Actions Of Hormones - Cell Signalling

Question 1

Where are the receptors for lipophilic and hydrophilic hormones

Answer 1

Hydrophilic peptides and catecholamines

• via cell surface recep on outer PM
• amines - adrenaline and noradrenaline
• peptides - insulin, glucagon, ADH and GH

Lipophilic steroid and thyroid hormone

• via intracellular receptor
• glucocorticoids( cortisol), mineralcorticoids(aldosterone), oestrogens, progesterone, androgens(testosterone) and thyroid hormone

Question 2

How do extracellular messengers bring about cell responses

Answer 2

Primarily by signal transduction

Question 3

What su signal transduction

Answer 3

Process where incoming signals are conveyed into the cell where they are transformed into dictated cellular response

Diffenrt mechanisms dept on messenger and receptor type

Question 4

How do hydrophillic hormones alter pre existing

Answer 4

Via seconday messenger systems

Question 5

What do most hydrophilic hormones bind to

Answer 5

GPCR G protein coupled receptor

Question 6

What are the two major secondary messenger pathways

Answer 6

Cyclic adenosine mono phosphate cAMP

CALCIUM

Question 7

What do both of the major secondary messenger pathways use

Answer 7

A G protein on the inner surface of the PM as an intermediary between receptor an effector proteins

Question 8

What bind to G proteins when they are active or inactive

Answer 8

GTP when active and GDP when inactive

Question 9

What dos San inactive G protein complex consist of

Answer 9

3 subunits - alpha beta and gamma

GDp binds to alpha

Question 10

How does signal transduction occur with GPCR’s

Answer 10

Hormone the first messenger binds to the receptor
Receptor then attaches to G protein - release of GDP form G protein complex
GTP then attaches to alpha subunit which activates alpha subunit
Alpha subunit dissociates from beta and gamma subunits and move to inner surface if PM until it reaches an effector protein Genzyme or ion channel)
The alpha unit links up with the effector protein and alters its activity

Question 11

What are the two major G protein coupled effectors

Answer 11

These are both mem bound enzymes

1) adenylyl cyclase (cAMP)
2) phospholipase C (calcium)

Question 12

What does adenylyl cyclase do

Answer 12

On the cytoplasmic side of PM it converts ATP to cAMP

cAMP activates a specific intracellular enzyme protein kinase A (PKA)

PKA phosphorylate a pre existing intracellular protein (threonine residues )

Question 13

What happens with phospholipase c and Calcium

Answer 13

Binding of a hormone via a GPCR activates an enzyme phospholipase c

Plc break ps down PIP2 to yield DAG and IP3

DAG remains in the PM IP3 diffuses into cytosol

IP3 stimulate the release of calcium from ER

DAG regulates PKC ( PKC phosphorylates serine residues on specific intracellular proteins)

Question 14

What kind of hormone is insulin

Answer 14

Peptide hormone.

Question 15

How does insulin act

Answer 15

Binds to its cell surface receptor and activates ‘autophosphorylation’

Insulin recep - tyrosine kinase

Question 16

What dos phosphorylation of tyrosine kinase receptor lead to

Answer 16

Recruitment of glucose transporters to plasma membrane which increases glucose uptake to muscle and fat cells

Repress catabolic induce anabolic

Activates glycogen synthase glucose storage

Increases lipogenesis

Question 17

What hormones can all cross the membrane and bind to intracellular receptors - cytoplasmic or nuclear

Answer 17

Steroid hormones, calcitriol and thyroid hormone

Question 18

What happens at the hormone response element

Answer 18

The hormone receptor complex binds with DNA at a specific attachment site

Question 19

How do hormones target specific cell types

Answer 19

Only target cells for particular hormone express receptors for binding with this hormone
Non target cells are not influenced