Explain how a lipid-soluble hormone produces a response in a target cell, including the role of the hormone–receptor complex.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Lipid‑soluble hormones are non‑polar and can diffuse directly across the phospholipid bilayer of the plasma membrane.
Once inside the cell they bind to a specific receptor protein that is located in the cytoplasm or nucleus, forming a hormone–receptor complex.
The complex then moves into the nucleus (or acts there) and functions as a transcription factor, binding to specific response elements on DNA.
Binding of the complex to DNA changes the rate of transcription of particular genes, which alters protein synthesis and produces the cellular response.
Once inside the cell they bind to a specific receptor protein that is located in the cytoplasm or nucleus, forming a hormone–receptor complex.
The complex then moves into the nucleus (or acts there) and functions as a transcription factor, binding to specific response elements on DNA.
Binding of the complex to DNA changes the rate of transcription of particular genes, which alters protein synthesis and produces the cellular response.
Examiner tips
- Show the hormone’s ability to cross the membrane first; this is a key point. Explain the formation of the hormone–receptor complex and its location. Describe the complex acting as a transcription factor. Link altered transcription to changes in protein synthesis and the final response.
Common mistakes
- Forgetting that the hormone is lipid‑soluble and can cross the membrane. Failing to mention that the receptor is intracellular. Confusing the complex with a membrane receptor or omitting the transcription‑factor role.
Mark scheme (4 marks)
- Lipid-soluble hormones can diffuse directly across the phospholipid bilayer of the plasma membrane (because they are non-polar / hydrophobic).
- The hormone binds to a specific receptor protein located in the cytoplasm or nucleus of the target cell, forming a hormone–receptor complex.
- The hormone–receptor complex moves into (or acts within) the nucleus and functions as a transcription factor, binding to specific regions of DNA (response elements / promoter regions).
- Binding of the hormone–receptor complex to DNA alters the rate of transcription of specific genes, leading to changes in protein synthesis and hence a cellular response.
Key terms in this question
lipid-soluble hormone · hormone–receptor complex · target cell
Related
- All IB DP Biology Higher Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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