Answer all questions. Write your answers in the spaces provided.
1. GPR120 is a trans-membrane protein that functions as a receptor for long-chain unsaturated
fatty acids. When fatty acids outside the cell bind to the receptor, the receptor changes shape and
as a result a signal is passed to the interior of the cell. This causes
an increase in the intracellular
calcium concentration (Ca), which has a wide range of effects on cell
activity.
A strain of mice was developed that did not produce GPR120 protein. Groups of these GPR120
deficient mice were fed from the age of 5 weeks until they were 16 weeks
old either on a high
fat
diet containing 60 % fat or on a normal diet containing 13 % fat. Control groups of mice that did
produce GPR120 protein were fed on the same diets. The bar chart shows the mean body mass of
each group when the mice were 16 weeks old.
40-
30-
Mean body mass/
gram
20-
10-
GPR deficient Control
GPR deficient Control
normal diet
high fat diet
[Source: adapted from A Ichimur, et al., (2012), Nature, 483, pages 350-354, Reprinted by permission from Macmillan Publishers Ltd]
(a) Compare and contrast the body mass of GPR120 deficient mice and the control mice
on a normal diet and a high fat diet. [3]