70. G-proteins can be described by all of the following properties except ______

Question

70. G-proteins can be described by all of the following properties except __________.

A. G-proteins are trimeric.

B. G-proteins bind to magnesium.

C. G-proteins bind to GDP.

D. G-proteins bind to GTP.
E. G-proteins possess 7 transmembrane alpha helices.

71. Binding of agonists to protein membrane receptors can result in which of the following events?

A. Conformational changes

B. Intracellular release GDP

C. Intracellular activation of kinase activity

D. Intracellular formation of cGMP and/or cAMP
E. All of these events can occur upon agonist binding.

Explanation / Answer

70. The appropriate answer is E.

(reason : G proteins are involved in cellular signal transmission, there are two classes of G proteins

Mg2+ ions plays a significant role as its presence at the active site of g protein is required for the hydrolysis of GTP.

G protein binds to both GTP and GDP; when bound to GTP the receptor is in on state, when bound to GDP, receptor is in off state.

Gprotein coupled receptor is a complex formed by

The two are different entities, and the transmemembrane segment is not a structural part of th g protein.)

71. The appropriate answer is E

(reason : An agonist is a chemicalcompound which binds to a receptor, activating the receptor to produce a biological response.

The response upon binding of an agonist to the cell membrane receptors activates one or more signal transduction systems, which initiate a cascades of different events which may change alter the concentration of intracellular second messengers, such as cAMP or Ca2+,and the signals are then transduced to the cytoplasm and then to the nucleus through a combination of second-messenger molecules, kinase/phosphorylation cascades, and transcription factor translocation to effect changes in genetic expression and protein translations.

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