Signal Transduction Pathways · Voies de transduction du signal
| English | Français |
|---|---|
| signal transduction pathway/ˈsɪɡnl trænsˈdʌkʃn ˈpæθweɪ/ | voie de transduction du signal |
| second messenger/ˈsekənd ˈmesɪndʒə/ | second messager |
| amplification/ˌæmplɪfɪˈkeɪʃn/ | amplification |
| apoptosis/əpəpˈtəʊsɪs/ | apoptose |
One message can change a cell in different ways
- An adrenaline signal can make a liver cell release glucose rapidly. Another signal can change gene expression or tell a damaged cell to die.
- A cellular response depends on the pathway components and cell type; receiving the same external signal does not make every cell perform the same action.
The pathway is a chain
- A signal transduction pathway 信号转导通路 is a chain of molecules.
- Molecule A activates B, B activates C, and so on.
- Each step is a switch, turning on the next part of the chain.
- This relay carries the message from the receptor deep into the cell.
A signal transduction pathway is…
A pathway is a relay: molecule A activates B, B activates C, and so on inside the cell.
Second messengers 第二信使 spread it fast
- Some pathways use a second messenger — a small molecule that floods the cell.
- It carries the signal quickly to many places at once.
- This lets the response start almost instantly.
- A single receptor can release a burst of second messengers.
A signalling cascade · Une cascade de signalisation
Step down the cascade — each molecule activates many of the next, so one signal becomes a huge response.
What is a second messenger?
A second messenger is a small molecule that rapidly relays and spreads the signal within the cell.
When one signal produces a huge response through a cascade, we call it ____.
Each step activates many of the next, so amplification turns a tiny signal into a large effect.
Amplification 放大: small in, big out
- At each step, one molecule activates many of the next.
- So the numbers multiply down the chain — this is amplification.
- A handful of signal molecules can end in millions of active molecules.
- This is how a tiny signal produces a large response.
A cascade lets a very small signal cause a very large response.
Because each step multiplies the numbers, a few signal molecules can drive millions of active molecules.
Select all · tout true statements about signalling pathways.
Amplification means one signal makes many active molecules, not just one. The other three are correct.
A signal can change enzyme activity or gene expression
- An adrenaline signal in a liver cell can activate a pathway that breaks stored glycogen into material used to release glucose. This is a change in enzyme activity, not a need to make a new gene.
- Other pathways activate transcription factors and change which genes are expressed. Some signals trigger apoptosis 细胞凋亡, a controlled cell-death programme that removes unwanted or damaged cells.
A cellular response can include programmed cell death.
Apoptosis is a regulated response, not necessarily accidental injury.
A liver cell rapidly activates existing enzymes that break down glycogen. Which response is described?
The pathway can alter proteins already present; not all responses require new transcription.
A mutation can switch a pathway off or leave it on
- If a receptor can no longer bind its ligand, the normal response may disappear. If a downstream relay protein becomes permanently active, the cell may respond even when no ligand is present.
- Worked comparison: remove the ligand, then measure the output. A normal pathway switches off; a permanently active downstream component can keep the output high. The prediction depends on where the mutation acts.
A mutation makes a downstream relay permanently active. What can happen after the ligand is removed?
Constitutive relay activity can bypass the need for the upstream signal.
A signalling cascade · Une cascade de signalisation amplifies: one signal molecule does not make just one product — it makes a flood of them. Never assume "one signal, one response." A few molecules at the top can drive a huge effect at the bottom.
Adrenaline releasing your energy:
- A few adrenaline molecules bind receptors on a liver cell.
- Each triggers a cascade that activates more and more enzymes.
- The result: millions of glucose molecules released into the blood — a giant response from a tiny signal.
A signal transduction pathway is a relay chain where each molecule activates the next, often using a second messenger to spread the signal fast. Because each step activates many of the next, the pathway causes amplification — a tiny signal produces a large response.