Unit 4 - All Topics

Many signal transduction pathways use second messengers to:

• transport a signal through the lipid bilayer portion of the plasma membrane.

• relay a signal from the outside to the inside of the cell.

• relay the message from the inside of the membrane throughout the cytoplasm.

• amplify the message by phosphorylating proteins.

Which of the following can activate a protein by transferring a phosphate group to it?

• cAMP

• G proteins

• phosphodiesterase

• protein kinase

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

• the active site of an enzyme in the cytoplasm that binds to a specific substrate.

• RNA specifying the amino acids in a polypeptide.

• genes making up a chromosome.

• an enzyme with an optimal pH and temperature for activity.

What could happen to the target cells in an animal that lack receptors for local regulators?

• They could compensate by receiving nutrients via an α factor.

• They could develop normally in response to neurotransmitters instead.

• They could divide but never reach full size.

• They would not be able to multiply in response to growth factors from nearby cells.

A signal molecule that binds to a plasma-membrane protein is a

• ligand
• second messenger
• protein kinase
• receptor protein

What is a G protein?

• specific type of membrane-receptor protein
• protein on the cytoplasmic side of a membrane
• membrane-bound enzyme
• relay protein

The 3 steps of signal transduction in order are

• reception, transduction, response
• response, transduction, reception
• reception, response, transduction
• transduction, reception, response

What is being depicted in the image?

• Amplification of the signal molecule

• Enzymatic proteins inhibiting process of the signal transduction pathway

• Kinase groups adding dimer groups to other enzymes

• Diffusion of molecules within the cell due to the signaling molecule

Do plant cells communicate using hormones?

• yes
• no

What determines whether a signal molecule binds on the surface or enters the cell?

• size
• polarity
• ability to cross the membrane
• all of these are correct