Formative Practice 7.3 (Form 4 Biology Textbook Exercise and Answer)

Question 1:
State where the process of fermentation usually occurs.

Human muscle cells, some bacteria, yeasts and plants.

Question 2:
Give three examples of microorganisms and food produced by the fermentation process.

Organism: Saccharomyces
Product of fermentation: CO2, ethanol
Example: wine, beer

Organism: Aspergillus
Product of fermentation: lactic acid
Example: soy sauce

Organism: Acetobacter
Product of fermentation: Acetic acid
Example: vinegar

Question 3:
While helping your father to cut the grass at the farm, you come across a snake. Terrified, you run away from the snake. Explain the cellular respiration that takes place in the muscle cells of your legs.

When you sprint, the lungs and blood supply are unable to supply oxygen quickly enough to meet the demands of the muscles to produce ATP. In this condition, the muscle cells undergo fermentation, whereby ATP is produced without oxygen.
Fermentation in muscle cells produces lactic acid.

Question 4:
State the differences between aerobic respiration and fermentation.

• Aerobic respiration involves the complete breakdown of organic substances in the presence of oxygen whereas fermentation involves incomplete breakdown of organic substances in the presence of limited oxygen or absence of oxygen.

• Aerobic respiration takes place in cytoplasm and mitochondria but fermentation only takes place in the cytoplasm.

• Aerobic respiration produces water whereas fermentation does not.

• In aerobic respiration, glucose is oxidised completely into carbon dioxide and water whereas in fermentation, glucose is oxidised to ethanol or lactic acid.

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