G protein coupled receptors

Question 1

what are g protein coupled receptros and what are their synoynms

Answer 1

proteon receprtos found at the cytoplamsic membranethey have a g protein complex attached to them

the synonyms are 7-transmembrane, heptahelical receprtos, g port

Question 2

why is g protein called the way it is

Answer 2

because it binds to guanone

Question 3

function of gpcr

Answer 3

function is singla transduction which means to transfer infrotmation from outise od the cell to thie inside

Question 4

how do gpcr amplify the singal coming into the cell

Answer 4

they prodcue or inhibit of production of secondary messagers using enzymes

Question 5

what are gcpr used for

Answer 5

vision, taste, smell

nerve impulese both the sympathic and parasympathethic receptors

metabloism, immune system and reproduction

Question 6

maine xmaples of gpcrs

Answer 6

GABA recptors, bittersweet and umami taste, adrenergic - adrenaline and noradrenaline, opird and somatosin

olfactory receptors haas 300 members the biggest portion involved anad it involved in smell

vasopressin sexual motivation pair bonding

Question 7

what are orphan receptors

Answer 7

the ligand hasnt been idenitified they dont know why and when it has been indentified it is known as deorphanisation

Question 8

GPCR structure describe it

Answer 8

Question 9

what are homodimers and the functional outcome

Answer 9

two of the sma receptros actas a dimer and only one functional outcome possible

Question 10

what are heterodimers and the fnuctional outcome

Answer 10

they have there receprtros but they are different are two functional outcomes

Question 11

what are trimeric RMS

Answer 11

three different gproteincoupled receptors with the functional outcome of six

Question 12

the g proteins what are they

Answer 12

known as guanine nucelotide binding proteins, are hetero trimeric molecular switches

has theree subunits G alpha G beta G gamma

the g alpha protein subunit is the one bound to guanosine diphosphate

when bound to gtp the protein turns on

Question 13

signalling via GqA

Answer 13

ligands are proinflammatory - hostamnines leukotrienees and methacholine

g alpha subunit binds to phospholipase c beta

plcb will cleave phospholipid PIP2

products are DAG and IP3 and IP3 binds to the IP3 receptor on the sarcoplasmic reticulum

this causes release of the calcium from stores and binds to enzyme calmodulin

this results in the upregulating myolin light chain kinase and causes the downregulation of myosin light chain phosphatase

increased phosphorlation of myosin light chain causes the myosin light chain to walk across the actin filaments

causes contraction of the cells and causes the contraction of the muscles bundles in the smooth muscles - bronchoconstriction

Question 14

signalling via Gsα

Answer 14

ligands is adrenaline

Gs alpha subunit is activated once ligand is bound and will activate adenyl cyclase

ac will convert ATP into cAMP

cAMP binds to tritamer protein kinase a regulatory units which allows the release of the catalytic units

catalytic units phosphorlates and resulats in opening in calcium activated potassium channels

cause downregulation is myosin light chain kinase and upregulation in myspin light chain phosphotase

results in smooth muscle relaxation

Question 15

signalling via Giα

Answer 15

ligads are opoids serotonin and chemokines,

i for giα means inhibitory

when gi alpha subunit binds to adenly cyclase it inhibits the production of cAMP

this causes proten kinase a regulatory and catalyic units to reassociate

Question 16

what are chemokines

Answer 16

chemokines are molcules produced at the site of infection by cells

immune cells have chemokines receptors and will cause the cells to move

the immune cells will travel up along the gradient to reach the area of infection

Question 17

how Gα subunits regulated

Answer 17

when bound to GDP they are off and on when bound to GTP

When bound to gdp the alpha subunit needs to dissocaite from GDP and bind to GTP

Guanine nucelotide exchange factors binds to the Gα can cause GDP to dissociate by changing the structure of the Gα and leave an empty pocket for GTP to bind to

when bound to GTP the GTP molcule is hydrolysed, by Gα, into GDP and an inorganic phosphate ion is relased

GTPase activating protein or GAP binds to the Gα they boost the GTPase activity from the Gα subunit