eoy exam questions

Question 1

outline the role of B memory cells in the secondary immune system [2]

Answer 1

B memory cells divide to form plasma cells
produce and release antibodies
which bind to antigens

Question 2

outline the roles of phagosomes and lysosomes in phagocytosis [3]

Answer 2

phagocyte engulfs pathogen in a phagosome
lysosomes combine with phagosome
enzymes destroy pathogens

Question 3

explain how haemoglobin acts as a buffer [2]

Answer 3

CO2 +H20 –> carbonic acid
carbonic acid dissociates to form H+ ions
H+ binds to Hb
CO2 can be carried as HCO3-

Question 4

explain why the Bohr effect is important during exercise [2]

Answer 4

• more CO2 during exercise - curve shifts to the right
• pO2 Hb has a lower % saturation of O2
• O2 dissociates from Hb more readily
• more oxygen needed for anaerobic respiration

Question 5

explain how the properties of water are related to the transport role of water in a stem [3]

Answer 5

cohesion holds water molecules together
- chains of H2O molecules pulled up xylem
adhesion allows H2O to stick to xylem walls
- by capillary action
acts as a solvent to dissolve assimilates
- for transport in phloem

Question 6

explain the role of meristem tissue in a stem [2]

Answer 6

meristem is undifferentiated cells
growth and repair of damaged tissues

Question 7

explain how Fig. 21.1 shows that insulin has a quaternary structure [2]

Answer 7

made of 2 polypeptide chains

Question 8

suggest why insulin glargine is long lasting [1]

Answer 8

change in primary structure changes tertiary structure
no longer complementary
less likely to be broken down by enzymes
change in solubility

Question 9

outline the steps involved in the process of making the modified polypeptides that form insulin glargine [4]

Answer 9

1. modified gene undergoes transcription in nucleus
2. production of mRNA
3. mRNA leaves nucleus
4. translation at ribosome
5. tRNA with specific amino acids binds its anticodon
6. formation of peptide bonds between amino acids