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Form 6 Biology: 6th revision test Marking scheme
Question 1
(a) The frozen layer cuts off the atmospheric oxygen from dissolving into the pond water.
The dissolved oxygen in the pond water is used up by the aquatic lives.
(b) The goldfish carries out anaerobic respiration
The amount of energy produced from anaerobic respiration of glucose is one-nineteenth of that
produced from aerobic respiration of the same amount of glucose molecule.
(c) Skeletal mucle
(d) Lactate is water soluble/ dissolve in blood or tissue fluid
causing outward movement of water from the tissue cells by osmosis.
(e) Amino acid acts as buffer.
Some ions such as HPO4=/ PO43- is a buffer.
Haemoglobin of red blood cells is also a buffer. (any TWO)
(f) Amino acids can be converted into appropriate alpha keto acids
which enter glycolysis or Krebs cycle.
(g) Alanine
Glutamate
Question 2
(a) A > B > C
(b) In the step of conversion of triose phosphate to Glycerate phosphate
with formation of hydrogen/ NADH2
which reduce pyruvic acid
to ethanol and carbon dioxide
(c) Glucose is the substrate of glycolysis and therefore adding glucose to tube A accounts for its fastest
rate.
(d) C > B / A> A/B
In test tube C, fluoride inhibits the step of Glycerate phosphate to PEP,
with formation of no or less pyruvic acid.
Pyruvic acid compete with methylene blue for the reducing agent / H produced. OR
Without pyruvic acid, the reducing agent will reduce the methylene blue rapidly.
(e) E is Adenosine triphosphate.
The roles of ATP in human metabolism:
a. ATP is hydrolysed by enzyme ATPase to ADP + Pi with liberation of energy in various forms:
1. mechanical energy for muscle contraction
2. bio-electrical energy for transmission of nerve impulse or action potential along neuron.
3. heat energy for regulation of body temperature
4. other forms of energy for active transport e.g. absorption of foods in ileum, reabsorption in
nephron of kidneys.
TWO of the above forms.
b. ATP is the raw materials to build up dinucleotides and polynucleotides.
c. ATP is the phosphorylating agent such as converting glucose to glucose phosphate in
glycolysis.
Question 3
Both takes place in anaerobic condition.
Both are incomplete breakdown of glucose.
Both involves glycolysis only, without Krebs cycle and oxidative phosphorylation.
The by-product of both still have a large amount of energy reserve.
Both produces 2 ATP per glucose molecule/ produces a small amount of energy
Both involve reduction of pyruvate by NADH2
Both takes place in cytoplasmic matrix only.
Mitochondria are NOT involved in both.
Lactic acid fermentation
takes place in animal cells
Lactic acid is formed as the by-product.
Accept the other alternative answers
Alcoholic fermentation
takes place in plant and yeast cells
The by-products are ethanol and carbon dioxide.
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