AP - Advanced Placement Biology MCQ 1

Question 1

In a signal transduction pathway, cAMP (cyclic AMP) functions as a:

Accepted Answer

Second messenger that relays the signal inside the cell

Answer

Primary messenger that binds to cell-surface receptors

Answer

Transcription factor that directly activates gene expression

Answer

Receptor protein embedded in the plasma membrane

Question 2

Competitive inhibition of an enzyme differs from noncompetitive inhibition in that competitive inhibition:

Accepted Answer

Can be overcome by increasing substrate concentration

Answer

Permanently alters the enzyme's active site

Answer

Lowers the maximum reaction rate (Vmax) even at high substrate levels

Answer

Binds only to the enzyme-substrate complex

Question 3

Crossing over between homologous chromosomes occurs during which phase of meiosis?

Accepted Answer

Prophase I

Answer

Metaphase I

Answer

Anaphase II

Answer

Prophase II

Question 4

Which of the following conditions would violate Hardy-Weinberg equilibrium and cause allele frequencies to change over generations?

Accepted Answer

Gene flow due to migration into the population

Answer

Random mating among all individuals

Answer

A very large, isolated population

Answer

Absence of new mutations

Question 5

In the E. coli lac operon, maximal transcription occurs when:

Accepted Answer

Lactose is present and glucose is absent

Answer

Glucose is abundant and lactose is absent

Answer

The lac repressor is bound to the operator sequence

Answer

Both glucose and lactose are present in equal amounts

Question 6

Facilitated diffusion differs from active transport in that facilitated diffusion:

Accepted Answer

Uses membrane proteins but moves solutes down their concentration gradient

Answer

Moves solutes against their concentration gradient

Answer

Requires ATP hydrolysis to power movement

Answer

Only transports water molecules across the membrane