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Flashcards in Membrane Transport Deck (38)
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1

Definition of selective permeability

Only specific molecules can pass freely through the membrane

2

Definition of passive diffusion

Down conc grad, across membrane, passive until equilibrium reached

3

Definition of the partition coefficient

The rate at which the solute equilibrates
The more hydrophobic, greater the PC, the greater the rate of equilibration

4

Definition of facilitated diffusion

Down conc grad, through membrane channel proteins
Passive until equilibrium reached

5

Definition of gated ion channels

Ion channels allow facilitated diffusion selective for different ions

6

Definition of active transport

Solutes move against conc grad w membrane protein, ATP hydrolysis

7

Definition of primary active transport

ATP hydrolysis directly causes solute movement

8

Definition of uniport

Transport of 1 solute

9

Definition of symport

Transport of 2 solutes, same direction

10

Definition of antiport

Transport of 2 solutes, different directions

11

Definition of secondary active transport

ATP hydrolysis does not directly cause solute movement

12

What is permeable through the plasma membrane

Hydrophobic molecules
Small uncharged polar

13

Transport mechanisms

Simple diffusion
Facilitated diffusion
Gated ion channels
Primary active transport
Secondary active transport

14

Simple diffusion

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

15

Facilitated diffusion

Down conc grad until equilibrium reached
Requires channel protein

16

Kinetics of transport with simple and facilitated diffusion

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

Tranporter affinity in diffusion

Low Km = High affinity

18

Types of glucose transporter

GLUT 1
GLUT 2
GLUT 3
GLUT 4
SGLUT

19

Location of GLUT 1

Everywhere, abundant in RBC
Low in skeletal muscle

20

Function of GLUT 1

Low Km, mediates constitutive glucose uptake in tissue

21

Location of GLUT 2

Liver, pancreas b cells

22

Function of GLUT 2

High Km, high Jmax
Transports glucose => hepatocytes and beta cells when [blood glucose] increases

23

Location of GLUT 3

Neurones

24

Function of GLUT 3

Low Km

25

Location of GLUT 4

Muscle, adipocytes

26

Function of GLUT 4

Km=5mM, similar to fed state [blood glucose]
Insulin regulated, can change glucose uptake ability

27

Insulin stimulated uptake of glucose

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

Gated ion channels

Allow facilitated diffusion selective for different ions
Open/close in response to stimuli

29

Types of gated ion channels

Ligand gated
Voltage gated

30

Active transport

Up conc grad, w membrane protein
ATP hydrolysis