Passive transport

solute

stuff dissolved

solvent

dissolving agent

passive trans

no energy

active trans 

cell uses ATP 

Passive- Diffusion

important in all cells

Passive- Filtration

occurs in some specific locations in the biyd

→ kidneys and capillaries

diffusion

• kinetic energy

• random mix of particles that occurs in solution as a result of particle’s kinetic energy

  • high concentration→ low

Diffusion: molecules move…

along/down a concentration gradient 

diffusion eventually reaches

equilibrium

speed of diffusion

• influjenced by molecules size, temp, and concentration gradient

• particles NEVER STOP MOVING

  • small=faster, heat=faster, larger difference=faster

gradients across plasma mem 

difference in concentration of chemicals between 1 side of membrane and other 

plasma mem physical barrier to diffusion b/c

hydrophobic core

→ anything wt charge, polar covalent bonds, cant cross

simple diffusion

• unassisted of nonpolar lipid soluble or very small particles

  • oxygen, CO2, fat soluble vitimans (A, D, C, and K) steroid hormones

facilitated: via channel 

• transmem proteins transport substance thru aqueous channels from one side of mem to the other 

• selective 

• down concentration 

• can be inhibited, show saturation 

  • → can be blocked/controlled 

leakage channel

always open 

gated channel

mostly closed

chem gated channel (ligan)

chemical binds to receptor and opens channel briefly

mechanically gated channel

tension opens for a brief period (physical deformation)

voltage gated channel 

• different charge (+,-) across mem 

• opens when charge switched/changed across mem

facilitated diffusion via carrier

• transmem integral protein moves substances too large for channels

• change shape of carrier to allow to envelop and release transported substance

• down concentration

• selective

facilitated diffusion via carrier: limited number of… 

• carriers when all in use (saturated) and transport of substance at max rate 

  • control when proteins involved to change number of carriers 

how can a cell keep taking glucose

• it changes it so more can enter

  • uses it for energy or storage

facilitated diffusion controllable because 

permeability of mem can be altered by regulating the activity/number of individual carriers/channels 

osmosis

• diffusion of solvent (water) thru selectively permeable mem

  • water CAN pass thru hydrophobic tails

aquaporins 

water specific channels of transmem proteins 

osmosis occurs when…

the water concentration differs on the 2 sides of the mem

osmolarity

total concentration of all solute particles in a solution

→ wherever salt goes water follows

→ high water to low water

→ not usually reach equilibrium

tonicity 

ability of a solution to change shape of cells by altering their internal water volume 

isotonic

concentration of solute outside cell= concentration inside

osmotic imbalances

cause cells to swell/shrink due to net water gain/loss

hypotonic

hypo=below

very watery, little salt, swelling, water into cell

→ red blood cells bursts and dies

hypertonic 

cell shrivels, creamates, dehydration, water out

simple diffusion and osmosis thru plasma mem…

are NOT SELECTIVE

→ bc no protein

facilitated diffusion is…

HIGHLY SELECTIVE

→ bc proteins

filtration

• forces water and solutes thru a mem or capillary wall by fluid or hydrostatic pressure (high→ low pressure) 

• passive (pressure gradient) 

is filitration selective

• NOT selective

• passive (pressure gradient