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Biochemistry I/II > Exam II-L10 > Flashcards

Exam II-L10 Flashcards

1
Q

How can we instruct the cell to change its behavior?

A

Cellular signaling or signal transduction pathway

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2
Q

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

A

True

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3
Q

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?

A

GPCR receptor

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4
Q

What are the three domains of the GPCR?

A

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

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5
Q

What subunits make up the G protein heterodimeric complex?

A

G alpha, G beta, and G gamma

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6
Q

How is G alpha activated and inactivated?

A

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

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7
Q

Steps of GPCR activation?

A

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

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8
Q

What subunits make up the Gs protein?

A

Gs = alpha, beta, gamma subunit + GDP

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9
Q

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.

A

conformational change

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10
Q

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

A

True

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11
Q

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

A

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

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12
Q

High levels of cAMP activates ___

A

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

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13
Q

How can you stop adenylyl cyclase signaling?

A

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

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14
Q

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

A

True

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15
Q

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

A

True

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16
Q

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

A

PKA

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17
Q

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

A

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

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18
Q

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

A

Second messengers

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19
Q

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

A

Converts PIP2 to DAG + IP3

20
Q

Release of what molecule is triggered by IP3?

A

Calcium

21
Q

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

A

Calcium and DAG

22
Q

What is the role of phospholipase C in GPCR activation?

A

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

23
Q

Which subunits activate PLC?

A

Gaq

24
Q

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

A

Calmodulin

25
Q

____is a disease characterized by hyperglycemia

A

Diabetes mellitus

26
Q

___ 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

A

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

27
Q

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

A

GPCR - in the liver

28
Q

What three processes are stimulated by glucagon?

A

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

29
Q

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

A

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

30
Q

What three stimuli initiates secretion of glucagon?

A

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

31
Q

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

A

True

32
Q

Glycogenolysis is triggered by ____

A

glucagon

33
Q

In glucagon signaling, Gas activates adenylyl cyclase, which converts ___ → ___

Elevated cAMP leads to activation of ___ →_____ and _____

A

ATP to cAMP

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

34
Q

What is the function of PPb (glycogen phosphorylase) ?

A

Glycogen → Glucose

35
Q

True or False: Glucagon signaling enhances gluconeogenesis and glycogenolysis

A

True

36
Q

What type of receptors are used by insulin?

A

RTK
(liver, muscle, adipose tissue)

37
Q

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

A

Insulin !!

38
Q

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

A

Insulin

39
Q

What tissues is GLUT4 present on?

A

Adipose and muscle

40
Q

True or False: GLUT4 lowers blood glucose

A

True

41
Q

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

A

glucose transport

42
Q

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

A

Insulin

43
Q

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

A

Insulin

44
Q

Cholera toxin permanently activates what two effector proteins? Effect?

A

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

45
Q

How does pertussis toxin take effect to cause whopping cough?

A

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

46
Q

What is the function of adenylyl cyclase?

A

Converts ATP to cAMP and PPi

Biochemistry I/II (23 decks)

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