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IB Biology HL C2.1 Chemical Signalling Hl Only Questions

Practise IB Biology HL C2.1 by comparing ligands, receptors, hormones, quorum sensing and intracellular signalling pathways.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Identify receptor proteins as specific ligand-binding sites and explain signalling specificity.
  • Explain quorum sensing through autoinducer thresholds and coordinated bacterial behaviour.
  • Compare animal signalling categories and local or distant communication, using leptin.
  • Classify hormones and distinguish peptide versus steroid receptor routes.
  • Compare transmembrane and intracellular receptor pathways for hydrophilic and steroid ligands.
  • Trace signal transduction through second messengers, gene-regulatory proteins and phosphorylation cascades.
  • Trace epinephrine GPCR signalling through G protein, adenylyl cyclase and cyclic AMP.
  • Explain intracellular steroid or thyroxine-like receptor complexes regulating transcription.
  • Explain negative feedback as an opposite response returning a regulated variable toward prior levels.

Covered syllabus points

C2.1.1 (HL)—Receptors as proteinsC2.1.2 (HL)—Quorum sensing in bacteriaC2.1.3 (HL)—Functional categories in animalsC2.1.4 (HL)—Chemical diversityC2.1.5 (HL)—Localized vs. distant effectsC2.1.6 (HL)—Transmembrane vs. intracellular receptorsC2.1.7 (HL)—Signal transduction pathwaysC2.1.8 (HL)—Neurotransmitter receptors and membrane potentialC2.1.9 (HL)—G protein-coupled receptorsC2.1.10 (HL)—Epinephrine (adrenaline) mechanismC2.1.11 (HL)—Tyrosine kinase receptorsC2.1.12 (HL)—Intracellular receptorsC2.1.13 (HL)—Effects of oestradiol and progesteroneC2.1.14 (HL)—Regulation by feedback

Question 1

[Maximum number: 4]

The complementarity of shapes and chemical properties allows molecules to bind to each other.

Describe, with examples, the types of molecule within cell-to-cell signalling systems that are complementary to each other.

Question 2

[Maximum number: 2]

State, giving one specific example, how individual bacteria change their characteristics when they form aggregates.

Question 3

[Maximum number: 1]

What releases leptin?

A

Thyroid gland

B

Hypothalamus

C

Pineal gland

D

Adipose tissue

Question 4

[Maximum number: 1]

State one example of a hormone that is a protein.

Question 5

[Maximum number: 3]

Distinguish between the mode of action of steroid hormones and peptide hormones.

Question 6

[Maximum number: 2]

The diagram demonstrates the action of steroid and peptide hormones in a section of cell and adjacent capillary.

Figure for Question 6 — IB Biology HL

On the diagram, label a
(i) second messenger.
(ii) gene regulatory protein.

Question 7

[Maximum number: 3]

The diagram shows a G protein, bound to a G protein-coupled receptor (GPCR), a transmembrane receptor which responds to epinephrine (adrenaline).

Figure for Question 7 — IB Biology HL

Explain how epinephrine exerts its effects in the cell.

Question 8

[Maximum number: 3]

The image shows an example of a label showing nutritional information

Figure for Question 8 — IB Biology HL

Describe the mode of action of steroid hormones.

Question 9

[Maximum number: 1]

What is an example of negative feedback in the menstrual cycle?

A

High levels of estrogen inhibit FSH secretion.

B

High levels of LH stop progesterone secretion.

C

High levels of FSH delay ovulation.

D

High levels of progesterone make follicles less receptive to FSH.

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