L11. Transport across cell membrane Flashcards
what do membrane transport proteins facilitate
the movement of water soluble molecules
what does the rate of diffusion depend on
molecular size and solubility
rate of diffusion - molecules ranked from highest to lowest diffusion
- small nonpolar molecules (all pass through)
- small uncharged, polar molecules
- larger uncharged polar molecules
- ions (none pass through)
ion concentrations - Na+
- sodium
- low inside cell
- high outside cell
ion concentrations - K+
- potassium
- low inside cell
- high outside cell
ion concentrations - Ca2+
- calcium
- really low inside cell
- high outside cell
explain the two components of an electrochemical gradient
- electro: membrane potential
- chemical: concentration gradient
- they can either work together or oppose each other
two components of an electrochemical gradient - what happens as concentration gradient and membrane potential work together
increases solute movement
two components of an electrochemical gradient - what happens as concentration gradient and membrane potential oppose each other
the electrochemical driving force is decreased
what solutes can transporters and channels move across the membrane
inorganic ions and small, polar organic molecules
explain how transporters can move molecules
- taking a molecule from one side and physically move it to another side via conformational changes
- can be used with active or passive transport
explain how channels can move molecules
- they do not stay open
- only uses passive transport
- faster then transporters
explain active transport
- molecules are moved against the concentration gradient (less -> more)
- requires energy (not only ATP)
- only transporters can do this
explain the types of transporters
- uniport
- symport
- antiport
explain passive transport
- molecules move down their concentration gradient (more -> less)
- occurs spontaneously (no energy needed)
- can be transporter- or channel-mediated
types of transporters - uniport
- only moves one molecule
- can be against or toward the gradient
types of transporters - symport
- type of coupled transport
- both molecules go in the same direction
types of transporters - antiport
- type of coupled transport
- molecules to in opposite directions
types of transporters - what is coupled transport
using the movement of one molecule going toward the gradient to pay for the movement of another molecule moving against the gradient
what are the three mechanisms of active transport
- coupled pump
- ATP-driven pump
- light driven pump
passive transport - explain the conformational change in transporters
- outward-open
- occluded
- inward-open
passive transport with transporters - outward-open
binding sites are exposed on the outside of the cell