1. MOLECULES TO METABOLISM
A1. 4 A2. The synthesis of complex molecules from simpler ones, requiring an input of energy. A3. A molecule consisting of two identical molecules linked together A4. D A5. A. fructose/ribose/deoxyribose/ribulose/other monosaccs 1 B. (i) disaccharide 1 (ii) hydrolysis 1
J WERBA – IB BIOLOGY 1

2. WATER A1. and A2. B A3. coolant in sweat/in transpiration;
water has a high latent heat of vaporisation / heat taken when hydrogen bonds break;
water is cohesive so can pulled up/so can be moved under tension in xylem;
water is an excellent/universal solvent/dissolves many different substances;
medium for transport in blood/xylem/phloem;
medium for metabolic reactions / (metabolic) reactions happen dissolved in water;
surface tension due to cohesion allows organisms to live on water surface;
water has high specific heat capacity so much energy required to change its temperature;
ice floats so lakes/oceans do not freeze allowing life under the ice;
high heat capacity so stable habitat/so temperature of water changes slowly;
used in chemical reactions/photosynthesis/hydrolysis in organisms;
There were a lot of possible answers to this question on the importance of water so strong candidates had no difficulty in reaching five marks. Weaker answers were vague and incomplete and sometimes muddled up the properties of water such as coherence and adherence and the various thermal properties.
J WERBA – IB BIOLOGY 2

3. CARBOHYDRATES & LIPIDS
A1 A2
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4. CARBOHYDRATES & LIPIDS
A3 A
A4 B A5
hydrolysis: [3 max] when larger molecules are broken to smaller molecules/subunits; with the addition of water; fatty acids produced by the hydrolysis of fats/triglycerides; breaking of ester bonds; with release of glycerol;
condensation: [3 max] when molecules/subunits are joined to form a larger molecule; water formed/removed; fatty acids linked to glycerol; up to three fatty acids can be linked to each glycerol; through formation of ester bonds;
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5. PROTEINS A1 D A2 structural – collagen / membrane proteins;
transport – hemoglobin / protein channels;
movement – actin / myosin;
hormones – insulin / vasopressin / growth hormone;
defense – antibodies / immunoglobins;
Award any other valid function and example.
J WERBA – IB BIOLOGY 5

6. ENZYMES
A1. C
A2. A
A3. B
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7. ENZYMES
A4.
at low temperatures, rate of reaction increases as temperature increases (or vice versa);
more kinetic energy / faster movement of molecules means more collisions between enzyme / active site and substrate;
optimum temperature is temperature at which rate of enzyme-catalyzed reaction is fastest;
at high temperatures enzymes are denatured and stop working;
denatured means change of structure in enzyme / protein resulting in loss of its biological properties / no longer can carry out its function;
too much kinetic energy / vibrations breaks bonds that give enzyme specific shape;
optimum pH is one at which rate of enzyme-catalyzed reaction is fastest;
rate of reaction reduced as increase or decrease pH (from optimum);
strong acids and alkalis can denature enzymes;
affect (weak, ionic, hydrogen) bonds that hold enzyme in specific shape;
at low substrate concentrations, as increase concentration get increase in rate of reaction;
more chance of collision between substrate and enzyme / active site;
at high substrate concentration, have no change in rate as increase concentration;
all active sites occupied;
J WERBA – IB BIOLOGY 7