Acids, Bases, and Buffers

Question 1

Law of mass action

Answer 1

A + B –> C + D
Vf= kf[A][B]
Vr=kr[C][D]

keq= products/ reactants

Question 2

Keq

Answer 2

Keq = kf/kr = [C][D]/ [A][B]

Products/reactants.
Measures position of the equilibrum.

Question 3

Acid

Answer 3

Likes to give away protons

Question 4

pH of ECF

Answer 4

7.4

Question 5

pH of ICF

Answer 5

6.9

Question 6

Neutral solution

Answer 6

[H+]=[OH-]

ph=pOH=7

Question 7

Arterial and Venous blood pH

Gastric juice

Answer 7

Arterial: 7.34-7.44
Venous: 7.28-7.42
gastric: 1.4-3.0

Question 8

Equilibrium between acid and its conjugate base in aqueuous sol’n

Answer 8

HA + H20 –> H30+ + A-

HA –> H+ + A-

Question 9

Strong vs weak acids/bases

Answer 9

Strong are completely dissociated in water, weak are reversibly protonated/deprotonated

Question 10

pKa

Answer 10

How strong is your acid/base?
Measure of how much you like to give away/accept protons
low pka= strong acid. High pka= strong base.
pka= -log10Ka

Question 11

Henderson-Hasselbach

Answer 11

ph= pka + log([proton acceptor]/[proton donor])

[A-]/[HA]

or ph = pka + log([acid]/[base])

Question 12

Medically important weak acids

Answer 12

H2Co3
H2Po4

Histidine is important regulator of pH (often is changed)
Diabetics, acetoacedic acid.

Question 13

Medically important weak bases

Answer 13

Purines, pyrimidines

Amphetamines, AZT, loca anesthetics.

Question 14

Lidocaine

Answer 14

weak base. In more alkaline ECF it is uncharged and freely diffuse, and when it gets to more acidic ICF it gets protonated and charged so it’s trapped in ICF and can have effects.

Question 15

Bacteria in the stomach

Answer 15

How does it survive low ph? it creates local enviro that is neutral pH. Produces urease to change urea to bicarb and ammonia ions (neutralizes HCl acid locally on surface of mucosa and bacteria can live).

Question 16

Aspirin

Answer 16

Take aspirin with pka 3.5, at low pH predominantly protonated and gets absorbed.. lower down in duodenum where pH is higher aspirin is in dissociated neg charged state and is absorbed by a diff. mechanism (antacids can raise pH of stomach and affect drug absorption of weak acids/bases)

Question 17

ph= pka when?

Answer 17

The acid or base is 50% dissociated and conc of A- =HA

Question 18

AH + B –> A- +BH+

Answer 18

AH is acid, A- is conjugate base

BH+ is conjucate acid

Question 19

Ka

Answer 19

Ka = (h30+)(A-)/ (AH)

AH + H20 –> A- + H30=

Question 20

ph

Answer 20

Ph= pka - log (AH/ A-)

Question 21

ph > pka

Answer 21

acid exists as A- in H2-, and is fairly soluble

Question 22

ph < pka

Answer 22

acid is HA is water and is LESS soluble. (vice versa for a base).

Question 23

Titration Curve

Answer 23

Effective buffering occurs in range from [A-] / [HA] = 0.1 to 10 or w/in 1 ph on either side of Pka
Henderson-hasselbach determines shape of this. when ph=pka slope flattens (don’t get large effect on changing conc of bicarb or Co2)

Question 24

When pH changes by 0.3 units

Answer 24

The H ion concentration doubles from 40 to 80

Question 25

Respiratory acidosis

Answer 25

High pC02 (have increased Co2, compensate by increasing Hco3- absorption).

Question 26

Buffer

Answer 26

A mixture of weak acid HA and its conjugate base A-

Question 27

Bicarbonate buffer system

Answer 27

H+ + HCO3- --> H2Co3 --> H20 + CO2 (d) --> Co2 (g) First parts are aqueous phase in blood, last is air phase in lung. Open system. Conc of carbonic acid determined by amount of CO2 dissolved in blood (regulated by breathing). Co2 regulated at other end by selective retention/secretion of bicarbonate by the kidney.

Question 28

Memorize Normal Concentrations

Answer 28

pCo2= 40mmHg [HCO3-] = 24mM [CO2]= 1.2 mM Blood pH = 7.4 Kidney and lung regulate this (kidney excretes H/Hco3-)

Question 29

Memorize this equation

Answer 29

pH= 6.1 + log[HCO3-] / 0.3*PCo2 Normal: ph = 6.1 + log24/0.3*40 ph= 7.4

Question 30

Effect of Co2 levels

Answer 30

High levels Co2, make more acidic, respiratory acidosis | Low levels of CO2 more basic, respiratory alkalosis.

Question 31

Effect of carbonic acid levels

Answer 31

Low carbonic acid level, lower pH, metabolic alkalosis | High carbonic acid levels, metabolic acidosis.