BIOD 121 MODULE 4 2025”2026 EXAM REVIEW 150 QUESTIONS AND
CORRECT ANSWERS WITH RATIONALES COVERING THE MOST TESTED
QUESTIONS GUARANTEE OVER 80% PASSMARK
1. Which type of bond is primarily responsible for the secondary structure of proteins?
A. Ionic bonds
B. Covalent bonds
C. Hydrogen bonds
D. Peptide bonds
Rationale: Hydrogen bonds between the backbone atoms of amino acids stabilize α-helices and β-
pleated sheets in proteins.
2. Which macromolecule functions as the main source of energy for cells?
A. Carbohydrates
B. Lipids
C. Proteins
D. Nucleic acids
Rationale: Carbohydrates are broken down into glucose to provide ATP through cellular respiration.
3. A triglyceride is composed of:
A. Three fatty acids and glycerol
B. Three amino acids
C. Three nucleotides
D. One glycerol and three fatty acids
Rationale: Triglycerides store energy as fats; glycerol forms the backbone with three fatty acids
attached.
4. Which macromolecule stores genetic information?
A. Protein
B. Carbohydrate
C. Nucleic acid
D. Lipid
Rationale: DNA and RNA are nucleic acids responsible for storing and transmitting genetic information.
,5. Which level of protein structure involves the overall 3D shape of a polypeptide?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Rationale: Quaternary structure forms when multiple polypeptide chains assemble into a functional
protein.
6. What is the functional group of an amino acid that gives it its acidic or basic properties?
A. Hydroxyl group
B. Carboxyl group
C. R group (side chain)
D. Phosphate group
Rationale: The R group varies among amino acids, influencing their chemical properties.
7. Which type of lipid is amphipathic and forms cell membranes?
A. Triglycerides
B. Phospholipids
C. Steroids
D. Waxes
Rationale: Phospholipids have hydrophilic heads and hydrophobic tails, forming bilayers in membranes.
8. Which carbohydrate is a polysaccharide used for energy storage in plants?
A. Glucose
B. Fructose
C. Starch
D. Glycogen
Rationale: Starch is a polymer of glucose units stored in plant cells for energy.
9. Which macromolecule catalyzes biochemical reactions?
A. Lipids
B. Carbohydrates
,C. Proteins (enzymes)
D. Nucleic acids
Rationale: Enzymes are proteins that lower activation energy for chemical reactions.
10. Which of the following is a saturated fatty acid?
A. Contains double bonds in the hydrocarbon chain
B. Contains no double bonds in the hydrocarbon chain
C. Has a branched chain
D. Forms phospholipids only
Rationale: Saturated fatty acids have no double bonds; all carbons are fully saturated with hydrogen.
11. Which polysaccharide is used by animals for energy storage?
A. Cellulose
B. Starch
C. Glycogen
D. Chitin
Rationale: Glycogen is a branched glucose polymer stored in liver and muscle cells.
12. Which nucleotides pair together in DNA?
A. A-U, C-G
B. A-G, C-T
C. A-T, C-G
D. A-C, G-T
Rationale: In DNA, adenine pairs with thymine, and cytosine pairs with guanine via hydrogen bonds.
13. Which macromolecule is hydrophobic and serves as long-term energy storage?
A. Proteins
B. Carbohydrates
C. Lipids
D. Nucleic acids
Rationale: Lipids are nonpolar molecules storing energy and forming membranes.
14. Which type of bond links amino acids together in a protein?
, A. Hydrogen bond
B. Ionic bond
C. Peptide bond
D. Glycosidic bond
Rationale: Peptide bonds form between the carboxyl group of one amino acid and the amino group of
another.
15. Which macromolecule is a major component of cell membranes besides phospholipids?
A. Glycogen
B. Cholesterol
C. Starch
D. RNA
Rationale: Cholesterol provides membrane fluidity and stability in eukaryotic cells.
16. Which carbohydrate is a structural component of plant cell walls?
A. Starch
B. Glycogen
C. Cellulose
D. Chitin
Rationale: Cellulose is a polysaccharide providing rigidity to plant cell walls.
17. Which level of protein structure is stabilized by hydrogen bonds between backbone atoms?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Rationale: α-helices and β-pleated sheets are secondary structures stabilized by hydrogen bonding.
18. Which lipid has a four-ring structure and acts as a signaling molecule?
A. Phospholipid
B. Steroid
C. Triglyceride
D. Wax
Rationale: Steroids, like testosterone and estrogen, are signaling lipids with a four-ring carbon structure.
CORRECT ANSWERS WITH RATIONALES COVERING THE MOST TESTED
QUESTIONS GUARANTEE OVER 80% PASSMARK
1. Which type of bond is primarily responsible for the secondary structure of proteins?
A. Ionic bonds
B. Covalent bonds
C. Hydrogen bonds
D. Peptide bonds
Rationale: Hydrogen bonds between the backbone atoms of amino acids stabilize α-helices and β-
pleated sheets in proteins.
2. Which macromolecule functions as the main source of energy for cells?
A. Carbohydrates
B. Lipids
C. Proteins
D. Nucleic acids
Rationale: Carbohydrates are broken down into glucose to provide ATP through cellular respiration.
3. A triglyceride is composed of:
A. Three fatty acids and glycerol
B. Three amino acids
C. Three nucleotides
D. One glycerol and three fatty acids
Rationale: Triglycerides store energy as fats; glycerol forms the backbone with three fatty acids
attached.
4. Which macromolecule stores genetic information?
A. Protein
B. Carbohydrate
C. Nucleic acid
D. Lipid
Rationale: DNA and RNA are nucleic acids responsible for storing and transmitting genetic information.
,5. Which level of protein structure involves the overall 3D shape of a polypeptide?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Rationale: Quaternary structure forms when multiple polypeptide chains assemble into a functional
protein.
6. What is the functional group of an amino acid that gives it its acidic or basic properties?
A. Hydroxyl group
B. Carboxyl group
C. R group (side chain)
D. Phosphate group
Rationale: The R group varies among amino acids, influencing their chemical properties.
7. Which type of lipid is amphipathic and forms cell membranes?
A. Triglycerides
B. Phospholipids
C. Steroids
D. Waxes
Rationale: Phospholipids have hydrophilic heads and hydrophobic tails, forming bilayers in membranes.
8. Which carbohydrate is a polysaccharide used for energy storage in plants?
A. Glucose
B. Fructose
C. Starch
D. Glycogen
Rationale: Starch is a polymer of glucose units stored in plant cells for energy.
9. Which macromolecule catalyzes biochemical reactions?
A. Lipids
B. Carbohydrates
,C. Proteins (enzymes)
D. Nucleic acids
Rationale: Enzymes are proteins that lower activation energy for chemical reactions.
10. Which of the following is a saturated fatty acid?
A. Contains double bonds in the hydrocarbon chain
B. Contains no double bonds in the hydrocarbon chain
C. Has a branched chain
D. Forms phospholipids only
Rationale: Saturated fatty acids have no double bonds; all carbons are fully saturated with hydrogen.
11. Which polysaccharide is used by animals for energy storage?
A. Cellulose
B. Starch
C. Glycogen
D. Chitin
Rationale: Glycogen is a branched glucose polymer stored in liver and muscle cells.
12. Which nucleotides pair together in DNA?
A. A-U, C-G
B. A-G, C-T
C. A-T, C-G
D. A-C, G-T
Rationale: In DNA, adenine pairs with thymine, and cytosine pairs with guanine via hydrogen bonds.
13. Which macromolecule is hydrophobic and serves as long-term energy storage?
A. Proteins
B. Carbohydrates
C. Lipids
D. Nucleic acids
Rationale: Lipids are nonpolar molecules storing energy and forming membranes.
14. Which type of bond links amino acids together in a protein?
, A. Hydrogen bond
B. Ionic bond
C. Peptide bond
D. Glycosidic bond
Rationale: Peptide bonds form between the carboxyl group of one amino acid and the amino group of
another.
15. Which macromolecule is a major component of cell membranes besides phospholipids?
A. Glycogen
B. Cholesterol
C. Starch
D. RNA
Rationale: Cholesterol provides membrane fluidity and stability in eukaryotic cells.
16. Which carbohydrate is a structural component of plant cell walls?
A. Starch
B. Glycogen
C. Cellulose
D. Chitin
Rationale: Cellulose is a polysaccharide providing rigidity to plant cell walls.
17. Which level of protein structure is stabilized by hydrogen bonds between backbone atoms?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Rationale: α-helices and β-pleated sheets are secondary structures stabilized by hydrogen bonding.
18. Which lipid has a four-ring structure and acts as a signaling molecule?
A. Phospholipid
B. Steroid
C. Triglyceride
D. Wax
Rationale: Steroids, like testosterone and estrogen, are signaling lipids with a four-ring carbon structure.
