Cell Communication - Signal Transduction

Question 1

What is signal transduction?

Answer 1

Signal transduction involves incoming signals or instructions
from extracellular chemical messengers (ligands) that are
conveyed to the cell’s interior for execution.

Question 2

Signal Transduction Pictograph

Answer 2

Signal Transduction Pictograph

Question 3

How does signal transduction work?

Answer 3

• Signals are passed between cells when a particular type of molecule is produced by one cell:
  
  • —the signaling cell—and received by another
  • —the target cell—by means of a receptor protein that recognizes and responds specifically to the signal molecule
• In turn, the signaling molecules activate a path of intracellular protein kinases that results in responses:
  
  • grow and divide,
  • survive, or
  • differentiate

Question 4

What occurs if a cell is deprived of appropriate signaling?

Answer 4

most cells undergo a form of cell suicide known as programmed cell death or apoptosis.

Question 5

List 4 functions of signal transduction pathways (relay chains) of intercellular signaling molecules:

Answer 5

1. Physically transfer the signal
2. Amplify signal received
   
   • Example: 1 ligan molecule bind = activation of numerous adenylyl cyclase molecules
3. Distribute signal to influence processes in parallel
4. Modulated - by other interfering factors inside/outside cel

Question 6

What are the two general responses from binding of the extracellular signaling messenger (first messenger) to the cell’s membrane receptors?

Answer 6

1. Opening or closing specific ion-channels
   in the membrane to regulate the movement of ions into or out of the cell.
2. Transferring the signal to an intracellular messenger, or second messenger, which in turn triggers a cascade of
   biochemical events within the cell.

Question 7

How extracellular messengers regulate ion channels

Answer 7

How extracellular messengers regulate ion channels

Question 8

How to membrane channels open or close?

Answer 8

Opening and closing occur because of:

• conformational changes (shaping) of the proteins that form the channels—
  
  • blocking the channel (closing) or
  • permitting passage through it (opening).

Question 9

What is three ways channel opening/closing initiated?

Answer 9

• (1) by binding of a ligand to a specific membrane receptor that is closely associated with the channel
  
  • (for example, G proteins)
• (2) by making changes in the electrical current in the plasma membrane,
  
  • altering the flow of Na+ and K+; and
• (3) by stretching or other mechanical deformation of the channel.

Question 10

List the two major second messenger pathways:

Answer 10

• Cyclic adenosine monophosphate (cyclic AMP, cAMP)
• Ca++

Question 11

cAMP second messenger system

Answer 11

Blank on purpose

Question 12

Ca++ Second Messenger System