Biochemistry ACS Final Exam QUESTIONS AND CORRECT DETAILED
ANSWERS WITH RATIONALES (VERIFIED ANSWERS) 2025 LATEST
UPDATED AGRADE
Question 1
In a Fischer projection, what defines the D configuration of a monosaccharide?
A) The hydroxyl group on the chiral carbon furthest from the aldehyde or ketone is on the left.
B) The carboxyl group is at the top of the projection.
C) The hydroxyl group on the chiral carbon furthest from the aldehyde or ketone is on the right.
D) All hydroxyl groups are on the right.
E) The sugar contains a ketone functional group.
Correct Answer: C) The hydroxyl group on the chiral carbon furthest from the aldehyde or
ketone is on the right.
Rationale: In a Fischer projection, the D/L configuration of a sugar is determined by the
position of the hydroxyl group (-OH) on the chiral carbon atom that is furthest from the
carbonyl (aldehyde or ketone) functional group. If this hydroxyl group is on the right side
of the vertical line, the sugar has a D configuration.
Question 2
In a Fischer projection, what defines the L configuration of a monosaccharide?
A) The hydroxyl group on the chiral carbon furthest from the aldehyde or ketone is on the right.
B) The carboxyl group is at the bottom of the projection.
C) The hydroxyl group on the chiral carbon furthest from the aldehyde or ketone is on the left.
D) All hydroxyl groups are on the left.
E) The sugar contains an aldehyde functional group.
Correct Answer: C) The hydroxyl group on the chiral carbon furthest from the aldehyde or
ketone is on the left.
Rationale: The L configuration of a monosaccharide in a Fischer projection is defined by
the hydroxyl group (-OH) on the chiral carbon furthest from the carbonyl group being
positioned on the left side of the vertical line.
Question 3
What is the primary structural difference between glycogen and amylopectin?
A) Glycogen is unbranched, while amylopectin is branched.
B) Amylopectin is composed of glucose and galactose, while glycogen is only glucose.
C) Glycogen is more highly branched, with branches occurring approximately every 10 residues,
whereas amylopectin branches less frequently (about every 25 residues).
D) Amylopectin is a linear polymer, and glycogen is a circular polymer.
E) Glycogen is found in plants, and amylopectin is found in animals.
Correct Answer: C) Glycogen is more highly branched, with branches occurring
approximately every 10 residues, whereas amylopectin branches less frequently (about
every 25 residues).
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Rationale: Both glycogen and amylopectin are branched polymers of glucose. However,
glycogen, the storage polysaccharide in animals, is significantly more branched than
amylopectin, the branched component of starch in plants. Glycogen typically has branches
every 8-12 glucose residues, while amylopectin branches every 20-25 residues.
Question 4
Amylose is a component of starch. What monosaccharide unit is amylose exclusively made up
of?
A) Fructose
B) Galactose
C) Glucose
D) Mannose
E) Ribose
Correct Answer: C) Glucose
Rationale: Amylose is a linear polysaccharide component of starch, and it is made up
entirely of repeating glucose monosaccharide units linked by alpha(1→4) glycosidic bonds.
Question 5
Starch, a major energy storage carbohydrate in plants, is composed of which two
polysaccharides?
A) Glycogen and cellulose
B) Amylose and amylopectin
C) Sucrose and lactose
D) Fructose and glucose
E) Maltose and dextrose
Correct Answer: B) Amylose and amylopectin
Rationale: Starch is a complex carbohydrate found in plants, serving as their primary
energy storage. It consists of two main components: amylose (a linear chain of glucose
units) and amylopectin (a branched chain of glucose units).
Question 6
What type of bond links two monosaccharides together to form a disaccharide or a larger
polysaccharide?
A) Peptide bond
B) Ester bond
C) Phosphodiester bond
D) Glycosidic bond
E) Hydrogen bond
Correct Answer: D) Glycosidic bond
Rationale: A glycosidic bond is a covalent bond that links two monosaccharides together,
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typically between the anomeric carbon of one monosaccharide and a hydroxyl group of
another, forming disaccharides, oligosaccharides, and polysaccharides.
Question 7
What is the key difference between an alpha(1→4) and a beta(1→4) glycosidic linkage in
carbohydrates?
A) Alpha linkages are only found in DNA, while beta linkages are in RNA.
B) The orientation of the oxygen atom at the anomeric carbon, where in an alpha linkage it
points down, and in a beta linkage, it points up.
C) Alpha linkages involve carbon 1 and 6, while beta linkages involve carbon 1 and 4.
D) Alpha linkages are found in cellulose, while beta linkages are in starch.
E) Beta linkages can be digested by humans, while alpha linkages cannot.
Correct Answer: B) The orientation of the oxygen atom at the anomeric carbon, where in an
alpha linkage it points down, and in a beta linkage, it points up.
Rationale: The difference between alpha and beta glycosidic linkages refers to the
stereochemistry at the anomeric carbon. In an alpha linkage, the anomeric carbon's oxygen
points downwards relative to the plane of the ring, while in a beta linkage, it points
upwards. This orientation has significant implications for how enzymes recognize and
digest carbohydrates (e.g., humans can digest alpha linkages in starch but not beta linkages
in cellulose).
Question 8
What is the fundamental definition of a carbohydrate based on its functional groups?
A) All carbohydrates contain only carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio.
B) All carbohydrates possess hydroxyl (-OH) and carbonyl (C=O) functional groups.
C) Carbohydrates are exclusively composed of aldehyde functional groups.
D) Carbohydrates are polymers of amino acids.
E) Carbohydrates are long chains of fatty acids.
Correct Answer: B) All carbohydrates possess hydroxyl (-OH) and carbonyl (C=O)
functional groups.
Rationale: The definition of a carbohydrate is a polyhydroxy aldehyde or a polyhydroxy
ketone. This means all carbohydrates have multiple hydroxyl (-OH) groups and at least one
carbonyl (C=O) functional group, which can be either an aldehyde or a ketone.
Question 9
What is the structural difference between an aldose and a ketose?
A) An aldose has an ester group, while a ketose has a carboxyl group.
B) An aldose contains a ketone functional group, while a ketose contains an aldehyde functional
group.
C) An aldose has an aldehyde functional group, typically at the end of the carbon chain, while a
ketose has a ketone functional group, usually on an internal carbon.
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D) Aldoses are monosaccharides, while ketoses are disaccharides.
E) Aldoses are cyclic, while ketoses are linear.
Correct Answer: C) An aldose has an aldehyde functional group, typically at the end of the
carbon chain, while a ketose has a ketone functional group, usually on an internal carbon.
Rationale: The distinction between an aldose and a ketose lies in the position of their
carbonyl group. An aldose possesses an aldehyde group (R-CHO), typically at the end of its
carbon chain, whereas a ketose contains a ketone group (R-CO-R'), usually at an interior
position on the carbon chain.
Question 10
Sucrose, commonly known as table sugar, is a disaccharide composed of which two
monosaccharides?
A) Glucose and Galactose
B) Fructose and Galactose
C) Glucose and Fructose
D) Glucose and Mannose
E) Two Glucose units
Correct Answer: C) Glucose and Fructose
Rationale: Sucrose is a disaccharide formed by the glycosidic linkage between one glucose
monosaccharide and one fructose monosaccharide.
Question 11
Lactose, the sugar found in milk, is a disaccharide composed of which two monosaccharides?
A) Fructose and Glucose
B) Glucose and Galactose
C) Mannose and Glucose
D) Two Fructose units
E) Two Galactose units
Correct Answer: B) Glucose and Galactose
Rationale: Lactose is a disaccharide that consists of a glucose monosaccharide linked to a
galactose monosaccharide.
Question 12
Mannose is a monosaccharide. Which of the following describes the composition of "mannose"
in relation to glucose?
A) Mannose is composed of two glucose monosaccharides.
B) Mannose is an epimer of glucose, differing in configuration at one chiral center (typically
C2).
C) Mannose is a disaccharide of glucose and fructose.
ANSWERS WITH RATIONALES (VERIFIED ANSWERS) 2025 LATEST
UPDATED AGRADE
Question 1
In a Fischer projection, what defines the D configuration of a monosaccharide?
A) The hydroxyl group on the chiral carbon furthest from the aldehyde or ketone is on the left.
B) The carboxyl group is at the top of the projection.
C) The hydroxyl group on the chiral carbon furthest from the aldehyde or ketone is on the right.
D) All hydroxyl groups are on the right.
E) The sugar contains a ketone functional group.
Correct Answer: C) The hydroxyl group on the chiral carbon furthest from the aldehyde or
ketone is on the right.
Rationale: In a Fischer projection, the D/L configuration of a sugar is determined by the
position of the hydroxyl group (-OH) on the chiral carbon atom that is furthest from the
carbonyl (aldehyde or ketone) functional group. If this hydroxyl group is on the right side
of the vertical line, the sugar has a D configuration.
Question 2
In a Fischer projection, what defines the L configuration of a monosaccharide?
A) The hydroxyl group on the chiral carbon furthest from the aldehyde or ketone is on the right.
B) The carboxyl group is at the bottom of the projection.
C) The hydroxyl group on the chiral carbon furthest from the aldehyde or ketone is on the left.
D) All hydroxyl groups are on the left.
E) The sugar contains an aldehyde functional group.
Correct Answer: C) The hydroxyl group on the chiral carbon furthest from the aldehyde or
ketone is on the left.
Rationale: The L configuration of a monosaccharide in a Fischer projection is defined by
the hydroxyl group (-OH) on the chiral carbon furthest from the carbonyl group being
positioned on the left side of the vertical line.
Question 3
What is the primary structural difference between glycogen and amylopectin?
A) Glycogen is unbranched, while amylopectin is branched.
B) Amylopectin is composed of glucose and galactose, while glycogen is only glucose.
C) Glycogen is more highly branched, with branches occurring approximately every 10 residues,
whereas amylopectin branches less frequently (about every 25 residues).
D) Amylopectin is a linear polymer, and glycogen is a circular polymer.
E) Glycogen is found in plants, and amylopectin is found in animals.
Correct Answer: C) Glycogen is more highly branched, with branches occurring
approximately every 10 residues, whereas amylopectin branches less frequently (about
every 25 residues).
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Rationale: Both glycogen and amylopectin are branched polymers of glucose. However,
glycogen, the storage polysaccharide in animals, is significantly more branched than
amylopectin, the branched component of starch in plants. Glycogen typically has branches
every 8-12 glucose residues, while amylopectin branches every 20-25 residues.
Question 4
Amylose is a component of starch. What monosaccharide unit is amylose exclusively made up
of?
A) Fructose
B) Galactose
C) Glucose
D) Mannose
E) Ribose
Correct Answer: C) Glucose
Rationale: Amylose is a linear polysaccharide component of starch, and it is made up
entirely of repeating glucose monosaccharide units linked by alpha(1→4) glycosidic bonds.
Question 5
Starch, a major energy storage carbohydrate in plants, is composed of which two
polysaccharides?
A) Glycogen and cellulose
B) Amylose and amylopectin
C) Sucrose and lactose
D) Fructose and glucose
E) Maltose and dextrose
Correct Answer: B) Amylose and amylopectin
Rationale: Starch is a complex carbohydrate found in plants, serving as their primary
energy storage. It consists of two main components: amylose (a linear chain of glucose
units) and amylopectin (a branched chain of glucose units).
Question 6
What type of bond links two monosaccharides together to form a disaccharide or a larger
polysaccharide?
A) Peptide bond
B) Ester bond
C) Phosphodiester bond
D) Glycosidic bond
E) Hydrogen bond
Correct Answer: D) Glycosidic bond
Rationale: A glycosidic bond is a covalent bond that links two monosaccharides together,
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typically between the anomeric carbon of one monosaccharide and a hydroxyl group of
another, forming disaccharides, oligosaccharides, and polysaccharides.
Question 7
What is the key difference between an alpha(1→4) and a beta(1→4) glycosidic linkage in
carbohydrates?
A) Alpha linkages are only found in DNA, while beta linkages are in RNA.
B) The orientation of the oxygen atom at the anomeric carbon, where in an alpha linkage it
points down, and in a beta linkage, it points up.
C) Alpha linkages involve carbon 1 and 6, while beta linkages involve carbon 1 and 4.
D) Alpha linkages are found in cellulose, while beta linkages are in starch.
E) Beta linkages can be digested by humans, while alpha linkages cannot.
Correct Answer: B) The orientation of the oxygen atom at the anomeric carbon, where in an
alpha linkage it points down, and in a beta linkage, it points up.
Rationale: The difference between alpha and beta glycosidic linkages refers to the
stereochemistry at the anomeric carbon. In an alpha linkage, the anomeric carbon's oxygen
points downwards relative to the plane of the ring, while in a beta linkage, it points
upwards. This orientation has significant implications for how enzymes recognize and
digest carbohydrates (e.g., humans can digest alpha linkages in starch but not beta linkages
in cellulose).
Question 8
What is the fundamental definition of a carbohydrate based on its functional groups?
A) All carbohydrates contain only carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio.
B) All carbohydrates possess hydroxyl (-OH) and carbonyl (C=O) functional groups.
C) Carbohydrates are exclusively composed of aldehyde functional groups.
D) Carbohydrates are polymers of amino acids.
E) Carbohydrates are long chains of fatty acids.
Correct Answer: B) All carbohydrates possess hydroxyl (-OH) and carbonyl (C=O)
functional groups.
Rationale: The definition of a carbohydrate is a polyhydroxy aldehyde or a polyhydroxy
ketone. This means all carbohydrates have multiple hydroxyl (-OH) groups and at least one
carbonyl (C=O) functional group, which can be either an aldehyde or a ketone.
Question 9
What is the structural difference between an aldose and a ketose?
A) An aldose has an ester group, while a ketose has a carboxyl group.
B) An aldose contains a ketone functional group, while a ketose contains an aldehyde functional
group.
C) An aldose has an aldehyde functional group, typically at the end of the carbon chain, while a
ketose has a ketone functional group, usually on an internal carbon.
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D) Aldoses are monosaccharides, while ketoses are disaccharides.
E) Aldoses are cyclic, while ketoses are linear.
Correct Answer: C) An aldose has an aldehyde functional group, typically at the end of the
carbon chain, while a ketose has a ketone functional group, usually on an internal carbon.
Rationale: The distinction between an aldose and a ketose lies in the position of their
carbonyl group. An aldose possesses an aldehyde group (R-CHO), typically at the end of its
carbon chain, whereas a ketose contains a ketone group (R-CO-R'), usually at an interior
position on the carbon chain.
Question 10
Sucrose, commonly known as table sugar, is a disaccharide composed of which two
monosaccharides?
A) Glucose and Galactose
B) Fructose and Galactose
C) Glucose and Fructose
D) Glucose and Mannose
E) Two Glucose units
Correct Answer: C) Glucose and Fructose
Rationale: Sucrose is a disaccharide formed by the glycosidic linkage between one glucose
monosaccharide and one fructose monosaccharide.
Question 11
Lactose, the sugar found in milk, is a disaccharide composed of which two monosaccharides?
A) Fructose and Glucose
B) Glucose and Galactose
C) Mannose and Glucose
D) Two Fructose units
E) Two Galactose units
Correct Answer: B) Glucose and Galactose
Rationale: Lactose is a disaccharide that consists of a glucose monosaccharide linked to a
galactose monosaccharide.
Question 12
Mannose is a monosaccharide. Which of the following describes the composition of "mannose"
in relation to glucose?
A) Mannose is composed of two glucose monosaccharides.
B) Mannose is an epimer of glucose, differing in configuration at one chiral center (typically
C2).
C) Mannose is a disaccharide of glucose and fructose.
