AP Biology Practice Exam– Section I: Multiple
Choice (200 Questions) real!!! Real!! 2026\27
Unit 1: Chemistry of Life (Questions 1–25)
1. Which property of water allows insects to walk on its surface?
A) High specific heat
B) Cohesion and surface tension
C) Universal solvent ability
D) Expansion upon freezing
Answer: B
Rationale:
• A: High specific heat resists temperature change, not surface walking.
• B: Correct – Cohesion (water molecules stick to each other) creates surface tension.
• C: Solvent ability dissolves polar substances, unrelated to surface support.
• D: Expansion upon freezing is why ice floats.
2. A dehydration reaction between two glucose molecules produces:
A) Sucrose + water
B) Maltose + water
C) Cellulose + water
D) Starch + water
Answer: B
Rationale:
• A: Sucrose is glucose+fructose.
• B: Correct – Maltose is two glucose units linked by dehydration.
• C: Cellulose is a polymer, not a disaccharide from two glucoses.
• D: Starch is a polysaccharide.
3. Which functional group is characteristic of amino acids?
A) Carboxyl and amino
,B) Hydroxyl and methyl
C) Carbonyl and phosphate
D) Sulfhydryl and carboxyl
Answer: A
Rationale:
• A: Correct – amino acids have both -NH₂ and -COOH.
• B: Hydroxyl (alcohols), methyl (nonpolar).
• C: Carbonyl (ketones/aldehydes), phosphate (nucleic acids).
• D: Sulfhydryl (cysteine), but missing amino group.
4. A solution with pH 3 has how many more H⁺ ions than pH 6?
A) 3 times
B) 30 times
C) 100 times
D) 1000 times
Answer: D
Rationale: pH is log scale; each unit = 10×. 3 units difference = 10³ = 1000× more H⁺.
5. Which of the following is a polysaccharide stored in animal liver and muscle?
A) Starch
B) Cellulose
C) Glycogen
D) Chitin
Answer: C
Rationale:
• A: Starch is plant energy storage.
• B: Cellulose is plant structural.
• C: Correct – Glycogen is animal storage.
• D: Chitin is fungal cell walls and arthropod exoskeletons.
6. A saturated fatty acid has:
A) Only single bonds between carbons
B) One or more double bonds
C) A hydrophilic head and hydrophobic tail
D) A ring structure
Answer: A
Rationale:
• A: Correct – Saturated = no double bonds.
, • B: Unsaturated.
• C: True of all fatty acids but not defining saturation.
• D: Steroids have rings.
7. Which level of protein structure is determined solely by amino acid sequence?
A) Primary
B) Secondary
C) Tertiary
D) Quaternary
Answer: A
Rationale: Primary = sequence of amino acids. Secondary = H-bonding (α-helix/β-sheet). Tertiary = 3D
folding. Quaternary = multiple subunits.
8. Denaturation of a protein involves disruption of:
A) Peptide bonds
B) Primary structure
C) Secondary, tertiary, and quaternary structure
D) Only quaternary structure
Answer: C
Rationale: Denaturation unfolds protein without breaking peptide bonds;
secondary/tertiary/quaternary lost, primary remains.
9. Which bond is primarily responsible for base pairing in DNA?
A) Covalent
B) Hydrogen
C) Ionic
D) Peptide
Answer: B
Rationale: A-T (2 H-bonds), G-C (3 H-bonds). Covalent = sugar-phosphate backbone.
10. A nucleotide consists of:
A) Sugar + phosphate
B) Sugar + base
C) Phosphate + base
D) Sugar + phosphate + nitrogenous base
Answer: D
Rationale: All three components.
11. Which of the following is a reducing sugar?
A) Sucrose
B) Glucose
C) Cellulose
D) Starch
, Answer: B
Rationale: Glucose has free aldehyde group; sucrose is non-reducing (glycosidic bond between anomeric
carbons).
12. The α-helix is stabilized by:
A) Disulfide bridges
B) Hydrogen bonds between carbonyl O and amide H
C) Hydrophobic interactions
D) Ionic bonds
Answer: B
Rationale: H-bonds between every 4th amino acid.
13. Which element is found in proteins but not in carbohydrates?
A) Carbon
B) Hydrogen
C) Oxygen
D) Nitrogen
Answer: D
Rationale: Proteins have N in amino groups; carbs are C,H,O.
14. Hydrolysis of a triglyceride yields:
A) Glycerol + 3 fatty acids
B) Glycerol + 3 phosphate groups
C) 3 glycerols + fatty acid
D) Glycerol + 2 fatty acids + phosphate
Answer: A
Rationale: Triglyceride = glycerol + 3 fatty acids.
15. Which pH value is most basic?
A) 2
B) 5
C) 7
D) 12
Answer: D
Rationale: pH > 7 = basic; 12 is highest.
16. A buffer resists pH change by:
A) Donating or accepting H⁺
B) Changing temperature
C) Precipitating ions
D) Increasing surface tension
Answer: A
Rationale: Buffers neutralize added H⁺ or OH⁻.
Choice (200 Questions) real!!! Real!! 2026\27
Unit 1: Chemistry of Life (Questions 1–25)
1. Which property of water allows insects to walk on its surface?
A) High specific heat
B) Cohesion and surface tension
C) Universal solvent ability
D) Expansion upon freezing
Answer: B
Rationale:
• A: High specific heat resists temperature change, not surface walking.
• B: Correct – Cohesion (water molecules stick to each other) creates surface tension.
• C: Solvent ability dissolves polar substances, unrelated to surface support.
• D: Expansion upon freezing is why ice floats.
2. A dehydration reaction between two glucose molecules produces:
A) Sucrose + water
B) Maltose + water
C) Cellulose + water
D) Starch + water
Answer: B
Rationale:
• A: Sucrose is glucose+fructose.
• B: Correct – Maltose is two glucose units linked by dehydration.
• C: Cellulose is a polymer, not a disaccharide from two glucoses.
• D: Starch is a polysaccharide.
3. Which functional group is characteristic of amino acids?
A) Carboxyl and amino
,B) Hydroxyl and methyl
C) Carbonyl and phosphate
D) Sulfhydryl and carboxyl
Answer: A
Rationale:
• A: Correct – amino acids have both -NH₂ and -COOH.
• B: Hydroxyl (alcohols), methyl (nonpolar).
• C: Carbonyl (ketones/aldehydes), phosphate (nucleic acids).
• D: Sulfhydryl (cysteine), but missing amino group.
4. A solution with pH 3 has how many more H⁺ ions than pH 6?
A) 3 times
B) 30 times
C) 100 times
D) 1000 times
Answer: D
Rationale: pH is log scale; each unit = 10×. 3 units difference = 10³ = 1000× more H⁺.
5. Which of the following is a polysaccharide stored in animal liver and muscle?
A) Starch
B) Cellulose
C) Glycogen
D) Chitin
Answer: C
Rationale:
• A: Starch is plant energy storage.
• B: Cellulose is plant structural.
• C: Correct – Glycogen is animal storage.
• D: Chitin is fungal cell walls and arthropod exoskeletons.
6. A saturated fatty acid has:
A) Only single bonds between carbons
B) One or more double bonds
C) A hydrophilic head and hydrophobic tail
D) A ring structure
Answer: A
Rationale:
• A: Correct – Saturated = no double bonds.
, • B: Unsaturated.
• C: True of all fatty acids but not defining saturation.
• D: Steroids have rings.
7. Which level of protein structure is determined solely by amino acid sequence?
A) Primary
B) Secondary
C) Tertiary
D) Quaternary
Answer: A
Rationale: Primary = sequence of amino acids. Secondary = H-bonding (α-helix/β-sheet). Tertiary = 3D
folding. Quaternary = multiple subunits.
8. Denaturation of a protein involves disruption of:
A) Peptide bonds
B) Primary structure
C) Secondary, tertiary, and quaternary structure
D) Only quaternary structure
Answer: C
Rationale: Denaturation unfolds protein without breaking peptide bonds;
secondary/tertiary/quaternary lost, primary remains.
9. Which bond is primarily responsible for base pairing in DNA?
A) Covalent
B) Hydrogen
C) Ionic
D) Peptide
Answer: B
Rationale: A-T (2 H-bonds), G-C (3 H-bonds). Covalent = sugar-phosphate backbone.
10. A nucleotide consists of:
A) Sugar + phosphate
B) Sugar + base
C) Phosphate + base
D) Sugar + phosphate + nitrogenous base
Answer: D
Rationale: All three components.
11. Which of the following is a reducing sugar?
A) Sucrose
B) Glucose
C) Cellulose
D) Starch
, Answer: B
Rationale: Glucose has free aldehyde group; sucrose is non-reducing (glycosidic bond between anomeric
carbons).
12. The α-helix is stabilized by:
A) Disulfide bridges
B) Hydrogen bonds between carbonyl O and amide H
C) Hydrophobic interactions
D) Ionic bonds
Answer: B
Rationale: H-bonds between every 4th amino acid.
13. Which element is found in proteins but not in carbohydrates?
A) Carbon
B) Hydrogen
C) Oxygen
D) Nitrogen
Answer: D
Rationale: Proteins have N in amino groups; carbs are C,H,O.
14. Hydrolysis of a triglyceride yields:
A) Glycerol + 3 fatty acids
B) Glycerol + 3 phosphate groups
C) 3 glycerols + fatty acid
D) Glycerol + 2 fatty acids + phosphate
Answer: A
Rationale: Triglyceride = glycerol + 3 fatty acids.
15. Which pH value is most basic?
A) 2
B) 5
C) 7
D) 12
Answer: D
Rationale: pH > 7 = basic; 12 is highest.
16. A buffer resists pH change by:
A) Donating or accepting H⁺
B) Changing temperature
C) Precipitating ions
D) Increasing surface tension
Answer: A
Rationale: Buffers neutralize added H⁺ or OH⁻.
