Biol reading 22-09- membrane transport

membrane separates cell from

outside env

membrane creates very specific contrallable

internal environenemnt

small non polar molecules

high permeability

small uncharged polar molecule

some permeability

large polar molecules

very low permeability

ions

extremely low permeability

macromolecules

extremely low permeability

diffusion

net movement of molecules from high to low conc

diffusion at equilibrium

no net movement, molecules continue moving randomly in both directions

diffusion is energetically

favorable and increases entropy

osmosis

net movement of water molecules from an area of low solute concentration to high

hypertonic

higher ouside solute —> water moves out of cell —> cell shrinks

isotonic

same outside solute —> no net movement —> cell maintains size

hypotonic

lower outside solute —> water moves into cell —> cell swells

simple diffusion

molecules move by diffusion, down their conc gradient

hydration shells

formed by water molecules associated with an ion

hydration shells make ions

larger

cation

positive ion

anion

negative ion

concentration of potassium ions (K+)

high inside nerve cells

low outside

leak/ open channels proteins

in nerve cells

very slow movement

gated channels

open due to signal

K+ channels in nerve cells

very fast

channels are selective for specific molecules

Ions (K+, Na+, Cl-, Ca2+)

Small polar molecules (H2O)

channel protein provides a

hydrophilic passageway for molecules

carrier proteins/ conc of glucose

high in blood plasma

low inside cytoplasm

glucose trasnporters are

carrier proteins

Carrier proteins bind

molecules and changee shape to move them across

glucose moves

down conc gradient

carrier protein energy input

none

why active transport

take up nutrient when more concentrated inside

remove substances when theyre more concentrated ouside

active transport moves substances

against their conc gradient

active transport requires

energy

primary active transport

uses ATP directly to move against conc gradient

coupled transporters

use movement of one substance to drive movement of another

symporter

2 different substances

move in same direction

antiporter

2 different substances

move in opposite directions

secondary active transport uses

potential energy stored in an electrochemical gradient

1 build a gradient

protons are pumped across using ATP

2. create an electrochemical gradient

the gradient stores potential energy

3. use the gradient

protons move down their electrochemical gradient, driving another molecule against its conc gradient