Signal Transduction Pathways
| English | Chinese | Pinyin |
|---|---|---|
| signal transduction pathway | 信号转导通路 | xìn hào zhuǎn dǎo tōng lù |
| second messenger | 第二信使 | dì èr xìn shǐ |
| amplification | 放大 | fàng dà |
A relay race inside the cell
- Once a signal is received, the message must travel through the cell.
- It does this as a relay — one molecule handing off to the next.
- Along the way, the signal can grow enormously.
- These chains are called signal transduction pathways.
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 spread it fast
- Some pathways use a second messenger 第二信使 — 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
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: small in, big out
- At each step, one molecule activates many of the next.
- So the numbers multiply down the chain — this is amplification 放大.
- 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 true statements about signalling pathways.
Amplification means one signal makes many active molecules, not just one. The other three are correct.
A signalling cascade 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.