Choose the incorrect statement regarding the Van der Waals interactions & Hydrogen bonds

1. In Van der Waals interactions greater the area of contact the stronger the interaction.

2. In Van der Waals interactions greater the area of contact the weaker  the interaction.

3. Hydrogen bonds Relative strength is inversely proportional to the polarity More polar atoms form weak H bonds.

4. Hydrogen bonds Relative strength is directly proportional to the polarity More polar atoms form stronger H bonds.

#Question id: 1223

#Unit 4. Cell Communication and Cell Signaling

The receptors for steroid hormones are located inside the cell instead of the membrane surface like most other signal receptors. How do steroids gain access to their receptors?

#Question id: 1224

#Unit 4. Cell Communication and Cell Signaling

Put the steps of the process of signal transduction in the order they occur.

1. A conformational change in the signal-receptor complex activates an enzyme.

2. Protein kinases are activated.

3. A signal molecule binds to a receptor.

4. Target proteins are phosphorylated.

5. Second messenger molecules are released.

#Question id: 1225

#Unit 4. Cell Communication and Cell Signaling

The dissociation constant Kd for a receptor-ligand complex is

a. a measure of the affinity of the receptor for the ligand.

b. the concentration of the ligand at which half of the receptors contain bound ligand.

c. a measure of the time it takes for a ligand to be converted to a product.

d. equal to koff/kon 

#Question id: 1226

#Unit 4. Cell Communication and Cell Signaling

GTPase switch proteins

a. are active when bound to GDP but inactive when bound to GTP.

b. are active when bound to GTP but inactive when bound to GDP.

c. are converted from the inactive to active state by a guanine nucleotide exchange factor (GEF).

d. synthesizes GTP from GDP.

#Question id: 1227

#Unit 4. Cell Communication and Cell Signaling

Which of the following is a mechanism for down regulation of signaling from G protein-coupled receptors?

a. a change in the Kd of the receptor-hormone complex

b. proteolysis of the Gα subunit                     

c. hydrolysis of cAMP to 5´-AMP

d. dephosphorylation of adenylyl cyclase

#Question id: 1228

#Unit 4. Cell Communication and Cell Signaling

Place the events that follow the binding of a ligand to a G protein-coupled receptor that acts on adenylyl cyclase in the correct order:

a. GTP is hydrolyzed to GDP.           

b. GDP is displaced from Gα.           

c. the Gα-GTP complex dissociates from the Gβγcomplex.  

d. GTP is bound to Gα.