Short-Answer 1) How does a signal molecule bring about specific changes in the c

Question

Short-Answer

1) How does a signal molecule bring about specific changes in the cell to which it binds?

2) Amplification is an important characteristic of signal transduction pathways involving surface receptors. What is amplification and how is it accomplished in the cell?

4) Differentiate between reception, transduction and response in cell signaling and provide an example.

5) Arrange the following steps in the pathway activated by G protein-coupled receptors. Write the letter of the first step next to 1 and the letter of the last step next to 5.

A. Activation of effector

B. Activation of protein kinases

C. Receptor binds first messenger

D. Production of second messenger

E. Activation of G protein

1.

2.

3.

4.

5.

Explanation / Answer

1)The signaling molecule binds with a receptor molecule present inthe cell which causes a change in the conformation of the receptor, called receptor activation which further activates messenger molecule causing intracellular/intercellular signalling cascade  through cell-substratum interactions and finally activates effector protein complex.

2) Receptor proteins interact with the signal molecule at the surface of the cell.Mostly signals are released to the cytoplasm or to the nucleus bysecond messenger which influence the activity of one or more enzyme or genes inside the cell.But signalling molecules are present in very low concentration that their effect in the cytoplasm would be minial unless the signals are amplified.therefore receptors use a chain of other protein messenger to amplify the signals. In case of protein kinase cascade one cell surface receptor activates many G-protein molecules.Each G- protein activates many adenylyl cyclase. Each cyclic AMP will in turn activate protein kinases which then activates several molecule of specific enzyme. The end result is high level of final product.

3) Reception is the binding of the ligand with the receptor which causes conformational changes.But transduction is the change in the series of different molecule along a pathway which arises due to the ligand receptor interaction. Activation of a specific cellular activity by the transduced signal is called response.Example is G- protein coupled receptor.

4) 1 - C , 2- E,  3- D,   4- B,   5- A

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