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)
