DLA 4 Titration Of A. Acids, Blood Buffers And Affecting Charges On Biomolecules By Changes In Ph

Question 1

What is the Henderson-Hasselbach equation?

Answer 1

The HH equation defines the relationship between the pH a solution, the Ka of the acid, and the extent of acid dissociation

pH= pKa+ log[ [A] / [HA]]

Question 2

Describe amino acids in low pH

Answer 2

Both groups are protonated ( carboxy and amino)

-so there is -COOH and -NH3+ (so a +1 charge)

Question 3

Describe amino acids in a high pH

Answer 3

Both groups give away their dissociable proton(carboxyl and amino)

  -so there is COO- and -NH2(so a -1)

Question 4

What happens during the titration of alanine?

Answer 4

• If the -COOH undergoes dissociation (forms COO-) and the -NH2 group accepts a proton to form -NH3+
  
  • Then there is no overall net charge on the amino acid(-1+1=0)
  • At intermediate pH(close to neutral), alanine takes this form: zwitterions or its isoelectric form

Question 5

Describe amino acids in low pH

Answer 5

Both carboxyl and amino groups are protonated

-so there is -COOH and -NH3+ (so a +1 charge)

Question 6

Describe amino acids in High pH

Answer 6

Both groups give away their dissociable proton (carboxyl and amino)

-so there is COO- and NH2( so a -1 charge)

Question 7

How many ionizable groups exist in histidine, what are there?

Answer 7

3 groups- COOH, NH+ and NH3+

Question 8

Histidine has 3 ionizable groups, so how can pI be calculated?

Answer 8

pI= pK2 + pK3/ 2

Question 9

How much acid is produced by normal metabolism?

Answer 9

22,000 milliequivalents of acid/ day

Question 10

What is the normal pH of blood?

Answer 10

7.36-7.44

Question 11

What is the widest pH range where metabolic function can be maintained and where?

Answer 11

pH 6.8-7.8 and in the heart, liver and nerve conduction

Question 12

How are excess acid in extra cellular fluids, dealt with?

Answer 12

Excess acid in extracellular fluids needs to be buffered until it is exhaled as CO2 or excreted in urine

Question 13

Give the pH equation for the bicarbonate blood buffer

Answer 13

pH= pK1 + log[HCO3-][CO2]

Question 14

Give the pH equation, of the hydrogen phosphate buffer

Answer 14

=pK2 + log[HP4 ^-2][H2PO4-]

Question 15

Give the pH equation of the protein buffering system?

Answer 15

pH= pK3+ log[protein-]\ [Hprotein]

Question 16

Give the buffering components of extracellular fluids

Answer 16

Respiratory- lungs

Blood: plasma and red blood cells- these buffers include bicarbonate,phosphate and hemoglobin

Renal- kidney

Question 17

What are the major physiological buffers?

Answer 17

• Bicarbonate-carbonic acid= extracellular fluids, blood
• hemoglobin= red blood cells
• Phosphate buffer= most cells, urine
• Protein buffers= plasma and cells
• NH3/NH4+ =urine

Question 18

How does metabolism form buffers?

Answer 18

Normal metabolism generates acids

• Organic acids such as lactic acid/lactate and ketone bodies
• Inorganic acids(sulfric acid, hydrochloric acid)
• Carbon dioxide may react with water to form carbonic acid, which will dissociate to form bicarbonate and a proton

Question 19

What are some applications of Henderson-Hassalbach equation?

Answer 19

• Calculate how the pH of physiological fluids(plasma) is affected by changes in concentrations of weak acids/bases
• calculate abundance of ionic forms of acidic and basic molecules
• Predict change on a drug and predict patterns of absorption
  - uncharged drugs cross the intestinal lumen much more readily than charged drugs
  - the pH will be different in the stomach compared to the intestine

Question 20

Which type of drug crosses the intestinal lumen faster? Charged or uncharged?

Answer 20

Uncharged drugs cross the intestinal lumen much more readily than charged drugs