Extracellular Hormone

Question 1

List plasma protein membrane receptor ( 2nd messenger) types and examples and their synthetic paths

Answer 1

1 peptide - insulin / glucagon. Proteolytic processing of prohormone

2 eicosanoid - PGE. From arachidonate

3 catecholamine - epinephrine. From tyrosine

Question 2

List nuclear receptor ( 2nd messenger) types and examples and their synthetic paths

Answer 2

1 steroid - testosterone. From cholesterol

2 thyroid - T3/ triidothyromine. From Tyr in thyroglobulin

3 retinoids - retinoic acid. From vitamin A

4 Vitamin D - 1,25 dihydroxycholecalciferol. From cholesterol

Question 3

List cystolic receptor ( 2nd messenger) types and examples and their synthetic paths

Answer 3

Nitric oxide - nitric oxide. From arginine + O2

Question 4

List the 6 steps of cell to cell communication

Answer 4

1 signal cell produces signal molecule
2 release of signal molecule 
3 transport of signal molecule 
4 binding of signal molecule to receptor
5 cellular response 
6 removal of signal and termination of cellular response

Question 5

What is cellular response and what causes it

Answer 5

• change in cellular metabolism , function and morphology

- ligand receptor complex

Question 6

List types of receptors

Answer 6

1 seven membrane transmembrane protein

2 enzyme linked receptor

3 intracellular receptor

4 ion channel receptor

Question 7

How does a ion channel receptor function and its outcome

Answer 7

• ligand binds to receptor causing conformational changes and this allows specific ions to pass through
• causes change in membrane or cytosolic ionic conc

Question 8

Describe how a tyrosine kinase linked enzyme works

Answer 8

• binding of ligand causing 2 receptors to form cross link dimer
• the tyrosine of opposite receptors phosphorylate each other
• activated tyrosine acts as docking platforms for diff proteins which are phosphorylated and activated
• signal transduction into cytosol

Question 9

What does a kinase have the ability to do

What type of proteins bind to tyrosine kinase receptor

Answer 9

-transfer of phosphate from high source substrate

/those with SH2 receptor

Question 10

Why are tyrosine kinase receptors in pairs

Describe structure of g coupled protein receptor

Answer 10

• so that they can cross phosphorylate each other

- 7 helical proteins transmembrane and with C terminal in cytosol and N terminal in extra cellular domain

Question 11

List the protein needed for 2nd messenger system

Answer 11

1 hormone receptor
2 G protein
3 adenylate Cyclase

Question 12

What is transduction

Answer 12

-conformational changes triggered by formation triggered by ligand receptor complex

Question 13

Property of g property

What is 2nd messenger

Answer 13

• able to bind to guanine triphosphate

- substrate released into cyto after receptor activation

Question 14

How is cAMP made and by what

Answer 14

-by adenylate cyclase wc is uses ATP as substrate after activated by G protein

Question 15

List 2nd messengers and type of hormones that utilize the system

Answer 15

cAMP - epinephrine, calcitonin , FSH

Protein kinase activity - oxytocin ,insulin

cGMP - nitrogen oxide

Calcium or / and phosphoinosites - epinephrine, GnRH , thyroid releasing hormones

Question 16

How does 2nd messenger amplify hormone

Answer 16

• single hormone binds to single receptor
• numerous G proteins activated
• each stimulates numerous adenylate cyclases
• 2 cAMP active a protein kinase
• each PK phosphorylates numerous proteins

Question 17

How is signal terminated and what happens

Answer 17

• phosphatase 1 removes phosphate groups from diff enzymes

- cAMP is continuously degraded and when hormone dissociates from receptor cAMP levels drop

Question 18

Describe how R-triggered hydrolysis of phosphatidyl inositol 4,5 biphosphate ( PIP2 ) occurs

Answer 18

• active G protein activates phospholipase wc hydrolyses PIP2 into DAG and IP3 ( both 2nd messengers
• DAG actives PKC and IP3 forms channels at ER to releases Ca and both cause response in target cell

Question 19

What does DAG and IP3 stand for

What does PKC do

Where is PIP2 found

Answer 19

• diacyglycerol
• inositol triphosphate

-phosphorylates Ser and threonine of certain target cells

/in cell membrane

Question 20

How is hormonal response regulated

What does GAP do

What does GEP do

Answer 20

-by slowly cleaved GTP to GDP by G protein

/ gtpase activating protein ( GAP ) assist in GTP cleaving

• guanine exchange factor aids in transfer of GDP to GTP on G protein

Question 21

What does Gi do and how

Answer 21

/it responses to adenylate inhibition by binding to it and decrease cAMP synthesis

Question 22

Describe G protein cycle

Answer 22

-inactive G protein has GDP changed to GTP by GEF due to bound receptor and is now active
/active G protein actives adenylate with the aid of GAP via alpha adenylate cyclase complex
-g protein now has gdp but adenylate active and complex dissociates
-g protein reacquires beta and gamma subunits and now inactive

Question 23

Describe mechanism of coupling by cholera toxin and its effects

Answer 23

/cholera has 2 peptide chains ( A and B )

• B bind to membrane and A enters cell and catalyses transfer of ADP ribose for NAD plus to G protein
• product is ADP ribosyl GTP protein + water and nicotiamide
• ADP ribosyl is a covalent modification preventing hydrolysis to GDP and go protein kept in active state leading to influx of water and Na in gut

Question 24

Examples of effects of cAMP

Answer 24

• in adipose actives PKA to stimulate more fatty acid production
• in ovarian cycle PkA stimulated to produce more estrogen

Question 25

Describe mechanism of g coupled protein

Answer 25

• ligand binds to receptor causing conformational change to receptor and it reacts with g Protein to change GDP to GTP
• actives AC
• AC create cAMP
• cAMP active PK which phosphorylate proteins to activate them
• cellular response