Membrane Transport Pt 2

Question 1

channels or carriers: form a pore that can be open or closed

Answer 1

channels

Question 2

channels or carriers: can be highly selective for individual ions or they can be nonselective

Answer 2

channels

Question 3

channels or carriers: bind specific substrates and allow them to move across the membrane only when they undergo conformation changes

Answer 3

carriers

Question 4

channels or carriers: binding sites must become available to bind (or release) a transported molecule on one membrane side and then also on the other side

Answer 4

carriers

Question 5

we call this form of transport is called an “alternating access model” of transport

Answer 5

carriers

Question 6

channels or carriers: limited in how fast they can operate bc they must recognize and bind their substrates during the transport process

Answer 6

both!

Question 7

facilitated diffusion takes place by ( )

Answer 7

uniporters

Question 8

facilitates diffusion of a solute across a membrane

Answer 8

uniporters

Question 9

movements of one ion type through the membrane drive (or push) the movement of another ion tyoe or a solute, often against its gradient

Answer 9

secondary active transport

Question 10

which carrier is the simplest

Answer 10

uniporters

Question 11

2 types of secondary active transport:

Answer 11

1) symporters (cotransporters)

2) antiporters (exchangers)

Question 12

energy is invested, usually by ATP hydolysis, to carry out transport

Answer 12

active transport

Question 13

channel types:

Answer 13

1) water channels

2) ion channels

Question 14

carrier types:

Answer 14

1) uniporters
2) symporters
3) antiporters
4) pumps

Question 15

facilitated diffusion types

Answer 15

GLUT1-GLUT4 Transporters

Question 16

a specific solute (glucose) is bound on one side of the membrane, translocated across the membrane, and released on the other side of the membrane. The empty binding sites then rearrange to bind another substrate.

Answer 16

facilitated diffusion

Question 17

all of the reactions are reversible and only the energy of the solute gradient across the membrane drives the reaction in one direction

Answer 17

facilitated diffusion

Question 18

facilitated diffusion: glucose can be taken up in to hepatocytes through ( ). How is it stored?

Answer 18

• GLUTs

- glycogen

Question 19

if glucose concentrations are high both inside and outside of cells, the transporter exhanges one glucose insode for one glucose outside

Answer 19

glucose glucose self-exchange; facilitated diffusion

Question 20

how cotransporters transport solutes against their gradient

Answer 20

secondary active transport

Question 21

symporters/cotransporters function similarly to uniporters excep that ( )

Answer 21

two substrates must bind for transport steps to take place

Question 22

driving force of cotransport

Answer 22

energy of one substrate gradient can be used to drive the transport of the other substrate

Question 23

10:1 (Na)(glucose) thing

Answer 23

cotransports

Question 24

law of mass action

Answer 24

[glucose]in= [glucose]out * ([Na]out/[Na]in)^2

Question 25

secondary active transport depends on what?

Answer 25

active transport by Na pumps that use ATP

Question 26

binding site re-orient only when substrates are bound and NOT when binding sites are empty

Answer 26

antiporters

Question 27

ex. of antiporters

Answer 27

Na/Ca exchanger

Question 28

the energy of one ion gradient can be used to drive a different ion in the other direction

Answer 28

antiporters

Question 29

in antiporters, ions are exchanged in a constant ratio called

Answer 29

stoichiometry

Question 30

extrudes Ca from heart cells and many neurons

Answer 30

Na/Ca exchange

Question 31

Law of mass activation for Na/Ca exchangers

Answer 31

20:1

Question 32

what would happen if exchangers were open at both ends like an ion channel

Answer 32

ions would diffuse through the channels without ‘coupled’ movement and a large Ca gradient could not be generated

Question 33

how do antiporters make sure they don’t open both sides at one time?

Answer 33

there is a stage where the transporter is closed on both ends

Question 34

P-tye ion pump example

Answer 34

Na/K Pump

Question 35

Primary active transport

Answer 35

P-type

Question 36

P-Type: Enzyme states with binding sites open to the cytoplasmic side are called ( )

Answer 36

E1 states

Question 37

P-Type: Enzyme states with binding sites facing the extracellular side ared called ( )

Answer 37

E2 states