Evaluating Cell Signaling Statements

Steps:

• Statement 1 claims signal chemicals match receptor shape exactly; incorrect, as they bind via complementary shapes like lock-and-key model.
• Statement 2 notes temperature rise may reduce signaling; correct, as heat can denature proteins, disrupting receptor function or pathways.
• Statement 3 states membrane mutation may lower active receptors; correct, as genetic changes in membrane protein genes impair synthesis or activity.
• Only statements 2 and 3 hold, matching option D.

Why D is correct:

• Cell signaling requires precise ligand-receptor complementarity and protein stability, per induced fit model and enzyme kinetics.

Why the others are wrong:

• A includes false statement 1 on shape matching.
• B omits true statement 2 on temperature effects.
• C selects only incorrect statement 1.

Final answer: D