SIGNAL I & II

Question 1

Where do Neurocrine signals originate?

Answer 1

Nervous system

Question 2

Where do Endocrine signals originate

Answer 2

Distant sites

Question 3

Where do Paracrine signals originate

Answer 3

Nearby Cells

Question 4

Where do Autocrine signals originate

Answer 4

From same cell

Question 5

Where do Juxtacrine signals originate

Answer 5

From a fixed adjacent structure

Question 6

What are the 6 categories of Signaling molecules

Answer 6

Proteins and peptides

Amino acids/derivatives

Steroids

Eicosanoids

Gases

Attached ligands

Question 7

How are cell signals recieved?

Answer 7

By receptors

Question 8

What is a ligand?

Answer 8

Soluble or external signal

Question 9

Where are receptors located?

Answer 9

• In the plasma membrane
  
  • Most are these
  • Protein, peptide, neurotransmitters
• Cytoplasm and nucleus
  
  • Steroid/retinoid receptors.

Question 10

TM Receptors: Three domain structure

What is the role of the extracellular domain (Ectodomain)

Answer 10

Ligand binding

Question 11

What is the Function of the intracellular or cytoplasmic domain?

Answer 11

Contacts signal transduction system

May have intrinsic enzyme activity.

Question 12

Important Characteristics of Receptors

Answer 12

• Specific: Binding only to their molecule
• Saturable: Only bind so many molecules of the ligand before they cannot bind any more.
• Threshold: Activity exhibits threshold
  
  • Certain number of receptors that must be engaged before a biological response can be seen.

Question 13

Examples of Endocrine cytokines?

Answer 13

PRL/GH

Leptin

Question 14

Paracrine Cytokine examples

Answer 14

Interleukins

Interferons

Epo

Question 15

Receptors and dimerization?

Answer 15

• All receptors are either
  
  • Dimers
  • Monomers that dimerize in response to ligand.

Question 16

Down stream actions of cell signalling?

Answer 16

Cell growth, differentiation, specific tissue funtions

Question 17

What are two off mechanisms of receptors?

Answer 17

Dephosphorylation

De novo synthesis of pathway inhibitors

Question 18

Pathway transduction outline of the four players that develop a signaling cascade?

Answer 18

Signal -> Reciever -> Adaptor -> Effector

Question 19

Important contraints to cell signaling

Answer 19

• Accuracy - specificty both up- and downstream
• Fidelity - Passed without diminution and often requires amplification
• Regulatable - Must have a way to turn it on and off.

Question 20

Second messenger?

Answer 20

Is a small molecule that is generated in response to or is released in response to a ligand receptor interaction that then is able to activate the rest of the response.

Question 21

Secondary messengers side functions

Answer 21

• Regulatory factors for other molecules
• Nearly always regulate enzymes and enzyme activators
• Very often regulate kinases and phosphatases.

Question 22

Mechanism to end signal transduction?

Answer 22

• The signal must be turned OFF to reset cellular sensitivity to this and other signals.
  
  • Systems that do this
    
    • Contitutively active enzymes
    • Activated by the signal pathway itself
    • Feedback and feed-forward mechanisms.