Lecture 1: Membrane Transport I

Question 1

function of cell membrane

Answer 1

maintains intra and extracellular environment

also subdivides organelles

Question 2

describe the differences in concentration across the cell membrane for ions.
which has the biggest gradient?

Answer 2

Most important difference: blood - extracellular sodium and extracellular potassium. If those are off, something
is very wrong.

what are the big differences: giant K inside the cell bc potassium is only ion high inside the cell; sodium, calcium, chloride
are high on the outside. Differences are very important. Critical to remember the ratio.

which ion in table has largest difference: Calcium is fundamentally important bc controlls so many cellular processes. SO the
biggest gradient is with calcium. This must be maintained incredibly low for cell to survive. 10,000 fold difference.
**concept: intracellular calcium must be very low.

Question 3

which organelles are high in calcium?

Answer 3

SER and mitochondria

Question 4

ficks law of diffusion

Answer 4

flux is directly proportional to area and concentration gradient , and permeability
but
inversely proportional to distance diffused

Question 5

which substances cannot cross plasma membrane freely?

what do they need?

Answer 5

ions
hydrophilic
need channel or pore

Question 6

what is the force behind simple diffusion?

Answer 6

electrochemical gradient: charge and concentration gradient

Question 7

channels have what property?

Answer 7

hydrophilic and gated

Question 8

describe GABA *high yield!

clincal correlation?

Answer 8

inhibitory NT in brain that can bind to GABA receptor. Has ligand gated chloride channel. When GABA binds, channel opens and Cl flows in

clinical correlation: 
targets for drugs:
beta: propofol, neurosteroids
alpha: ethanol, anesthetics
gama :benzodiazepines

Question 9

how do pores determine life or death?

Answer 9

life: permeability of outer and inner membrane of mitochondria is restricted and tightly regulated to maintain oxidative phosphoyrlation

death: increase in permeability of outer and inner membrane .release of lots of mitochondrial contents. PTPC opens and allows free diffusion.
PTPC= permeability Transition Pore Complex

Question 10

importance of cell death normally?

Answer 10

50% of neurons we make die bc we make too much

-also during limb formation, digits evolve by death of inter digital mesenchymal tissue

Question 11

when is cell death pathological?

Answer 11

stroke- mitochondrial pores can open and damage tissue

*we actually want to increase this in cancer cells