Biology Test Biology Cellular and Molecular 3

Question 1

What is the role of ATP synthase in cellular respiration?

Accepted Answer

Uses the proton gradient to synthesize ATP

Answer

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?

Accepted Answer

Osmosis

Answer

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?

Accepted Answer

The repressor protein binds to the operator and blocks transcription

Answer

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?

Accepted Answer

Microfilaments (actin)

Answer

Actin microfilaments form a network beneath the plasma membrane that supports cell shape and enables cell movement.

Question 5

What is a nucleosome?

Accepted Answer

DNA wrapped around a histone octamer

Answer

A nucleosome consists of approximately 147 base pairs of DNA wrapped around a core of eight histone proteins, forming the basic unit of chromatin.

Biology Practice Test