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Cell Biology And Signaling > Membrane Transport > Flashcards

Membrane Transport Flashcards

1
Q

Definition of selective permeability

A

Only specific molecules can pass freely through the membrane

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2
Q

Definition of passive diffusion

A

Down conc grad, across membrane, passive until equilibrium reached

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3
Q

Definition of the partition coefficient

A

The rate at which the solute equilibrates

The more hydrophobic, greater the PC, the greater the rate of equilibration

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4
Q

Definition of facilitated diffusion

A

Down conc grad, through membrane channel proteins

Passive until equilibrium reached

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5
Q

Definition of gated ion channels

A

Ion channels allow facilitated diffusion selective for different ions

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6
Q

Definition of active transport

A

Solutes move against conc grad w membrane protein, ATP hydrolysis

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7
Q

Definition of primary active transport

A

ATP hydrolysis directly causes solute movement

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8
Q

Definition of uniport

A

Transport of 1 solute

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9
Q

Definition of symport

A

Transport of 2 solutes, same direction

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10
Q

Definition of antiport

A

Transport of 2 solutes, different directions

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11
Q

Definition of secondary active transport

A

ATP hydrolysis does not directly cause solute movement

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12
Q

What is permeable through the plasma membrane

A

Hydrophobic molecules

Small uncharged polar

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13
Q

Transport mechanisms

A 
Simple diffusion
Facilitated diffusion
Gated ion channels
Primary active transport
Secondary active transport
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14
Q

Simple diffusion

A

Down conc grad until equilibrium reached
Rate depends on partition coefficient of solute
More hydrophobic, greater PC, equilibrate more quickly

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15
Q

Facilitated diffusion

A

Down conc grad until equilibrium reached

Requires channel protein

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16
Q

Kinetics of transport with simple and facilitated diffusion

A

As [S] increases, J increases in simple diffusion
As [S] increases, J increases more steeply initially, plates out in facilitated diffusion
1/2Jmax = Km

17
Q

Tranporter affinity in diffusion

A

Low Km = High affinity

18
Q

Types of glucose transporter

A 
GLUT 1
GLUT 2
GLUT 3
GLUT 4
SGLUT
19
Q

Location of GLUT 1

A

Everywhere, abundant in RBC

Low in skeletal muscle

20
Q

Function of GLUT 1

A

Low Km, mediates constitutive glucose uptake in tissue

21
Q

Location of GLUT 2

A

Liver, pancreas b cells

22
Q

Function of GLUT 2

A

High Km, high Jmax

Transports glucose => hepatocytes and beta cells when [blood glucose] increases

23
Q

Location of GLUT 3

24
Q

Function of GLUT 3

25
Q

Location of GLUT 4

A

Muscle, adipocytes

26
Q

Function of GLUT 4

A

Km=5mM, similar to fed state [blood glucose]

Insulin regulated, can change glucose uptake ability

27
Q

Insulin stimulated uptake of glucose

A

Stimulates glucose uptake in muscle, adipose, increase GLUT 4 in membrane
GLUT 4 on membranous vesicles in cytoplasm
Insulin binds to receptors, triggers movement of vesicles to membrane, merge, increase no on surface
Increase in GLUT4 in membrane, increase uptake of glucose into cell

28
Q

Gated ion channels

A

Allow facilitated diffusion selective for different ions

Open/close in response to stimuli

29
Q

Types of gated ion channels

A

Ligand gated

Voltage gated

30
Q

Active transport

A

Up conc grad, w membrane protein

ATP hydrolysis

31
Q

Conc of Na+ in and out of cell

A

12mM

145mM

32
Q

Conc of K+ in and out of cell

33
Q

Na+/K+ pump

A

Phosphorylation at cytoplasmic side with ATP = conformational change
Cytoplasmic end closes, external end opens
Pump binds 2K+ and releases 3Na+
Hydrolysis of Pi closes external end, opens cytoplasmic end
Release 2K+ into cell

34
Q

Structure of the Na+/K+ pump

35
Q

Cotransoprt systems

A

Preestablished gradient used to drive transport of solute across membrane against gradient
ATP hydrolysis used to establish primary gradient

36
Q

SGLUT cotrasnporter

A

Glucose absorption from intestine against gradient
Symport
Na+ gradient established by Na+/K+ pump, ATP hydrolysis drives glucose uptake
Secondary AT

37
Q

Na+/Ca2+ cotransporter

A

Ca2+ export from muscle cells against gradient
Na+/Ca2+ cotransporter=antiport
Na+ gradient established by Na+/K+ pump and ATP hydrolysis used to drive CA2+ export from cells
Secondary AT

38
Q

Secretion of insulin by B cells

A

Glucose =FD=> GLUT2 (b cells)
Glucose =metabolised=> ATP
Increase in ATP/ADP ration ==> closure of cell surface K ATP channels ==> cell membrane depolarisation
Voltage gated Ca2+ channels open, increase IC Ca2+
Increase Ca2+ ==>< exocytosis of insulin in vesicles

Cell Biology And Signaling (11 decks)

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