Biology Question Paper

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HKALE 1990 Biology Paper II1
HKALE 1993 Biology Paper II1
HKALE 1996 Biology Paper II1
HKALE 1999 Biology Paper II1
Suggested Solution3
HKALE 1990 Biology Paper II3
HKALE 1993 Biology Paper II4
HKALE 1996 Biology Paper II6


HKALE 1990 Biology Paper II

5.(b)Discuss the importance of carbohydrates, lipids, proteins and roughage in the human diet. (8 marks)

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HKALE 1993 Biology Paper II

6.Based upon its properties, discuss the role of water in the functioning of organisms .(20 marks)

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HKALE 1996 Biology Paper II

4.Describe the functions of lipids, proteins and nucleotides in living organisms. Illustrate your answer with examples and provide explanations where appropriate.(20 marks)

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HKALE 1999 Biology Paper II

1.(a)State four properties of water which make it essential for life and explain why they are essential. (6 marks)

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Suggested Solution

HKALE 1990 Biology Paper II

5 (b)carbohydratesstructural component of membranes0.5) nucleic acid0.5)any 2
and ATP0.5)
as energy source0.5)

lipidsas energy reserve0.5) as primary component of membrane0.5) as insulating layer0.5)
as carrier of fat soluble vitamins (e.g. A & D)0.5)

proteins : source of (essential) amino acids for growth and repair / structural proteins / enzymes0.5, 0.5, 0.5) hormones0.5)

antibodies0.5) any 4
contractile proteins0.5)
energy reserve in starvation0.5)

roughage : make food more bulky to stimulate peristalsis of the gut,0.5 prevent excessive absorption of water in colon / constipation0.5

Discussion :Each of the four food substances has at least one unique function which cannot be replaced by other food substance.0.5 therefore they are all important in the diet i.e. a balanced diet must consist all of them.0.5 However, there is still some possible interconversion of food substance0.5 e.g. between carbohydrates, lipids and proteins (excluding the essential a.a.) except roughage.0.5 (8)

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HKALE 1993 Biology Paper II

6.The following properties of water are essential to the normal physiological functioning of cells / living organisms :

(1)As a reagent participating in many of the metabolic activities of protoplasm e.g. -it provides the reducing hydrogen in the photosynthetic process of green plants it is essential to the multitude of hydrolytic reactions which take place in all living organisms(3)

(2)As the principal solvent for most of the substances concerned in protoplasmic activity e.g.all the materials which enter or leave living cells can do so only in aqueous solution (osmosis, diffusion) within the organism, transport takes place only in aqueous solution e.g. nutrients, excretory products, dissolved gases, inorganic ions, hormones, etc.(3)

(3)It has a high specific heat capacity and thus will not be subject to extremely rapid fluctuations in temperature which would affect the rate of all chemical changes. The chemical reactions in an organism's body may produce enormous amounts of heat. Were it not for the high capacity of water to absorb heat, an organism's temperature might rise so far that life would cease. That is, water offers a fairly stable temperature...
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