B2 2020

Question 1

3.1 Other than the thermometer, explain how two features of the calorimeter shown in Figure 2 would enable a valid measurement of the total heat energy released

Answer 1

Water has high specific heat capacity
Stirrer distributes heat energy

Question 2

5 Describe the sequence of events involved in transmission across a cholinergic synapse

Answer 2

Depolarisation of presynaptic membrane
Ca2+ channels open Ca2+ ions enter
Vesicle fuse with presynaptic membrane
Neurotransmitter diffuses across synaptic cleft
Bind to complementary receptors on post synaptic membrane
Na+ ions enter leading depolarisation

Question 3

9.1 Describe how enzymes could be used to insert the GH gene into a plasmid

Answer 3

Sticky ends created which are complementary to each other
DNA ligase joins sticky ends together forming phosphodiester bonds

Question 4

9.2 Suggest and explain how delayed insertion of GH gene could produce offspring of transgenic fish without desired characteristic

Answer 4

Mitosis started already without the gene
Gametes don’t receive gene

Question 5

10.2 The heart rate and the metabolic rate of black bears decrease. Use knowledge of nervous control of heart rate to describe how these are linked

Answer 5

Less CO2
Detected by chemoreceptor
In aorta
Fewer impulses to cardiac centre impulses along parasympathetic nerve
To SAN