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TLS Online TPP Program

#Question id: 12836

The final layer of control that is critical in the regulation of CDKs is a family of proteins known as CDK inhibitors, or CKIs, which bind directly to the cyclin-CDK complex and inhibit its activity. Which of the following function not done by CKIs?

#Unit 2. Cellular Organization
  1. Binding of INK4s to CDK4 and CDK6 blocks their interaction with cyclin D and hence their protein kinase activity. 
  2. p27 prevents the premature activation of S phase CDKs during G1.
  3. p21CIP plays an important role in the response of metazoan cells to DNA damage by inhibiting G1/S phase CDKs and S phase CDKs, and thereby blocking entry into or passage through S phase.
  4. During ongoing DNA replication and in response to replication stress (slow DNA replication fork movement or DNA replication fork collapse), the ATR-Chk1 protein kinase cascade phosphorylates and inactivates Cdc25C, thereby preventing the activation of mitotic CDKs and inhibiting entry into mitosis.
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TLS Online TPP Program

#Question id: 2149

#Unit 2. Cellular Organization

A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is:
TLS Online TPP Program

#Question id: 2150

#Unit 2. Cellular Organization

Which of the following increase(s) membrane fluidity?
TLS Online TPP Program

#Question id: 2151

#Unit 2. Cellular Organization

Which of the following statement(s) is (are) true of transmembrane proteins?

a. All contain a hydrophobic α helix.

b. Some serve as membrane attachment sites for peripheral membrane proteins.

c. Some contain more than one membrane-spanning domain.

d. All are asymmetrically oriented in the lipid bilayer.
TLS Online TPP Program

#Question id: 2152

#Unit 2. Cellular Organization

Precursors of membrane phospholipids are

a. soluble in the cytosol.                    

b. incorporated into biosynthetic intermediates.

c. sometimes complexed with fatty-acid-binding proteins.

d. stored in glycerolosomes.

e. sometimes activated by conjugation with CDP.
TLS Online TPP Program

#Question id: 2153

#Unit 2. Cellular Organization

Membrane phospholipids include

a. cholesterol.            

b. plasmologens.        

c. sphingolipids.         

d. triglycerides.                      

e. bile acids.
TLS Online TPP Program

#Question id: 2154

#Unit 2. Cellular Organization

Membrane lipids are distributed appropriately between the two leaflets of a given membrane by

a. dockases.    

b. trumpases.              

c. fatty acid desaturases.        

d. flippases.    

e. transmembrane tunnelases.