Lesson 1 of 4 / Cell signalling and glucose control
Reception, transduction and response
Why does the same signal affect only some cells?
In this lesson: Explain membrane receptor specificity and the stages of cell signalling.
About 6 min
The key ideaA target cell needs a suitable receptor and downstream machinery; binding starts a pathway that changes cell behaviour.
Explore the idea
Find the first step that fails
A ligand is outside the cell. Predict whether this cell can reach a gene-expression response, then follow the steps.
Arrows mean information passed through a pathway. They do not mean the extracellular ligand travels through each box. The shown response is increased transcription; other pathways can repress genes or change existing protein activity.
Explanation
A signalling molecule, or ligand, binds a receptor with suitable complementary shape and chemical properties. A cell without the relevant receptor may not respond even when exposed to the ligand. Receptor distribution therefore contributes to tissue specificity.
Ligand binding changes a membrane-bound receptor's conformation or association with other proteins, initiating signal transduction. Intracellular relay components pass information through the cell; the external ligand need not cross the membrane and physically contact every responding enzyme.
The response may change existing enzyme activity, membrane transport or gene expression. A transcription factor activated by a pathway can alter the production of proteins, creating a slower but sustained response compared with modification of an existing protein.
Different cells can respond differently to the same ligand because they have different downstream components. Distinguish reception, transduction and response in an unfamiliar pathway diagram, and use an inhibitor or receptor-deficient comparison to locate where signalling fails. Intracellular receptors are outside the specified scope.
Step by step
- 1
Find the receptor
Identify the first specific recognition event.
- 2
Trace the relay
Follow arrows between intracellular components.
- 3
Name the output
State what changes in the cell, not just that a signal occurs.
Worked example
Work through the evidence
Two cells bind the same ligand, but only one activates a target gene. Suggest a reason.
One way to explain it
The cells may differ in downstream signalling proteins or transcription factors, so equal receptor binding need not produce the same response.
Why this answer works
- Receptor presence is necessary in the model but may not be sufficient.
- The divergence can occur after reception.
Is this true? "A hormone must enter the nucleus itself to change gene expression."
A membrane receptor can initiate a relay that activates nuclear transcription factors without the hormone entering the cell.