Chapter 10: signaling

Question 1

The general features of signaling pathways

Answer 1

a. A ligand carrying a signal bind specifically to a receptor bound to cell membrane
b. Their interaction triggers some kind of response inside the cell
c. This is known as** signal transduction**
d. Ligand does not enter the cell, but information is transmitted

Question 2

Examples of extracellular signals

Answer 2

a. Most are hormones
b. Adrenaline prepares the body for action
c. Ligands carrying the signals are usually called hormones other signals are light, odorants, mechanical stress etc

Question 3

Meaning of Kd and how to calculate it

Answer 3

b. Follows a hyperbolic trend
c. Kd reflects the affinity

Question 4

Interpretation of receptor-ligand binding plot

Answer 4

For the sample equation you just need to memorize the Kd formula

Question 5

Definition and examples of agonists and antagonists

Answer 5

b. Agonists term used when the substance is natural
c. The Antagonist term used when the substance is not natural. It will bind to the receptor because it looks normal to the natural substance.

Question 6

What is going on in the tyrosine kinase signaling pathway.

What are the kinases

Answer 6

Kinases catalyze the phosphorylation of other proteins

Question 7

What is going on in the tyrosine kinase signaling pathway.

Ligand of the pathway

Answer 7

• Tyrosine kinase signaling pathway used by insulin
• Ligand is signaling that the BG is high

Question 8

What is going on in the G protein signaling pathway

Ligands of pathway

Answer 8

i. Ligand binds to the receptor. And there is a conformational change and it activates the G protein. And it activates the g protein will activate the enzyme. And that will catalyze the substrate. The second messenger will bind to different proteins and that will phosphorylate other proteins.
ii. This is also known as the cascade effect

Question 9

What is going on in the G protein signaling pathway

Receptor of pathway

Answer 9

.

Question 10

What is going on in the G protein signaling pathway

G protein cycle

Answer 10

i. G protein signaling pathways
ii. Responsible for transducing the majority of extracellular signals
iii. Involves G protein-coupled receptors (GPCR)
iv. GPCR are known as 7TM receptors
1. 7TM=7 transmembrane helices

Question 11

What is going on in the G protein signaling pathway

Adenylate cyclase role

Answer 11

• A major target of the activated G protein is an integral membarne enzyme called adenylate cyclase.
• When the alpha subunit of the G protein binds, to the enzyme’s catalytic domains covert ATP to a moleculte known as cAMP
• It hydrolyzes the phosphodiester bond release PPi. And if forms a cyclic structure known as cAMP

Question 12

What is going on in the G protein signaling pathway

Second messenger of pathway and its role

Answer 12

• cAMP is the second messanger that freely diffuses in the cell
• cAMP activates protein kinase A (PKA)
• cAMP is an ollosteric activator of PKA
• PKA is an inacctive tetramer
• The two regulatory subunits (R) block the active sites of the two catalystic subunits.

Question 13

What is going on in the G protein signaling pathway

Protein kinase A

Answer 13

1. Kinases catalyze the phosphorylation of other proteins
2. Composition; it is also known as Ser/Thr Kinase
3. Activation: PKA transfers a phosphoryl group from ATMp to the serine or theronine side chain of a target protein

Question 14

What is going on in the G protein signaling pathway

How the pathway is switched off

Answer 14

• By reversing the pohsporylations catalysed by PKA
• this is accomplished by** protein phosphatases **
• By removing the second messenger, cAMP