Practice IB Biology Topic C2.1 Chemical Signalling with authentic exam-style questions for both SL and HL students. This question bank focuses on the exact syllabus content for C2.1 Chemical Signalling and mirrors Paper 1A, 1B, 2 style where relevant.
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Refer to the diagram showing epinephrine binding to a beta-adrenergic receptor and subsequent activation of intracellular signalling.
Epinephrine-stimulated cAMP synthesis
Which process best explains the first intracellular event in signal transduction immediately after epinephrine binds to the receptor?
A researcher measured the effect of a ligand binding to a GPCR on cAMP production in liver cells. The data is shown below:
| Ligand Concentration (nM) | cAMP Production (pmol min) |
|---|---|
| 0 | 1.0 |
| 5 | 3.8 |
| 10 | 7.5 |
| 25 | 15.2 |
| 50 | 18.5 |
| 100 | 19.0 |
Describe the relationship between ligand concentration and cAMP production using the data provided.
Explain why cAMP production reaches a maximum level when ligand concentration exceeds 50 nM.
Researchers investigated the effects of oxytocin (OT) on cognitive recovery after ischemic stroke in a mouse model. The figure below summarizes several interacting molecular pathways influenced by OT, including calpain-1, NF-B, GDNF, VEGF, AQP4, and cytokines such as TGF- and IL-.
Identify which type of signalling molecule oxytocin belongs to and explain why it can exert distant effects after release into the body.
Explain why cytokines such as TGF- and IL- are classified separately from hormones and neurotransmitters.
Using the diagram, name one signalling molecule that acts locally (near its release site) and one that acts at distant sites, and justify your choices.
State one reason why animals use a wide range of chemical substances (such as amines, proteins, peptides, and steroids) for signalling.
The signalling pathway shown in the diagram involves the activation of Calpain-1, which is a calcium-dependent enzyme. Describe the role of calcium ions () in intracellular signalling and explain their importance in the nervous system.
What type of receptor is associated with the hormone insulin?
Which signaling molecules are involved in synaptic transmission?