Membrane Transport And Osmosis

Front 1

Transport of non-lipid soluble molecules across cell membrane

Back 1

1) Pores
2) Channels
3) Transporters

Front 2

Pores

Back 2

- non gated channel
- always open (may be regulated)
- movement via diffusion down gradient (concentration, electrical, chemical)
- only small molecules can pass
- gap junctions - connexins
- aquaporin - selective for water

Front 3

Channels

Back 3

- ECM to ICM
- complex can be open or closed with gate at a specific end of channel
- open state regulated
- little energetic interaction between channel and molecule
- selective
- movement due to diffusion across a gradient

Front 4

Classification of Channels

Back 4

- mechanical ex. stretch activated Ca channels in vascular smooth muscle
- ligand gated ex. acetylcholine activated Na- channels
- voltage gated ex. Na ion channel in nerve

Front 5

Transporter

Back 5

- ion channel with 2 gating domains
- open state determined by physical interaction of molecule with transport protein
- only one gate open at a time
- must bind to transport protein (induces a conformational change in it)
- movement can be against gradient
- selective

Front 6

symporter

Back 6

- 2 or more molecules move toeghter in the same direction
- must have both to transport

Front 7

antiporter

Back 7

- 2 or more molecules move in opposite directions
- must have both to transport

Front 8

primary active transport (pump)

Back 8

- transport protein is an enzyme that uses ATP to move one or more molecules across cell membrane
- move against electrochemical gradient

Front 9

secondary active transport

Back 9

- transporter NOT an enzyme
- uses [ ] gradient established through active transport to move molecule against a gradient

Front 10

Movement of molecules via pores and channels

Back 10

1) rate of transmembrane flux dependent on electrical and chemical gradients
2) does not saturate
3) faster rate than movement via transporters

Front 11

Movement of molecules via transporters

Back 11

1) max flux rate is limited by # of available transport proteins
2) transporter saturates
3) characterized by Km and Vmax

Front 12

tetrodotoxin

Back 12

- covalently binds to voltage gated Na channels in nerves
- channels don't open so, action potentials can't propagate

Front 13

dihydropyridines

Back 13

- blocks Ca channels in cardiac and vascular smooth muscle

Front 14

digitalis

Back 14

- inhibits Na-K pump in cardiac muscle

Front 15

malignant hyperthermia

Back 15

- altered muscle Ca channel

Front 16

myotonias

Back 16

- excessive muscle contractions
- defective Cl or Na channels

Front 17

Long QT Syndrome

Back 17

- alteration in electrical conduction in the heart
- defective K or Na channels

Front 18

Osmosis

Back 18

- aquarporin channels, passive diffusion
- [ ]= # of solute molecules in a given molecule
- mosmoles/L
- more solute = lower [H2O]

Front 19

osmotic pressure

Back 19

- Pressure needed to prevent water movement
- 1 mosmoles/L = 19 mmHg
-Osmolarity of extracellular and intracellular fluids is approximately 290 mosmoles/L, which is an osmotic pressure of 5,510 mmHg

Front 20

isoosmotic solution

Back 20

- solution with the same osmolarity of the cell
- same # of solute molecules per volume of H20

Front 21

isotonic

Back 21

- solution has same number solute molecules as cell
- no change in cell volume

Front 22

hypotonic

Back 22

- solution has fewer solute molecules than cell
- water enters cell

Front 23

hypertonic

Back 23

- solution has more solute molecules than cell
- water exits cell

Front 24

Gibbs-Donnan Equilibrium

Back 24

- intracell osmolarity is greater than extracellular due to negatively charged impermeable protiens
- cells swell unless osmotic work maintained

Front 25

Osmotic work

Back 25

- Na-K pump 3 Na out for 2 K in
- reduces number of osmotic particles

Front 26

Gibbs-Donnan on Capillaries

Back 26

- negatively charged blood protein repels negative permeant ions
- interstitial negative ion content (Cl) slightly greater than blood