Exam II-L10

Question 1

How can we instruct the cell to change its behavior?

Answer 1

Cellular signaling or signal transduction pathway

Question 2

True or False: Phosphorylation or dephosphorylation of a protein can activate or inhibit its catalytic activity

Answer 2

True

Question 3

Ligand, GPCR, G-protein heterodimeric complex, effector proteins, 2 messenger, 2 messenger kinase, and activated kinase target are all components of what type of receptor?

Answer 3

GPCR receptor

Question 4

What are the three domains of the GPCR?

Answer 4

1) Seven transmembrane helices
2) Extracellular domain - has binding site for ligand
3) Intracellular domain - interacts w/G proteins

Question 5

What subunits make up the G protein heterodimeric complex?

Answer 5

G alpha, G beta, and G gamma

Question 6

How is G alpha activated and inactivated?

Answer 6

Activation: GEF will replace GDP for GTP
Inactivation: GAP will replace GTP with GDP

Question 7

Steps of GPCR activation?

Answer 7

1) Ligand binds
2) GDP is exchanged for GTP (GEF)
3) Ga subunit is activation and dissociates
4) Effector proteins are activated
5) Second messengers are generated

Question 8

What subunits make up the Gs protein?

Answer 8

Gs = alpha, beta, gamma subunit + GDP

Question 9

Once ligand binds to receptor, the receptor undergoes a _____ and interacts with Gs proteins. Ga releases GDP (binds GTP) and dissociates from beta and gamma subunits.

Answer 9

conformational change

Question 10

True or False: Unoccupied GPCR receptors do not interact with Gs protein

Answer 10

True

Question 11

Once alpha subunit of Gs protein dissociates from beta/gamma subunits, what effector protein does it activate?

Answer 11

Adenyl cyclase
(activation of adenyl cyclase converts ATP to cAMP and PPi)

Question 12

High levels of cAMP activates ___

Answer 12

PKA
(PKA then goes on to phosphorylate a variety of target proteins)

Question 13

How can you stop adenylyl cyclase signaling?

Answer 13

1) hydrolysis of Ga GTP
2) phosphodiesterase (converts cAMP to 5 AMP = cannot activate PKA)
3) Gai (inhibit adenylyl cyclase activity)

Question 14

True or False: adenylyl cyclase converts ATP to cAMP and PPi

Answer 14

True

Question 15

True or False: cAMP binds to the regulatory subunit of PKA, allow catalytic subunit of PKA to be activated and behave as a kinase

Answer 15

True

Question 16

If you inhibit adenylyl cyclase, you also inhibit a downstream protein known as ___

Answer 16

PKA

Question 17

What are the three different types of G proteins + their functions?

Answer 17

Gas: Stimulates adenylyl cyclase
Gai: Inhibits adenylyl cyclase
Gaq: Activates phospholipase C (effector enzyme)

Question 18

What types of molecules are: IP3, DAG, and Ca2+?

Answer 18

Second messengers

Question 19

What is the function of Phospholipase C, a membrane-bound enzyme?

Answer 19

Converts PIP2 to DAG + IP3

Question 20

Release of what molecule is triggered by IP3?

Answer 20

Calcium

Question 21

__ and ___ activate PKC in the pathway involving Phospholipase C (PLC)

Answer 21

Calcium and DAG

Question 22

What is the role of phospholipase C in GPCR activation?

Answer 22

After ligand binds, activated receptor interacts with G protein, Gaq is activated and dissociates…
1) Phospholipase C (effector protein) is activated
2) IP3/DAG are made, leading to Calcium release
3) Calcium and DAG activate PKG
4) PKG phosphorylates target proteins

Question 23

Which subunits activate PLC?

Answer 23

Gaq

Question 24

____is a calcium binding protein that acts as a co-factor in many enzymatic reactions

Answer 24

Calmodulin

Question 25

____is a disease characterized by hyperglycemia

Answer 25

Diabetes mellitus

Question 26

___ is a catabolic hormone produced in the alpha cells of the pancreas that signals 'fast state' _____ is an anabolic hormone made in the beta cells of the pancreas

Answer 26

Glucagon: is a catabolic hormone produced in the alpha cells of the pancreas Insulin: is an anabolic hormone made in the beta cells of the pancreas

Question 27

What receptors are used by glucagon? Where are they located?

Answer 27

GPCR - in the liver

Question 28

What three processes are stimulated by glucagon?

Answer 28

Gluconeogenesis (liver) Lipolysis (adipose) Glycogenolysis Ketogenesis (liver)

Question 29

___ is a glucose storage molecule that is mostly stored in the liver for systemic use

Answer 29

Glucagon is a glucose storage molecule that is mostly stored in the liver for systemic use

Question 30

What three stimuli initiates secretion of glucagon?

Answer 30

1) low blood glucose 2) epinephrine 3) consumption of protein

Question 31

True or False: Stress hormones stimulate gluconeogenesis, glycogenolysis, and lipolysis in the liver

Answer 31

True

Question 32

Glycogenolysis is triggered by ____

Answer 32

glucagon

Question 33

In glucagon signaling, Gas activates adenylyl cyclase, which converts ___ → ___ Elevated cAMP leads to activation of ___ →_____ and _____

Answer 33

ATP to cAMP cAMP → PKA → PPK (phosphorylase kinase) → PPb (glycogen phosphorylase)

Question 34

What is the function of PPb (glycogen phosphorylase) ?

Answer 34

Glycogen → Glucose

Question 35

True or False: Glucagon signaling enhances gluconeogenesis and glycogenolysis

Answer 35

True

Question 36

What type of receptors are used by insulin?

Answer 36

RTK (liver, muscle, adipose tissue)

Question 37

What molecule stimulates... - glycogen synthesis - fat storage - GLUT4 (glucose transport into adipose/muscle)

Answer 37

Insulin !!

Question 38

What molecule signals for the GLU4 transporter to come to cell surface?

Answer 38

Insulin

Question 39

What tissues is GLUT4 present on?

Answer 39

Adipose and muscle

Question 40

True or False: GLUT4 lowers blood glucose

Answer 40

True

Question 41

In diabetes, less insulin results in less ____ into adipose and muscle tissue and, thus, sustained higher blood glucose levels

Answer 41

glucose transport

Question 42

What molecule stimulates glycogenesis and protein synthesis in muscle tissue and TAG synthesis in adipose tissue?

Answer 42

Insulin

Question 43

Which molecule inhibits gluconeogenesis and ketogenesis in the liver, as well as lipolysis in adipose tissue?

Answer 43

Insulin

Question 44

Cholera toxin permanently activates what two effector proteins? Effect?

Answer 44

Gas and AC Effect: hyperactivation of CFTR, electrolyte and water efflux

Question 45

How does pertussis toxin take effect to cause whopping cough?

Answer 45

1) Pertussis ribosylates Gai 2) G protein complex cannot interact with GPCR 3) AC cannot be turned off in lung epithelia 4) Whooping cough

Question 46

What is the function of adenylyl cyclase?

Answer 46

Converts ATP to cAMP and PPi