2 - molecular biology

Question 1

explain importance of hydrogen bonding for living organisms [8]

Answer 1

• cohesion in H2O allow molecules to stick (due to H-bonding)
• useful in transpiration stream to bring water up the xylem
• adhesion of H2O to polar molecules or surfaces (due to H-bonding)
• can help keep leaves moist
• high latent heat of vaporization, much energy needed for evaporation
• acts as good coolant
• solvent properties due to H-bonding with polar/hydrophilic molecules
• high SHC so there are little temp. fluctuations for organisms with water habitats

Question 2

compare energy storage abilities of glycogen and triglycerides (include their properties) [3]

Answer 2

• glycogen is a carbohydrate and is soluble
• triglycerides are lipids are are insoluble

glycogen: short-term storage, energy is not pure, easy to transport

trigly: long-term storage, energy is pure, difficult to transport

Question 3

mnemonics for drawing biological molecules (carbs, fatty acids, nucleic acid)

Answer 3

carbs
- ribose 5C, -OH UDD (C 1-3)
- a-glucose 6C, -OH DDUD (C 1-4)
- b-glucose 6C, switch -OH UDUD (C 1-4)

fatty acid
- no C=C is saturated
- yes C=C is unsaturated

nucleic acid
- ribose, C1 base, C5 phosphate
- phosphodiester from C3 to phosphate
- H-bonding between bases
- upright acid side is 5’ to 3’
- upside down acid side is 3’ to 5’

Question 4

list general functions of non-membrane proteins [4]

Answer 4

• enzymes
• hormones
• histones
• movement/contraction (actin myosin)
• immunity

Question 5

use of lactase in lactose-free milk production [8]

Answer 5

• lactose is a disaccharide found in milk
• can be broken down by lactase into glucose and galactose
• lactase can be added into milk to reduce lactose content
• accommodate those who are lactose-intolerant

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- glucose and galactose are monosaccharides, so sweeter
- lactose-free milk is generally sweeter, less sugar needed
- bacteria ferment glucose and galactose quicker, so production of yoghurt/cheese is quicker