NFS EXAM ONE 2026 (QUIZZES
COMBINED) – VERIFIED QUESTIONS &
ANSWERS WITH COMPLETE SOLUTIONS |
UPDATED EXAM PREP GUIDE
1. Which lipoprotein is primarily responsible for the reverse cholesterol transport
pathway?
• A. Chylomicron
• B. VLDL
• C. LDL
• D. HDL
RATIONALE: HDL (High-Density Lipoprotein) mediates reverse cholesterol transport
by collecting excess cholesterol from peripheral tissues and transporting it back to the liver for
excretion or recycling.
2. The rate-limiting enzyme in fatty acid synthesis is:
• A. Acetyl-CoA carboxylase II
• B. Fatty acid synthase
• C. Acetyl-CoA carboxylase I
• D. Malonyl-CoA decarboxylase
RATIONALE: Acetyl-CoA carboxylase I (ACC1) catalyzes the conversion of acetyl-CoA
to malonyl-CoA, which is the committed and rate-limiting step in fatty acid biosynthesis. It is
regulated by insulin and glucagon.
3. Which amino acid serves as the primary nitrogen donor in transamination reactions?
• A. Aspartate
• B. Glutamate
• C. Alanine
, • D. Glycine
RATIONALE: Glutamate is the central amino group collector in the body. It accepts
amino groups from other amino acids via transaminases and donates them to the urea cycle,
playing a pivotal role in nitrogen metabolism.
4. A patient presents with night blindness and Bitot's spots. Which vitamin deficiency is
most likely responsible?
• A. Vitamin A
• B. Vitamin D
• C. Vitamin E
• D. Vitamin K
RATIONALE: Vitamin A (retinol) is essential for rhodopsin synthesis in rod cells.
Deficiency leads to night blindness and, in advanced cases, Bitot's spots — foamy white patches
on the conjunctiva caused by keratinization.
5. Which of the following is a characteristic feature of essential fatty acids?
• A. They can be synthesized de novo in the liver
• B. They are saturated fats found primarily in animal products
• C. They contain double bonds that humans cannot introduce beyond carbon 9
• D. They are stored in adipose tissue and never used for energy
RATIONALE: Humans lack the Δ12 and Δ15 desaturases needed to introduce double
bonds beyond C-9. Therefore, linoleic acid (ω-6) and alpha-linolenic acid (ω-3) must be obtained
from the diet.
6. The Cori cycle involves the interconversion of:
• A. Glycerol and fatty acids between adipose and liver
• B. Lactate and glucose between muscle and liver
• C. Ketone bodies and acetyl-CoA between liver and brain
, • D. Amino acids and glucose between intestine and liver
RATIONALE: In the Cori cycle, anaerobic muscle glycolysis produces lactate, which is
transported to the liver and converted back to glucose via gluconeogenesis. This cycle is critical
during intense exercise.
7. Which mineral is a cofactor for over 300 enzymatic reactions and is critical in ATP
synthesis?
• A. Zinc
• B. Iron
• C. Magnesium
• D. Selenium
RATIONALE: Magnesium acts as a cofactor for ATP-dependent reactions since ATP in
cells exists as Mg-ATP complex. It is involved in DNA replication, protein synthesis, and energy
metabolism.
8. Which form of iron is most bioavailable from dietary sources?
• A. Non-heme iron from plant foods
• B. Heme iron from animal foods
• C. Ferric iron from fortified cereals
• D. Iron chelated with oxalate
RATIONALE: Heme iron (Fe²⁺ bound to porphyrin) is absorbed directly via HCP1
transporters with 15–35% bioavailability, compared to 2–20% for non-heme iron, which is
affected by enhancers and inhibitors.
9. Thiamine pyrophosphate (TPP) acts as a coenzyme for which key metabolic complex?
• A. Fatty acid synthase
• B. HMG-CoA reductase
• C. Pyruvate dehydrogenase complex
, • D. Succinate dehydrogenase
RATIONALE: TPP (active form of thiamine/B1) is a cofactor for pyruvate
dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase. Its deficiency impairs
glucose oxidation, leading to Wernicke's encephalopathy.
10. What is the primary role of vitamin K in coagulation?
• A. Activates thrombin directly
• B. Stimulates platelet aggregation
• C. Serves as cofactor for gamma-carboxylation of clotting factors
• D. Enhances fibrinogen synthesis
RATIONALE: Vitamin K is required for the gamma-carboxylation of glutamate residues
on clotting factors II, VII, IX, and X, enabling them to bind calcium and become activated in the
coagulation cascade.
11. Which dietary fiber type is most effective at lowering LDL cholesterol?
• A. Insoluble fiber (cellulose)
• B. Soluble fiber (beta-glucan)
• C. Resistant starch
• D. Lignin
RATIONALE: Soluble fibers like beta-glucan form a viscous gel in the intestine that
binds bile acids and prevents their reabsorption. This forces the liver to use cholesterol to
synthesize new bile acids, reducing LDL levels.
12. Hypercarotenemia causes which distinctive clinical sign?
• A. Blue discoloration of fingernails
• B. Yellow-orange pigmentation of the skin
• C. Scaly dermatitis
COMBINED) – VERIFIED QUESTIONS &
ANSWERS WITH COMPLETE SOLUTIONS |
UPDATED EXAM PREP GUIDE
1. Which lipoprotein is primarily responsible for the reverse cholesterol transport
pathway?
• A. Chylomicron
• B. VLDL
• C. LDL
• D. HDL
RATIONALE: HDL (High-Density Lipoprotein) mediates reverse cholesterol transport
by collecting excess cholesterol from peripheral tissues and transporting it back to the liver for
excretion or recycling.
2. The rate-limiting enzyme in fatty acid synthesis is:
• A. Acetyl-CoA carboxylase II
• B. Fatty acid synthase
• C. Acetyl-CoA carboxylase I
• D. Malonyl-CoA decarboxylase
RATIONALE: Acetyl-CoA carboxylase I (ACC1) catalyzes the conversion of acetyl-CoA
to malonyl-CoA, which is the committed and rate-limiting step in fatty acid biosynthesis. It is
regulated by insulin and glucagon.
3. Which amino acid serves as the primary nitrogen donor in transamination reactions?
• A. Aspartate
• B. Glutamate
• C. Alanine
, • D. Glycine
RATIONALE: Glutamate is the central amino group collector in the body. It accepts
amino groups from other amino acids via transaminases and donates them to the urea cycle,
playing a pivotal role in nitrogen metabolism.
4. A patient presents with night blindness and Bitot's spots. Which vitamin deficiency is
most likely responsible?
• A. Vitamin A
• B. Vitamin D
• C. Vitamin E
• D. Vitamin K
RATIONALE: Vitamin A (retinol) is essential for rhodopsin synthesis in rod cells.
Deficiency leads to night blindness and, in advanced cases, Bitot's spots — foamy white patches
on the conjunctiva caused by keratinization.
5. Which of the following is a characteristic feature of essential fatty acids?
• A. They can be synthesized de novo in the liver
• B. They are saturated fats found primarily in animal products
• C. They contain double bonds that humans cannot introduce beyond carbon 9
• D. They are stored in adipose tissue and never used for energy
RATIONALE: Humans lack the Δ12 and Δ15 desaturases needed to introduce double
bonds beyond C-9. Therefore, linoleic acid (ω-6) and alpha-linolenic acid (ω-3) must be obtained
from the diet.
6. The Cori cycle involves the interconversion of:
• A. Glycerol and fatty acids between adipose and liver
• B. Lactate and glucose between muscle and liver
• C. Ketone bodies and acetyl-CoA between liver and brain
, • D. Amino acids and glucose between intestine and liver
RATIONALE: In the Cori cycle, anaerobic muscle glycolysis produces lactate, which is
transported to the liver and converted back to glucose via gluconeogenesis. This cycle is critical
during intense exercise.
7. Which mineral is a cofactor for over 300 enzymatic reactions and is critical in ATP
synthesis?
• A. Zinc
• B. Iron
• C. Magnesium
• D. Selenium
RATIONALE: Magnesium acts as a cofactor for ATP-dependent reactions since ATP in
cells exists as Mg-ATP complex. It is involved in DNA replication, protein synthesis, and energy
metabolism.
8. Which form of iron is most bioavailable from dietary sources?
• A. Non-heme iron from plant foods
• B. Heme iron from animal foods
• C. Ferric iron from fortified cereals
• D. Iron chelated with oxalate
RATIONALE: Heme iron (Fe²⁺ bound to porphyrin) is absorbed directly via HCP1
transporters with 15–35% bioavailability, compared to 2–20% for non-heme iron, which is
affected by enhancers and inhibitors.
9. Thiamine pyrophosphate (TPP) acts as a coenzyme for which key metabolic complex?
• A. Fatty acid synthase
• B. HMG-CoA reductase
• C. Pyruvate dehydrogenase complex
, • D. Succinate dehydrogenase
RATIONALE: TPP (active form of thiamine/B1) is a cofactor for pyruvate
dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase. Its deficiency impairs
glucose oxidation, leading to Wernicke's encephalopathy.
10. What is the primary role of vitamin K in coagulation?
• A. Activates thrombin directly
• B. Stimulates platelet aggregation
• C. Serves as cofactor for gamma-carboxylation of clotting factors
• D. Enhances fibrinogen synthesis
RATIONALE: Vitamin K is required for the gamma-carboxylation of glutamate residues
on clotting factors II, VII, IX, and X, enabling them to bind calcium and become activated in the
coagulation cascade.
11. Which dietary fiber type is most effective at lowering LDL cholesterol?
• A. Insoluble fiber (cellulose)
• B. Soluble fiber (beta-glucan)
• C. Resistant starch
• D. Lignin
RATIONALE: Soluble fibers like beta-glucan form a viscous gel in the intestine that
binds bile acids and prevents their reabsorption. This forces the liver to use cholesterol to
synthesize new bile acids, reducing LDL levels.
12. Hypercarotenemia causes which distinctive clinical sign?
• A. Blue discoloration of fingernails
• B. Yellow-orange pigmentation of the skin
• C. Scaly dermatitis
