Summative Practice Chapter 7 – Question 6 & 7 (Form 4 Biology Textbook Exercise and Answer)

Question 6:
Photograph 1 shows the activities by two individuals, P and Q.

(a) (i) Based on Photograph 1, identify the respiration that occurs in the muscles of individuals P and Q.
(ii) State the products of respiration in P and Q.

(b) During the 100-metre sprint on Sports Day, a pupil experienced muscle cramps and had to stop running. Explain why muscle cramps happen.

(c) Paddy plants grown in waterlogged areas have tolerance to ethanol compared with other plants.
(i) State the type of fermentation that occurs in paddy plant cells.
(ii) Write the word equation for the fermentation process that occurs in the paddy plant cells.
(iii) Suggest another cell that can carry out the fermentation process as in question c(ii).

P: Aerobic respiration. Q: Fermentation

P: Carbon dioxide, water and energy
Q: Lactic acid and energy

When a person sprints, their muscle cells undergo fermentation in the absence of oxygen to produce ATPs. Muscles produce lactic acid that is toxic. Lactic acid causes cramps and muscle pain.

Alcohol fermentation

Glucose  Ethanol + carbon dioxide + energy


Question 7:
(a) Explain why energy is required in metabolic processes.
(b) Compare aerobic respiration with fermentation.
(c) Microorganisms such as yeast and bacteria usually play an important role in the fermentation process to produce food. Explain why yoghurt can spoil if it is not kept in the refrigerator.

• To maintain body temperature at the optimum temperature of 37 °C.

• For division as well as growth and development of cells.

• Both are cellular respiration.
• Both take place in animal and plant cells.
• Both produce energy in the form of ATPs.
• Both use glucose as the main substrate.


Aerobic respirationFermentation
Uses oxygenDoes not use oxygen or uses limited oxygen
Complete glucose oxidationIncomplete glucose oxidation
Respiration produces water, carbon dioxide and energyRespiration in yeast:
ethanol, carbon dioxide and energy

Respiration in muscle cell:
lactic acid and energy
Quantity of energy produced is big which is 2898 kJQuantity of energy produced is small
Yeast: 210 kJ
Muscle cell: 150 kJ
Process takes place in the cytoplasm and mitochondrionProcess takes place in cytoplasm.

The sugar in milk is oxidised by bacteria such as Lactobacillus and Streptococcus into lactic acid that solidifies the milk and produces a sour taste until curd is formed. When kept in the fridge, the low temperature controls bacterial activity from reproducing and spoiling the product. If kept at room temperature, the curd will spoil as bacteria will continue to grow and oxidise the milk sugar.

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