Weak Acids and Bases

Question 1

Conjugate acids and bases

Answer 1

Weak acids and bases partially dissociate in aqueous solution and there is an equilibrium between protonated and deprotonated forms. Protonated, can donate an H+ to solution (conjugate acid). The deprotonated form (can bind to H+ and lower the h+ in solution) is conjugate base.

Question 2

a in Ka

Answer 2

acid dissociation

Question 3

equilibrium constant

Answer 3

ratio of products divided by reactnats

Question 4

large Ka

Answer 4

strong net dissociation producing lots of H+ and a large numerator

strong acids

Question 5

small Ka

Answer 5

weak net dissociation

Question 6

Which way will a reaction lie?

Answer 6

lies further to the right (more dissociation)

Question 7

Anion exchange chromatography

Answer 7

Laboratory procedure for separating molecules having different net negative charges.

Column contains functional groups which are positive and binds negative anions. A mixture of biological anions are loaded on top of column where they are bound by positively charged resin. The column rinsed with NaCl solution. The Cl- starts binding to column competing with the biological anions for the positive sites on resin. The Cl- anion and biological anion EXCHANGE positions. Cl- sticks to the column and biological molecules re enters the solution. The most weakly bound biological anion, having the smallest net negative charge will be completed with dilute Cl- and will exit first from column. The most strongly bound biological anion having the largest negative charge will require high competing Cl- to loosen up from column. THE MOST NEGATIVE CHARGED BIOLOGICAL ANION ELUTES LAST.

Question 8

Three ionized atoms

Answer 8

N+, O- and S-
Positive N has four electrons
Neutral O or S has 6 electrons but with a negative has seven electrons

Question 9

Henderson Hasselbach relationship

Answer 9

pKa=log(protonated/deportonated) + pH

when pKa=pH, 0=log(protonated/deprotonated) which means protonated/deprotonated equals to one. The midpoint of this curve where 50% of each form will be is pH=pKa.

Question 10

Use of Henderson Hasselbach

Answer 10

when solution at low pH (lower than pKa) then pKa-pH is a positive quantity and numerator>denominator.

Question 11

What is an equivalent

Answer 11

One equivalent of NaOH is the amount of NaOH that is needed to completely titrate one functional group on the organic molecule (to cause one H+ ion to dissociate).

Question 12

Buffers

Answer 12

a solution containing a mixture of protonated and deprotonated forms of a weak acid or base

good buffering means a large change in amount of strong base/acid added (delta X) accompanied by small change in pH (delta y) 
              small slope (delta y/deltax) good buffer: having almsot horizontal line and maintain reactions at a relatively constant pH

half the buffer in the protonated (CH3-COOH) form is capable of neutralizing incoming OH- and half is in the deprotonated (CH3-COO-) form capable of neutralizing incoming H+

Question 13

Titration curve of glycine

Answer 13

low pH form at the extreme left side is fully protonated form. The fully protonated forms of amino and carboxyl groups are NH3+ and COOH so net charge is +1 at low pH.

Deprotonated form includes neutral NH2 and deprotonated COO- net charge -1 at high pH.

Question 14

Isoelectric point pI of glycine

Answer 14

pH where net charge on molecule is zero (positive charges equal negative charges)

structure in the middle is COO- NH3+

Question 15

CO2 effect on pH of blood

Answer 15

When CO2 dissolves in water, it combines with H2O to form carbonic acid (h2co3) which dissociates into bicarbonate (hco3-) and H+. Any process that adds/removes CO2 to system causes a shift in equilibrium.

Question 16

Effect of CO2 in lungs

Answer 16

CO2 is exhaled into atmosphere. Depletion of CO2 causes the reaction to shift towards repelenishing loss of CO2 and lowers the amount of acid, increasing the pH slightly. (7.4)

Question 17

Effect of CO2 in muscles

Answer 17

in muscles, metabolism converts glucose (c6h12o6) into co2 and h20. Excess co2 is added to the blood in muscles. Adding co2 to the right of the diagram causes a shift in the series of reaction towards the other end. Increasing CO2 will be to increase H+ lowering pH of blood in muscles.

Question 18

Hemoglobin CO2

Answer 18

Changes in pH influence the hcarge on a titratable NH+ group in hemoglobin. That group has pKa of 7 and turning the psotiive charge of this group on and off affects its attraction to a negative COO- nearby in the protein and causes structural changes which affect the ability of hemoglobin to bind oxygen.

Question 19

Structures of AMP, ADP, ATP

Answer 19

AMP: adenosine mono phosphate
ADP: adenosine di phosphate
ATP: adenosine tri phosphate

Different phosphorylates forms of adenosine

Question 20

Ion exchange purification of adenosine derivatives

Answer 20

Neutral adenosine eluts first after a low salt buffer has been used to rinse the column. Highly negative ATP ELUTES last when nigh salt buffer is passed through.

Order of elution of adenosine AMP ADP ATP is in the order of their net negative charge because the more negative molecules bind more tightly to the positive column and require higher concentrations of negative Cl- to compete with them for the positive sites on column