cGMP

Question 1

a passage through a cell membrane that uses energy to
move ions or other molecules AGAINST their
concentration gradient

Answer 1

Ion Transport

Question 2

Ion transporters use

Answer 2

energy like ATP

Question 3

types / examples Ion transportation

Answer 3

Plasma membrane Ca2+ ATPase
Sodium-calcium exchanger
Sodium chloride symporter
Glycine transporter

Question 4

Passage through a cell membrane that lets ions flow
DOWN their concentration gradient if it is open; not if it
is closed

Answer 4

Ion Channels

Question 5

________ equalizes the concentrations on either side of the cell
membrane

Answer 5

Ion Channels

Question 6

Ion channels accomplish this equalization via ____________ which is a type of _______transport

Answer 6

Facilitated diffusion

Passive

Question 7

________ is typically one type of ion and activated by changes in electrical membrane potential

Answer 7

Voltage gated Ion channel

Question 8

_____ is less selective and multiple ions

activated by extracellular ligand binding

Answer 8

Ligand gated ion channels

Question 9

What are the three classifications for mechanosensitive ion channels

Answer 9

cation
anion
non-selective

Question 10

_________ activated by mechanical deformation in the membrane

Answer 10

stretch-gated / mechanosensitive

Question 11

______ ion channel is G-protein regulated

Answer 11

signal-gated

Question 12

ion channels can be ______________ for fast acting mediation of ion flow across membrane

Answer 12

Ligand gated receptors

Question 13

Ion channels can be ______________ regulated to mediate slow acting ion channel opening for longer period of time

Answer 13

G-Protein regulated

Question 14

How are ion channels regulated by GPCR (3)

Answer 14

G protein alpha or beta-gamma subunit
cAMP, cGMP or DAG
PKA or PKC phosphorylation

Question 15

how do cAMP, cGMP and DAG regulate ion channels?

Answer 15

by directly binding to the channels

Question 16

what are targets of G proteins so far? 3

Answer 16

AC
PLC
ion channels

Question 17

What is Rhodopsin

Answer 17

GPCR for retinal rods

in the intracellular membrane.

Question 18

why is rhodopsin a major GPCR prototype?

Answer 18

Retinal rod outer segment membranes are nearly pure
rhodopsin
therefore rhodopsin was easily identified, purified, studied

Question 19

what is the ligand for Rhodopsin?

how is it bound?

Answer 19

11-cis-retinal

covalently bound

Question 20

What is the signal and the detector?

Answer 20

signal : light photon

detector: 11-cis-retinal

Question 21

what happens when photon hits the 11-cis-retinal,

Answer 21

it causes a conformational change in the retinal, which then changes structure of receptor (C3 loop) and that activates the G-protein transducin

Question 22

explain the transition from 11-cis-retinaldehyde to all-trans-retinaldehyde ?
which one happens fast?

Answer 22

11-cis-retinaldehyde While bound to receptor; changes receptor conformation when light is detected

Once isomerized, it is clipped off, dissociates
from receptor;

enzymatic re-isomerization,
then covalently reattaches to Rhodopsin- happens fast

Question 23

What is Transducin?

Answer 23

Transducin is a G protein (alpha, beta and gamma)

abbreviated GT and is a Gi family member

Question 24

explain what Visual System – Rhodopsin & G protein messenger?

Answer 24

1. Rhodopsin is activated by light. 
Conformational change leads to 
activation of G-protein transducin (GT). (release GDP, bind GTP)
2. The GTα•GTP activates cGMP-PDE
3. The cGMP-PDE breaks down cGMP to 
GMP
4. When cGMP is broken down, it comes 
off the ion channel which leads to 
closing of the channel
5. Ions stop flowing, depolarizes 
membrane, sends electrical signal 
down optic nerve to the brain

Question 25

explain Rhodopsin pathway in light vs dark

Answer 25

``` When it is dark, we make cGMP continuously to keep ion channel open (Burning ATP to pump ions back out) Light turns the cGMP off, closes the ion channel ```

Question 26

GT is substrate for what?

Answer 26

a substrate for both cholera and pertussis toxin

Question 27

In Rhodopsin pathway ________ is secondary messenger ________ is the effector _________ regulated step

Answer 27

Second messenger = cGMP Effector for G protein = cGMP phosphodiesterase that cGMP degradation is the regulated step;

Question 28

what is the target for cGMP?

Answer 28

membrane ion channel

Question 29

how is cGMP phosphodiesterase activated?

Answer 29

by alpha-GTP of GT (Gi family)

Question 30

cGMP is synthesized by

Answer 30

guanylyl cyclase

Question 31

The ion channels that are the target | of cGMP are________

Answer 31

cation channels for | movement of Calcium and Sodium

Question 32

__________ the ion channel

Answer 32

cGMP

Question 33

__________ is degraded by PDE (that is activated by Gt

Answer 33

cGMP

Question 34

Synthesized by how many guanylyl cylases?

Answer 34

two particulate membrane GC soluble (cytosolic) GC

Question 35

Activates _________ kinase?

Answer 35

PKG

Question 36

what is the similarity between AMP and cGMP and their Cyclases

Answer 36

They all share that | “anti-parallel dimer” at the catalytic domain

Question 37

Membrane Guanylyl Cyclase is ____________

Answer 37

enzyme-linked receptor | ▪ Receptor and cyclase combined in a single molecule

Question 38

where dose the hormone and enzyme activity found on enzyme-linked receptor

Answer 38

hormone binding site on | outside, enzyme activity on inside

Question 39

which part of GC is antiparallel “dimer

Answer 39

cytosolic and that's where catalytic domain is too

Question 40

what is Atrial natriuretic factor (ANF, ANP)?

Answer 40

is a peptide hormone | released from the heart

Question 41

ANP activates what form of guanylyl cyclase

Answer 41

membrane form

Question 42

high cGMP in kidney ___________ and in blood vessel ________________

Answer 42

Kidney: decreases sodium retention | blood vessel: low blood pressure and volume

Question 43

_____________ activates Soluble (cytoplasmic) Guanylyl Cyclase

Answer 43

Nitric oxide (NO)

Question 44

How does NO activates soluble GC and where does it form and where does it act

Answer 44

Changes conformation of the Heme, and then the dimeric GC forms in blood vessel endothelial cells in response to stretch and acts in adjacent smooth muscles cells

Question 45

the activity of the catalytic domain of soluble GC is is regulated by ______

Answer 45

NO

Question 46

_______ makes NO

Answer 46

NOS- nitric oxide synthase

Question 47

receptor for NO is _________

Answer 47

soluble GC

Question 48

NO is _________ signaling whereas ANP is ________ signaling

Answer 48

NO- paracrine | ANP- endocrine

Question 49

Similarities between AC, mGC and sGC is

Answer 49

- dimers in catalytic domains | - catalytic domains are highly homologous

Question 50

Differences between AC, mGC and sGC is

Answer 50

- Membrane association - The regulators - The sites at which the regulators bind

Question 51

what is PKG (cyclic GMP-dependent protein kinase):

Answer 51

- cGMP target - ser-thr kinase - regulatory/ receptor and catalytic "domains" on a single peptide chain

Question 52

cGMP targets

Answer 52

- PKG - Ion channels - cAMP phosphodiesterase's and cAMP

Question 53

Phosphodiesterase (PDE) breaks __________

Answer 53

a phosphodiester bond

Question 54

how many PDE families and how do they vary

Answer 54

12 - vary by tissue distribution, substrate specificity, pharmacological properties,

Question 55

how do we regulate cGMP? (3)

Answer 55

``` 1. by controlling cGMP breakdown by phosphodiesterases 2. a "soluble" or "cytosolic" guanylyl cyclase 3. a "particulate" or "membrane" guanylyl cyclase ```