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Flashcards in 19 Membrane Transport Deck (20):

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

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


passive transport

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


active transport

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



transport of one compound across the membrane 



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



exhange of two molecules acros the membrane in opposite directions



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 


simple diffusion

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


facilitated diffusion 

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. 


gated channels

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


Transporter proteins in facilitated diffusion

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


primary active transport

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


secondary active transport

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


GLUT type glucose transporters

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


Na+/K+ ATPase (antiport)

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) 


Na+ glucose cotransporters (symport) 

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. 



ABC transporters (CFTR)

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 


Ca2+ ATPase  examples (pmca and serca)  


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



Na+-Ca2+ exchanger (antiport)

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