Insulin from bacteria
314 words over 30 numbered lines, then 6 parts worth 13 marks (Modular Unit 2 (4WBI2) style, 12–13 marks). Read the article, answer each part, then open its mark scheme and set your mark.
Illustrative article written for Scholar Lab, not a Pearson text. The biology is real; the studies, people and figures are invented or rounded for practice unless a source is named.
Insulin from bacteria
People with type 1 diabetes cannot make the hormone insulin, so they
must inject it every day. For about sixty years, the insulin used came
from the pancreases of pigs and cattle collected from slaughterhouses.
The supply was limited, and the animal insulin was slightly different
from human insulin, so a few patients reacted badly to it. Some people
also objected to using animal products for religious or ethical
reasons.
In 1982, insulin made by genetically modified bacteria became the
first medicine of its kind to go on sale. To make it, scientists cut
the human insulin gene out of human DNA using a restriction enzyme.
The same restriction enzyme was used to cut open a plasmid, a small
ring of DNA found in bacteria. The cut ends of the plasmid and the
gene matched, and an enzyme called DNA ligase joined them together.
The plasmid acted as a vector, carrying the human gene into a
bacterial cell.
The genetically modified bacteria are grown in a large steel container
called a fermenter. Nutrients are added, and sterile air is bubbled
through the liquid. A water jacket around the fermenter keeps the
temperature steady, and a probe monitors the pH. Paddles stir the
mixture. Everything that enters the fermenter must be sterile. When
conditions are right, the bacteria divide about every twenty minutes.
A company tested how the temperature of the fermenter affected the
mass of insulin produced in 48 hours. The company used the same strain
of bacteria and the same volume of nutrient solution in each run. The
results are shown in Figure 1.
At the end of each run, the insulin is separated from the bacteria and
purified. Because the bacteria reproduce rapidly, large amounts of
insulin can be made, and every batch is identical to human insulin.
Today most people with diabetes use insulin made by genetically
modified microorganisms, including yeast.
Figure 1 Mass of insulin produced in 48 hours at different fermenter temperatures
Read the article and study the figure. Use the information in the article and your own knowledge to answer the questions. The lines in brackets show where to look; select them to highlight the text.
Use the information in the article and your own knowledge to answer the questions. The lines in brackets show you where to look; select them to highlight the text.
State what is meant by the term vector.
(1)Describe how the human insulin gene is inserted into a plasmid.
(3)Use Figure 1 to calculate the percentage decrease in the mass of insulin produced when the temperature is raised from 37 °C to 45 °C.
(2)Explain why the fermenter needs a water jacket to keep the temperature steady.
(2)Explain why everything that enters the fermenter must be sterile.
(2)Suggest three advantages of using insulin from genetically modified bacteria rather than insulin from pigs and cattle.
(3)Total for this question: 13 marks
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