,CHEM 210 Module 5 Exam | Biochemistry |
Portage Learning | Q & A | 2026 Edition
1. How is the definition of a lipid different from that of a protein or carbohydrate?
A) Lipids are defined by their function in energy storage, while proteins and carbohydrates are defined
by structure
B) Lipids are defined by their solubility in non-polar solvents, while proteins and carbohydrates are
defined by structure
C) Lipids are defined by their structure, while proteins and carbohydrates are defined by solubility
D) Lipids are defined by their nitrogen content, while proteins and carbohydrates are defined by oxygen
content
Correct Answer: Lipids are defined by their solubility in non-polar solvents, while proteins and
carbohydrates are defined by structure
Rationale: The lipid definition is based on a functional property—solubility in non-polar organic solvents
—rather than a specific chemical structure. Proteins and carbohydrates, in contrast, are defined by their
characteristic structural features (amino acid polymers and sugar polymers, respectively). This functional
definition allows lipids to include diverse molecules like fats, oils, steroids, and waxes.
2. What are three primary functions of lipids in biological systems?
A) Energy storage, membrane structure, and insulation
B) Catalysis, oxygen transport, and genetic storage
C) Enzyme regulation, signal transduction, and replication
D) pH buffering, osmotic balance, and waste excretion
Correct Answer: Energy storage, membrane structure, and insulation
Rationale: Lipids serve multiple essential functions: they store energy as triacylglycerols, form the
structural framework of cell membranes as phospholipids, and provide insulation and protection.
Additional functions include vitamin absorption and hormone signaling. Catalysis, oxygen transport, and
genetic storage are performed by proteins and nucleic acids.
,3. What is the difference between a fat and an oil at room temperature?
A) Fats are liquid; oils are solid
B) Fats are solid; oils are liquid
C) Fats contain only saturated fatty acids; oils contain only unsaturated fatty acids
D) Fats are found in plants; oils are found in animals
Correct Answer: Fats are solid; oils are liquid
Rationale: Fats are solid at room temperature because they contain a higher proportion of saturated
fatty acids, which pack tightly due to straight hydrocarbon chains. Oils are liquid because they contain
more unsaturated fatty acids with cis double bonds that introduce kinks, preventing tight packing and
lowering the melting point.
4. Which of the following is a carboxylic acid that serves as a structural component of lipids?
A) Amino acid
B) Carotenoid
C) Fatty acid
D) Cholesterol
Correct Answer: Fatty acid
Rationale: Fatty acids are carboxylic acids with long hydrocarbon chains that serve as structural
components of many lipids, including triacylglycerols, phospholipids, and sphingolipids. Amino acids are
protein building blocks, carotenoids are pigments, and cholesterol is a steroid.
5. Which of the following is a polyunsaturated fatty acid (PUFA)?
A) A fatty acid with one double bond
B) A fatty acid with two or more double bonds
C) A fatty acid with no double bonds
, D) A fatty acid with a ring structure
Correct Answer: A fatty acid with two or more double bonds
Rationale: Polyunsaturated fatty acids (PUFAs) contain two or more carbon-carbon double bonds in their
hydrocarbon chains. Monounsaturated fatty acids have one double bond, saturated fatty acids have
none, and fatty acids do not typically contain ring structures (that is characteristic of steroids).
6. What is the correct notation for a fatty acid with 14 carbons and two double bonds located at carbons
9 and 12?
A) 14:2(Δ9,12)
B) 14:1(Δ9,12)
C) 14:2(Δ12,15)
D) 2:14(Δ9,12)
Correct Answer: 14:2(Δ9,12)
Rationale: Fatty acid notation C:D(Δ positions) indicates the number of carbons (C), the number of
double bonds (D), and the positions of those double bonds (Δ). A 14-carbon fatty acid with two double
bonds at carbons 9 and 12 is correctly written as 14:2(Δ9,12).
7. Which simplified notation indicates a 20-carbon omega-3 fatty acid that contains one double bond?
A) 20:1(Δ11)
B) 20:1(Δ18)
C) 20:1(Δ17)
D) 20:1(Δ3)
Correct Answer: 20:1(Δ17)
Portage Learning | Q & A | 2026 Edition
1. How is the definition of a lipid different from that of a protein or carbohydrate?
A) Lipids are defined by their function in energy storage, while proteins and carbohydrates are defined
by structure
B) Lipids are defined by their solubility in non-polar solvents, while proteins and carbohydrates are
defined by structure
C) Lipids are defined by their structure, while proteins and carbohydrates are defined by solubility
D) Lipids are defined by their nitrogen content, while proteins and carbohydrates are defined by oxygen
content
Correct Answer: Lipids are defined by their solubility in non-polar solvents, while proteins and
carbohydrates are defined by structure
Rationale: The lipid definition is based on a functional property—solubility in non-polar organic solvents
—rather than a specific chemical structure. Proteins and carbohydrates, in contrast, are defined by their
characteristic structural features (amino acid polymers and sugar polymers, respectively). This functional
definition allows lipids to include diverse molecules like fats, oils, steroids, and waxes.
2. What are three primary functions of lipids in biological systems?
A) Energy storage, membrane structure, and insulation
B) Catalysis, oxygen transport, and genetic storage
C) Enzyme regulation, signal transduction, and replication
D) pH buffering, osmotic balance, and waste excretion
Correct Answer: Energy storage, membrane structure, and insulation
Rationale: Lipids serve multiple essential functions: they store energy as triacylglycerols, form the
structural framework of cell membranes as phospholipids, and provide insulation and protection.
Additional functions include vitamin absorption and hormone signaling. Catalysis, oxygen transport, and
genetic storage are performed by proteins and nucleic acids.
,3. What is the difference between a fat and an oil at room temperature?
A) Fats are liquid; oils are solid
B) Fats are solid; oils are liquid
C) Fats contain only saturated fatty acids; oils contain only unsaturated fatty acids
D) Fats are found in plants; oils are found in animals
Correct Answer: Fats are solid; oils are liquid
Rationale: Fats are solid at room temperature because they contain a higher proportion of saturated
fatty acids, which pack tightly due to straight hydrocarbon chains. Oils are liquid because they contain
more unsaturated fatty acids with cis double bonds that introduce kinks, preventing tight packing and
lowering the melting point.
4. Which of the following is a carboxylic acid that serves as a structural component of lipids?
A) Amino acid
B) Carotenoid
C) Fatty acid
D) Cholesterol
Correct Answer: Fatty acid
Rationale: Fatty acids are carboxylic acids with long hydrocarbon chains that serve as structural
components of many lipids, including triacylglycerols, phospholipids, and sphingolipids. Amino acids are
protein building blocks, carotenoids are pigments, and cholesterol is a steroid.
5. Which of the following is a polyunsaturated fatty acid (PUFA)?
A) A fatty acid with one double bond
B) A fatty acid with two or more double bonds
C) A fatty acid with no double bonds
, D) A fatty acid with a ring structure
Correct Answer: A fatty acid with two or more double bonds
Rationale: Polyunsaturated fatty acids (PUFAs) contain two or more carbon-carbon double bonds in their
hydrocarbon chains. Monounsaturated fatty acids have one double bond, saturated fatty acids have
none, and fatty acids do not typically contain ring structures (that is characteristic of steroids).
6. What is the correct notation for a fatty acid with 14 carbons and two double bonds located at carbons
9 and 12?
A) 14:2(Δ9,12)
B) 14:1(Δ9,12)
C) 14:2(Δ12,15)
D) 2:14(Δ9,12)
Correct Answer: 14:2(Δ9,12)
Rationale: Fatty acid notation C:D(Δ positions) indicates the number of carbons (C), the number of
double bonds (D), and the positions of those double bonds (Δ). A 14-carbon fatty acid with two double
bonds at carbons 9 and 12 is correctly written as 14:2(Δ9,12).
7. Which simplified notation indicates a 20-carbon omega-3 fatty acid that contains one double bond?
A) 20:1(Δ11)
B) 20:1(Δ18)
C) 20:1(Δ17)
D) 20:1(Δ3)
Correct Answer: 20:1(Δ17)
