Signal Transduction

Question 1

What are the 3 requirements fro signal transduction?

Answer 1

Detector, Transducer, Amplifier

Question 2

What is a detector?

Answer 2

A detector is a receptor that specifically recognizes extracellular signal.

Question 3

What is a transducer?

Answer 3

A transducer transmits information from the receptor to the cell and maintains sensitiviety of the system.

Question 4

What is an amplifier?

Answer 4

An amplifier is a cellular messenger induced by activation of enzyme transport system

Question 5

What are the 4 components of the signal transduction machinery?

Answer 5

specificity, amplification, desensitization/adptation, amplification and integration

Question 6

Define specificity

Answer 6

Signal molecule fits binding site on its complementary receptor; other signals do not fit

Question 7

Define Amplification

Answer 7

When enzymes activate enzymes, the number of affected molecules increases geometrically in an enzyme cascade.

Question 8

Define desensitization/adpatation

Answer 8

Receptor activation triggers a feedback circuit that shuts off the receptor or removes it from the cell surface

Question 9

Define integration

Answer 9

When two signals have opposite effects on a metabolic characteristic such as the concentration of a second messenger x, or the membrane potential, the regulatory outcome results from the integrated input from both receptors

Question 10

What are the 3 major types of receptor-mediated signaling Systems?

Answer 10

Plasma membrane receptors, adhesion receptors, intracellular receptors

Question 11

Define G protein-coupled receptor

Answer 11

External ligand binding to receptor activates an intracellular GTP-binding protein, which regulates an enzyme that genreates an intracellular second messenger

Question 12

Define receptor tyrosine kinase

Answer 12

Ligand binding activates tyrosine kinase activity by autophosphoylation

Question 13

Define receptor guanylyl cycle

Answer 13

Ligand binding to extracellular domain stimulates formation of second messenger cyclic GMP

Question 14

Define Gated ion channel

Answer 14

Opens or closes in response to concentration of signal ligand or membrane potential

Question 15

Define Nuclear receptor

Answer 15

Steroid binding allows the receptor to regulate the expression of specific genes

Question 16

Define adhesion receptor (integrin)

Answer 16

Binds molecules in extracellular matrix, changes conformation, thus altering its interaction with cytoskeleton

Question 17

What are the 4 major types of cell surface receptor-signaling systems?

Answer 17

receptor-ion channels, receptor-enzyme, g-protein-coupled receptors, receptor guanylyl cyclases

Question 18

Explain the acetylcholine receptor

Answer 18

In the resting position the gate is closed. Ach binds causing a conformational change which opens the gate and allows na and ca to enter the cell.

Question 19

Explain the receptor tyrosine kinase

Answer 19

Insulin binds to alpha subunit, which activates the alpha subunit which leads to the activation/ autophosphorylation of beta subunits, which leads to the phosphorylation of TYR resides, then phosphorylated tyrosine actviates sh2-carrying proteins