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IB DP Biology Mock Exam HL Paper 2 Set 5 - 2025 Syllabus

IB DP Biology Mock Exam HL Paper 2 Set 5

Prepare for the IB DP Biology Exam with our comprehensive IB DP Biology Exam Mock Exam HL Paper 2 Set 5. Test your knowledge and understanding of key concepts with challenging questions covering all essential topics. Identify areas for improvement and boost your confidence for the real exam

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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.
▶️ 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.

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