, CHEM 212 MODULE 5 EXAM
Biochemistry w/Lab
Portage Learning
100-Question Practice Examination
2026/2027 Edition
CHEM 212 Module 5 Exam | Biochemistry w/Lab | Portage Learning | Q & A | 2026/2027
Actual (PDF)
1. A compound extracted from a biological sample dissolves readily in hexane but poorly in water.
Which classification is most consistent with this behavior?
A) Carbohydrate
B) Peptide
C) Nucleic acid
D) Lipid
Correct Answer: Lipid
Rationale: Lipids are functionally recognized by their preference for nonpolar solvents, reflecting a high
proportion of hydrocarbon character. Carbohydrates, peptides, and nucleic acids contain many polar or ionizable
groups and generally interact more strongly with water. Solubility behavior therefore supports classifying the
compound as a lipid.
2. Which structural feature is present in every fatty acid?
A) A glycerol backbone with three hydroxyl groups
B) A phosphate group linked to choline
C) Four fused hydrocarbon rings
D) A terminal carboxylic acid group attached to a hydrocarbon chain
Correct Answer: A terminal carboxylic acid group attached to a hydrocarbon chain
Rationale: A fatty acid consists of a hydrocarbon chain and a terminal carboxylic acid group. Glycerol is the
backbone of many glycerolipids, phosphate-containing head groups characterize phospholipids, and four fused
rings are typical of sterols. Those features are not universal to fatty acids.
3. A fatty acid designated 18:0 contains which combination of carbon atoms and carbon-carbon
double bonds?
A) 18 carbons and 1 double bond
B) 16 carbons and 2 double bonds
C) 18 carbons and 0 double bonds
D) 20 carbons and 0 double bonds
Correct Answer: 18 carbons and 0 double bonds
Rationale: In standard fatty-acid shorthand, the number before the colon gives the carbon count and the number
after it gives the number of carbon-carbon double bonds. Thus 18:0 is an 18-carbon saturated fatty acid. The
notation does not describe branching or hydroxyl groups.
4. What is the major structural effect of a cis double bond in a fatty-acid chain?
A) It introduces a bend that disrupts tight packing
B) It removes the terminal carboxyl group
CHEM 212 Module 5 Practice Examination | 2026/2027 Edition | Page 1
, C) It converts the fatty acid into a sterol
D) It creates a positively charged region
Correct Answer: It introduces a bend that disrupts tight packing
Rationale: A cis double bond places substituents on the same side of the double bond, producing a kink in the
hydrocarbon chain. This bend reduces the ability of neighboring chains to pack tightly and usually lowers melting
temperature. The carboxyl group remains intact and no charge or sterol ring system is created.
5. Two 18-carbon fatty acids differ only in that one is saturated and the other contains two cis double
bonds. Which one would generally have the lower melting point?
A) The saturated fatty acid
B) Both would necessarily have the same melting point
C) The one with the larger carboxyl group
D) The fatty acid with two cis double bonds
Correct Answer: The fatty acid with two cis double bonds
Rationale: Cis double bonds introduce bends that reduce van der Waals contacts between adjacent hydrocarbon
chains. Weaker packing lowers the energy required to disrupt the ordered state, so polyunsaturated chains
generally melt at lower temperatures than equally long saturated chains. Their carboxyl groups are comparable in
size.
6. A fatty acid is described as omega-3. From which end is the position of the first double bond
counted?
A) The carboxyl carbon
B) The carbonyl oxygen
C) The glycerol backbone
D) The methyl end
Correct Answer: The methyl end
Rationale: Omega nomenclature counts from the terminal methyl end of the fatty acid, also called the omega
end. An omega-3 fatty acid has its first double bond beginning at the third carbon from that end. Standard delta
notation instead numbers from the carboxyl carbon.
7. Which statement best distinguishes cis and trans unsaturated fatty acids?
A) Cis fatty acids contain no double bonds, whereas trans fatty acids do
B) Cis double bonds usually bend chains, whereas trans double bonds allow more nearly linear packing
C) Trans fatty acids always contain shorter hydrocarbon chains
D) Cis fatty acids are ionic but trans fatty acids are neutral
Correct Answer: Cis double bonds usually bend chains, whereas trans double bonds allow more nearly
linear packing
Rationale: The geometry around a double bond controls chain shape. Cis geometry introduces a pronounced
bend, while trans geometry leaves the chain relatively straight and able to pack more like a saturated fatty acid.
Both cis and trans forms are unsaturated and neither geometry by itself makes the molecule ionic.
8. A researcher hydrogenates an unsaturated fatty acid completely. What change is expected?
A) The carboxyl group becomes a phosphate group
B) The hydrocarbon chain is cleaved into glycerol
C) The fatty acid becomes an amino acid
D) Carbon-carbon double bonds are converted to single bonds
CHEM 212 Module 5 Practice Examination | 2026/2027 Edition | Page 2
Biochemistry w/Lab
Portage Learning
100-Question Practice Examination
2026/2027 Edition
CHEM 212 Module 5 Exam | Biochemistry w/Lab | Portage Learning | Q & A | 2026/2027
Actual (PDF)
1. A compound extracted from a biological sample dissolves readily in hexane but poorly in water.
Which classification is most consistent with this behavior?
A) Carbohydrate
B) Peptide
C) Nucleic acid
D) Lipid
Correct Answer: Lipid
Rationale: Lipids are functionally recognized by their preference for nonpolar solvents, reflecting a high
proportion of hydrocarbon character. Carbohydrates, peptides, and nucleic acids contain many polar or ionizable
groups and generally interact more strongly with water. Solubility behavior therefore supports classifying the
compound as a lipid.
2. Which structural feature is present in every fatty acid?
A) A glycerol backbone with three hydroxyl groups
B) A phosphate group linked to choline
C) Four fused hydrocarbon rings
D) A terminal carboxylic acid group attached to a hydrocarbon chain
Correct Answer: A terminal carboxylic acid group attached to a hydrocarbon chain
Rationale: A fatty acid consists of a hydrocarbon chain and a terminal carboxylic acid group. Glycerol is the
backbone of many glycerolipids, phosphate-containing head groups characterize phospholipids, and four fused
rings are typical of sterols. Those features are not universal to fatty acids.
3. A fatty acid designated 18:0 contains which combination of carbon atoms and carbon-carbon
double bonds?
A) 18 carbons and 1 double bond
B) 16 carbons and 2 double bonds
C) 18 carbons and 0 double bonds
D) 20 carbons and 0 double bonds
Correct Answer: 18 carbons and 0 double bonds
Rationale: In standard fatty-acid shorthand, the number before the colon gives the carbon count and the number
after it gives the number of carbon-carbon double bonds. Thus 18:0 is an 18-carbon saturated fatty acid. The
notation does not describe branching or hydroxyl groups.
4. What is the major structural effect of a cis double bond in a fatty-acid chain?
A) It introduces a bend that disrupts tight packing
B) It removes the terminal carboxyl group
CHEM 212 Module 5 Practice Examination | 2026/2027 Edition | Page 1
, C) It converts the fatty acid into a sterol
D) It creates a positively charged region
Correct Answer: It introduces a bend that disrupts tight packing
Rationale: A cis double bond places substituents on the same side of the double bond, producing a kink in the
hydrocarbon chain. This bend reduces the ability of neighboring chains to pack tightly and usually lowers melting
temperature. The carboxyl group remains intact and no charge or sterol ring system is created.
5. Two 18-carbon fatty acids differ only in that one is saturated and the other contains two cis double
bonds. Which one would generally have the lower melting point?
A) The saturated fatty acid
B) Both would necessarily have the same melting point
C) The one with the larger carboxyl group
D) The fatty acid with two cis double bonds
Correct Answer: The fatty acid with two cis double bonds
Rationale: Cis double bonds introduce bends that reduce van der Waals contacts between adjacent hydrocarbon
chains. Weaker packing lowers the energy required to disrupt the ordered state, so polyunsaturated chains
generally melt at lower temperatures than equally long saturated chains. Their carboxyl groups are comparable in
size.
6. A fatty acid is described as omega-3. From which end is the position of the first double bond
counted?
A) The carboxyl carbon
B) The carbonyl oxygen
C) The glycerol backbone
D) The methyl end
Correct Answer: The methyl end
Rationale: Omega nomenclature counts from the terminal methyl end of the fatty acid, also called the omega
end. An omega-3 fatty acid has its first double bond beginning at the third carbon from that end. Standard delta
notation instead numbers from the carboxyl carbon.
7. Which statement best distinguishes cis and trans unsaturated fatty acids?
A) Cis fatty acids contain no double bonds, whereas trans fatty acids do
B) Cis double bonds usually bend chains, whereas trans double bonds allow more nearly linear packing
C) Trans fatty acids always contain shorter hydrocarbon chains
D) Cis fatty acids are ionic but trans fatty acids are neutral
Correct Answer: Cis double bonds usually bend chains, whereas trans double bonds allow more nearly
linear packing
Rationale: The geometry around a double bond controls chain shape. Cis geometry introduces a pronounced
bend, while trans geometry leaves the chain relatively straight and able to pack more like a saturated fatty acid.
Both cis and trans forms are unsaturated and neither geometry by itself makes the molecule ionic.
8. A researcher hydrogenates an unsaturated fatty acid completely. What change is expected?
A) The carboxyl group becomes a phosphate group
B) The hydrocarbon chain is cleaved into glycerol
C) The fatty acid becomes an amino acid
D) Carbon-carbon double bonds are converted to single bonds
CHEM 212 Module 5 Practice Examination | 2026/2027 Edition | Page 2
