B6.2B6. Respiration and Gas Exchange
Respiration in cells: aerobic and anaerobic — Combined Science 0653 - Biology Revision Notes & Topical Questions
5 min read 8 parts Lesson 4 of 8 Unit quiz
Lesson summary
B6.2 Respiration (Part 2): anaerobic respiration and oxygen debt — COMBINED SCIENCE notes: Describe anaerobic respiration in animals and yeast, compare it with aerobic respiration and explain oxygen debt.Anaerobic respiration = the chemical reactions in cells that break down nutr…
- Incomplete breakdown
- Word equation
- Carbon dioxide
- Balanced equation
- Bread making
- After exercise
Section 1 of 8Anaerobic respiration
Anaerobic respiration
Anaerobic respiration the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.
Incomplete breakdown
- Incomplete breakdown glucose is only partly broken down, so a relatively small amount of energy is released.
Products
- Products they depend on the type of organism.
Section 2 of 8Anaerobic respiration in animals
Where
- Where mainly in muscle cells during vigorous exercise.
Why
- Why the muscles need energy faster than oxygen can be delivered, so some glucose is broken down without oxygen.
Product
- Product lactic acid, which still holds energy in its bonds.
Word equation
- Word equation glucose → lactic acid.
Carbon dioxide
- Carbon dioxide it is not a product of anaerobic respiration in animals.
Section 3 of 8Anaerobic respiration in yeast
Word equation
- Word equation glucose → alcohol + carbon dioxide.
Balanced equation
- C6H12O6 → 2C2H5OH + 2CO2.
Bread making
- Bread making the carbon dioxide makes the dough rise.
Brewing
- Brewing the ethanol makes beer alcoholic and the carbon dioxide makes it fizzy.
Section 4 of 8Oxygen debt
1
Lactic acid builds up in muscle cells and lowers their pH.
2
The lower pH could denature enzymes, so the lactic acid must be removed.
3
The cells release the lactic acid into the blood.
4
The blood carries it to the liver, where liver cells take it up.
5
In the liver it reacts with oxygen to make carbon dioxide and water.
Oxygen debt
Oxygen debt the extra oxygen needed after exercise to remove the lactic acid.
After exercise
- After exercise breathing and heart rate stay high to carry lactic acid to the liver and supply oxygen, which is repaying the oxygen debt.
Section 5 of 8Comparison of aerobic and anaerobic respiration
| Feature | Aerobic | Anaerobic |
|---|---|---|
| Oxygen | Needed | Not needed |
| Glucose breakdown | Complete | Incomplete |
| Products | Carbon dioxide and water | Lactic acid in animals, ethanol and carbon dioxide in yeast |
| Energy per glucose molecule | Relatively large | Relatively small |
Section 6 of 8More from the specification
More from the specification
Aerobic vs Anaerobic Respiration
- Aerobic respiration completely breaks down glucose using oxygen to yield a large amount of energy (ATP), water,
- and carbon dioxide,
- whereas cells respiring anaerobically break down glucose incompletely without oxygen,
- producing lactate in mammals or ethanol and CO2 in yeast.
Investigating Respiration with Methylene Blue
- In an experiment investigating yeast respiration, methylene blue solution acts as an artificial electron acceptor that changes colour from dark blue to colourless as it is reduced by hydrogen atoms taken from respiratory substrates.
Temperature Effect on Respiration Rate
- A graph of temperature versus respiration rate shows that rate increases up to the optimum temperature due to greater kinetic energy and collision frequency,
- then drops sharply as respiratory enzymes become denatured.
Experimental Variables in Respiration Investigations
- When testing the effect of temperature on yeast respiration, the independent variable is temperature, the dependent variable is time taken for the indicator colour change,
- and controlled variables include yeast suspension volume, glucose concentration,
- and pH.
Aerobic vs Anaerobic Respiration
- Aerobic respiration completely breaks down glucose using oxygen to yield a large amount of energy (ATP), water,
- and carbon dioxide,
- whereas cells respiring anaerobically break down glucose incompletely without oxygen,
- producing lactate in mammals or ethanol and CO2 in yeast.
Investigating Respiration with Methylene Blue
- In an experiment investigating yeast respiration, methylene blue solution acts as an artificial electron acceptor that changes colour from dark blue to colourless as it is reduced by hydrogen atoms taken from respiratory substrates.
Temperature Effect on Respiration Rate
- A graph of temperature versus respiration rate shows that rate increases up to the optimum temperature due to greater kinetic energy and collision frequency,
- then drops sharply as respiratory enzymes become denatured.
Experimental Variables in Respiration Investigations
- When testing the effect of temperature on yeast respiration, the independent variable is temperature, the dependent variable is time taken for the indicator colour change,
- and controlled variables include yeast suspension volume, glucose concentration,
- and pH.
Independent variable
- The variable that is changed on purpose.
Temperature
- Average energy of the particles in an object.
Variable
- Anything that might change during an experiment.
Section 7 of 8Key terms
| Term | Meaning |
|---|---|
| Anaerobic respiration | Respiration without oxygen that releases a small amount of energy. |
| Lactic acid | The product of anaerobic respiration in animal cells. |
| Ethanol | The alcohol made by yeast in anaerobic respiration. |
| Oxygen debt | The extra oxygen needed after exercise to remove lactic acid. |
| Fermentation | Anaerobic respiration by yeast. |
| Vigorous exercise | Hard exercise in which oxygen supply cannot meet demand. |
Section 8 of 8Exam technique
1
Listing carbon dioxide as a product of anaerobic respiration in muscle — the only product is lactic acid.
2
Saying anaerobic respiration releases more energy than aerobic — it releases less.
3
Saying yeast makes lactic acid — yeast makes ethanol and carbon dioxide.
4
Saying oxygen debt is a lack of oxygen during rest — it is the extra oxygen needed after vigorous exercise.
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