Cell Membranes And Transport Flashcards
What are the biochemical components in a cell membrane?
phospholipids and protein molecules
why do phospholipids form a bilayer?
head= hydrophilic. tails= hydrophobic
4 functions of internal membranes (membrane bound organelles)
1) compartmentalisation. 2) chemical reactions. 3) increase SA for enzymes. 4) transport systems
4 functions of external membranes
1) selectively permeable- barrier to large polar molecules, permeable to non-polar molecules and small polar molecules. 2) take up nutrients. 3) secretes chemicals. 4) cell to cell recognition and communication.
describe the fluid mosaic model
fluid= proteins free to move in bilayer. mosaic= proteins arranged randomly between phospholipids.
describe the proteins found in membrane
globular. extrinsic= found on surface, charge on top contacts environment, change on bottom contacts cytoplasm . intrinsic= extend across bilayer charged on both ends
where are the carbohydrates found and state their function
pointing on outside of cell. glycoprotein= attached to protein. glycolipid= attached to phospholipid. for cell recognition and adhesion
where is cholesterol found and what is it’s function?
found between phospholipids. controls membrane fluidity.
what’s the distance across a cell membrane?
7nm
define passive transport
doesn’t use ATP (diffusion, facilitated diffusion, co transport, osmosis)
define active transport
uses ATP ( active transport and bulk transport?
define diffusion
movement of molecules or ions from a region of high conc to low conc down conc gradient
What does rate of diffusion depend on?
SA, conc gradient, temp, size, lipid solubility, availability of channels, thickness of membrane
describe channel proteins
water filled channels- hydrophilic pores- allows water soluble molecules through by FACILITATED DIFFUSION. highly selective
describe carrier proteins
movement of large polar molecules (attach to binding site, protein changes shape to release molecule) FACILITATED DIFFUSION AND ACTIVE TRANSPORT (movement from low conc to high conc)
describe co transport
type of facilitaed diffusion- 2 substances simultaneously transported across membrane. eg) glucose + 2 Na+ attach to carrier protein. carrier protein changes shape and releases all into cell together. diffuse through membrane
define osmosis
movement of water from high water potential to low water potential down water potential gradient
define water potential
potential of water to enter or exit system measure in kPa
What happens when a cell is in a dilute solution?
low solute potential so water moves into cell HYPOTONIC. animal cell= Lysis (bursts) plant cell= turgid
What happens when a cell is in an isotonic solution?
same water potential so animal cell= normal and plant cell= incipient plasmolysis
What happens when a cell is in a concentrated solution?
high solute potential so water leaves cell. animal cell= crenated. plant cell= flaccid/ plasmolysed
why don’t plant cells burst?
inelastic cell wall
What makes plant cells flaccid?
vaculow shrinks so cytoplasm moves away from cell wall
describe bulk transport
requires ATP. cell obtains solid material that’s too large to enter by osmosis or active transport
describe endocytosis
membrane ENGULFS material. membranes fuses behind forming vesicle
describe phagocytosis (solid material)
sold matter binds to receptor. cell membrane imvaginates and taken into phagosome by endocytosis. lysosomes fuse with phagosome and secrete digestive enzymes. matter digested and reabsorbed into cytoplasm
describe pinocytosis (liquids)
same as phagocytosis but smaller vesicles
describe exocytosis
exit of substances after being transported through cytoplasm I’m vesicle
