Cell membranes and transport unit 1

Fluid- phospholipid bilayer can move around
Mosaic- Proteins are all diff sizes

They only allow certain molecules thru

Temp-increase vibrations of phospolipids, moving them further apart
Organic solvents- dissolve phospholipids

Lipid soluble substances, eg. Vitamin A
Small mols, eg. O2 and CO2

Water soluble substances
Cant get thru hydrophobic tails
Has to use intrinsic proteins to pass thru

Pores lined with polar (hydrophobic) groups, allow charged ions thru

Allow large polar mols thru, eg. amino acids, water soluble sugars
Cell changes shape as mol binds to move it in or out

Whether its extrinsic or intrinsic

Hydrophilic phosphate head
Hydrophobic fatty acid tail

Found on outer surface of bilayer
Can have a sugar attached

Glycoproteins

A glycocalyx layer of the membrane

Plays a role in cell to cell recognition or hormone receptor sites

Found inbetween the phospholipids
Makes them more rigid and stable

Diffusion of water
High to low wp
Across selectively permeable membrane

The tendency of water molecules to move

The osmotic strength of the solution, measures how easily water mols move out of solution

Harder for water mols to move out of solution, held together more tightly

Lots of water moves into plant cell
Pressure potential of cell increases
Cytoplasm pushes on cell wall, cw becomes turgid to stop it from exploding

Plant cell has lost enough water for cell membrane to seperate from cell wall
Pressure potential is 0

Cell becomes flaccid when in hypertonic solution

Because they lack a cell wall

They burst

They shrink

The concentration of solute

High conc of solute, low water potential

Low conc of solute, high water potential

Same conc of solute and same water potential
No net movement of water between the solutions

Movement of molecules
High conc to low conc, down conc gradient
Passive process
Thru phospholipid bilayer

Higher conc gradient
Shorter diffusion distance (thinner membrane)
Large surface area
Smaller mols
Non-polar / fat soluble mols
High temp

Same as simple diffusion but for polar mols or ions that cant get thru bilayer
Use the channel / carrier proteins

Because its a passive process

Type of faciliated diffusion
2 diff substances use same carrier protein at same time

Movement of mols against conc gradient
Low to high conc
Requires ATP from respiration (activates the carrier proteins to move mols)

Prevents ATP from being avaliable, prevents transport

Movement of large molecules across cell membrane

Endocytosis
Exocytosis

Phagocytosis (solids enter cell)
Pinocytosis (liquids enter cell)

Plas membrane fold in
Engulfs material
Vesicle formed enters cell

Vesicle formed by golgi moves to plas membrane
Fuses with plas membrane
Vesicle empties contents of cell

Active process, requires ATP to move vesicles