Lecture 3

Question 1

Chemical Messengers

Answer 1

1. ) intercellular communication
   
   • direct
     a. ) gap junctions
   • indirect
     a. ) chemical messengers
2. ) signal transduction

Question 2

Properties of Receptors

Answer 2

• specificity
• saturation
• affinity

Question 3

Intracellular Receptors

Answer 3

• lipid-soluble chemical messengers
• bind to receptors in cytoplasm or nucleus
• transcription factors

Question 4

Membrane-bound Receptors

Answer 4

• water-soluble chemical messengers
• first messenger - bind to specific receptor
• second messenger - generated in response to first messenger
• protein kinase - phosphorylates another protein

Question 5

Receptors that are Ligand-gated Ion Channels

Answer 5

1. ) first messenger binding to receptor opens channel
2. ) ion cross membrane
3. ) change in electrical properties of cell

Question 6

G-protein Subunits

Answer 6

1. ) alpha - can bind GDP and GTP
2. ) beta - help anchor alpha subunit in membrane
3. ) gamma - same as beta

Question 7

G-proteins

Answer 7

1. ) affect ion channels
2. ) stimulatory G proteins
3. ) inhibitory G proteins

Question 8

Action of G-proteins on Ion Channels

Answer 8

1. ) binding of first messenger
2. ) affinity increases
3. ) moves to ion channel
4. ) ion channel opens or closes

Question 9

Action of G-proteins on Enzymes

Answer 9

1. ) binding of first messenger
2. ) affinity increases
3. ) moves to enzyme
4. ) activation/inhibition of protein
5. ) alters second messenger

Question 10

cAMP Second Messenger System

Answer 10

• Gs - activates cAMP
• cAMP second messenger system
• Gi - inhibits cAMP