what are plasma membranes formed from
phospholipid bilayer
decribe the structure of a phospholipid bilayer
hydrophillic head
phydrophobic tail
describe fluid mosaic model
bcs the bilayer is free to move and thing giving them soace to move bcs the proteins are differebt shapes and sizes like a mosaic
describe intrinsic proteins and give me examples
Embedded in both layers ON MEMBRANE have hydrophobic R group on surface that reacts with the hydrophic core keeping it in place
channel (down conc gradient held together by Rgroups) and carrier proteins(downAND against gradient & change proteins shape)- movement of polar molecules and ions down a gradient through membrane
glycoprotein- plays a role in adhesion and recepor for chemicals
glycolipids-cell markers that can be recognised by immune system
exaples of extrinsic proteins
On the outside of the membrane and have hydrophillic r groups (can be IN OR BETWEEN layers)
cholesterol- regulates fluididty of membranes
factirs affecting memberanes
temp-phospholipids are constantly moving, high temp more kinetic energy, too much permeability and break down
Denature of channel and carrier
solvents-alchol dissolves membrane or cause damage and when damaged it becomes more permiable
factors effecting diffusion accross a membrane
temp- high temp=more kinetic energy and rate is higher
conc- different conc the rate will be faster
what effects the rate at which moleculs or ions diffuse by are
SA- more soace more chance of diffusion
thickness of membrance- thin membrane=easier diffusion
describe facillitated diffusion
didfusion across membrane across protein Chanel’s
Also may involve carrier proteins which changes shape when certain molecules bind
what si active transport
movement of molecule and ions from low to high
Requiring energy and carrier proteins
how does active transportation happen across a membrane
molecule binds to receptor
ATP brind to carrier proteins and hydrolised into ADP
Binding of molecules to carrier protein changes its shaped and opens inside of cell
Molecule released into cell
carrier protein cahnges shale
ADP turns into ATP
carrier protein back to normal
drscribe endocytosis and exocytosis
endo- molecule in cell cell membrane bends inwards encapsulation the molecules turning into vesicle then moves to cytoplasm to be digested
exo- vesicle formed by golgi fuse with membrane and release molecules. Energy is needed to move vehicles along cytoskeleton and to change shape of cells and to fuse with membrane
what is water potential
pressure of water exerted by water molecules when they collide with membrabe
What does selectively permiable mean
Membranes with protein channels that only allow certain molecules in and out of the
Things that effect facilitated diffusion
Tenp
Concentration gradient
Surface area
Thickness
Number of channel proteins present (more=higher rate)
What is bulk transport
Large molecules like enzymes and hormones are too big to move through channels so moves by end and exocytosis
What is hydrostatic pressure
Water going into a closed system increasing the pressure and volume
What happens in an animal cell when there is hydrostatic pressure
cytolysis- the cell will burst
What happens when the water potential is lowkey outside the cytoplasm
Cell will go through cremation and ‘pucker’ or reduce volume
If the water potential outside a plant cell is more than inside what happens?
water moves in
Hydrostatic pressure increases and becomes turgid
If the water potential inside a plant cell is more than inside what happens?
Water inside cell is lost and becomes plasmolysed
what is facillitated diffusion
movement of molecules like glucose and amino acids ancross a membrane from high to low conc
DOESNT USE ATP
