Transportation across membranes Flashcards
What can rapidly diffuse across a cell membrane?
Small nonpolar molecules (O2 and CO2) as well as small uncharged polar molecules to a lesser extent
Lipid bilateral membranes are almost completely impermeable to _______________
All charged molecules (ions) regardless of size
To avoid destruction from electrical forces, the charges of the ions inside the cell must balance to some degree. The same is true outside the cell. The Na+ ions are abundant (inside/outside) the cell, and the K+ ions are abundant (inside/outside) the cell.
NA+ = outside
K+ = inside
What is membrane potential?
The small amount of charges that accumulate in the membrane due to a minor imbalance of charges
What is a normal resting membrane potential?
-20n-200 mV (millivolts)
Why is membrane potential expressed as a negative value?
The interior of the cell is more negatively charged than it’s exterior
What determines whether or not a molecule can pass through s specific channel in the plasma membrane?
The molecules charge and size
How do transporters selectively allow passage of certain molecules?
The molecule must attach to the transporters binding site in order to pass through
In what ways can molecules be passively transported across a cell membrane?
Simple diffusion, through an ion channel, or through a transporter. (As long as they are traveling down their conc. gradient)
In what ways can molecules be actively transported across a cell membrane?
Via special transporters called pumps that require an energy source
Where can an Na+ pump acquire the energy it needs to operate?
Hydrolysis of ATP, transmembrane ions moving down their gradients or sunlight
What is the electriochemical gradient?
The net force acting on a charged particle crossing a cell membrane by the membrane potential and that particle’s concentration gradient
What is a coupled pump?
Active transport pumps powered by the down-gradient transport of one solute, in order to move another solute against its gradient.
List the types of active transporters
Light Pump, Coupled Pump, ATP-Driven Pump
You’re observing the passive transport of glucose through a transporter. You notice that only some glucose is able to be transported across the membrane while the transporter seems to reject some of the glucose molecules. Why is this?
Transporters are serious specific.
In this case dextro-glucose may be able to bind to the transporter, but Levo-glucose may not.
