19 Membrane Transport

Question 1

the relative ion concentrations of the cell relative to the inside and the outside of the cell

Answer 1

The inside of the cell is relatively negative, compared to the outside of the cell which is positively charged.

Question 2

passive transport

Answer 2

diffusion of molecules in a net movement from high to low concentration, no energy applied

Question 3

active transport

Answer 3

net movement from a region of low concentration to a region of high concentration, uses energy to move substances against their gradient

Question 4

uniport

Answer 4

transport of one compound across the membrane

Question 5

symport

Answer 5

simultaneous transport of two molecules across the membrane in the same direction

Question 6

antiport

Answer 6

exhange of two molecules acros the membrane in opposite directions

Question 7

aquaporins

Answer 7

water can move through these aquaporins, large protein pores, either in or out of the cell depending on its concentration gradient, water flows from an area of high concentration to an area of low concentration

Question 8

simple diffusion

Answer 8

movement of gases and lipid soluble molecules down their concentration gradient from high to low concentration, no energy required

Question 9

facilitated diffusion

Answer 9

transport mediated by protein transporters or carrier proteins, usually involves a conformational change, net mov’t down its concentration gradient and thus, no energy is required.

Question 10

gated channels

Answer 10

channels form a pore for ions that is opened or closed in response to stimuli

Question 11

Transporter proteins in facilitated diffusion

Answer 11

the transported molecule binds to a specific carrier protein, conformational change takes place and then release of molecule on the other side. high specificity

Question 12

primary active transport

Answer 12

the energy is applied directly to the transport protein, example Na+/K+ ATPase, to move molecules against its concentration gradient

Question 13

secondary active transport

Answer 13

the energy is applied more indirectly, by the establishment of a concentration gradient, and this drives the movement of another compound

Question 14

GLUT type glucose transporters

Answer 14

Moves glucose from a high concentration to a low concentration, either into or out of the cell, passive transporter, moves the glucose down its gradient

Question 15

Na+/K+ ATPase (antiport)

Answer 15

primary active transport , it pumps 3 Na+ ions out of the cell and 2 K+ ions are driven inside the cell, they are both against their concentration gradient ,

ATP supplies the

ENERGY to cause the conformational change to releases the bound Na+ ions to the other side of the membrane (antiport)

Question 16

Na+ glucose cotransporters (symport)

Answer 16

2 active transport, symport. Na+ gradient established, the Na+ moves down its concentration gradient to move the glucose against its gradient, 1:1 transport across the membrane together.

Question 17

ABC transporters (CFTR)

Answer 17

a ligand gated channel controlled by phosphorylation.

1. Protein kinase A phosphorylates this regulatory binding domain, causes a conformational change which allows ATP to bind to the 2 ABD binding domains.
2. Hydrolysis of the ATP drives the opening of the channel

contains two regulatory binding domains which controls the opening of the channel

Question 18

Ca2+ ATPase examples (pmca and serca)

Answer 18

both channels work to lower Ca2+ concentration inside the cell, by pumping it out through the PM or into the sarcoplasmic reticulum

SERCA, active transport, uniport, located in the SR, Moves Ca2+ into the SR, and then ATP is needed to release Ca2+ into the lumen of the SR,

PMCA, active transport, uniport, located at the PM, pumps Ca2+ against its gradient from the cytosol, through PM and into the extracellular space

Question 19

Na+-Ca2+ exchanger (antiport)

Answer 19

secondary active transport, antiport example NCX

pumps 3 Na+ into cell down its gradient while pumping 1 Ca2+ out of cell against its gradient

cell membrane transporter