Biology aqa paper 3
1. Explain why the sevretion of osteocalcin by osteoblasts is controlled by
positive feedback: osteocalcin causes more release of insulin insulin causes more
osteocalcin release
2. The acidic pH conditions created by oesteoclasts cause the inactive form
of osteocalcin to change into the active form. Suggest how: pH stresses ionic and
hydrogen bonds so changes the tertiary structure
3. Binding of insulin leads to an increase in the rate of respiration in cells such
as osteoblasts. Explain how: Insulin leads to more channel proteins for glucose so more
glucose enters the cell where it is used as respiratory substrate
4. From this data, what can you conclude about the effectiveness of
Rituximab
in treating CLL: The more cd20, the higher the percentage of B cells destroyed and
thus more effective At best, only destroys 80% of cells so wont cure CLL
Dont know percentage of cancer cells killed
5. Suggest how the mutation of notch1 led to the difference in the
percentage of
B cells destroyed: mutation changes tertiary structure of transcription factor so it is no
longer complementary to CD20 gene and thus cannot bind. This means no mRNA for CD20
is transcribed so little Rituximab to bind to so few
B cells destroyed
6. A method to prevent passing on faulty mitochondria involves removing
nucleus of an egg cell from healthy person and replacing with contents of polar
body of affected person. Suggest how this treatment prevents inheritance of
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, mitochondrial disease: egg has DNA from affected mother but has lots of normal
mitochondria from the unaffected woman
7. When mitochondria is faulty, it prevents or slows down many enzyme-
catalysed reactions. Suggest and explain one reason why: Not enough ATP
produced in aerobic respiration
ATP provides energy for these reactions
8. To obtain protein CENP-W, scientists broke open cells and organelles using
a detergent that dissolves lipids in water. Suggest how the detergent releases
CENP-W from cells: Cell membranes are made from phospholipid so detergent dissolves
phospholipid bilayer
9. Explain how ultracentrifugation separates CENP-W from other molecules:
Spin at high speed
Molecules separated depending on density
10 Figure 5 shows the results of the electrophoresis. The size of each band is
proportional to the amount of CENP-W present. Suggest how the sirna produced these
results: siRNA binds to mRNA for CENP-W prevents translation of CENP-W
as CENP-W reduces so does tubulin production
11. Scientists concluded that the soil mixture experiment showed there were
different communities of bacteria in soils A and B. What evidence from figure 6 supports
their conclusion: B has fastest rate of ammonia breakdown
A + B is slower than A or B
Suggests community of bacteria at pH 4.3 doesnt work well at pH 6.9
12. This method allowed the scientists to estimate the expression of the amoA gene in
each culture but not the growth of the bacterial population in each culture. explain why:
They didnt count bacteria
Copies of mRNA relate to the amount of amoA
Dont know how much amoA produced by each cell
Dont know if amoA is linked to growth of population
13. Suggest one suitable method for sterilising the bottles and explain why it
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1. Explain why the sevretion of osteocalcin by osteoblasts is controlled by
positive feedback: osteocalcin causes more release of insulin insulin causes more
osteocalcin release
2. The acidic pH conditions created by oesteoclasts cause the inactive form
of osteocalcin to change into the active form. Suggest how: pH stresses ionic and
hydrogen bonds so changes the tertiary structure
3. Binding of insulin leads to an increase in the rate of respiration in cells such
as osteoblasts. Explain how: Insulin leads to more channel proteins for glucose so more
glucose enters the cell where it is used as respiratory substrate
4. From this data, what can you conclude about the effectiveness of
Rituximab
in treating CLL: The more cd20, the higher the percentage of B cells destroyed and
thus more effective At best, only destroys 80% of cells so wont cure CLL
Dont know percentage of cancer cells killed
5. Suggest how the mutation of notch1 led to the difference in the
percentage of
B cells destroyed: mutation changes tertiary structure of transcription factor so it is no
longer complementary to CD20 gene and thus cannot bind. This means no mRNA for CD20
is transcribed so little Rituximab to bind to so few
B cells destroyed
6. A method to prevent passing on faulty mitochondria involves removing
nucleus of an egg cell from healthy person and replacing with contents of polar
body of affected person. Suggest how this treatment prevents inheritance of
1/7
, mitochondrial disease: egg has DNA from affected mother but has lots of normal
mitochondria from the unaffected woman
7. When mitochondria is faulty, it prevents or slows down many enzyme-
catalysed reactions. Suggest and explain one reason why: Not enough ATP
produced in aerobic respiration
ATP provides energy for these reactions
8. To obtain protein CENP-W, scientists broke open cells and organelles using
a detergent that dissolves lipids in water. Suggest how the detergent releases
CENP-W from cells: Cell membranes are made from phospholipid so detergent dissolves
phospholipid bilayer
9. Explain how ultracentrifugation separates CENP-W from other molecules:
Spin at high speed
Molecules separated depending on density
10 Figure 5 shows the results of the electrophoresis. The size of each band is
proportional to the amount of CENP-W present. Suggest how the sirna produced these
results: siRNA binds to mRNA for CENP-W prevents translation of CENP-W
as CENP-W reduces so does tubulin production
11. Scientists concluded that the soil mixture experiment showed there were
different communities of bacteria in soils A and B. What evidence from figure 6 supports
their conclusion: B has fastest rate of ammonia breakdown
A + B is slower than A or B
Suggests community of bacteria at pH 4.3 doesnt work well at pH 6.9
12. This method allowed the scientists to estimate the expression of the amoA gene in
each culture but not the growth of the bacterial population in each culture. explain why:
They didnt count bacteria
Copies of mRNA relate to the amount of amoA
Dont know how much amoA produced by each cell
Dont know if amoA is linked to growth of population
13. Suggest one suitable method for sterilising the bottles and explain why it
2/7
