Lecture 28

Question 1

What are hormones?

Answer 1

extracellular signals that are released from controller cells in the endocrine system and travel to target cells where they interact with specific receptor, a process called signal transduction

Question 2

What are the five major classes of signaling molecules?

Answer 2

neurotransmitters, hormones, cytokines, growth factors, and pheromones

Question 3

What can hormones be?

Answer 3

peptides(insulin and glucagon), steroids(glucocorticoids & sex hormones), amino acids derivs(epinephrine)

Question 4

What is true about signaling molecules?

Answer 4

They are not all hormones

Question 5

What are the three main classes of cell surface receptors?

Answer 5

ion-channel linked receptors, G protein coupled receptors, ligand-gated ion channels

Question 6

What are Gprotein coupled receptors?

Answer 6

glucagon and epinephrine/adrenaline): influence synthesis of second messengers

Question 7

What are receptor tyrosine kinases?

Answer 7

(ie. insulin): extracellular ligand binding causes auto-phosphorylation and activation of intracellular kinase domain.

Question 8

What are ligand-gated ion channels?

Answer 8

ion transport and nerve transmission (acetylcholine receptor)

Question 9

What is true about ligand-receptor interaction?

Answer 9

very specific such that receptors don’t exert their downstream effects until the corresponding ligand binds

Question 10

What is hormone secreted by?

Answer 10

secreted by endocrine glands into the bloodstream.

Question 11

How does hormonal action work?

Answer 11

At low concentrations and is short-lived, so that tissues can respond to changes quickly.

Question 12

What stimulates hormone release?

Answer 12

from endocrine cells is stimulated by chemical signals from regulatory cells that occupy a higher position in the hierarchy

Question 13

What controls hormone action?

Answer 13

Controlled by the central nervous system that receives signals from the environment and sends this information to the hypothalamus

Question 14

What is somatotropin? What does it stimulate?

Answer 14

from the pituitary gland stimulates pancreatic islet cells to produce either glucagon alpha cells) or insulin (beta cells) to act on liver or muscle cells.

Question 15

What are the receptors that bind to G protein coupled receptors?

Answer 15

beta-adrenergic that responds to adrenaline and epinephrine

Question 16

What activates G protein?

Answer 16

adenylate cyclaze enzyme

Question 17

What is the structure of beta-adrenergic?

Answer 17

7 highly conserved alpha helical domains that are common to all GPCRs that have a high degree of hydrophobic amino acids and linked by hydrophilic loops that project into the cytosol and the extracellular environment

Question 18

What does adenylate cyclase catalyze?

Answer 18

catalyzes the conversion of ATP to cyclic AMP

Question 19

What does cAMP acts as?

Answer 19

a secondary messenger for intracellular signal transduction

Question 20

What does Gi do?

Answer 20

inhibits adenylate cyclase

Question 20

What does Gs do?

Answer 20

stimulate adenylate cyclase

Question 21

What are examples of cell surface receptors?

Answer 21

G protein coupled receptor and tyrosine kinases

Question 22

How G proteins works?

Answer 22

It works by g protein coupled to receptors. Receptor + G protein. The amino acids

Question 23

What does G bind to when active and inactive?

Answer 23

GDP when inactive and GTP when active

Question 24

What is the action of epinephrine?

Answer 24

Hormone binds to surface receptor and stimulates cAMP formation which influences phosphorylation of target enzymes and distribution determines certain tissues

Question 25

How do tyrosine kinases?

Answer 25

Kinases that take away a phosphate group from ATP and phosphorylate a substrate

Question 26

How does RTK work?

Answer 26

Works as a single polypeptide. They come together and dimerize. Then it takes a phosphate and loads to other group. Goes back and forth(auto-phos). This increase kinase activity and makes new sites for binding.

Question 26

What does the N terminal do?

Answer 26

ligand binding

Question 27

What does the C terminal do?

Answer 27

catalytic activity

Question 28

What is EGF? What does it do?

Answer 28

It promotes growth and like cell proliferation and division

Question 29

How does insulin receptor exist?

Answer 29

dimer form

Question 30

What do the proteins do in the insulin receptor?

Answer 30

keep glycogen synthase active and promote glucose uptake and transcribing genes that promote cell division and growth. Also works similar to TRK like auto-phos

Question 31

What do nuclear receptors act as?

Answer 31

transcription factors upon hormone binding

Question 32

What is true about nuclear receptors?

Answer 32

Tend to be longer-term changes in growth and differentiation because receptor acts on DNA and effects gene transcription. Also, hormones can transverse the cell membrane, bind receptor and enter nucleus to bind to specific DNA elements and start transcription

Question 33

Where is the nuclear receptor?

Answer 33

Inside the cell, no longer on the surface

Question 34

How does the nuclear receptor work?

Answer 34

They promote gene expression and bind directly to DNA sequences. Have more long term effect. Start transcription

Question 35

How does tamoxifen work?

Answer 35

It binds to estrogen receptor, keeps it from turning on estrogen responsive genes (acts as an antagonist) that are important to growth of some types of breast cancer

Question 36

How does the abortion pill work? What is the receptor?

Answer 36

RU486 is a progesterone receptor antagonist and is also known as the “abortion pill”. It prevents a fertilized ovum from implanting in the uterus

Question 37

What do nuclear receptors have in their terminals?

Answer 37

possess a zinc containing N-terminal DNA binding domain and a C-terminal hormone binding domain

Question 38

What type of mutation do tumors have?

Answer 38

genetic mutations in proteins involved in signal transduction: protein kinases, G proteins, nuclear receptors, growth factor/receptors. Can also have excess of normal signal transduction

Question 39

What are examples of oncogenes?

Answer 39

Ras, Myc, p53

Question 40

What is an example of a tumor suppressor genes?

Answer 40

p 53, a DNA-binding protein that regulates metabolic processes following DNA damage

Question 41

How does p53 work?

Answer 41

it inhibits cell division