Biological Membranes Flashcards
what is the roles of membranes within cells and at the surface of cells
- compartmentalisation
- separates named organelles from the cytoplasm
- attachment sites for enzymes
- site of chemical reactions e.g the ETC
describe the fluid mosaic model
fluid - phospholipids move freely
mosaic - proteins randomly scattered
roles and functions of cholesterol
- Maintains membrane stability/fluidity
- high temp - prevents fluidity
- low temp - prevents rigity
roles and functions of glycoproteins and glycolipids
- Antigens on cell surfaces
- for cell signalling
What is facilitated diffusion?
- passive movement of particles across a cell membrane
- via a channel protein or carrier protein
how does surface area affect rate of diffusion?
- greater SA = greater diffusion
what happens in a hypertonic solution (plant cells)
. cells have a higher water potential than solution
. net movement of water out
. shrivelled cells , plasmolysed
role of membrane bound receptors
- cell signalling (hormones,neurotransmitters or drugs)
how does temp affect membrane permeability
- Low temp → Less permeable (rigid).
- High temp → More permeable (fluid, proteins denature).
how do solvents affect permeability
- ethanol dissolves membranes - increases permeability
what are the 3 passive transport methods?
diffusion
facilitated diffusion
osmosis
what are 3 active methods of transport?
active transport
endo/exocytosis
osmosis definition
net movement of water molecules across a partially permeable membrane down a water potential gradient
hypotonic sol.
- more water outside
- animal cells - swell and burst
- plant cells - turgid
isotonic
- same water potential in and outside
- animal and plant cells - normal
hypertonic sol.
- less water outside
- animal cells - shrink
- plant cells - plasmolysed
