ch 9 -biological membranes and transport Flashcards
what are the 6 biological functions of biological membranes?
- separate cells from external medium to create unique and contained intracellular environment
- selective transport of substrates in/out of cell
- location for specialized pathways and processes
- rapid changes in electric potential across the membrane of neurons as basis of nervous system
- localization of receptors to facilitate response to physiological signals
- mediate cell-cell recognition and interaction
how and why are liposomes formed?
flat bilayer sheets fold so this internal volume can have an aqueous cavity for hydrophobic tales
true or false. more active membranes have higher ratios of lipids.
False. More active membranes have higher ratios of protein
what are peripheral membrane proteins?
- the face of the membrane and interact either directly or through a tail (charge-charge or hydrogen bond)
- links to membrane may be through protein or membrane lipids
what are integral membrane proteins?
- immersed and often span the entire membrane
- internal part often hydrophobic residues and it is very specific the placement through the membrane
Alpha-helixes usually pass through the membrane in one of these 2 ways:
one pass or 7 times through
what do type I-VI of integral membrane proteins represent?
I. single pass. N outside cell. points in
II. single pass. N inside cell. points out
III. multiple passes through with a single polypeptide (tertiary)
IV. single pass through membrane with multiple polypeptides (quaternary)
V. lipid-linked (lipid anchored)
VI. lipid-linked with transmembrane region
true or false. A more solid structure is the result of a longer tail and less double bonds
True. A more solid structure is made of longer tail and less double bonds where a more fluid structure is made of shorter tails and more double bonds
what are lipid rafts?
- glycosphingolipids form clusters where longer ones cluster and almost jut out. they are the long chain fatty acids
- demonstrates that lipid distribution is not random within membrane leaflet
what is simple diffusion?
non-polar gases and hydrophobic molecules directly cross membrane where direction of movement is down concentration gradient
what 2 ways can facilitated diffusion occur?
- channels: only transport molecules down the electrochemical gradient. have high conductance rates (bind substrates very weakly), dont show saturation behavior)
- carriers: substrates bind to protein to transport it and they generally have lower transport rate than channels
what are the two types of coupled transport?
- symport: both molecules move the same direction (have opposite charges)
- antiport: molecules move opposite directions (same charge)
what allows molecules to move against their concentration gradient?
active transport
how does primary active transport help for secondary active transport to occur?
primary active transport uses ATP for energy and establishes a concentration gradient. when this concentration gradient is established, secondary active transport is able to occur
what is the difference between V-type ATPases and F-type ATPases?
V-type are involved in the acidification of intracellular compartments where F-type are used in reversing a proton gradient to generate ATP (mitochondria and chloroplast)
