UNE MEDICAL BIOCHEMISTRY UNIT 3 MIDTERM TEST
EXAM LATEST VERSION 2025/2026 QUESTIONS AND
CORRECT DETAILED ANSWERS (VERIFIED ANSWERS
WITH RATIONALES) |ALREADY GRADED A+
Question 1
In an individual who has been fasting overnight, the hormonal profile is characterized by high
glucagon and low insulin. Which of the following metabolic processes is predominantly active as a
result?
A) Glycogen synthesis
B) Fatty acid synthesis
C) Beta-oxidation
D) Glycolysis
E) Pentose phosphate pathway
Correct Answer: C) Beta-oxidation
Rationale: High glucagon and low insulin signal a fasted state, where the body must mobilize
stored energy. Glucagon activates hormone-sensitive lipase in adipose tissue, releasing free
fatty acids (lipolysis). These fatty acids are taken up by peripheral tissues like the liver and
muscle and are broken down through beta-oxidation to produce acetyl-CoA, FADH2, and
NADH for energy.
Question 2
During the fasted state, which molecule does the liver primarily use as fuel, and which pathway
supplies this fuel?
A) Glucose, Muscle glycogenolysis
B) Fatty acids, Lipolysis in the adipose
C) Amino acids, Protein synthesis
D) Ketones, Ketogenesis in the adipose
E) Lactate, Cori cycle
Correct Answer: B) Fatty acids, Lipolysis in the adipose
Rationale: In the fasted state, the liver's primary role is to produce glucose for the rest of the
body via gluconeogenesis and glycogenolysis. To power these anabolic processes, the liver
itself oxidizes fatty acids. These fatty acids are supplied by the adipose tissue, where high
glucagon levels have activated lipolysis to release them into the bloodstream.
Question 3
In the fasted state, red blood cells exclusively use glucose as fuel. From which metabolic pathways
is this glucose supplied?
A) Lipolysis in the adipose and ketogenesis in the liver
B) Muscle glycogenolysis and muscle gluconeogenesis
C) Hepatic glycogenolysis and gluconeogenesis
D) Dietary absorption and lipolysis
E) Beta-oxidation and the TCA cycle in the liver
,Correct Answer: C) Hepatic glycogenolysis and gluconeogenesis
Rationale: Red blood cells lack mitochondria and are therefore completely dependent on
glucose for energy via anaerobic glycolysis. In the fasted state, the only source of blood
glucose is the liver. The liver maintains blood glucose levels by breaking down its glycogen
stores (glycogenolysis) and by synthesizing new glucose from precursors like lactate,
glycerol, and amino acids (gluconeogenesis).
Question 4
After an overnight fast, which molecule is the primary fuel for the brain, and what is its source?
A) Fatty acids, supplied by lipolysis in the adipose
B) Ketone bodies, supplied by hepatic ketogenesis
C) Glucose, supplied by hepatic glycogenolysis and gluconeogenesis
D) Amino acids, supplied by muscle protein catabolism
E) Lactate, supplied by red blood cells
Correct Answer: C) Glucose, supplied by hepatic glycogenolysis and gluconeogenesis
Rationale: In the early fasted state (e.g., overnight fast), the brain is an obligate user of
glucose. Fatty acids cannot cross the blood-brain barrier. Therefore, the brain relies on the
liver to maintain blood glucose levels through the breakdown of liver glycogen and the
synthesis of new glucose.
Question 5
During a prolonged fast, what is the primary fuel source utilized by resting skeletal muscle?
A) Glucose from hepatic gluconeogenesis
B) Stored muscle glycogen
C) Fatty acids from lipolysis in the adipose
D) Branched-chain amino acids
E) Ketone bodies from the liver
Correct Answer: C) Fatty acids from lipolysis in the adipose
Rationale: In the fasted state, resting skeletal muscle switches its fuel preference to conserve
glucose for the brain and red blood cells. It primarily takes up free fatty acids released from
adipose tissue via lipolysis and oxidizes them through beta-oxidation to meet its energy
needs.
Question 6
What is the name of the process that generates acetyl-CoA, NADH, and FADH2 from the oxidation
of free fatty acids within the mitochondria of peripheral tissues?
A) Lipolysis
B) Ketogenesis
C) Fatty acid synthesis
D) β - oxidation
E) Glycolysis
, Correct Answer: D) β - oxidation
Rationale: This is the definition of beta-oxidation. It is the mitochondrial catabolic pathway
that breaks down fatty acyl-CoA molecules in a spiral of four recurring steps, cleaving off
two-carbon acetyl-CoA units in each round and producing the reduced cofactors NADH and
FADH2.
Question 7
What is the process of releasing free fatty acids and glycerol from triacylglycerols stored in adipose
tissue during the fasted state called?
A) Lipogenesis
B) Esterification
C) Beta-oxidation
D) Lipolysis
E) Ketogenesis
Correct Answer: D) Lipolysis
Rationale: Lipolysis is the hormonal-regulated catabolic process of breaking down stored
triacylglycerols (fats) in adipocytes. It is stimulated by glucagon and epinephrine, which
activate hormone-sensitive lipase to hydrolyze the triacylglycerols into free fatty acids and
glycerol, releasing them into the bloodstream.
Question 8
In which cellular compartment does beta-oxidation of long-chain fatty acids occur?
A) Cytosol
B) Endoplasmic reticulum
C) Peroxisome
D) Lysosome
E) Mitochondria
Correct Answer: E) Mitochondria
Rationale: The enzymes required for the beta-oxidation spiral, as well as the electron
transport chain and TCA cycle which use its products, are all located within the
mitochondrial matrix. Therefore, fatty acids must be transported into the mitochondria before
they can be oxidized for energy.
Question 9
Before a free fatty acid can enter the mitochondria for oxidation, it must first be activated in the
cytosol. What enzyme performs this activation step by attaching CoA, and what does it form?
A) Thiolase, forming Acetyl-CoA
B) Acyl-CoA synthetase, forming Acyl-CoA
C) CPT I, forming Acylcarnitine
D) HMG-CoA synthase, forming HMG-CoA
E) Acetyl-CoA carboxylase, forming Malonyl-CoA
EXAM LATEST VERSION 2025/2026 QUESTIONS AND
CORRECT DETAILED ANSWERS (VERIFIED ANSWERS
WITH RATIONALES) |ALREADY GRADED A+
Question 1
In an individual who has been fasting overnight, the hormonal profile is characterized by high
glucagon and low insulin. Which of the following metabolic processes is predominantly active as a
result?
A) Glycogen synthesis
B) Fatty acid synthesis
C) Beta-oxidation
D) Glycolysis
E) Pentose phosphate pathway
Correct Answer: C) Beta-oxidation
Rationale: High glucagon and low insulin signal a fasted state, where the body must mobilize
stored energy. Glucagon activates hormone-sensitive lipase in adipose tissue, releasing free
fatty acids (lipolysis). These fatty acids are taken up by peripheral tissues like the liver and
muscle and are broken down through beta-oxidation to produce acetyl-CoA, FADH2, and
NADH for energy.
Question 2
During the fasted state, which molecule does the liver primarily use as fuel, and which pathway
supplies this fuel?
A) Glucose, Muscle glycogenolysis
B) Fatty acids, Lipolysis in the adipose
C) Amino acids, Protein synthesis
D) Ketones, Ketogenesis in the adipose
E) Lactate, Cori cycle
Correct Answer: B) Fatty acids, Lipolysis in the adipose
Rationale: In the fasted state, the liver's primary role is to produce glucose for the rest of the
body via gluconeogenesis and glycogenolysis. To power these anabolic processes, the liver
itself oxidizes fatty acids. These fatty acids are supplied by the adipose tissue, where high
glucagon levels have activated lipolysis to release them into the bloodstream.
Question 3
In the fasted state, red blood cells exclusively use glucose as fuel. From which metabolic pathways
is this glucose supplied?
A) Lipolysis in the adipose and ketogenesis in the liver
B) Muscle glycogenolysis and muscle gluconeogenesis
C) Hepatic glycogenolysis and gluconeogenesis
D) Dietary absorption and lipolysis
E) Beta-oxidation and the TCA cycle in the liver
,Correct Answer: C) Hepatic glycogenolysis and gluconeogenesis
Rationale: Red blood cells lack mitochondria and are therefore completely dependent on
glucose for energy via anaerobic glycolysis. In the fasted state, the only source of blood
glucose is the liver. The liver maintains blood glucose levels by breaking down its glycogen
stores (glycogenolysis) and by synthesizing new glucose from precursors like lactate,
glycerol, and amino acids (gluconeogenesis).
Question 4
After an overnight fast, which molecule is the primary fuel for the brain, and what is its source?
A) Fatty acids, supplied by lipolysis in the adipose
B) Ketone bodies, supplied by hepatic ketogenesis
C) Glucose, supplied by hepatic glycogenolysis and gluconeogenesis
D) Amino acids, supplied by muscle protein catabolism
E) Lactate, supplied by red blood cells
Correct Answer: C) Glucose, supplied by hepatic glycogenolysis and gluconeogenesis
Rationale: In the early fasted state (e.g., overnight fast), the brain is an obligate user of
glucose. Fatty acids cannot cross the blood-brain barrier. Therefore, the brain relies on the
liver to maintain blood glucose levels through the breakdown of liver glycogen and the
synthesis of new glucose.
Question 5
During a prolonged fast, what is the primary fuel source utilized by resting skeletal muscle?
A) Glucose from hepatic gluconeogenesis
B) Stored muscle glycogen
C) Fatty acids from lipolysis in the adipose
D) Branched-chain amino acids
E) Ketone bodies from the liver
Correct Answer: C) Fatty acids from lipolysis in the adipose
Rationale: In the fasted state, resting skeletal muscle switches its fuel preference to conserve
glucose for the brain and red blood cells. It primarily takes up free fatty acids released from
adipose tissue via lipolysis and oxidizes them through beta-oxidation to meet its energy
needs.
Question 6
What is the name of the process that generates acetyl-CoA, NADH, and FADH2 from the oxidation
of free fatty acids within the mitochondria of peripheral tissues?
A) Lipolysis
B) Ketogenesis
C) Fatty acid synthesis
D) β - oxidation
E) Glycolysis
, Correct Answer: D) β - oxidation
Rationale: This is the definition of beta-oxidation. It is the mitochondrial catabolic pathway
that breaks down fatty acyl-CoA molecules in a spiral of four recurring steps, cleaving off
two-carbon acetyl-CoA units in each round and producing the reduced cofactors NADH and
FADH2.
Question 7
What is the process of releasing free fatty acids and glycerol from triacylglycerols stored in adipose
tissue during the fasted state called?
A) Lipogenesis
B) Esterification
C) Beta-oxidation
D) Lipolysis
E) Ketogenesis
Correct Answer: D) Lipolysis
Rationale: Lipolysis is the hormonal-regulated catabolic process of breaking down stored
triacylglycerols (fats) in adipocytes. It is stimulated by glucagon and epinephrine, which
activate hormone-sensitive lipase to hydrolyze the triacylglycerols into free fatty acids and
glycerol, releasing them into the bloodstream.
Question 8
In which cellular compartment does beta-oxidation of long-chain fatty acids occur?
A) Cytosol
B) Endoplasmic reticulum
C) Peroxisome
D) Lysosome
E) Mitochondria
Correct Answer: E) Mitochondria
Rationale: The enzymes required for the beta-oxidation spiral, as well as the electron
transport chain and TCA cycle which use its products, are all located within the
mitochondrial matrix. Therefore, fatty acids must be transported into the mitochondria before
they can be oxidized for energy.
Question 9
Before a free fatty acid can enter the mitochondria for oxidation, it must first be activated in the
cytosol. What enzyme performs this activation step by attaching CoA, and what does it form?
A) Thiolase, forming Acetyl-CoA
B) Acyl-CoA synthetase, forming Acyl-CoA
C) CPT I, forming Acylcarnitine
D) HMG-CoA synthase, forming HMG-CoA
E) Acetyl-CoA carboxylase, forming Malonyl-CoA
