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Physiology I > Protein-Mediated Transport > Flashcards

Protein-Mediated Transport Flashcards

1
Q

What family do water channels belong to?

A

aquaporins

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2
Q

channels are only capable of facilitating what kind of transport

A

downhill

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3
Q

describe water channels

A

pores/channels with diameter greater than water but less than solute molecules so it only lets water through

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4
Q

where are you likely to find nonselective pores

A

epithelia, brain, smooth muscle, cardiac muscle

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5
Q

what weight do gap junctions allow molecules to pass through

A

up to 1200-1500

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6
Q

you will find what kind of junction being used for nonselective pores

A

gap junction

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7
Q

what kind of molecules can pass through gap junction

A

water soluble

up to 1200-1500 weight

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8
Q

lower km = ?

A

higher affinity

generates faster rate of solute entry

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9
Q

carriers are only capable of facilitating

A

downhill transport

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10
Q

where are active sites accessible in channels

A

both sides

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11
Q

where are active sites accessible in carriers

A

one side at a time

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12
Q

pumps are only capable of faciliating

A

trick question!

pumps can oppose the equilibrium

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13
Q

what cells are you likely to find water channels

A

RBC

epithelium of lung, kidney, intestines

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14
Q

channels (non-selective pores) allow for synchronization of

A

electrical activity of heart and gut

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15
Q

the only significant transport of charged ions is through

A

protein ion channels

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16
Q

in ion channel where is active site

A

on both sides

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17
Q

channels and carriers want to do what

A

equilibriate

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18
Q

pumps do what to equilibrium

A

oppose it

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19
Q

rate of entry for protein mediated transport is much faster than what

A

if there is no aid from protein

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20
Q

describe reaction rate with protein mediated transport

A

reaction rate is much faster with protein mediated transport

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21
Q

saturation

A

solute entry rate in protein mediated transport is always maximized

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22
Q

why is it always maximized

A

active sites are full

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23
Q

Tm and Vmax are another way of describint

A

saturation - when all the binding sites are full

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24
Q

Specificity

A

things with similar structure can compete for same binding site

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25
Q

competitive inhibition

A

common property of protein mediated transport
just glucose - certain rate of entry for glucose
glucose + galactose - transport for glucose goes down b/c galactose competes for same site

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26
Q 
d-galactose
d-arabinose
d-xylose
d-mannose
describe in relation to protein mediated transport
A

sugar structure that can bind to binding site
d isomer will bind to the binding site
L won’t bind (specificity!)

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27
Q

Km is defined as

A

half max (half of Vmax)

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28
Q

what are three main categories of PMT

A

channels
carriers
pumps

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29
Q

what determines what direction an ion will flow

A

chemical & electircal gradient

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30
Q

what has to happen in any PMT for it to work

A

conformational change

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31
Q

carrier mediated transport is a form of

A

PMT

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32
Q

carrier mediated transport is also called

A

facilitated diffusion

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33
Q

can water normally go into a cell

A

yes - they are so small they can go through

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34
Q

what is the name of the pores in nonselective pores

A

connexon channels

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35
Q

what is the normal state of non-gated ion channels

A

open

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36
Q

how do we generate our resting membrane potential

A

non-gated ion channels

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37
Q

what is another name for non-gated ion channgels

A

leak ion channels

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38
Q

what is RMP of cell

A

-70 millivolts

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39
Q

what does RMP stand for

A

resting membrane potential

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40
Q

there are a lot of what kind of leak ion channels and not as much

A

lots of potassium
not as much sodium
(ICF)

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41
Q

describe how RMP is numbered

A

inside relative to outside, so -70 means negative 70 milivolts relative to positive outside

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42
Q

gated ion channels at resting are

A

closed

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43
Q

do gated ion channels contribute to RMP

A

no

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44
Q

when do gated ion channels change conformation

A

from stimulus

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45
Q

the probability that gated ion channels is open is dependent on

A

membrane potential, specific ligands or chemicals, and mechanical distortion.

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46
Q

describe gated ion channels that are controlled by membrane potential

A

Some channels only open when the membrane potential changes beyond a certain threshold value, and are called voltage-gated ion channels.

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47
Q

describe voltage-gated ion channels

A

closed at resting membrane potential
open when depolarized, then they will have conformational change and open
they are specific to a certain ion, so there are potassium voltage-gated ion channels, etc

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48
Q

describe gated ion channels that are controlled by specific ligands

A

Ligand-gated ion channels cannot open unless they first bind to a specific stimulus or agonist.

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49
Q

nicotinic receptor at nuromuscular junction

A

protein receptor ion channel that is on the skeletal muscle and have alpha motor neuron innervating skeletal muscle

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50
Q

what are an examples of ligand-gated ion channels

A

ACh-gated nicotinic receptor

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51
Q

describe gated ion channels controlled by mechanical distortion

A

Mechanosensitive ion channels only open when the membrane is mechanically stretched

52
Q

membrane potential inside the cell is neg. or pos.

A

negative

53
Q

membrane potential outside cell is neg. or pos

A

positive

54
Q

what are some examples of cells that use mechanical distortion

A

mechanosensitive sodium channels in hair cells of the auditory-vestibular system
stretch-sensitive channels in muscle spindles.

55
Q

in the acetylcholine-gated nicotinic receptor describe the amount of Na+ and K+ going into cell

A

more Na+ going into cell than K+

56
Q

what is another name for carrier-mediated diffusion

A

facilitated diffusion

57
Q

describe how carriers work

A

something binds to carrier’s active site, only one at a time (on one side of membrane at a time) and is then moved to lower concentration gradient

58
Q

do glucose transporters need sodium

A

no

59
Q

what is example of glucose transporter

A

GLUT1-5

60
Q

what are categories of aa transporters (carriers)

A

neutral AAs
Basic AAs
Acidic AAs

61
Q

what do pumps do to quilibrating system

A

oppose to maintain asymetric distribution of all solutes

62
Q

describe diffusion potential in regards to potassium

A

there is electrical driving force because insid ethe cell it is negatively charged

63
Q

what is net driving force for potassium in regards to cell and why

A

to leave cell

b/c the chemical driving force for potassium is a little stronger than the electrical driving force

64
Q

why do we need potassium pumps

A

b/c of the stronger chemical driving force, need to keep potassium levels higher in cell. pump trying ot maintian concentration of potassium inside and have it be low outside

65
Q

what are two types of active transport for pumps

A

primary active transport

secondary active transport

66
Q

what is primary active transport

A

uses ATP directly to drive solute back

67
Q

what is secondary active transport

A

uses energy derived secondarily from energy stored in form of ionic concentration differences b/w two sides of membrane

68
Q

what is example of secondary active transport

A

sodium glucose transport

SGLT1 transport

69
Q

in secondary active transport what is the driver solute

A

sodium

70
Q

what are two kinds of secondary transport

A

co-transport

or countertransport

71
Q

what is SGLT1

A

co-transporter

72
Q

in primary active transport the active site is accessible

A

one side at a time

73
Q

what is main way digestive system spew out hyrogen for Hydrochloric acid

A

primary active transport

74
Q

what is level of calcium inside cell

A

.0001 mM

75
Q

list levels of ions inside and outside of cell

A

pg 5 of homeostasis power point

76
Q

what is the most abundant pump in higher organisms

A

Na+K+ ATPase

77
Q

describe the makeup of sodium potassium pump

A

Heterodimer of an alpha subunit of 100,000 MW and

a beta subunit of 55,000 MW

78
Q

What does the sodium potassium pump out exactly

A

3 Na+ out of cell for every 2 K+ pumped into cell

79
Q

what is the function of the sodium potassium pump

A

maintains low Na+ and high K+ inside cell
controls cell volume
helps keep RMP

80
Q

Where is the Ca2+ ATPase pump located

A

in cell membrane & organelles

81
Q

what organelles is Ca2+ ATpase pump located

A

Sarcoplasmic reticulum

mitochondria

82
Q

what is the function of Ca2+ ATPase

A

keep a very low level of Ca2+ inside cell

83
Q

In the SR what is calcium bound by

A

calreticulin & calsequestrin

84
Q

Where is H+K+ATPase pump located

A

gastric glands of GI tract

epithelial cells of renal system

85
Q

What is the purpose of H+K+ATPase pump

A

acidify urine, controls acid-base balance

basis for secreting hydrochloric acid in the stomach for digestive secretions

86
Q

Ion pumps are a form of what kind of transport

A

primary active transport

87
Q

describe the basis of secondary active transport

A

the cell keeps higher concentrations of some things inside vs. outside the cell which ultimately creates stored energy. when an ion moves down its electrochemical gradient it releases energy

88
Q

what do most secondary active transports use as the driver solute

A

sodium

89
Q

describe how sodium works as driver solute

A

the energy released from sodium going down its gradient allows uphill transport of another solute

90
Q

draw out primary and secondary for symporter, antiporter, and channel

A

pg 22

91
Q

whats another word for cotransport

A

symport

92
Q

what are different mechanisms for secondary active transport

A

cotransporter

countertransporter

93
Q

describe what happens with a cotransporter

A

solute being transported moves in same direction as driver solute (sodium!) and almost always inside cell

94
Q

cotransporter almost always moves solute in what direction

A

inside cell

95
Q

What are examples of solutes being moved with a cotransporter

A 
Na-glucose
Na-AA
NaK2Cl
NaCl
KCl
96
Q

what are other names for countertransporter

A

antiports

exchangers

97
Q

what do countertransporters do

A

exchange one type of anion for another anion

or one cation for another cation

98
Q

name examples of countertransporters

A

Na+ Ca+ exchanger
Cl- HCO3-
Na+ H+ exchanger

99
Q

What does HCO3- stand for

A

bicarbonate

100
Q

What is purpose/function of Na+ Ca+ exchanger

A

maintains low calcium levels in cell

3 sodium in cell for one calcium out

101
Q

What is purpose/function of Cl- HCO3- exchanger

A

RBC!

helps carry carbon dioxide from tissues to lungs

102
Q

what is purpose/function of Na+ H+ exchanger

A

controls intracellular pH

103
Q

what are the similarities b/w carrier-mediated and secondary active transport

A

conformational change once solute binds
Both mechanisms uses specific carrier proteins*
Both are saturable
Affinity plays a role in both mechanisms *

104
Q

what are the differences b/w carrier-mediated & secondary active transport

A

For carrier-mediated transport - downhill transport of solute occurs, while secondary active transport - uphill transport of solute occurs

*Secondary active transport needs the driver solute to expend energy for the uphill transport of solute to occur, while carrier-mediate transport does not require energy to be expended for downhill transport of solute.

105
Q

if you just had leak non/gated channels for K+ and Na+ what would happen

A

would equilibriate

106
Q

for every phosphorylation/dephosphorylation cycle what does sodium potasium pump do

A

3 sodiums pumepd out for every 2 potassiums pumped in

107
Q

what is purppose of Na+K+ATPase do

A

making sure concentration of potassium and sodium in ICF and ECF maintaing number they need to be

108
Q

what happens if there is not functioning NA+K+ATPase?

A

cell would move towards equilibrium

109
Q

how many sodium binding sites on Na+K+ATPase

A

3

110
Q

how many potassium binding sites on Na+K+ATPase

A

2

111
Q

why is Na+K+ATPase called an electrogenic pump

A

generates electrical potential difference across cell membrane. losing a positive charge inside cell each time. makes the cell a little bit more negative inside each time

112
Q

how does Na+K+ATPase control cell volume

A

water follows solute, it puts an extra ion outside the cell

113
Q

does Na+K+ATPase trigger RVI or RVD

A

RVI - it is trying put more water back into cell b/c water leaves cell due to Na+K+ATPase pump

114
Q

for RVI do you want Na+K+ATPase activity increased or decreased

A

decreased - want to slow loss of solute to gain osmotic pressure in cell

115
Q

if there is hypotonic solution what would happen in regards to Na+K+ATPase

A

RVD mechanism, Na+K+ATPase would increase activity

116
Q

miliequivalent =

A

valence x concentration

117
Q

chemical gradient for Ca2+ to go into cell is

A

HUGE!

118
Q

Ca2+ ATPase primary function

A

opposing system to bring calcium back down in cell by pumping it out of cell

119
Q

H+K+ATPase function

A

pumps hydrogen against electrochemical gradient into lumen of stomach
the reason we can have hydrochloric acid

120
Q

what direction is K+ pumped in H+K+ATPase function

A

into cell

121
Q

what is an example of antiporter

A

H+K+ exchanger

122
Q

a cell on one side is lumen other side is blood which is apical and basolateral side

A

lumen is apical side

blood is basolateral side

123
Q

in KCL which is driver solute

A

potassium

124
Q

some drugs block sodium potassium ATPase, so what would that do to calcium (CHF)

A

the gradient went down so not as much sodium will go into cell, which means not as much calcium will leave cell. when there is more calcium in cell it will result in longer strong contraction of muscle (and cardiac muscle?)

125
Q

pancreas has specialized epithelial cells that have

A

Cl-HCO3 exchangers

Physiology I (9 decks)

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