Membrane Transport (week 2)

2 types of passive transport

diffusion, osmosis

2 types of active transport

primary, secondary

energy needed for active transport

ATP

Solvent

dissolving agent in solution, water most commonly in living organisms

solute

substance dissolved in solvent

solute concentration of a solution

how much solute is dissolved per unit volume of solute

Osmolarity

total # of osmotically active particles / L solution, expressed in osmoles/L

What is the normal mOsM for bodily fluids?

ECF = ICF = 300 mOsm

0.9% NaCl is ____ to a cell?

isotonic

Diffusion

movement of substances down their concentration gradient (higher concentration to lower concentration)

Facilitated diffusion

transport of molecules down concentration gradient with help of transmembrane proteins

2 types of facilitated diffusion

carrier mediated facilitated diffusion, channel mediated facilitated diffusion

carrier mediated facilitated diffusion

Protein carriers move substances across membrane, usually for larger substances, eg: glucose

What determines rate of diffusion?

Size of diffusing substance, Size of concentration gradient, Temperature, Diffusion distance / membrane thickness

How does temperature affect diffusion rate?

Higher temp = higher diffusion rate

How does diffusion distance / membrane thickness affect diffusion rate?

shorter distance / thinner membrane = faster rates of diffusion

Osmosis

diffusion of water across a membrane

how does water move directly through the membrane?

via aquaporins

direction of water movement is defined by:

solute concentrations of solutions on either side of membrane

water moves from area of ___ solute concentration to _____ solute concentration

lower, higher

Osmotic Pressure

tendency of solution to gain water via osmosis, greater the solute concentration, greater the osmotic pressure

Hydrostatic pressure

pressure due to fluid in a system, ex: blood pressure

Hypertonic Solution

Solution surrounding cell has a higher solute concentration, cell will shrink

Isotonic Solution

nothing changes

Hypotonic Solution

Solute concentration of liquid outside cell is less than inside cell, cell swells and bursts

ACTIVE TRANSPORT

substances moved against concentration gradient, low to high

primary active transport

carrier protein breaks down ATP and uses resultant energy to pump one or more substances against gradient

secondary active transport

also called cotransport, relies on energy stored in ion gradients created by primary active transport

how many substances involved in cotransport

2 substances, one moves against gradient, other moves down gradient

Symport

substances moved in same direction

Antiport

substances moved different direction

per ATP used, the sodium potassium pump pumps:

3 Na+ out of the cell, 2 K+ into the cell

Endocytosis

making a vesicle to intake molecules

Exocytosis

secreting out a vesicle to outtake molecules