiovascular health
DPromote the synthesis of triglycerides
Correct Answer:
C. Reduce inflammation and support cardiovascular health
EXPLANATION
Omega-3 polyunsaturated fatty acids (found in fish, flaxseed) have anti-inflammatory properties and support heart health by reducing triglycerides and blood pressure.
What is the primary function of HDL cholesterol in the body?
AProvide energy to cells
BTransport cholesterol from tissues to the liver for elimination
CForm cell membranes
DInsulate nerve fibers
Correct Answer:
B. Transport cholesterol from tissues to the liver for elimination
EXPLANATION
HDL (High-Density Lipoprotein) is known as 'good cholesterol' because it transports cholesterol from peripheral tissues back to the liver for degradation and excretion.
