cell organization? forget what lecture is called Flashcards
protein in membrane
N side extracellular, C side intracellular, alpha helix inside membrane
functions of membrane proteins (6)
transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining/adhesing, attachment to cytoskeleton and extracellular matrix
peripheral proteins
, sit on other proteins attached to plasma membrane
solution
solvent the liquid, in which the solute is dissolved
solute
could be molecule
isotonic solutions
when comparing two solutions, same concentrations
hypotonic solution
when comparing two solutions, one with lower concentration
hypertonic solution
when comparing two solutions, one with higher concentration
H-bonds in water
electronegativity gives attraction for H-bonds, dissolve things (ex. NaCl); hydration shells
passive transport
diffusion, osmosis
diffusion
the movement of solutes down a concentration gradient, a permeable membrane does not impede diffusion, diffuse until equilibrium
osmosis
the movement of WATER along a concentration gradient through a semi or selectively permeable membrane to one or more solutes
osmosis in red blood cells
cell will burst/lyse in hypotonic solution, cell will shrivel in hypertonic solution, *normal in isotonic
osmosis in plant cells
cell turgid *(normal) in hypotonic solution because pressure in cell wall gives turgidy, cell flaccid in isotonic solution, cell plasmolyzed in hypertonic solution (shrinks)
unicellular organisms and osmoregulation
hypotonic outside, hypertonic inside, collects water in contractile vacuole (when full, will expel water)
simple/passive diffusion
passes through membrane (semi, selectively, or permeable)
passive facilitated diffusion
through channel/transport protein in membrane
active transport
require ATP and energy to bring in solute against concentration gradient
polar molecules permeability
amino acids, sugars, and charges substances such as ions, cannot easily diffuse across lipid bilayers even if concentration gradient exists
high permeable molecules
small, non-polar molecules: ex. O2, CO2, N2
permeable molecules
small uncharged polar molecules: ex. H2O, glycerol
semi-permeable molecules
large uncharged polar molecules: ex. glucose, sucrose
low permeable molecules
ions, Na+, Cl-, K+. Ca2+
how polar molecules enter cells
facilitated diffusion, involving channel proteins and carrier/transport proteins (in plasma membrane)
channel protein structure
membrane proteins that form channels through the plasma membrane, lined with polar (hydrophilic) amino acids, non-polar (hydrophobic) amino acids face the outside of the channel, towards fatty acid tails of lipid molecules
Aquaporins
water channel proteins, main ways water moves through membrane
ion channels
ion channels are GATED, gates open or close to facilitate the movement of ions, when opened, ions flow down concentration gradient
potassium channel
ion channel that allows passage of potassium,
transport/carrier proteins
form channels but they are also specifically bind the transported substance, have binding sites, allows transport to be selective
transport/channel proteins and selectivity
transport of sugars and amino acids, allow diffusion in both directions, concentration gradient can be maintained by metabolizing the transported substance once it enters the cell ex. glucose metabolized when enters the cell so glucose levels remain low and movement continues
active transport
requires the expenditure of energy, moves AGAINST concentrations (from low to high), energy direct or indirectly from ATP hydrolysis
direction of active transport
uniport, symport, antiport
uniport transporters
move a single type of solute (ex. calcium ions) in one direction against its concentration gradient
symport transporters
move two solutes in the same direction, only ONE of which is against its concentration gradient (ex. amino cid transport coupled with sodium ion transport, sodium moves down, amino acids move against)
antiport transporters
move two solutes in opposite directions, one into the cell, one out of the cell, both of which are AGAINST their concentration gradients (ex. sodium potassium pump, sodium out, potassium in, each 1 ATP 3 Na+ out and 2 K+ in)
sodium transport across membrane
cells use loss of energy from sodium movement through protein to push in K+; if sodium channel is open, sodium goes into cell until equilibrium is reached; inside of cell reaches 15mM then pushes extra sodium out with ATP, while K+ is pushed into cell (opposite direction, against concentration gradient)
sodium-potassium pump process
3 sodium ions bind to pump, Na+ binding stimulates phosphorylation (phosphate and ADP) by ATP, this causes protein to change shape and Na+ is expelled, then + binds on extracellular side and triggers release of phosphate group, protein goes back to original shape and 2 K+ are pumped in (cycle repeats!)
electrogenic pump (proton pump)
moves ions against an ionic gradient aand generate a voltage difference across the membrane; proton pump causes + or - difference; ACTIVE
cotransport
transport mechanism for one ion or molecule can help out another transporter to move and different ion or molecule
coupled transport processes
cooperate to facilitate the movement of ions or molecules across membranes, requires energy (ACTIVE), cotransport
active transport by concentration gradient
electrogenic pumps can be used to help drive symporters such as the sucrose transporter by maintaining an ionic gradient
active transport by concentration gradient examples
sucrose-proton cotransporter; glucose-sodium/potassium pump cotransporter
bulk transport across membranes
food or other particle is engulfed by membrane and is put in food vacuole, food particle + extracellular fluid/solutes enter via endocytosis
receptor endocytosis
a coated pit and a coated vesicle formed during receptor-mediated endocytosis
