Transport across membranes Flashcards
what does partially permeable mean
lets some moelcules in but not others
what are the 3 types of transport across momebranes
active transport
osmosis
difficult (simple/facilitated)
what is the membrane structure
composed of phospholipids , proteins and carbohydrates
fluid moasic model what does it mean
describe the arranegment of moelcules in the membrane
fluid - the phospholipid layer is flexible as constantly moving
moasic - many different proteins, carbohydrates all of different shapes and szies
what is a bilayer
phospholipid moelcules form a continous, double layer
what types of proteins are there and what do they do
- channel proteins and carrier proetins - allow larger moelcules and ions pass through
- receptor proteins - all cell to detect chemicals released from other cells
what is glycoprotein
protein have a carbohydrate atatched
what is a glycolipid
lipid with carbohydrate attached
what is cholesterol role
- gives membrane stabilitu
- type of lipid
- fits between the phospholipids
- binds to hydrophobic tail
- causing them to pack closely together
- restricts moevemnt of phospholipid - makes membrane less fluid and more rigid
- helps to maintain shape of animal cells
- also has a hydrophobic region, able to create further barrier
phospholipid role
- barrier to dissolved substance
- as center is hydrophobic so doesn’t allow water through
phospholipid structure
- hydrophilic head
- hydrophobic tail
- so moelcules arrange into a bilayer
- head facing outwards on either side
what is the membrane like below 0
- not much energy
- packed cloesly together
- rigid membrane
- channel proteins/carrier denature
- increasing perm of membrane
- ice crystals pierce membrane - highly perm when thaws
what is the membrane like between O and 45
- phospholipids can move around
- not tightly packed together
membrane partially permeable - temperature increases the phospholipids move more energy
- increases perm of mem
what is the membrane like above 45
- phospholipid bilayer starts to break down
- becomes more perm
- water inside expands
- putting pressure on mem
channel/carrier proteins denature cant control what leaves/enter - increasing perm
what is diffiussion
net movement of particles from area of higher conc to area of lower conc
what is simple diffiusion
when moelcules directly diffuse through a cell membrane
what effetcs ROD
- conc m
- thickens
- SA
what is facilitated diffusion
- large/charged molecules diffuse through carrier proteins/channel proteins in cell membrane
how does a carrier protein work in facilitated diffusion
- larger mol attached to carrier protein
- protein changes shape
- releases molecule on opp side of mem
how does a channel protein work in facilitated diff
charged particles diffuse through
different channel proteins facilitated diffusion of different charged particles
what affects the rate of FD
conc m
number of channel/carrier proteins
what is osmosis
diffusion of water moelcules across partially permeable membrane from area of high water potential to an area of low water potential
what is water potential
likelihood of water moelcules to diffuse out
what is isotonic
water pot same
