Hard questions

Question 1

Describe why facilitated diffusion requires no metabolic energy

Answer 1

1. Particles have their own kinetic energy

2. Move down the concentration gradient

Question 2

Explain why glucose cannot pass through a cell membrane by simple diffusion

Answer 2

1. Phospholipids act as a barrier

2. The molecules are too large

Question 3

Suggest how the leaf of pondweed is supported

Answer 3

1. Air spaces give buoyancy

2. Supported by surrounding water

Question 4

Suggest why antibodies specific to nuclear proteins are not normally made

Answer 4

1. Nuclear proteins normally hidden in the nucleus

Question 5

Suggest how water is being lost from the cut stem when leaves have been treated with petroleum jelly in a potometer experiment

Answer 5

1. Evaporation form upper leaf surfaces

Question 6

Suggest two sources of error in a potometer experiment

Answer 6

1. Not all lower leaf surfaces covered
2. leaks in apparatus
3. Shoot not cut under water
4. Error in reading position of the meniscus

Question 7

Explain why bone is described as a tissue and gills are described as organs

Answer 7

1. Tissue has few types of cells and performs one function
2. Bone has a few types of cells and performs one function
3. Organs consist of several tissues
4. Gills contain blood, bones, epithelial and connective tissue

Question 8

How would the calculated rate differ form the true initial rate of reaction in an enzyme reaction

Answer 8

1. Initial rate is likely to be greater

2. Because higher concentration of substrate at start, so more chance of substrate entering the active site

Question 9

Give ways to refine an experiment so reproducible results would be obtained

Answer 9

1. Specify volumes of reactants added
2. Specify volume that should be removed for testing
3. Stir before taking the sample
4. Test with iodine- for starch, or other chemicals
5. Carry them all out at the same temperature

Question 10

Explain why vaccinations are examples of active immunity

Answer 10

1. Antibodies are produced
2. Activation of lymphocytes
3. Memory cells remain

Question 11

State 3 properties of fibrous proteins that are different to globular proteins

Answer 11

1. Insoluble
2. Strong
3. Unreactive

Question 12

How could haemoglobin be identified in urine

Answer 12

1. Add biurets reagent
2. Colour change from blue to purple
3. Compare with control

Question 13

Outline how the difference in lumen size between arteries and veins is related to their function

Answer 13

1. In arteries small lumen maintains high pressure
2. In veins large lumen- low resistance needed because of low pressure
3. Same flow rate is achieved by having a larger volume

Question 14

Why is movement of molecules from the plasma membrane towards the centre of living cells greater than in an experiment

Answer 14

1. Involvement of vesicles/ cytoskeleton