Buffers

Question 1

What are buffers?

Answer 1

Mixed of a weak acid and its conjugate base or a weak base and its conjugate acid

Question 2

What is the purpose of a buffer?

Answer 2

Resist change in pH when strong acids or bases are added in limited quantity

Question 3

Buffer Capacity

Answer 3

Limit to the amount of acid/base that can be added before the buffer loses its ability to resist change

Question 4

Chemical perspective buffer capacity

Answer 4

Withstand change of +/- 1

Question 5

T/F: Buffers are important for a variety of chemical and biological processes that must occur in a controlled pH range.

Answer 5

TRUE

Question 6

How is blood pH controlled?

Answer 6

Buffer system in combination with respiratory & renal system

Question 7

3 Main buffer systems

Answer 7

Bicarbonate
Phosphate
Protein buffer

Question 8

How does the respiratory system impact the buffer system?

Answer 8

Impacts carbonic acid to control CO2 levels

Question 9

How does the renal system impact the buffer system?

Answer 9

Works to remove H ions through kidneys

Question 10

IF you have a weak acid present and add more acid which way will equilibrium move?

Answer 10

Towards the reactant

Question 11

If you have a weak acid and add a base which way will equilibrium move?

Answer 11

Towards the product

Question 12

If you have a weak base and add an acid which way will equilibrium move?

Answer 12

Move to the product side

Question 13

If you have a weak base and add another base which way will equilibrium move?

Answer 13

Towards the reactant

Question 14

If a drug is highly ionized will it mass through a cell membrane?

Answer 14

Most likely NOT

Question 15

T/F: Charge of a drug is controlled by BOTH the pH of the solution and the pKa of the drug

Answer 15

TRUE

Question 16

What happens to the equilibrium when an unionized portion of the drug crosses the membrane?

Answer 16

Will produce more of the unionized drug (varies on how fast it will happen)

Question 17

The Henderson Hasselbalch equation can be used to ..?

Answer 17

Determine the amounts of charged species at a particular pH

Question 18

Drug absorption via passive diffusion is directly related to the amount of ?

Answer 18

Ionized : unionized drug

Question 19

Local anesthetics are weak bases so they are closer to physiological pH. Will they exist in which the ionized or unionized form more?

Answer 19

More in lipid soluble unionized form = better cross axonal membrane

Question 20

Extracellular Blood Buffers

Answer 20

Bicarb/ Carbonic Acid
Plasma Proteins (albumin)

Question 21

Intracellular Blood Buffers

Answer 21

Hemoglobin
Phosphate

Question 22

What system alters the pH the fastest? Buffer, Renal or Resp system?

Answer 22

Buffer system- Very Rapid (seconds)

Resp- rapid (minutes)

Renal- Slow (hours to days, but more effective then respiratory)

Question 23

Bicarb Buffer system

Answer 23

> 50% of extraceullar buffering
CO2 regulated by lungs
HCO3- regulated by kidneys

Not powerful

Question 24

Total Buffer capacity of serum albumin?

Answer 24

2.3 mEq/L

Question 25

Buffer capacity of carbonic acid/bicarb?

Answer 25

2.5 mEq/L

Question 26

Total buffer capacity of phosphates?

Answer 26

2.8 mEq/L

Question 27

Total buffer capacity of hemoglobin

Answer 27

17.5 (HbO2)/ 19.2 (Hb) Largest capacity to buffer

Question 28

Unassigned buffer capacity

Answer 28

5-10 mEq/L

Question 29

Protein Buffer system

Answer 29

75% of all intracellular buffering Varies w oxygenation (hemoglobin) MOST POWERFUL

Question 30

Phosphate Buffer System

Answer 30

H2PO4- & HPO4(2-) Important renal buffering Not powerful

Question 31

Answer 31

IN plasma 1) CO2 produced by aerobic metabolism 2) Diffuses into RBC mix H2O= H2CO3 3) Equilibrium forms HCO3- and H+ 4) HCO3 leaves plasma goes to lungs; Cl- comes in due to (-) in plasma since HCO3 left 5) H+ binds to oxygenated hemoglobin= loses O2 IN LUNGS 1) H+ now with deoxygenated hemoglobin= taken to lungs 2) Inhaled O2 binds to hemoglobin; H+ falls off 3) H+ mix w H2O= H2CO3 4) Broken down to CO2 5) Exhaled out

Question 32

Is the resp buffer a complete response to pH changes?

Answer 32

No; incomplete because change in alveolar ventilation brings pH back to normal -------then stimulus response for change in ventilation decreases

Question 33

Renal Response to Acidosis

Answer 33

Rate of H+ secretion > HCO3 filtration

Question 34

Renal Response- Alkalosis

Answer 34

Rate of HCO3 filtration > H+ secretion

Question 35

Answer 35