module 9 Flashcards

Question

what are lipid-anchored membrane proteins?

Answer 1

-covalently attached lipids can anchor proteins to the membrane -these protein modifications are sometimes reversible, allowing for regulation of cellular location -GPI anchored proteins always at outer layer -proteins with single chain hydrocarbons always to inner face -diff fatty acid attach to diff part of the membrane (amino aicd)

Answer 2

-immersed in, and usually span, the membrane -protein positioning withing a membrane is specific and directional -tend to be of three varieties: single pass a-helical, a-helical bundles (7), and B-barrels

Answer 3

-blue=charged residues, mostly within the intra and extracellular portions of the protein -white= residues with non-polar side chains, dominate inside the hydrophobic slab of the bilayer -red=tryptophan -orange=tyrosine cluster at the interface between the hydrocarbon chain and polar head group region

Answer 4

-predicted from the amino acid sequence -stretch of 20 hydrophobic residues in a row are likely membrane spanning -a hydropathy index look at the hydrophobic characteristics of a protein to predict transmembrane regions -magnificent 7

Answer 5

-side chains within the transmembrane region tend to be non-polar, however the carbonyl and amid groups of each peptide bond are polar -polar unpaired carbonyl and amide groups in the bilayer core are energetically unfavorable -carbonyl and amide groups of the proteins backbone within the bilayer have to be hydrogen-bonded

Answer 6

-non-polar gases (O2 and CO2) and hydrophobic molecules can directly cross the membrane -their direction and rate of movement is determined by their concentrations on either side of the membrane -can only result in the net movement down a concentration gradient

Answer 7

-membrane transporters lower the activation energy barrier of crossing the bilayer -activation energy for removing the hydration shell from a polar solute and transferring it into the non-polar environment in the core of the bilayer is very high -membrane transporters lower the activations energy for crossing the membrane by replacing the hydration shell with interactions with polar groups along the transfer path in the protein interior

Answer 8

-membrane pores to transport molecules down concentration gradient -high conductance rates because they bind the substrate very weakly -do not saturate

Answer 9

-membrane proteins that undergo substrate-induced conformational change, or membrane positioning, to release substrate to the other side of the membrane -slower because they bind the substrate quite strongly -can saturate

Answer 10

facilitated diffusion through a carrier -facilitated diffusion of glucose at 50,000X faster than simple diffusion -specific for D-glucose -the rate of uptake follows a pattern resembling M-M kinetics -Kt about 1/3 the concentration of blood glucose so the transporter is nearly saturated and operates near V-max (75% of max capacity)

Answer 11

-in diffusion, co-transport through antiport or symport depends on the charge of the molecules in order to have a net neutral change -in secondary active co-transport, system couples a molecule moving down its gradient to one moving up its gradient

Answer 12

-uniport=transport of a single molecules -antiporters= move molecules in different directions -symporters=move molecules in same direction

Answer 13

-input of energy allows movement of molecules against concentration gradients -primary active and secondary active

Answer 14

-driven by direct source of energy (ATP) -includes P-type, V-type and ABC transporters

Answer 15

-couples the movement of one molecules up its conc gradient within the movement of another molecule down its gradient

Answer 16

vacuoles -use the energy of ATP to move protons against a concentration gradient -acidification of organelles -in chloroplasts and mitochondria, F-type ATP synthases reverse this reaction to use proton gradient to generate ATP

Answer 17

-contain ATP-binding domains (ATP-Binding-Cassette) -transport a variety of biomolecules out of the cell against a concentration gradient -multi-drug resistance protein pumps drugs (chemotherapeutic) out of the cell, rendering the drugs ineffective -detoxifying system

Answer 18

-Na, K ATPase uses the energy of ATP hydrolysis to pump three Na out of the cell and two K into the cell -called a P-type transporter as it undergoes a phosphorylated intermediate

Answer 19

-cells maintain high gradients of Na outside the cell and K inside the cell -this gradient controls cell volume, electrical excitability, and enables uptake of nutrients through secondary active transport systems -maintaining the activity of Na K pump requires about a third of your energy

Answer 20

-glucose uptake into intestinal epithelial cells

Answer 21

-in intestinal epithelial cells, glucose uptake from the gut is driven through symport with Na -the movement of glucose up its concentration gradient is enabled by the movement of Na ions down their concentration -active transport of glucose from the gut depends on the action of the Na K ATPase to establish the gradient of Na ions

Answer 22

-enable rapid movement of ions across the membrane -actions of ion channels can cause changes in membrane potential (action potentials) in neurons -tightly regulated; voltage-gated channels and ligand-gated channels -are highly selective for the molecule to be transported

Answer 23

-faster -no saturation limits -gated/regulated (open and close in response to signal)

Answer 24

-K channels allows rapid movement of K ions out of cells -although Na is smaller, the channel is 100-fold more permeable to K -selectivity filter discriminates K and Na based on their ability to shed water molecules to form electrostatic interactions within backbone carbonyls

Answer 25

-selectivity filter has four equivalent binding sites for K -as K ions enter the filter, the electrostatic repulsion from other incoming K ions helps to push the flow of ions from inside to outside of the cell

module 9 Flashcards

(51 cards)