Biology Test Biology Cellular and Molecular 3 — Questions and Answers
Question 1: What is the role of ATP synthase in cellular respiration?
- Splits water molecules in the matrix
- Uses the proton gradient to synthesize ATP (Correct answer)
- Transfers electrons to oxygen
- Converts pyruvate to acetyl-CoA
Correct answer: Uses the proton gradient to synthesize ATP
ATP synthase harnesses the flow of protons down their electrochemical gradient across the inner mitochondrial membrane to drive ATP synthesis.
Question 2: Which process describes the movement of water across a selectively permeable membrane from low to high solute concentration?
- Active transport
- Facilitated diffusion
- Osmosis (Correct answer)
- Endocytosis
Correct answer: Osmosis
Osmosis is the passive movement of water molecules through a semipermeable membrane toward the region of higher solute concentration.
Question 3: In the lac operon of E. coli, what happens when lactose is absent from the environment?
- RNA polymerase binds and transcribes the operon
- The repressor protein binds to the operator and blocks transcription (Correct answer)
- The CAP-cAMP complex activates transcription
- The structural genes are constitutively expressed
Correct answer: The repressor protein binds to the operator and blocks transcription
Without lactose, the repressor protein remains active and binds to the operator, preventing transcription of the lactose-metabolizing genes.
Question 4: Which cytoskeletal element is primarily responsible for maintaining cell shape in animal cells?
- Microtubules
- Intermediate filaments
- Microfilaments (actin) (Correct answer)
- Centrioles
Correct answer: Microfilaments (actin)
Actin microfilaments form a network beneath the plasma membrane that supports cell shape and enables cell movement.
Question 5: What is a nucleosome?
- A single-stranded RNA molecule in the nucleus
- DNA wrapped around a histone octamer (Correct answer)
- The site of ribosome assembly
- A small membrane-bound organelle containing enzymes
Correct answer: DNA wrapped around a histone octamer
A nucleosome consists of approximately 147 base pairs of DNA wrapped around a core of eight histone proteins, forming the basic unit of chromatin.
Question 6: Which stage of cellular respiration produces the most ATP per glucose molecule?
- Glycolysis
- Pyruvate oxidation
- Krebs cycle
- Oxidative phosphorylation (Correct answer)
Correct answer: Oxidative phosphorylation
Oxidative phosphorylation (the electron transport chain coupled with chemiosmosis) produces approximately 32–34 of the 36–38 ATP generated per glucose.
Question 7: What is the function of telomeres?
- Initiate DNA replication at origins
- Protect chromosome ends from degradation and fusion (Correct answer)
- Encode for essential structural proteins
- Regulate gene expression through methylation
Correct answer: Protect chromosome ends from degradation and fusion
Telomeres are repetitive DNA sequences at chromosome ends that protect them from deterioration and prevent chromosomes from fusing with one another.
Biology Test Biology Cellular and Molecular 3
What is the role of ATP synthase in cellular respiration?