week 10

Question 1

what are the three main classes of membrane proteins that transport molecules and ions across cellular membranes

Answer 1

• channels
• transporters
• atp powered pump

Question 2

channels

Answer 2

ions and hydrophilic molecules can flow down their concentration gradient. can be non gated or gated

Question 3

transporters

Answer 3

include uriporters, symporters and antipoerters that have one molecule moving down the gradient (at least)

Question 4

cotransporters

Answer 4

sympeorters and antiporters that move another molecule against its gradient.

Question 5

facilitated transporers

Answer 5

• channels and transportersa

Question 6

tp powered pumps

Answer 6

energy from atp hydro to move a variety of ions and small molecules against concentration gradient

Question 7

facilitated transporters

Answer 7

include channels, gates and transporters, the driving force being concentration gradients, specific to certain molecules
- hydrophilic substances are moved through a protein lined pathway so that there is no contact with the hydrophobic interior of the membrane.
- faster than if they are to use passive diffusion
- saturable meaning that at some point they can reach the max of how much can get through at a given time
-

Question 8

is atp required for facilitated transport

Answer 8

• no but it might be required to set up concentration gradient

Question 9

example of an open channel;

Answer 9

the potassium resting channel

Question 10

is channel opening/closing based on ligand binding?

Answer 10

no, due to chemical or electrical signals

Question 11

voltage gated channel

Answer 11

depends on the charge across the plasma membrane
- e.g. SR calcium release channel.S

Question 12

SR calcium release channe

Answer 12

• when muscle contraction occurs, there is a lot of calcium please
• electrical charge from the nerve down to the t tubule
• hits teh voltage gated channel that opens and releases caclm
• ## ca flows out of the channel and can be pumped back in

Question 13

specificity of channes

Answer 13

• integral membrane proteins can create holes in membrane large enough for solutes to pass throughsi

Question 14

size based exclusion in facilitated transport change;l

Answer 14

• having size-based exclusion
• specificity can lead to membrane potential

Question 15

• what is meant by size-based exclusion- hydrophilic interior to channel
• ae abc class pumps for big or small molecules

Question 16

K+ resting channel, size selectivity

Answer 16

• only potassium interacts oropperoly with the polar amino ids oto shed its hdyration shell and pass through the channe’l, needs the right energy to get rid of the water , and the oxygens in teh channel prove it the same energy
• Na in potassium pore is too small to interact with he all the oxygen that are spaced specifically for K,

Question 17

how does speciciicty/size based exclusion lead to creation of electric potential

Answer 17

• K+ resting channel only allows potassium, not Na or Cl to pass0 when K flows down the concentration gradient, a negative charge is left on teh side that it leaves
• this leads to all cells having a negative charge on the inside of the PM

Question 18

transporters

Answer 18

are normally closed, requires ligand binding to open, in this case the ligand is the molecule that is being transported. this involves significant conformation changes.
- not an “open” channel

Question 19

uniporters

Answer 19

• ## open and close in response to a ligand

Question 20

WHAT IS glut 1 transporter

Answer 20

• it is a glucose transporter that has high affinity glucose binding sites, driving force is concentration gradient of glucose
• a uniporter specific to glucose

Question 21

active transport

Answer 21

• pumping molecules against concentration gradient using ATP
• are considered pumps

Question 22

V class pumps

Answer 22

H+ only
- important for lysosome acidity, pump protons from cytosolic to exoplasmic side (pumping out of cell)

Question 23

F class

Answer 23

H+ only, in mito and chloroplasts, pump protons from exopalsmic to cytolsic side, e.g atp syntheses

Question 24

P class pumps

Answer 24

H+, Na+. K+, or Ca2+

Question 25

ABC class pumps

Answer 25

• are used to export ions, sugars, amino acids, peptides, proteins phosplipipds, cholesterol , toxin , foreign substances
• some are able to flip components from one membrane leaflet to another

Question 26

ion concentrations in a cell

Answer 26

• high Ca outside
• high K inside
• high Na outside
• these are the directions in which these ions are pumped

Question 27

Muscle Calcium ATPase, a

Answer 27

• an example of a P class pump
• sits on the SR
• using atp hydrolysis to pump ca out of cytoplasm into the SR
• ## voltage gated channel releases calcium and allows muscle ATPase to pump calcium back into SR

Question 28

Na/K P class pump***

Answer 28

• K+ resting channel allows K outside of cell, most cells have negative charge on the plasma memvrane
• atp is used to pump 3 sodium out and 2 potassium in per ATP
• end up with high concentration of sodium outside of cell

Question 29

secondary active transport (xo transport)

Answer 29

by antiports and symports
- coupled transport between two different molecules
one is with the gradient, one is against

Question 30

how does secondary active transport work

Answer 30

• ion gradients generated by atp powered pumps
• fre energy associated with these ions going back along concentration gradient is coupled with the import or export of other molecules against their concentration gradient