IB Biology HL C2.1 Chemical signalling questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

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Question 1

Multiple choiceMedium1 mark

After epinephrine is added to a responsive cell, the concentration of cAMP in the cytoplasm rises. Which sequence explains this response?

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Answer: D. Epinephrine binds its transmembrane receptor, which activates a G protein. The activated G protein stimulates adenylate cyclase to produce cAMP inside the cell; cAMP acts as the second messenger that relays the signal to intracellular targets.
A: omits the G protein, incorrectly making the receptor activate adenylate cyclase directly.
B: gives the pathway correctly but misidentifies cAMP as the first messenger; epinephrine is the first messenger.
C: reverses the order of G protein and adenylate cyclase activation.
Remember: the first messenger binds the receptor; the second messenger relays the signal inside the cell.

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