Intracellular Signalling 5

Question 1

What are the three types of basic messenger molecules?

Answer 1

Hydrophobic molecules (diacylglycerol, phosphatidylinositols)-usually membrane bound and detach to reach effector proteins

Hydrophilic molecules (cAMP cGMP) - located within cytosol

Gases (NO, CO, hydrogen sulphide) - diffuse through anything in cell

Question 2

What does GPCR stand for?

Answer 2

G protein coupled receptors

Question 3

7TM receptors, span the membrane 7 times in six loops how?

Answer 3

Three extraC loops interact with ligand
Three intraC loops interact with G proteins

And two principle signalling pathways activated - cAMP and PLC

Question 4

How does GPCRs work?

Answer 4

Signal molecule causes receptor to activate G proteins and exchange GDP for GTP leading to effector interaction

(Works like a cycle of life goes back to step one)

Question 5

What is the most frequent target for G proteins?

Answer 5

Most frequent targets of G proteins are the enzymes:

Adenyl cyclase

Phospholipase C (PLC)

Leading to production of second messengers (small intracellular signalling molecules)

Question 6

What’s cyclic nucleotides?

Answer 6

Cyclic nucleotides are second messengers

Question 7

What does adenylyl cyclase make?

Answer 7

Adenylyl cyclase makes cyclic AMP (cAMP)

Question 8

Why do cAMP levels sometimes increase rapidly?

Answer 8

cAMP levels increase rapidly when in response to extracellular signal

Question 9

What does cAMP activate?

Answer 9

cAMP activates cyclic AMP dependent protein kinase (PKA)

(Downstream effects eg glycogen breakdown in skeletal muscle)

(-Can also take effect in transcriptional regulation)

Question 10

How does the GCPR interact with membrane bound phospholipase C (PLC)

Answer 10

G protein activates the PLC

Leading to two small second messenger molecules being activated (inositol and diaglycerol)

Question 11

What can inositol release activated by the PLC lead to?

Answer 11

Inositol leads to ER releasing calcium which activates PKC (protein kinase C)

Question 12

What does changes in calcium levels do?

Answer 12

Increase in calcium levels trigger many biological processes (eg fertilisation)

Question 13

How does steroid hormone signalling work?

Answer 13

Steroid hormones diffuse through PM (cos they are lipids) and bind to intracellular receptor (in cytoplasm or nucleus) and form a complex

-modulate transcription of target genes

Question 14

What are two types of steroid hormones?

Answer 14

Corticosteroids - made in the adrenal cortex

Sex steroids - made in the gonads or placenta

Question 15

What are the five subdivided categories of steroid hormones? (NB- vitamin D derivatives are related closely and similar)

Answer 15

Glucocorticoids

Mineralocorticoids

Androgens

Oestrogens

Progestogens

Question 16

What functions does steroid hormone signalling have?

Answer 16

-metabolism
-inflammation
-immunity
-salt and water balance
-reproduction
-secondary sexual characteristics

Question 17

What are steroids used to describe?

Answer 17

Steroids are used to describe natural hormones and synthetic meds that duplicate their actions

Question 18

Where is cortisol produced?

Answer 18

Produced by adrenal glands in response to stress

Question 19

What are some biological effects of cortisol?

Answer 19

-mainly metabolic ;

Stress response
Blood pressure
Blood sugar
Inflammation
Memory

Question 20

Cortisol receptors found nearly every cell in the body, how is it released?

Answer 20

Released via hypothalamic-pituitary- adrenal axis negative feedback loop

Elevated cortisol - Cushing’s syndrome
Reduced cortisol - Addison’s disease

Question 21

Where can steroid hormone receptors be found?

Answer 21

Found in nuclear, cytosolic, and PM