Home / IB DP Biology- C2.1 Chemical signaling- IB Style Questions For HL Paper 2

IB DP Biology- C2.1 Chemical signaling- IB Style Questions For HL Paper 2 -FA 2025

IBDP Biology HL Paper 2 -FA 2025- All Chapters

Question

The illustration shows a G protein interacting with a G protein–coupled receptor (GPCR), a membrane-bound receptor that responds to epinephrine (adrenaline).
(a) Identify the molecule that acts as the ligand in this signalling pathway.
(b) Explain the mechanism by which epinephrine produces its effects inside the cell.
(c) Describe two physiological ways in which epinephrine enhances strong muscle contraction in the body.

Most-appropriate topic codes (CED):

• TOPIC C2.1: Chemical signalling — parts (a), (b)
• TOPIC C3.1: Integration of body systems — part (c)
▶️ Answer/Explanation
Detailed solution

(a)
The ligand is epinephrine (also known as adrenaline).

(b)
Epinephrine binds to its G protein–coupled receptor (GPCR) on the cell membrane. This binding activates the attached G protein, which then stimulates a series of intracellular reactions. One major effect is the production of cyclic AMP (cAMP), a second messenger that triggers specific cellular responses, depending on the cell type involved.

(c)
1. Epinephrine increases ventilation rate and causes dilation of the bronchi/bronchioles, allowing more oxygen to enter the bloodstream.
2. It raises heart rate and blood pressure, delivering a greater supply of oxygen-rich blood to active muscles.
Additional acceptable answer: Epinephrine promotes the release of glucose from the liver, boosting ATP production needed for contraction.

More DP Biology HL Paper 2 Questions..
Scroll to Top