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Physiology > Section 4 (Exam 1) > Flashcards

Section 4 (Exam 1) Flashcards

1
Q

A ligand is a ___

A

signaling molecule involved in the reception stage

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2
Q

A polar ligand is located on the _____an example is_______

A

receptor on the cell membrane
peptide

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3
Q

A nonpolar ligand is located on the _____ and an example is ____

A

intracellular receptor

steriod

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4
Q

receptors can have _______ligands (s)

A

more than one and do different things
ex=epinephrine

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5
Q

name the 5 types of receptors

A

1) ion channel
2) Receptor Tyrosine Kinase
3) Janus Kinases
4) G-protein coupled receptor
5) Steroid Receptor

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6
Q

Explain what a Ion Channel or Ligand Gated Receptor is

A

Can be akin to a lock and key format. Once the messenger binds and phosphorylates the receptor, it opens the ion channel attached to it.

Form of facilitated diffusion

can be selectivity filter depending on the size and charge of the ion channel

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7
Q

Explain the Tyrosine Kinase Receptor

A

1) receptor binds with messenger and receptor phosphorylates its own tyrosine residues (forms a bubble on base of receptor)

2)the bubble is now a docking site for other proteins

3) the bound docking proteins than bind and activate more signaling pathways

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8
Q

Explain the Janus Kinase (JAK) Receptor process

A

1) ligand binds to receptor and causes a conformational change (changes shape)

2)leads to activation of JAK (forms boob that JAK holds onto)

3) JAK phosphorylates proteins containing Tyrosine

4) JAK kinases phosphorylates different target proteins which increases the synthesis of proteins

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9
Q

What is the difference btw Tyrosine Kinase and JAK

A

Tyrosine is an independent man and auto-phosphorylates himself

JAK is a protein on the receptor that then phosphorylates

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10
Q

Explain the basic approach to G-protein coupled

A

1) 7 membrane spanning a-helical region coupled to separate G-protein

2) Ligand binds to receptor which releases GDP from alpha subunit and replaced with GTP

3) alpha subunit than dissascioates from G protein and moves across membrane to effector

4) GTP is replaced with GDP again on the alpha subunit, alpha heads back to beta and gamma. Effector begins its job

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11
Q

Explain the receptor for Steriods

A

found inside the nucleus (nuclear receptors)

acts as a transcription factor

non-polar steroids head straight into the cell because they are resemble cholesterol?

turns on transcription of genes (long lag time because you’re building new dna

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12
Q

Explain Down Regulation and Up-regulation

A

UP REGULATION:
lowers percentage of ligands for a bit
increases sensitivity for ligands

ex) low neurotransmitters in damaged muscle tissue, muscle will easily respond to less transmitters

DOWN REGULATION:
high percentage of ligands
reduces cell’s responsiveness (negative feedback)
occurs from receptor internalization (recycling of receptors)

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13
Q

What are some advantages to cells expressing receptors for certain ligands?

A

more likely for messenger or hormone to be picked up by their specific ligand. Allows the body to do very specific tasks without causing unwanted side effects

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14
Q

Explain the relationship btw binding of ligands to receptors as it relates to structure is a determinant of function.

A

because of the structure of receptors they can only bind to certain ligands which allows them to only “do their thing” when the body wants them too. Allows for specificity and affinity.

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15
Q

What is a benefit of G-protein coupled receptors

A

signal amplification (cascade effect)

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16
Q

What are some unique characteristics for Gas Pathway

A

uses adenylate cyclase as effector

2) amplification =cAMP-> PKA
through catalytic enzymes

3) creb->cre->transcription

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17
Q

cAMP is a ____ _____

A

second messenger

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18
Q

The effector of GAS is …..

A

adenylate cyclase (atp-cAMP)

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19
Q

cAMP binds to _____

A

mothership (PKA) which releases catalytic domains

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20
Q

How do we stop the G alpha s pathway?

A

hydrolyze GTP-GDP

and Phosphodiesterases (PDEs regulate cAMP)

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21
Q

In intestinal cells, cholera causes _______ ______ of G protein that activates adenylate cyclase (causes opening of Cl-channels)

A

sustained activation

Cl leaves with Na and H20, leaving the patient dehydrated despite water consumption

15-20 L PER DAY

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22
Q

Define Methylxanthines and give two examples

Also, how does this relate to dogs?

A

Methylxanthines INHIBIT phosphodiesterases (regulate cAMP) which causes CFTR channels to be constantly open.

ex) caffeine and dark chocolate

Dogs can break down Methylxanthines and have constant cascade effects and constant CFTR openings. This leads to diarrhea and vomiting and kills the patient via dehydration.

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23
Q

Gas pathway uses _____ ______ as the effector

A

adenylate cyclase

24
Q

ATP is generated into ______ which activates _______

A

cAMP, PKA

25
Q

PKA-> ________->which binds to ______ and initiates ______

A

phoporylates CREB which binds to CRE and initiates TRANSCRIPTION

26
Q

Methylzanthines inhibit _______ causing an increase in the _____ pathway

A

phosphodiesterase, signaling pathway

27
Q

Adenylate Cyclase is part of the ____ pathway

A

GAS

28
Q

cAMP is part of the ____ pathway

A

GAS

29
Q

cAMP binds to the _____ ______ _____ in the ______ pathway

A

Protein Kinase A, GAS pathway

30
Q

PKA catalysts head to the ______ which then binds to the _____ in the ______

A

CREB which phosphorylates and then binds to CRE located in the nucleus

31
Q

Effector in GAQ pathway

A

PLC (phospholipase C)

32
Q

1) PIP2 is in which pathway?

2) PIP2 is converted to what and sent where

A

GAQ pathway

PIP2 -> IP3 and DAG

33
Q

Receptor for IP3 is on what and leads to a ______ and creates an increase in what element

A

The receptor is on the Endoplasmic Reticulum which leads to opening the Ion Channel which leads to an increase in Calcium

34
Q

____ and DAG combine to activate ____

A

Ca+ and DAG combine to activate PKC which leads to a phosphorylation of protein

35
Q

name the 4 pathways calcium can take

also calcium is part of which pathway?

A

part of the GAQ pathway

1) binds to Calmodulin
-phosphorylates protein PKA, PKB, Creb= ++transcription
2)leads to vesicles being exocytosed
3)could open voltage gated Ca+ which increases other pathways
4) activates PKC with DAG

36
Q

What is the effector of the GAQ pathway?

A

phospolipase C (PLC)

37
Q

Ca2+ may activate process of ____ ______

A

muscle contraction

38
Q

Phospholipase C catalyzes the formation of the second messengers ____ and _____

A

DAG and IP3

39
Q

DAG activates ______ and ________ which leads to _____ release from the ER

A

PKC,
IP3
calcium

40
Q

T/F Calcium is a widespread second messenger

A

True

41
Q

Which of the following intracellular or cell membrane proteins requires calcium for activation?

a-calmodulin
b-Janus Kinase
c-PKA
d-Phospholipase C

A

a- calmodulin requires Ca2+

42
Q

What is a Ligand?

A

signaling molecule involved in the reception stage

43
Q

What is an example of a polar ligand?

A

peptide

44
Q

Why can’t a triglyceride pass through the cell membrane without help?

A

because it is polar and the membrane is non-polar.

the polar head of the membrane repels it

because it is a fat and fat does not dissolve in water

45
Q

What are the two types of Ligands

A

Polar (peptide)

Non-polar (steriod)

46
Q

Where is the ion Channel Located?

A

spanning across the membrane

47
Q

What is special about Ion Channels?

A

They operate like a lock and key, a receptor binds, and a change in membrane potential occurs and the ‘door’ opens

48
Q

What is special about Tyrosine Kinase?

A

receptor auto-phosphorylates

phosphotyrosines on cytoplasmic side of the cell form a docking site for other proteins

bound docking proteins bind and then continue on the cascade pathway

49
Q

What is special about Janus Kinase?

A

ligand binds to receptor and causes a conformational change of the receptor
-activation of Janus Kinase

result is an increase of the synthesis of proteins which mediate response to first messenger

JAK kinases phosphorylate the portions containing tyrosine
-some can act as transcription factors

50
Q

biggest difference btw tyrosine kinase and Janus Kinase?

A

Tyrosine Kinase auto-phosphorylates the receptor itself and JAK phosphorylates itself instead of the receptor

Tyrosine grows balls that other people play with and Jak grows b()()bs that proteins play with

51
Q

A G-Protein Coupled is a receptor with a _ _________ ________ __ ______ ______ ______ ____ _______ __ ________

A

7 membrane spanning a helical regions coupled to separate G Protein

different from a G-protein

52
Q

What are the benefits of G-protein coupled receptors?

A

one can lead to a massive increase in number of molecules

signal amplication

53
Q

What is a first messenger?

A

an extracellular substance (as the hormone epinephrine or the neurotransmitter serotonin) that binds to a cell-surface receptor and initiates intracellular activity

54
Q

what is the overall effect of second messengers?

A

Synaptic actions by second messengers can close ion channels that are open at the resting potential, thereby decreasing the conductance of the membrane.

Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers

ultimately responsible for the proliferation, differentiation, and maturation of nerve cells.

55
Q

Describe how a G-protein is activated and common G-protein cycle

A

1) G proteins held by GDP,

2) GDP lets go so a separates and attaches to effector

3) GTP is replaced with GDP and G protein is happy again

4) G protein goes to original position

56
Q

What does DAG do?

A

together with Calcium, it activates PKC

57
Q

What does Calmodulin do?

A

phosphorlyates proteins like PKA, PKB, CREB and leads to an increase in transcription

Physiology (14 decks)

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