MODERN NUTRITION IN HEALTH AND DISEASE 12TH EDITION EXAM
BANK (2026/2027 UPDATE) – 200 ADVANCED BOARD-STYLE
QUESTIONS WITH VERIFIED ANSWERS & FULL EXPLANATIONS
Question 1
Which of the following best describes the metabolic fate of dietary fructose in
the liver compared to glucose?
A) Fructose is phosphorylated by hexokinase, which is tightly controlled by
downstream energy status.
B) Fructose metabolism bypasses phosphofructokinase-1 (PFK-1), allowing
unrestrained substrate delivery to de novo lipogenesis.
C) Fructose enters glycolysis exclusively as glucose-6-phosphate, maintaining
normal glycogen regulation.
D) Fructose directly downregulates carbohydrate-responsive element-binding
protein (ChREBP).
,VERIFIED ANSWER: B) Fructose metabolism bypasses
phosphofructokinase-1 (PFK-1), allowing unrestrained substrate delivery to
de novo lipogenesis.
EXPLANATION: Unlike glucose, which is phosphorylated by glucokinase
and regulated by the rate-limiting enzyme phosphofructokinase-1 (PFK-1),
fructose enters hepatic glycolysis via fructokinase. Fructokinase converts it to
fructose-1-phosphate, which is then split into trioses downstream of PFK-1.
This bypasses the key regulatory checkpoint of glycolysis, flooding the liver
with acetyl-CoA and directly driving unrestrained de novo lipogenesis and
triglyceride accumulation.
Question 2
During prolonged starvation, what is the primary structural adaptation and
metabolic shift that occurs within skeletal muscle to preserve systemic glucose
homeostasis?
A) Immediate upregulation of GLUT4 translocation to clear circulating glucose.
B) Increased conversion of pyruvate to alanine via transamination to fuel
hepatic gluconeogenesis.
C) Massive activation of the mTORC1 pathway to accelerate protein
translation.
D) Downregulation of pyruvate dehydrogenase kinase (PDK) to maximize
carbohydrate oxidation.
VERIFIED ANSWER: B) Increased conversion of pyruvate to alanine via
transamination to fuel hepatic gluconeogenesis.
,EXPLANATION: During prolonged fasting or starvation, skeletal muscle
downregulates glucose utilization and switches to fatty acid and ketone
oxidation. Intracellular protein degradation provides amino acids; the amino
groups are transferred to pyruvate to form alanine via alanine
aminotransferase. Alanine is then exported to the liver, where it serves as a
primary carbon skeleton for gluconeogenesis (the glucose-alanine cycle).
Question 3
Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors lower
circulating LDL-cholesterol levels by utilizing which physiological mechanism?
A) Directly binding to dietary cholesterol inside the intestinal lumen via
NPC1L1.
B) Inhibiting the rate-limiting step of hepatic cholesterol synthesis by targeting
HMG-CoA reductase.
C) Preventing the lysosomal degradation of hepatic LDL receptors, thereby
increasing their recycling back to the cell surface.
D) Activating peripheral lipoprotein lipase to clear VLDL and chylomicron
remnants.
VERIFIED ANSWER: C) Preventing the lysosomal degradation of hepatic
LDL receptors, thereby increasing their recycling back to the cell surface.
EXPLANATION: Systemic PCSK9 binds to extracellular LDL receptors on
the surface of hepatocytes, escorting them into lysosomes for degradation
after endocytosis. By inhibiting PCSK9, hepatic LDL receptors are preserved
and recycled back to the hepatocyte membrane instead of being destroyed.
This dramatic increase in surface LDL receptor density significantly
enhances the clearance of circulating LDL-C.
, Question 4
Which specific molecular mechanism explains why individuals homozygous for
the MTHFR C677T polymorphism exhibit elevated plasma homocysteine levels
under conditions of low folate status?
A) The mutation causes complete deletion of the methionine synthase enzyme.
B) The mutation yields an altered methylenetetrahydrofolate reductase enzyme
with reduced thermal stability, decreasing the synthesis of 5-
methyltetrahydrofolate.
C) The genetic alteration enhances the transsulfuration of homocysteine to
cystathionine, depleting total folate storage.
D) The polymorphism directly blocks the intestinal absorption of vitamin B12
at the cubilin receptor.
VERIFIED ANSWER: B) The mutation yields an altered
methylenetetrahydrofolate reductase enzyme with reduced thermal stability,
decreasing the synthesis of 5-methyltetrahydrofolate.
EXPLANATION: The MTHFR C677T single-nucleotide polymorphism
causes a missense mutation that substitutes alanine with valine. This results
in a thermolabile MTHFR enzyme with reduced baseline activity. Because
MTHFR is responsible for generating 5-methyltetrahydrofolate (the sole
methyl donor for the remethylation of homocysteine to methionine), a
decrease in its function causes a backup of homocysteine, particularly when
dietary folate intake is inadequate.
Question 5
BANK (2026/2027 UPDATE) – 200 ADVANCED BOARD-STYLE
QUESTIONS WITH VERIFIED ANSWERS & FULL EXPLANATIONS
Question 1
Which of the following best describes the metabolic fate of dietary fructose in
the liver compared to glucose?
A) Fructose is phosphorylated by hexokinase, which is tightly controlled by
downstream energy status.
B) Fructose metabolism bypasses phosphofructokinase-1 (PFK-1), allowing
unrestrained substrate delivery to de novo lipogenesis.
C) Fructose enters glycolysis exclusively as glucose-6-phosphate, maintaining
normal glycogen regulation.
D) Fructose directly downregulates carbohydrate-responsive element-binding
protein (ChREBP).
,VERIFIED ANSWER: B) Fructose metabolism bypasses
phosphofructokinase-1 (PFK-1), allowing unrestrained substrate delivery to
de novo lipogenesis.
EXPLANATION: Unlike glucose, which is phosphorylated by glucokinase
and regulated by the rate-limiting enzyme phosphofructokinase-1 (PFK-1),
fructose enters hepatic glycolysis via fructokinase. Fructokinase converts it to
fructose-1-phosphate, which is then split into trioses downstream of PFK-1.
This bypasses the key regulatory checkpoint of glycolysis, flooding the liver
with acetyl-CoA and directly driving unrestrained de novo lipogenesis and
triglyceride accumulation.
Question 2
During prolonged starvation, what is the primary structural adaptation and
metabolic shift that occurs within skeletal muscle to preserve systemic glucose
homeostasis?
A) Immediate upregulation of GLUT4 translocation to clear circulating glucose.
B) Increased conversion of pyruvate to alanine via transamination to fuel
hepatic gluconeogenesis.
C) Massive activation of the mTORC1 pathway to accelerate protein
translation.
D) Downregulation of pyruvate dehydrogenase kinase (PDK) to maximize
carbohydrate oxidation.
VERIFIED ANSWER: B) Increased conversion of pyruvate to alanine via
transamination to fuel hepatic gluconeogenesis.
,EXPLANATION: During prolonged fasting or starvation, skeletal muscle
downregulates glucose utilization and switches to fatty acid and ketone
oxidation. Intracellular protein degradation provides amino acids; the amino
groups are transferred to pyruvate to form alanine via alanine
aminotransferase. Alanine is then exported to the liver, where it serves as a
primary carbon skeleton for gluconeogenesis (the glucose-alanine cycle).
Question 3
Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors lower
circulating LDL-cholesterol levels by utilizing which physiological mechanism?
A) Directly binding to dietary cholesterol inside the intestinal lumen via
NPC1L1.
B) Inhibiting the rate-limiting step of hepatic cholesterol synthesis by targeting
HMG-CoA reductase.
C) Preventing the lysosomal degradation of hepatic LDL receptors, thereby
increasing their recycling back to the cell surface.
D) Activating peripheral lipoprotein lipase to clear VLDL and chylomicron
remnants.
VERIFIED ANSWER: C) Preventing the lysosomal degradation of hepatic
LDL receptors, thereby increasing their recycling back to the cell surface.
EXPLANATION: Systemic PCSK9 binds to extracellular LDL receptors on
the surface of hepatocytes, escorting them into lysosomes for degradation
after endocytosis. By inhibiting PCSK9, hepatic LDL receptors are preserved
and recycled back to the hepatocyte membrane instead of being destroyed.
This dramatic increase in surface LDL receptor density significantly
enhances the clearance of circulating LDL-C.
, Question 4
Which specific molecular mechanism explains why individuals homozygous for
the MTHFR C677T polymorphism exhibit elevated plasma homocysteine levels
under conditions of low folate status?
A) The mutation causes complete deletion of the methionine synthase enzyme.
B) The mutation yields an altered methylenetetrahydrofolate reductase enzyme
with reduced thermal stability, decreasing the synthesis of 5-
methyltetrahydrofolate.
C) The genetic alteration enhances the transsulfuration of homocysteine to
cystathionine, depleting total folate storage.
D) The polymorphism directly blocks the intestinal absorption of vitamin B12
at the cubilin receptor.
VERIFIED ANSWER: B) The mutation yields an altered
methylenetetrahydrofolate reductase enzyme with reduced thermal stability,
decreasing the synthesis of 5-methyltetrahydrofolate.
EXPLANATION: The MTHFR C677T single-nucleotide polymorphism
causes a missense mutation that substitutes alanine with valine. This results
in a thermolabile MTHFR enzyme with reduced baseline activity. Because
MTHFR is responsible for generating 5-methyltetrahydrofolate (the sole
methyl donor for the remethylation of homocysteine to methionine), a
decrease in its function causes a backup of homocysteine, particularly when
dietary folate intake is inadequate.
Question 5
