Chapter 9: Cell Signaling

Question 1

What is a “Competence Factor” in bacterial cells?

Answer 1

A surface protein binds with extracellular DNA and ENABLES THE CELL TO UPTAKE FOREIGN DNA and to be transformed. Higher concentrations result in stimulated DNA uptake response.

Question 2

What are the 4 components needed for a successful signal?

Answer 2

1) Signaling Cell
2) Signaling Molecule (“Ligand”)
3) Receptor Molecule
4) Receptor Cell

Question 3

What are the 4 steps of cell response?

Answer 3

1) Receptor activation
2) Signal transduction
3) Response
4) Termination

Question 4

What are the 4 types of Cell Signaling? Give an example for each.

Answer 4

1) Endocrine: Travels far through bloodstream
(ex: testosterone)

2) Paracrine: Travels short distance to nearby cell
(ex: synaptic signaling, responses to allergens)

3) Autocrine: Signaling cell and receptor cell are the same
(ex: tumor cells)

4) Juxtracrine: Signaling in the absence of signaling molecule
(ex: contact-dependent cell regulation)

Question 5

What is a “Ligand”?

Answer 5

A chemical messenger (Signaling Molecule or Ion) released by one cell to signal either itself or a different cell.

(The binding results in a cellular effect, which manifests as any number of changes in that cell, including altering gene transcription or translation or changing cell morphology.)

Question 6

What are “Cytokines” and what do they do?

Answer 6

Tiny proteins that act as Signaling Molecules (“Ligands”)

• They SIGNAL THE IMMUNE SYSTEM TO DO ITS JOB. Cytokines CRUTIAL IN CONTROLLING GROWTH of all blood cells and other immune cells that help the body’s immune and inflammation responses.

Question 7

What are “Growth Factors” and what do they do?

Answer 7

Soluble molecules that act as Signaling Molecules (“Ligands”)

• Usually help with cell growth

Question 8

What is “Intracellular Signaling”? Give an example

Answer 8

When small, NONPOLAR signaling molecules are able to pass through the lipid bilayer and activate “Cytoplasmic Receptors” on the inside of the cell

• Example: Estrogen

Question 9

What are 3 types of “Cell Surface Receptors”? What do they do? Give an example of each.

Answer 9

1) G Protein Receptors:
Act as a switch between the “G Protein Receptor” and the “G Protein Kinase”. Response stops when ligand leaves.
(ex: powerful responses, accepting ADRENALINE)

2) Receptor Kinases:
Two intermembrane proteins that phosphorylate each other then transmit the response to various proteins once activated
(ex: accepting insulin, MAP KINASE)

3) Ligand-Gated Ion Channels:
When a ligand binds to the extracellular ligand-binding site, it opens up
(ex: neurons = fast communication, MUSCLES receiving signals from nerve cells)

Question 10

What is “MAP Kinase”? What is it used for?

Answer 10

Very important signal transduction pathway!

• Really good example of external signals leading to big response within the cell
  (USED WHEN THE CELLS NEED TO HEAL THE BODY AFTER INJURY)