PCB3023 Exam 1: Molecular Cell Biology 2026 |UCF
1. Which of the following is NOT a fundamental tenet of the original cell theory?
A. All organisms are composed of one or more cells.
B. Cells are the basic unit of structure for all organisms.
C. Cells arise only from preexisting cells.
D. Cells contain genetic material in the form of DNA.
Answer: D
Rationale: The original cell theory proposed by Schleiden, Schwann, and Virchow did not
include the molecular basis of inheritance (DNA), which was discovered later.
2. Which feature is characteristic of all prokaryotic cells?
A. Presence of a nuclear envelope
B. Membrane-bound organelles
C. Presence of a nucleoid region
D. Linear chromosomes
Answer: C
Rationale: Prokaryotes lack a nucleus; instead, their genetic material is concentrated in a
non-membrane-bound region called the nucleoid.
3. The endosymbiotic theory suggests that mitochondria evolved from:
A. Anaerobic archaea
B. Early eukaryotic vesicles
C. Photosynthetic cyanobacteria
D. Aerobic bacteria
Answer: D
,Rationale: Mitochondria are believed to have originated when an early eukaryotic
ancestor engulfed an aerobic bacterium.
4. Which type of bond involves the unequal sharing of electrons between
atoms?
A. Nonpolar covalent bond
B. Polar covalent bond
C. Ionic bond
D. Hydrogen bond
Answer: B
Rationale: Polar covalent bonds occur when atoms with different electronegativities share
electrons unequally.
5. What is the primary reason that water is a liquid at room temperature?
A. Extensive hydrogen bonding
B. High molecular weight
C. Ionic interactions
D. Van der Waals forces
Answer: A
Rationale: Hydrogen bonding between water molecules provides high cohesiveness,
keeping it liquid at temperatures where similar-sized molecules are gases.
6. A solution with a pH of 3 has how many times more H+ ions than a solution
with a pH of 6?
A. 1000 times
B. 30 times
C. 100 times
D. 3 times
Answer: A
, Rationale: The pH scale is logarithmic; a difference of 3 pH units represents a 10^3 (1000)
difference in H+ concentration.
7. Which functional group is characteristic of alcohols?
A. Carbonyl
B. Hydroxyl
C. Carboxyl
D. Amino
Answer: B
Rationale: The hydroxyl group (-OH) is the functional group that defines alcohols.
8. The primary structure of a protein is determined by:
A. Hydrogen bonds between backbone atoms
B. Disulfide bridges between R groups
C. Alpha helices and beta sheets
D. The sequence of amino acids
Answer: D
Rationale: Primary structure refers specifically to the unique linear sequence of amino
acids linked by peptide bonds.
9. Which level of protein structure is stabilized by hydrogen bonds between the
carbonyl and amide groups of the polypeptide backbone?
A. Primary
B. Quaternary
C. Tertiary
D. Secondary
Answer: D
Rationale: Secondary structures like alpha helices and beta-pleated sheets are formed by
hydrogen bonding in the backbone.
1. Which of the following is NOT a fundamental tenet of the original cell theory?
A. All organisms are composed of one or more cells.
B. Cells are the basic unit of structure for all organisms.
C. Cells arise only from preexisting cells.
D. Cells contain genetic material in the form of DNA.
Answer: D
Rationale: The original cell theory proposed by Schleiden, Schwann, and Virchow did not
include the molecular basis of inheritance (DNA), which was discovered later.
2. Which feature is characteristic of all prokaryotic cells?
A. Presence of a nuclear envelope
B. Membrane-bound organelles
C. Presence of a nucleoid region
D. Linear chromosomes
Answer: C
Rationale: Prokaryotes lack a nucleus; instead, their genetic material is concentrated in a
non-membrane-bound region called the nucleoid.
3. The endosymbiotic theory suggests that mitochondria evolved from:
A. Anaerobic archaea
B. Early eukaryotic vesicles
C. Photosynthetic cyanobacteria
D. Aerobic bacteria
Answer: D
,Rationale: Mitochondria are believed to have originated when an early eukaryotic
ancestor engulfed an aerobic bacterium.
4. Which type of bond involves the unequal sharing of electrons between
atoms?
A. Nonpolar covalent bond
B. Polar covalent bond
C. Ionic bond
D. Hydrogen bond
Answer: B
Rationale: Polar covalent bonds occur when atoms with different electronegativities share
electrons unequally.
5. What is the primary reason that water is a liquid at room temperature?
A. Extensive hydrogen bonding
B. High molecular weight
C. Ionic interactions
D. Van der Waals forces
Answer: A
Rationale: Hydrogen bonding between water molecules provides high cohesiveness,
keeping it liquid at temperatures where similar-sized molecules are gases.
6. A solution with a pH of 3 has how many times more H+ ions than a solution
with a pH of 6?
A. 1000 times
B. 30 times
C. 100 times
D. 3 times
Answer: A
, Rationale: The pH scale is logarithmic; a difference of 3 pH units represents a 10^3 (1000)
difference in H+ concentration.
7. Which functional group is characteristic of alcohols?
A. Carbonyl
B. Hydroxyl
C. Carboxyl
D. Amino
Answer: B
Rationale: The hydroxyl group (-OH) is the functional group that defines alcohols.
8. The primary structure of a protein is determined by:
A. Hydrogen bonds between backbone atoms
B. Disulfide bridges between R groups
C. Alpha helices and beta sheets
D. The sequence of amino acids
Answer: D
Rationale: Primary structure refers specifically to the unique linear sequence of amino
acids linked by peptide bonds.
9. Which level of protein structure is stabilized by hydrogen bonds between the
carbonyl and amide groups of the polypeptide backbone?
A. Primary
B. Quaternary
C. Tertiary
D. Secondary
Answer: D
Rationale: Secondary structures like alpha helices and beta-pleated sheets are formed by
hydrogen bonding in the backbone.
