Midterm 2

Question 1

How is the G protein composed?

Answer 1

The GPCR and the G protein work together with another enzyme to trigger a transduction pathway
3 different subunits: alpha, beta and gamma, bonded by lipids (heterotrimeric)

Question 2

What is the phosphorylation cascade?

Answer 2

phosphorylation of serine/ theronine (polar amino acids), activates a series of protein kinases, using ATP tp phorlyate the next, with the final goal of activating a protein

Question 3

Steps of GPCR?

Answer 3

1. ligand binds, shape changes (activates)
2. GPCR binds to G protein
3. GTP replaces GDP (unbinded), activates G protein
4. G protein binds to ligand, changes enzyme shape (activation)
5. Cellular response
6. GTP hydrolyzed (GDP+Pi, inactive)

Question 4

How does cholera modify G proteins?

Answer 4

1. G protein is modified and unable to hydrolyze GTP to GDP
2. The G protein is always activated
3. It continuously stimulates the adenylyl cyclase to make lots of cAMP (activates ligan channels)
4. The enterocytes secrete large amounts of salts into the intestinal lumen

Question 5

what are the 2 domains of a transcription factor?

Answer 5

Ligand-binding domain
DNA-binding domain

Question 6

Glycogen breakdown?

Answer 6

epinerphrine stimulates breakdown of glycogen- glucose 1P
CAMP by adylel cylase converts into AMP, stimulates gylcolysis by activating phosphofructokinase

Question 7

How is Ca used by the cell?

Answer 7

used by the cell as a second messenger because it is maintained at very low concentration in cell
Ca2+ tend to diffuse very rapidly inside the cell (very high equilibrium potential/current)

Question 8

What is the specifity of the response?

Answer 8

The response (cellular or nuclear) is specific to the signal and can also differ between tissues and organs for the same signal.

Question 9

What are scaffolding protiens?

Answer 9

large relay proteins, to which several other relay proteins are simultaneously attached, and that can help to amplify cellular response

Question 10

Steps in signal transduction pathway (3)

Answer 10

Signal reception: ligand binds to receptor
Signal transduction: conversion of the signal, creaes transduction pathway
Cellular response: the cellular response is specific to the transduced signal

Question 11

what is Kinase?

Answer 11

enzyme catalyzing the transfer of a phosphate group from ATP to a protein, thus phosphorylating the protein.

Question 12

What are G protein-coupled receptors?

Answer 12

Cell-surface transmembrane receptor that works with the help of a G protein, which is a protein that binds to GTP, and has a associated enzyme

Question 13

How can cells communicate (2)

Answer 13

cell junctions
cell-surface molecules (receptors)

Question 14

Characteristics of GPCRs? (4)

Answer 14

transmembrane domains (7 α helices)
one loop forms a binding sites for the signaling molecules, one loop forms a binding sites for the G proteins
loops are hydrophilic
amino acids in center are non-polar

Question 15

What is cAMP

Answer 15

second messenger of many biological pathways.i nvolved in epinephrine pathway

Question 16

Example of cAMP?

Answer 16

Epinephrine is produced and binds to a GPCR, activates a G protein, which activates an enzyme then adenyl cyclase (makes CAMP from ATP)
The rapid increase of [cAMP] inside the cell activates a protein kinase A (does cellular response)

Question 17

What is the nuclear response to signal

Answer 17

The cellular response is often amplified by the phosphorylation cascade.
Nuclear response: after the phosphorylation cascade, many signaling pathways regulate protein synthesis by turning specific genes ON or OFF

Question 18

What are intracellular receptors?

Answer 18

Some hydrophobic (not on membrane) and some small signaling molecules can cross the bilayer of phospholipids
The signaling molecule binds to its intracellular receptor,
The signaling molecule acts as a transcription factor.(regulate gene expression)

Question 19

How do RTKs work

Answer 19

1. 2 signalling molecules bind to 2 tyrosine monomers 2. Monomers joined, called dimerization
2. phosphylation of tyrosine, ATP to ADP
3. relay proteins bind, Triggers response,

Question 20

2 types of cell signaling?

Answer 20

Local signaling (paracrine signaling): a cell stimulates nearby cells
Long-distance signaling: a cell releases a hormone traveling through the circulatory system to transmit a signal to the target cells.

Question 21

What is Glycogenolysis?

Answer 21

glycogen breakdown into glucose molecules usable in the cellular respiration.
Once activated, the protein kinase A activates a phosphorylase kinase

Question 22

A gdp is….

Answer 22

Inactivte