Read the following paragraphs and carefully determine what the main idea is for each. The best way to approach these questions is to first read the paragraph and then, in your own words, restate what you think the author is trying to say. From the five choices, select the one statement that best supports the author’s point.

The best recipes for clam chowder all include onions and a bay leaf. The onions add a sharpness and zest to the blandness of the clams, and also help remove their slimy texture. The bay leaf complements the onion’s strong flavor.

This paragraph best supports the statement that

TLS Online TPP Program

#Question id: 14685

#Unit 4. Cell Communication and Cell Signaling

In dark-adapted rod cells, a high level of cGMP keeps cGMP-gated nonselective cation channels open, leading to hyperpolarization of the plasma membrane and neurotransmitter release. 

B - Light absorption generates activated rhodopsin, R*, which binds inactive, GDP-bound Gαt protein and mediates the exchange of GDP for GTP . 

C- The free Gαt∙GTP activates PDE by binding to its inhibitory γ subunits and dissociating them from the catalytic α and β subunits . Relieved of their inhibition, the α and β subunits of PDE hydrolyze GMP to cGMP . 

D- The resulting decrease in cytosolic cGMP leads to dissociation of cGMP from the cation channels in the plasma membrane and the closing of those channels . 

E- The membrane then becomes transiently hyperpolarized, and neurotransmitter release is reduced. 

TLS Online TPP Program

#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?

TLS Online TPP Program

#Question id: 13163

#Unit 4. Cell Communication and Cell Signaling

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

TLS Online TPP Program

#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?

TLS Online TPP Program

#Question id: 13161

#Unit 4. Cell Communication and Cell Signaling

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

TLS Online TPP Program

#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