The Biology Project
Cell Signaling > Problem
8: Protein Kinase Cascades
Tutorial to help answer the question
Some receptors for growth factors activate a protein kinase cascade,
with the participation of multiple enzymes to effect a change in gene
expression. Which of the following statements about a protein kinase cascade
||Multiple steps allow the amplification of the signal.
||External signals can lead to changes in gene expression.
||Multiple steps leading to kinase activations can result
in cells having different responses, depending on the presence or
absence of target proteins.
||Multiple steps in an activation mean that abnormal
stimulation of a cell response such as growth can occur with mutations
in more than one gene.
||All of the above are true.
Protein kinase cascade
systems need to be responsive to small concentrations of signaling
molecules (ligand), and yet may need to cause a rapid cellular response.
The figure shows a liver receptor system that binds the hormone
epinephrine causing a quick release of glucose into our blood.
Epinephrine is released when we are scared (fight or flight response),
and binds to its receptor in hepatocytes. A G-protein that stimulates adenyl
cyclase is released. The figure shows how the signal response is activated
multiple times by each step in the cascade.
Some cascade systems modify gene expression by activating kinases that
enter the cell nucleus (see question
Problem 8 |
Answer | Problem 9
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