Block 2 Lecture 19

Question 1

what is diffusion

Answer 1

net movement of particles from regions of high electrochemical potential to regions of low electrochemical potential

Question 2

what is ficks first law of diffusion

Answer 2

Jnet = D (deltaC/ delta X)

Question 3

what is Einsteins equation involving time

Answer 3

t = (deltaX^2)/2D

Question 4

how far can diffusion be effective

Answer 4

under a millimiter

Question 5

after a millimeter of distance how are molecules transported

Answer 5

convective (bulk) flow is required which requires a pump

Question 6

what equation describes “net diffusion across a membrane is proportional to the gradient across the membrane

Answer 6

Jnet = P(DeltaC)

Question 7

what influences P

Answer 7

size and lipophilicity

Question 8

what dies ionized vs non ionized species depend on

Answer 8

the pH

Question 9

what is ion trapping

Answer 9

accumulation of a compound in the compartment where it tends to be more ionized as a result of the difference in pH between compartments

Question 10

what type of molecules are found in alkaline compartments

Answer 10

weak acids (A-)

Question 11

what type of molecules are found in acidic compartments

Answer 11

weak bases (BH+)

Question 12

what effects does the addition of a solute have on osmosis

Answer 12

is reduces the chemical activity of water in the resulting solution

Question 13

how do you stop net flow of water

Answer 13

apply hydrostatic pressure to the solution with low water activity

Question 14

what is the Vant Hoff law

Answer 14

Pi = RTC

Question 15

what does the Vant Hoff law calculate

Answer 15

osmotic pressure

Question 16

what are the assumptions when calculating osmolarity

Answer 16

1. assume full dissociation of all salts
2. take account of valence of dissociating salts
3. add up the contribution of all the different particles in solution

Question 17

what is the equation for the difference in osmotic pressure between 2 solutions

Answer 17

DeltaPi = RT(Delta C)

Question 18

what is the “sequence of events” when transferring water between compartments

Answer 18

cells first transport solute then the resulting difference in osmotic pressure leads to a flow of osmotically obligated water

Question 19

what is Kw

Answer 19

the equilibrium constant for water, 1 x 10^-14

Question 20

what does an equilibrium constant less than 1 indicate

Answer 20

that the reaction prefers to stay on the side of the reactants so water tends to stay as water

Question 21

what happens to strong acids and strong bases in an aqueous solution

Answer 21

100% ionization

Question 22

what is the Henderson hasselbach equation

Answer 22

pH = pKa +log [base]/[acid]

Question 23

what happens when [A-] = [HA]

Answer 23

pH = pKa because log of 1 is 0

Question 24

what is the most common anionic residue? cationic?

Answer 24

anionic = COO-
cationic = NH3+

Question 25

what’s a good rule of thumb for carboxyl groups

Answer 25

they typically have pKa values less than 5. at normal pH it will be negatively charged

Question 26

what’s a good rule of thumb for amino groups

Answer 26

typically have pKa values greater than 8. at pH 7.4 it will be positively charged

Question 27

what does lower pKa mean

Answer 27

stronger acid

Question 28

what is a zwitterion

Answer 28

compound with basic and acidic moieties

Question 29

what do buffers do

Answer 29

allow solutions to resist large changes in pH by adding small amounts of OH- or H+ maintaining a near constant pH

Question 30

what are the most important buffer systems in the body

Answer 30

1. the bicarbonate/carbonic acid system
2. organic phosphates
3. proteins