Signaling I

Question 1

Define signaling in 3 steps.

Answer 1

o 1. Signal binds receptor
o 2. One or more intermediary molecules
o 3. Changes in target molecules cause changes in metabolic pathways, gene expression, etc

Question 2

What is Signal Transduction?

Answer 2

Lipid bilayers prevent entry of most molecules

Information must move across the membrane

Question 3

What are Ligand-gated ion Channels?

Answer 3

Simplest signaling

The signal comes from a ligand, the signal has a specific receptor.

Once that binding occurs, the ligand causes a change in the receptor and that opens the receptor gate to open.

Question 4

What is Epinephrine?

Answer 4

Also known as adrenaline

Question 5

What is Epidermal Growth Factor?

Answer 5

Protein that tells the cell it’s time to divide.

Question 6

What does Steroid hormone signaling look like?

Answer 6

The interaction between the receptor and the hormone happens after the hormone has entered the cell

Has the simplest signaling pathway

Can cross the lipid bilayer easily.

The receptor is therefore inside of the cell
-Some are in the nucleus

Question 7

What does non-steroid hormone signaling look like?

Answer 7

Receptor is embedded in the membrane

Very complex

Question 8

What are G-Protein Coupled Receptors (GPCR)?

Answer 8

Non-steroid binding receptor

Bound in the lipid bilayer

7TM- It crosses the membrane 7 times

Question 9

What are 7TM receptors?

Answer 9

They are Beta- adrenergic Receptors.

Question 10

What do Beta- adrenergic Receptors bind to?

Answer 10

Binds to adrenaline

Question 11

How does a G-Protein Coupled Receptor (GPCR) work?

Answer 11

1. Start with a hormone
2. Specific receptor binds to a hormone
3. Structural change of receptor and the interacting G-Protein
   a. It affects the receptors binding of an internal protein (G-protein)
4. G-protein replacement of GDP to GTP
   a. Lets go of GDP, Picks up GTP
5. Activation of an enzyme
   a. G-protein changes. One subunit breaks off (alpha subunit) and this activates an enzyme. Alpha subunit also breaks down G-protein GTP to GDP. So it can turn itself OFF
6. Return to Original State
   The cycle can start all over again.

Question 12

What happens a Membrane Receptor Proteins Internalize Messages?

Answer 12

Activates synthesis of second messengers

Covalent Modification of “downstream” proteins
Results in: Alteration of Gene Expression, Change in enzyme activity

Question 13

Name a type of Second Messenger?

Answer 13

Cyclic AMP (cAMP)

Question 14

How is a second messenger created?

Answer 14

The alpha subunit binds to adenylate cyclase.

Activated by binding to alpha-subunits of G-proteins.

This enzyme catalyzes the reaction of ATP to cAMP

Question 15

What happens when a Second Messenger(cAMP) Travels in the Cell?

Answer 15

Protein Kinase A binds to cAMP

Question 16

What happens when Protein Kinase A binds to cAMP?

Answer 16

It’s the next messenger in the process

It has 2 regulatory subunits and It has 2 catalytic subunits

The regulatory subunits block the catalytic subunits active sites

When cAMP binds to the regulatory subunits they release the catalytic subunits

Catalytic subunits

• Puts phosphates onto proteins
• Ser and Thr