A pancreas you can wear
366 words over 34 numbered lines, then 8 parts worth 16 marks (Linear Paper 2 (4BI1/2B) style, 14–18 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.
A pancreas you can wear
Twelve-year-old Amira (a fictional patient) has type 1 diabetes. Her
immune system has destroyed the cells in her pancreas that make
insulin, so her body cannot control the concentration of glucose in
her blood. Keeping a steady internal environment like this is called
homeostasis, and for Amira it no longer happens automatically.
Until last year Amira pricked her finger to test her blood several
times a day and injected insulin before every meal. Now she wears an
artificial pancreas. A small sensor under the skin of her arm measures
the glucose concentration in the tissue fluid every five minutes. It
sends the reading to a pump attached to her stomach, which delivers
insulin through a thin tube under the skin. A computer program in the
pump decides how much insulin to give. Because the sensor and pump
work together without Amira having to act, the system is called a
closed loop.
The system is not perfect. Glucose takes about ten minutes to pass
from the blood into the tissue fluid, so the sensor reading is always
a little behind. Insulin delivered under the skin also takes time to
reach the blood and start working. After a large meal containing
starch, the concentration of glucose in the blood can rise faster than
the pump can respond. Amira still has to tell the pump when she is
about to eat.
If the glucose concentration falls too low, the pump stops delivering
insulin. This is important, because very low blood glucose can make a
person confused or even unconscious.
In an illustrative trial, patients using an artificial pancreas spent
a mean of 17.8 hours a day with their blood glucose concentration in
the target range, compared with 15.1 hours a day before the trial.
Doctors say that the artificial pancreas has made life much easier for
many patients, but it is not a cure. The sensor must be replaced every
ten days and the tube every three days, and the equipment is
expensive. Researchers are now testing ways to replace the lost cells
in the pancreas, for example by growing new insulin-making cells from
stem cells. The difficulty is that the immune system may attack the
new cells too.
Read the article. 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 homeostasis.
(1)Describe how insulin lowers the concentration of glucose in the blood.
(2)Which part of the digestive system absorbs most of the glucose from a meal into the blood?
(1)Explain why the concentration of glucose in the blood rises after a meal containing starch.
(2)Calculate the increase in time spent in the target range each day. Give your answer in minutes.
(2)Explain why Amira still has to tell the pump when she is about to eat.
(3)Explain why very low blood glucose can make a person confused or unconscious.
(2)Suggest why doctors say that the artificial pancreas is not a cure.
(3)Total for this question: 16 marks
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