Anaerobic respiration
| English | Chinese | Pinyin |
|---|---|---|
| fermentation | 发酵 | fā jiào |
| lactate | 乳酸 | rǔ suān |
| anaerobic respiration | 无氧呼吸 | wú yǎng hū xī |
| aerenchyma | 通气组织 | tōng qì zǔ zhī |
| indicator | 指示剂 | zhǐ shì jì |
Respiring without oxygen
- With no oxygen, only glycolysis can run.
- To keep it going, the cell must regenerate its NAD.
- This is done by fermentation 发酵 — and it yields far less energy.
Fermentation
- Fermentation uses up reduced NAD so glycolysis can continue:
- in mammals, pyruvate → lactate 乳酸 (later broken down when oxygen returns).
- in yeast, pyruvate → ethanol + CO₂.
Anaerobic respiration 无氧呼吸: lactate or ethanol fermentation
Why fermentation matters
Step through it. Without oxygen, fermentation regenerates NAD so glycolysis can keep making a little ATP.
Why does fermentation matter when there is no oxygen?
Without oxygen, NAD must be regenerated by fermentation so glycolysis can continue making ATP.
Anaerobic respiration turns pyruvate into:
Mammals make lactate (lactate fermentation); yeast makes ethanol and CO₂ (ethanol fermentation).
In mammals anaerobic respiration produces lactate, while in yeast it produces ethanol and carbon dioxide.
Same problem (no oxygen), two different products: lactate in mammals, ethanol + CO₂ in yeast.
Match each to the right description.
Mammals make lactate, yeast makes ethanol; both regenerate NAD for a small ATP yield from glycolysis.
Much less energy
- Anaerobic respiration gains only the small amount of ATP from glycolysis.
- Aerobic respiration also runs the Krebs cycle and oxidative phosphorylation, releasing far more ATP.
- Rice copes with waterlogged roots: it grows aerenchyma 通气组织 (air spaces), uses ethanol fermentation, and grows stems fast to reach air.
Anaerobic respiration only gains ATP from ______ (there is no Krebs cycle or oxidative phosphorylation).
Aerobic respiration adds the Krebs cycle and oxidative phosphorylation, which release far more ATP.
One way rice survives waterlogged, low-oxygen roots is by:
Aerenchyma carries air to the roots; rice also uses ethanol fermentation and grows stems fast to reach air.
Measuring the rate
- A redox indicator 指示剂 like DCPIP or methylene blue loses its colour when it gains hydrogen from respiring cells.
- The faster the colour is lost, the faster respiration is — so you can test temperature or substrate effects. (A respirometer can also track oxygen uptake.)
How does DCPIP or methylene blue show the rate of respiration?
These redox indicators decolourise when reduced (gaining hydrogen); the faster they fade, the faster respiration.
You've got it
- no oxygen → only glycolysis; fermentation regenerates NAD to keep it running
- mammals → lactate; yeast → ethanol + CO₂
- anaerobic gives far less ATP (no Krebs / oxidative phosphorylation)
- rice: aerenchyma + ethanol fermentation + fast stems; rate measured with DCPIP / methylene blue