IBBiologyHLExam QuestionsInteraction & InterdependenceChemical Signalling

Syllabus Edition

First teaching 2023

First exams 2025

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Chemical Signalling (HL IB Biology)

Exam Questions

6 mins6 questions
Easy
Medium
11 mark

Which of the following signalling molecules functions as a neurotransmitter?

  • Calcium ions

  • Cytokines

  • Amines

  • Steroids

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Figure 1 shows the cascade of events that occurs in a cell triggered by the binding of adrenaline to a receptor in the cell surface membrane. 

Diagram of the cell membrane showing binding of adrenaline to a receptor activating an enzyme cascade.

Figure 1

Which is the second messenger shown in this response?

  • ATP

  • cAMP

  • Adrenaline

  • Adenyl cyclase

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Which of the following gives an example of positive feedback?

  • Thermoregulation

  • Regulation of blood glucose

  • Osmoregulation

  • Cervix dilation during childbirth

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Which of the following correctly describes the order of events after acetylcholine successfully binds to a receptor on the postsynaptic membrane?

  • Calcium ion channels open and calcium moves across the postsynaptic membrane triggering an action potential.

  • Positively charged ions diffuse through ion channels across the membrane causing a change in voltage across the plasma membrane.

  • An action potential is triggered when a threshold level of acetylcholine receptors are occupied.

  • Sodium ions are actively pumped across the membrane to initiate an action potential in the postsynaptic neurone.

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Which features are characteristic of transmembrane receptor proteins?

  External ligand binding site Hydrophilic amino acids Hydrophobic phospholipid tails Non-polar Intracellular domains
A ✓ ✓ ✓ ✗ ✓
B ✗ ✓ ✓ ✗ ✗
C ✓ ✗ ✗ ✓ ✓
D ✓ ✓ ✗ ✗ ✓

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    Which of the following statements correctly describes the mechanism of action and effects of the steroid hormones oestradiol and progesterone on their respective target cells?

    • Oestradiol binds to receptors in hypothalamic cells, activating gonadotropin-releasing hormone (GnRH) secretion, by preventing the receptor from binding to specific DNA sequences and halting transcription of inhibitory genes.

    • Progesterone binds to intracellular receptors in endometrial cells, promoting gene transcription that supports endometrial thickening by binding to specific DNA sequences.

    • Oestradiol binds to receptors in endometrial cells, activating gene transcription to promote thickening of the uterine lining.

    • Progesterone binds to receptors in hypothalamic cells, promoting the release of GnRH by directly activating receptors on the plasma membrane.

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