[94-II-2d] (P.125 #5 )
1. Explain why protein is less efficient for energy production when compared with
(i) lipid; and
(ii) carbohydrate. (optional bonus)
(i) - energy yield is less than lipid
(ii) - energy generation is less efficient compared to carbohydrate because it involves more complex metabolic pathway
(1 marks)
(1 marks)
1
1
[HKALE 82 I]
2. Distinguish between starch and cellulose
2. (b) Cellulose
(1) Long chains of

glucose molecules.
(2) Straight chains
(3)
(4)
Building material
Not stained dark blue with iodine
Starch
Long chains of

glucose molecules.
Molecules with branches
Storage form
Stained dark blue with iodine solution. solution
(any other reasonable differences will be acceptable)
(any two points) 2
(2 marks)
[GCE Nov. 92 Paper II] Q.2 (P.130 #26)
3. The table below gives some figures for the metabolism of carbohydrate and lipid in a mammal.
Energy source Metabolic energy produced / kJ g -1 food
Metabolic water produced / g g -1 food
Oxygen consumed / dm 3 g -1 food
Carbohydrate
Lipid
17.2
38.9
0.56
1.07
0.83
2.02
a. Using the information given in the table above, state two advantages to mammals of storing lipid rather than carbohydrates.
b. Suggest two other reasons why mammals might store lipids in preference to carbohydrates.
(2 marks)
(4 marks)
3. a. According to the information given in the table above, the two advantages to mammals of storing lipid rather than carbohydrates are: i.. Each gram of lipids produce more energy than carbohydrates when metabolically broken down. ii. More metabolic water per gram of respiratory substrate is produced when ‘burning’ lipids compared to carbohydrates. This metabolic water is very useful to the organism.
1
1
b. The other reasons why mammals might store lipids in preference to carbohydrates are: 2 x 1

Lipids are most useful for animals where insulation is required. This is because the heat conductance of lipids is low and it help to retain body heat, such as in the subcutaneous fat beneath the skin of mammals.
Lipids are also less dense in water as compared with carbohydrates. This feature is especially useful to many aquatic animals like sharks and whales, as th lipids aid in their buoyancy.
Lipids, as stored fat, can be used as a packing material around delicate organs because they can absorb shock and help to prevent the organs form physical injury .
Carbohydrates are unable to perform such a function.
(any two of above)
4. The following diagrams represent the structure of some common carbohydrates.
(a) Suggest a suitable name for each structure, A-D.
(a) A – cellulose B – amylose C –maltose/ disaccharide
5. Use the following terms to construct a short description of chemicals that are found in cells:
amino acid , hydrogen bond, helix structure, unbranched, β-glucose, chains
(4 marks)
D – amylopectin / glycogen