,CHEM 210 Module 4 Exam | Biochemistry |
Portage Learning | Q & A | 2026 Edition
1. Which of the following best defines a lipid?
A) Polymers of amino acids linked by peptide bonds
B) Water-soluble macromolecules that form cell membranes
C) Hydrophobic or amphipathic biomolecules soluble in nonpolar solvents
D) Carbohydrate derivatives that store genetic information
Correct Answer: Hydrophobic or amphipathic biomolecules soluble in nonpolar solvents
Rationale: Lipids are defined by their solubility in nonpolar organic solvents rather than by a specific
chemical structure. They include fats, oils, steroids, phospholipids, and waxes. They are hydrophobic or
amphipathic, unlike proteins (amino acid polymers) or carbohydrates.
2. What is the primary function of triacylglycerols in the human body?
A) To form the structural framework of cell membranes
B) To serve as the primary storage form of energy in adipose tissue
C) To act as signaling molecules in inflammatory responses
D) To transport oxygen in the bloodstream
Correct Answer: To serve as the primary storage form of energy in adipose tissue
Rationale: Triacylglycerols (triglycerides) are the main storage form of energy in the body, stored in
adipose tissue. They provide more than twice the energy per gram compared to carbohydrates or
proteins. They are not major membrane components (phospholipids are), nor are they primary signaling
molecules or oxygen transporters.
3. According to the fluid mosaic model, which statement about membrane structure is correct?
A) Membrane proteins are fixed in place and do not move laterally
,B) The lipid bilayer is rigid and impermeable to all molecules
C) Phospholipids and proteins can diffuse laterally within the membrane bilayer
D) Cholesterol is absent from all biological membranes
Correct Answer: Phospholipids and proteins can diffuse laterally within the membrane bilayer
Rationale: The fluid mosaic model describes membranes as a fluid lipid bilayer in which phospholipids
and proteins can move laterally. This fluidity allows membrane proteins to function and membranes to
be dynamic. Membranes are selectively permeable, and cholesterol is a key component of animal cell
membranes.
4. What is the penultimate carbon in a monosaccharide?
A) The first carbon in the chain
B) The carbon adjacent to the carbonyl carbon
C) The second-to-last carbon in the chain
D) The terminal carbon at the end of the chain
Correct Answer: The second-to-last carbon in the chain
Rationale: The penultimate carbon is the second-to-last carbon in a monosaccharide chain. This carbon
is critical because its configuration (whether the hydroxyl group is on the right or left in a Fischer
projection) determines whether the sugar is designated as D or L.
5. Which type of lipid is completely hydrophobic and contains no polar head group?
A) Phospholipid
B) Triacylglycerol
C) Sphingolipid
D) Ganglioside
Correct Answer: Triacylglycerol
, Rationale: Triacylglycerols consist of three fatty acids esterified to a glycerol backbone. They have no
charged or polar head group, making them completely hydrophobic (neutral, nonpolar). Phospholipids,
sphingolipids, and gangliosides all contain polar head groups and are amphipathic.
6. When two monosaccharides are epimers, what is true about their structures?
A) They differ only in the configuration about the penultimate carbon
B) One is an aldose and the other is a ketose
C) They differ only in the configuration about one carbon atom
D) They form O-glycosidic bonds with each other
Correct Answer: They differ only in the configuration about one carbon atom
Rationale: Epimers are carbohydrates that differ in configuration at exactly one chiral carbon atom. This
is distinct from anomers (which differ at the anomeric carbon) and from aldose/ketose differences
(which involve the carbonyl group position).
7. Which of the following monosaccharides is a ketose?
A) Galactose
B) Glucose
C) Dihydroxyacetone
D) Glyceraldehyde
Correct Answer: Dihydroxyacetone
Rationale: Dihydroxyacetone is a ketose because it contains a ketone functional group (C=O) on an
internal carbon. Galactose, glucose, and glyceraldehyde are all aldoses, containing an aldehyde group at
the terminal carbon.
8. What is the backbone molecule used in the formation of storage fats (triacylglycerols)?
A) Ceramide
Portage Learning | Q & A | 2026 Edition
1. Which of the following best defines a lipid?
A) Polymers of amino acids linked by peptide bonds
B) Water-soluble macromolecules that form cell membranes
C) Hydrophobic or amphipathic biomolecules soluble in nonpolar solvents
D) Carbohydrate derivatives that store genetic information
Correct Answer: Hydrophobic or amphipathic biomolecules soluble in nonpolar solvents
Rationale: Lipids are defined by their solubility in nonpolar organic solvents rather than by a specific
chemical structure. They include fats, oils, steroids, phospholipids, and waxes. They are hydrophobic or
amphipathic, unlike proteins (amino acid polymers) or carbohydrates.
2. What is the primary function of triacylglycerols in the human body?
A) To form the structural framework of cell membranes
B) To serve as the primary storage form of energy in adipose tissue
C) To act as signaling molecules in inflammatory responses
D) To transport oxygen in the bloodstream
Correct Answer: To serve as the primary storage form of energy in adipose tissue
Rationale: Triacylglycerols (triglycerides) are the main storage form of energy in the body, stored in
adipose tissue. They provide more than twice the energy per gram compared to carbohydrates or
proteins. They are not major membrane components (phospholipids are), nor are they primary signaling
molecules or oxygen transporters.
3. According to the fluid mosaic model, which statement about membrane structure is correct?
A) Membrane proteins are fixed in place and do not move laterally
,B) The lipid bilayer is rigid and impermeable to all molecules
C) Phospholipids and proteins can diffuse laterally within the membrane bilayer
D) Cholesterol is absent from all biological membranes
Correct Answer: Phospholipids and proteins can diffuse laterally within the membrane bilayer
Rationale: The fluid mosaic model describes membranes as a fluid lipid bilayer in which phospholipids
and proteins can move laterally. This fluidity allows membrane proteins to function and membranes to
be dynamic. Membranes are selectively permeable, and cholesterol is a key component of animal cell
membranes.
4. What is the penultimate carbon in a monosaccharide?
A) The first carbon in the chain
B) The carbon adjacent to the carbonyl carbon
C) The second-to-last carbon in the chain
D) The terminal carbon at the end of the chain
Correct Answer: The second-to-last carbon in the chain
Rationale: The penultimate carbon is the second-to-last carbon in a monosaccharide chain. This carbon
is critical because its configuration (whether the hydroxyl group is on the right or left in a Fischer
projection) determines whether the sugar is designated as D or L.
5. Which type of lipid is completely hydrophobic and contains no polar head group?
A) Phospholipid
B) Triacylglycerol
C) Sphingolipid
D) Ganglioside
Correct Answer: Triacylglycerol
, Rationale: Triacylglycerols consist of three fatty acids esterified to a glycerol backbone. They have no
charged or polar head group, making them completely hydrophobic (neutral, nonpolar). Phospholipids,
sphingolipids, and gangliosides all contain polar head groups and are amphipathic.
6. When two monosaccharides are epimers, what is true about their structures?
A) They differ only in the configuration about the penultimate carbon
B) One is an aldose and the other is a ketose
C) They differ only in the configuration about one carbon atom
D) They form O-glycosidic bonds with each other
Correct Answer: They differ only in the configuration about one carbon atom
Rationale: Epimers are carbohydrates that differ in configuration at exactly one chiral carbon atom. This
is distinct from anomers (which differ at the anomeric carbon) and from aldose/ketose differences
(which involve the carbonyl group position).
7. Which of the following monosaccharides is a ketose?
A) Galactose
B) Glucose
C) Dihydroxyacetone
D) Glyceraldehyde
Correct Answer: Dihydroxyacetone
Rationale: Dihydroxyacetone is a ketose because it contains a ketone functional group (C=O) on an
internal carbon. Galactose, glucose, and glyceraldehyde are all aldoses, containing an aldehyde group at
the terminal carbon.
8. What is the backbone molecule used in the formation of storage fats (triacylglycerols)?
A) Ceramide
