Chapter 9: Hormones

Question 1

Are prostaglandins paracrine or telecrine hormones?

Answer 1

paracrine

Question 2

Are neurotransmitters paracrine or autocrine hormones?

Answer 2

paracrine

Question 3

What is a protein kinase?

Answer 3

an enzyme that phosphorylates other proteins changing their activity

Question 4

What are examples of hormones that bind to p21ras?

Answer 4

Insulin
Insulin-like growth factor (IGF)
Platelet-derived growth factor (PDGF)
Epidermal growth factor (EGF)

Question 5

Are there second messengers required for receptors with intrinsic protein kinase activity (often tyrosine kinases)?

Answer 5

no

Question 6

Describe the steps in G protein activation.

Answer 6

when a hormone binds to its receptor, the receptor becomes activated and, in turn, engages the corresponding G protein

The GDP is replaced with GTP, enabling the alpha subunit to dissociated from the B and y subunits

activated alpha subunit alters the activity of AC. If the a subunit is as then the enzyme is activated; if the a subunit is ai then the enzyme is inhibited.

The GTP in the activated a subunit will be dephophorylated to GDP and will rebind to the B and y subunits, rendering the G protein inactive

Question 7

Describe the G protein coupled receptor membrane structure

Answer 7

7-helix membrane

Question 8

cAMP and CGMP are slowly degraded by a class of enzymes called what?

Answer 8

phosphodiesterases PDEs

Question 9

Explain how E.coli heat stable toxin causes diarrhea?

Answer 9

A GC receptor in the enterocytes is STa target.

Toxin binds to and stimulates, the guanylate cyclase increasing cGMP.

This causes increased activity of CFTR and concurrently diarrhea

Question 10

What is STa?

Answer 10

E. coli heat stable toxin

Question 11

Describe the ANF receptor?

Answer 11

has intrinsic guanylate cyclase activity not a 7-helix membrane spanning domain

Question 12

What binds the receptor after autophosphorylation of insulin receptors?

Answer 12

IRS-1 (Insulin receptor substrate -1) binds the receptor and is phosphorylated on tyrosine residues allowing proteins with SH2 (src homology) domains to bind to the phosphotyrosine residues on the IRS-1 and become active

Question 13

What events are associated with activation of PI-3 kinase?

Answer 13

One effect of phosphatidylinositol-3 kinase (PI-3) is to increase GLUT-4 in the membranes of adipose and muscle tissue

Question 14

What does PI-3 stand for?

Answer 14

phosphatidylinositol

Question 15

What is p21ras?

Answer 15

a monomeric G protein encoded by ras oncogene that if there is a gain of function mutation can lead to cancer

Question 16

Glucagon is associated with what state in the body?

Answer 16

the fasting and postabsorptive metabolism

Question 17

What favors activation of protein phophatases? In the well fed state to control glycogen phosphorylase to glycogen synthase activity?

Answer 17

Insulin so it may dephosphorylates enzymes that were phosphorylated by glucagon

Question 18

Cholera toxin activates what G protein?

Answer 18

Gsα

Question 19

Ecoli stimulates which G protein?

Answer 19

Gsα

Question 20

Pertussis stimulates what G protein?

Answer 20

Giα

Question 21

Explain ADP ribosylation by bacterial toxins.

Answer 21

Certain bacterial exotoxins are enzymes which attach the adenosine diphosphate ADP-ribose residue of NAD to Gα subunits is known as ADP ribosylation