An experiment of Anfinsen on ribonuclease A (RNase A) showed that proteins can be denatured reversibly by 2-mercaptoethanol and 8 M urea. The protein must therefore renature spontaneously;

a) Remove mercaptoethanol and then removal of the urea

b) Removal of the mercaptoethanol allows the protein to re-form disulfide bonds in the presence of oxygen and then removal of the urea

c) Removal of the denaturant (urea) and reductant (mercaptoethanol) allows the protein to renature and re-form disulfide bonds in the absence of oxygen

d) Adding a small amount of mercaptoethanol to the scrambled protein in the absence of O2 catalyzes its conversion to the active enzyme

Which one of the following steps will leads to regaining of the full activity of ribonuclease A (RNase A)

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#Question id: 13164

#Unit 4. Cell Communication and Cell Signaling

Match the following.

Column I	Column II	Column III
A. G Protein–Coupled Receptors That Activate PDE	i. cAMP	a. Increase in conversion of glycogen to glucose
B. G Protein–Coupled Receptors That Activate Adenylyl Cyclase	ii. cGMP	b. Hyperpolarization or depolarization of photoreceptor membrane
C. G Protein–Coupled Receptors That inhibit Adenylyl Cyclase	iii. DAG	c. activates genes necessary for cell division
D. G Protein–Coupled Receptors That Trigger Elevations in Cytosolic and Mitochondrial Calcium		d. increase in K+ permeability hyperpolarizes the membrane

Which one of the following is correct?

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#Question id: 13163

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to the interaction between β2-adrenergic receptor and G- protein.

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#Question id: 13162

#Unit 4. Cell Communication and Cell Signaling

In the amoeba Dictyostelium discoideum, cAMP acts as an extracellular signalling molecule and binds to and signals via a G protein–coupled receptor; it is not a second messenger. Amoeba cells were transfected with genes encoding two fusion proteins: a Gα fused to cyan fluorescent protein (CFP), and a Gβ fused to yellow fluorescent protein (YFP). CFP normally fluoresces 490-nm light; YFP, 527-nm light. In which conditions fluorescence

energy transfer occur from CFP to YFP?

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#Question id: 13161

#Unit 4. Cell Communication and Cell Signaling

Which of the following mechanism depends on the activation of heterotrimeric G proteins?

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#Question id: 13160

#Unit 4. Cell Communication and Cell Signaling

According to the Switching mechanism, monomeric G proteins exist in two states. Match the following states (Column I) with correct mechanism (Column II).

Column I	Column II
A. “ON” state	i. switch I and switch II, are bound to the terminal γ phosphate of GTP through interactions with the backbone amide groups of conserved threonine and glycine residues.
B. “OFF” state	ii. GTPase-activating proteins
	iii. guanine nucleotide exchange factor
	iv. Due to the removal of the γ phosphate by GTPase-catalyzed hydrolysis causes switch I and switch II to relax into a different conformation

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#Question id: 13159

#Unit 4. Cell Communication and Cell Signaling

How signaling is involved in ensuring that yeast cells fuse only with cells of the opposite mating type?