Membrane Transport

Front 1

Give the names of the two main body fluid compartments and the percentage of total body water in each.

Back 1

2/3 Intracellular fluid (ICF)
1/3 Extracellular fluid (ECF)
ECF= plasma + interstitial fluid

Front 2

Facilitated transport/diffusion (Passive)

Back 2

carrier protein-mediated (uniporter)

Front 3

Simple Diffusion (Passive)

Back 3

straight through lipid bilayer; for non-polar substances (e.g. O2, CO2, N2 (gases); ethanol, anesthetics

Front 4

Osmosis (Passive)

Back 4

diffusion of WATER across a semipermeable membrane separating two aqueous solutions

Front 5

State what factors control simple diffusion through membrane.

Back 5

Steepness of con. gradient;
surface area through which diffusion takes place;
distance through which diff takes place;
permeability of membrane to substance;
temp;
molecular size;
pressure differences across membrane;
charge

Front 6

State what factors control diffusion through pores or channels in the membrane.

Back 6

For small, uncharged molecules: water channels (Aquaporin), water selectivity, water moves down its concentration gradient
For Ions: ion channels, ion selectivity, ions also move down their electrochemical gradient

Front 7

State factors that influence rate of carrier-mediated diffusion. (still no energy required)

Back 7

Concentration gradient;
transporter number,
affinity of binding
(we looked at glucose transport/uniporter in lecture)

Front 8

Compare and contrast the properties of carrier-mediated diffusion and active transport

Back 8

BOTH need some sort of molecule-specific transporter protein
Carrier-mediated diffusion- uniporter; no energy required; things only move down their concentration gradient
Active transport- use pumps, symporter, antiporter; require energy; can transport uncharged substances against their concentration gradient and can transport ions against an electrochemical gradient

Front 9

Uniport

Back 9

Uniport- carrier transports only one substance; (glucose example above)

Front 10

Symport (co-transport)

Back 10

Symport- 2 molecules go thru channel in same direction, 1 down its electrochemical gradient, 1 against its gradient E.g. Sodium co-transport of glucose into epithelial cells of kidney tubules—Sodium ions move into a cell down their conc gradient. This “energy loss” drives the movement of another molecule (glucose) against its electrochemical gradient.

Front 11

Antiport (exchange transport/countertransport).

Back 11

Antiport- 2 molecules use same channel going opposite directions, 1 travels down its conc. gradient 1 against its gradient E.g. Na+/Ca2+ exchanger; Na+/H+ exchanger

Front 12

Be able to describe or give the role of clathrin, coated pits

Back 12

Clathrin- these are “cages” that form, along with adaptin, coated pits assisting in fluid phase or receptor-mediated endocytosis (requires energy).
Once vesicle is fully endocytosed, clathrin disassociates and is recycled in cell

Front 13

Aquaporins

Back 13

Water Channels

Front 14

Be able to give a brief definition of ABC proteins. Be able to recognize clinical roles of ABC proteins/transporters discussed in lecture and/or handout.

Back 14

ABC= ATP binding cassette
all of these proteins have a common ATP-binding domain (the cassette) (though they may or may not hydrolyze ATP to allow transport)
CFTR (cystic fibrosis transmembrane conductance regulator) is an ABC proteinMDR-proteins (multi-drug resistant) when these are overexpressed in tumors they are very resistant to cancer drug therapy—cancer drug is transported out of cell before it can be effective

Front 15

Endocytosis

Back 15

cells absorb molecules by engulfing them; requires energy

Front 16

Pinocytosis

Back 16

cell drinking; ALL cells perform pinocytosis
Like sipping on pinot noir!

Front 17

Phagocytosis

Back 17

cell eating; only done by specialized cells such as macrophages and neutrophils

Front 18

Fluid-phase endocytosis

Back 18

uptake of materials that are dissolved in the ECF (material is NOT bound to receptors)

Front 19

Receptor-mediated endocytosis

Back 19

specific receptor proteins concentrated at the site; a receptor on the surface of the cell binds the ligand (thing the cell wants to endocytose); the cytoplasmic tails of the receptor proteins bind to adaptins in the cell which then associate with clathrin to form coated pits; the receptor proteins are included in the membrane that becomes the endocytic vessel

Front 20

Caveolae endocytosis

Back 20

similar to clathrin mediated endocytosis but the process uses caveolae and caveolin as the coating protein

Front 21

Exocytosis

Back 21

cell directs contents of secretory vesicles out of cell membrane into ECF; requires energy