Exam 2

Question 1

Bacteriohdopsin serves as

Answer 1

Structural model that has an extracellular N terminus and an intracelular C terminus

Question 2

What is the general function of G protein coupled receptors (GPCR)

Answer 2

This pathwa starts by ligand binding to a receptor, this results in a change in receptor confromation so it can then interact with a G protein. The G protein will then interact with a membrane bound enzyme which will then produce second messengers and activate ser/ thr kinases which will send messages to the cell

Question 3

Beta 2 adenergic receptors serves as…… and what

Answer 3

The functional model and are what activate the flight or flight response by acitivating adelnyl cyclase and cAMP which then signals the flight or flight throughout the cell

Question 4

Alpha 2 adrenergic receptors do what

Answer 4

Inhibit the adenyly cyclase and stop cAMP. This inhibits the flight or fight response

Question 5

Removal of any transmembrane segment was?

Answer 5

Detrimental to ligand binding, so where did adrenaline bind?

Question 6

The binding characteristics of the chimeric receptors for Adrenaline correlated to what helix

Answer 6

Correlated to helix 3 and 5

Question 7

Change of what AA in helix 3 and 5 of GPCR

Answer 7

Aspartic acid 113 in helix 3 and ser 204 and 207 in helix 5 which would decrease affinity (chance) of binding adrenaline

Question 8

CDNA does not have

Answer 8

Introns

Question 9

CAMP level is associated with which loop of the adrenergic receptor

Answer 9

Loop 3 and alpha 2 there is decrease and beta 2 there is increase in camp levels

Question 10

The packing interaction Model

Answer 10

The outside cell ends are spread apart allowing for a ligand to bind the intracelular ends are tightly packed

Question 11

When adrenaline binds …

Answer 11

Rotates tryptophan 286 at bottom of binging pocket of receptor. Pro 288 kink changes and pushes each R group of Helix 6 which ultimately results in outward swing of the helix. Significance… allow G protein to interact with 3rd loop (remember 3rd loop most important)

Question 12

3 form of the GCPR receptor inactivation

Answer 12

Desensitization
Sequestration
Down regulation

Question 13

Desensitization

Answer 13

The ligand can be bound to receptor but cant talking to the G protein. This is done by phosphorylation which allows for new interaction with arrestin (arrest) signal transduction and block further signal.

Question 14

Sequestration

Answer 14

Receptors are brought into the cell. Arrestin from desensitization then binds clathrin which brings the receptor inside the cell. The ligand is then taken off and phosphates and arrestin recycle it back to cell surface

Question 15

Down Regulation

Answer 15

Long term decrease in number of receptors at cell surface. After being sequestered, the endosome can fuse with lysosome and degrade the receptor. Now new receptors must be made for binding in the GPCR pathway

Question 16

Kinases do what

Answer 16

Enzyme that add phosphate

Question 17

Phosphotases do what

Answer 17

Take phosphate off

Question 18

Ser/Thr kinases

Answer 18

Transfer the phosphate to the Oh-R group of thr and ser

Question 19

Tyrosine kinases

Answer 19

Transfer phosphate to OH group of tyrosine

Question 20

Why phosphate groups

Answer 20

It exchanges uncharged polar groups (oH) for group with 2 - charges. This results in pulling of r group somewhere else in the chain and gives different function and interaction with protein

Question 21

2 lobes within the kinase structure

Answer 21

The binding site for ATP
And c helix- contains consensus sequence

Lastly activation loop within the cleft between the two lobes

Question 22

The Thr on the activation loop in the kinase cleft phosphorlates results in

Answer 22

Wants to go to positive AA which twist and closes the cleft which brings atp and substrate close tougher for interaction

Question 23

What is glycogen metabolism

Answer 23

Storage form of glucose in animals found mainly in the liver

Question 24

Quick version pathway way of glycogenolysis

Answer 24

Glucose insulin comes in and tells the cell to take up glucose and make glycogen. Breakdown Glycogen is broke down by adrenaline to form glucose 1 p and atp which is used for fight or flight

Question 25

Glycogen synthase is activated by

Answer 25

Dephosphorlyation

Question 26

To synthesize glycogen both glycogen synthase and glycogen phosporlase must be in

Answer 26

De phosphorylation state

Question 27

To break down Glucsose to make ATP both synthase (on) and phosphorlase (OFF)must be

Answer 27

Phosphrolated

Question 28

Essay: Phosphorylation of G at site 1

Answer 28

This occurs at the surface of the liver cells where insulin can bind to the receptor. This results in active of ISPK which phosphorlates G and makes the strength between G and PPI strong. The catalytic subunit is positioned then to de phosphorlates glycogen synthase and phosphorylase which allows for gylocgenesis, and blocks glycogenolysis

Question 29

Camp pathway

Answer 29

A ligand will bind the receptor which has alpha, beta, and gamma subunits. When gdp is made to GTP ti will bind to membrane bound adenyl cyclase and activate it which converts the ATP to cAMP (2nd messenger). Camp will activate protein kinase A and phosphorlate for correct cell response

Question 30

4 classes of alpha subunits for the G protein

Answer 30

G alpha s - stimulates adenyl cyclase G alpha I Inhibits adenyl cyclase G alpha q stimulate phospholipase c beta G 12/13 activate small G protein

Question 31

functions of alpha subunit in G protein

Answer 31

1. Interact with receptor 2bind guanine nucleotides 3 hydrolyze GTP 4 interact with beta gamma Interact wiht membrane bound enzyme

Question 32

Structure of G protein

Answer 32

Helical Domain- bundle of alpha helices regulate GTP hydrolysis GTPase domain Central 6 stranded beta sheets surrounded by 5 alpha helices 2 switch regions- where conformational change occurs

Question 33

Beta subunit of G protein structure

Answer 33

Beta propellor

Question 34

Gamma subunit of G protein structure

Answer 34

2 alpha helices with either Farnesyl or Geranyl geranyl at c terminus

Question 35

Beta gamma of G protein are always

Answer 35

Associated with one another

Question 36

G protein in inactivated state

Answer 36

Disorder structure fo strtucture and there is gap between helical and gtpase domain

Question 37

Activated state of G protein

Answer 37

Ligand binds receptor and changes the 3rd loop of receptor so it can insert in the gap of G2 and tickle G5 pop out GDP switch 2 throw off beta gamma unveil switch 2 and interact with second messenger

Question 38

Inappropriate activation of G proteins Vibrio cholera

Answer 38

Attach to epithelial cells of the small intestine and secrete cholera toxin Composed of 2 subunits alpha and beta Beta provides a bring for entrance into the host cell Alpha has adp ribosylate which is GDP bound on G2 s and g3 loop which result in prolonged activation of adenyl cyclase and will increase camp production. This activates a pump which will pump ions out of intestine cell and water follows the ions by osmosis. Significance Need Gtp to turn off alpha but cant be turned off because GDP Simple alpha subunit is adp. Ribosyalted alpha subunit cant be turned off make lots of camp and pull of ions out of intestine. Bypasses receptor