4. What is the difference between a tyrosine kinase and a serine/threonine kinase?
(a) One is involved in signal transduction and one is not.
(b) One adds phosphate groups to proteins, the other removes them.
(c) One adds phosphate groups to proteins, the other adds phosphate groups to sugars.
(d) One is used in animals, the other in plants.
(e) They add phosphate groups to different amino acid side chains in proteins.
5. Kinase cascades are useful in signal transduction because:
(a) they are species specific
(b) they amplify the signal
(c) the number of molecules used is small and fixed
(d) they counter the harmful effects of phosphatases
(e) they always lead to the same cellular response
6. Cholera is a disease caused by bacteria. The bacteria produce a toxin that prevents the hydrolysis of GTP to GDP by a G protein. What would happen to the signal transduction pathway that the G protein is part of?
(a) The signal would go forward, but not produce the desired response.
(b) The signal would go to the wrong cell.
(c) The signal would be sent following activation of the wrong receptors
(d) The signal could never be turned on.
(e) Once on, the signal could not be turned off.
7. Which of the following statements about second messengers is false?
(a) Ca2+ ions and cAMP are examples of second messengers
(b) They are used as intracellular signals in signal transduction pathways, following activation of a receptor.
(c) They are produced in very small amounts following cell activation, and are difficult to detect experimentally.
(d) They activate other molecules, such as kinases
(e) There are mechanisms that enable the messages to be “turned off” after they are generated
1) OPTION E
As,both the signal transducers functions same except on the type of protein they act. the other options are incorrect, except the option e which says that they attach phosphate gropus to different amino acid side chains
2) OPTION B
they amplify the signal by attaching next phosphate group to the upcoming signal receptors
3) OPTION C
The signal will be sent of due to the activation of wrong receptors like cAMP. the cholera bacteria results in production of high level of cAMP which nullify the conversion.
4) OPTION C
as they can be detected , therefore, option c is incorrect.
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