Basic of Acid Base

Question 1

Types of Acids

Volatile
Fixed
Organic

Answer 1

Endogenous:
- Respiration: H2CO3 (Volatile)
- Phospholipids: H3PO4 (Fixed)
- Anino Acids: H2SO4 (Fixed)
- Exercise: Lactic Acid (Organic)
- Diabetes: Acetoacetic acid (Organic)

Exogenous:
- Drugs: Acetylsalicylic acids
- Toxins:
– Methanol (formic acid)
– Ethylene Glycol (oxalic acid)

CO2 + H2O = H2CO3 = H(+) + HCO3(-)

Question 2

Henderson-Hasselbach Equation

Answer 2

pH = pK + log (anion/acid)
pH = pK+ log (HCO3-/H2CO3)
HCO3- = 24mEq/L
H2CO3= 1.2 (pCO2 & solubility of CO2)

Normal (Base/Acid)=20/1
Control:
- Base: Renal
- Acid: Respiratory (lung)

Question 3

Acid-Balance Disturbance

Answer 3

Ratio Shift to 16/1.2 then pH = 7.2
- Uncompensated Acidosis

Ration return to 20/1 (Value still abnormal)
- Compensation

Values return to normal (24/1.2)
- Correction

Question 4

Uncompensated Acidosis

Answer 4

Ratio Shift to 16/1.2 then pH = 7.2

Question 5

Compensation

Acid-Base disturbance

Answer 5

Ration return to 20/1 (Value still abnormal)

Question 6

Correction

Acid Base Disturbance

Answer 6

Values return to normal (24/1.2)

Question 7

Mechanism to Control Acid-Base

Answer 7

Minutes:
- Intracellular Buffering
- Extracellular Buffering

Minutes to Hours:
- Respiratory Compensation (related to acid)

Hours to Days:
- Renal Compensation

Question 8

Intracellular Buffering

Answer 8

Protein: albumin, globulin
Phosphate (Occur quickly kidney and bones)
- Minutes

Question 9

Extracellular Buffering

Answer 9

Bicarbonate
Ammonia
Proteins
- Minutes

Question 10

Respiratory Compensation

Answer 10

Alter CO2 excretion
- Minutes to Hours

Question 11

Renal Compensation

Answer 11

Generate HCO3-
Alter H+ secretion
Ammonium
- Hours to Days

Question 12

Instantaneous Buffering System

Answer 12

Bicarbonate: H(+) + HCO3(-) = H2O + CO2
Hemoglobin: HHb = H(+) +Hb(-)
Phosphate: H2PO4 = H(+) + HPO4-
Plasma Protein: HPr = H(+) + Pr (-)

Ex. RNH3+ = RNH2 + H+
- pH=pK(RNH3) + log ((RNH2)/(RNH3+))

Question 13

Hemoglobin

Answer 13

Buffer in Blood
- After releasing O2 to peripheral tissues => binds to CO2 and H+ (NH+)
– As blood reaches the lung it releases CO2 & H+
— H+ and HCO3- ions form carbonic acid

Question 14

Where CO2 is found

Answer 14

23% wil be attached to Hemoglobin
7% dissolved in plasma
70% in Bicarbonate Ions

Question 15

Respiration

Answer 15

Second line of defense 12 to 24 hr
- H2CO3 (carbonic acid) converted to CO2 and excreted by lungs
– Cannot exhale fixed acids

Question 16

Effect of Ventilation on pH

Answer 16

When Ventilation Increase => pH increase with it
When Ventilation decrease => pH decrease with it

Question 17

Effect of pH on Ventilation

Answer 17

When pH increase => Ventilation decrease with it
When pH decrease => Ventilation increase with it

Question 18

pH and Ventilation

Answer 18

The goal is to stay consistent
- Venti Increase => pH Increase => Venti decrease => pH decrease => Venti Increase
– as you can see it’s just a cycle to keep everything in control

Question 19

Renal Compensation

Answer 19

Nephrons cannot produce urine with pH < 4.5
Mechanism for Compensation:
1) Reabsorption of HCO3- (Bicarbonate)
2) Excretion of H+
3) Excretion of ammonium ions

Occurs over hours to days

Question 20

Bicarbonate Buffering System

Proximal Tubules

Answer 20

• Na+/H+ Exchanger (Na reabsorbed with H secreted)
• Carbonic anhydrase
• Na+/K+ ATPase and HCO3- Exchanger
• 85% HCO3- Reabsorption
• High capacity, low gradient system H+ secretion (Can’t change pH much)
• Achieve urine pH = 6.7-7.0

Question 21

Bicarbonate Buffering System

Distal Tubule/Collecting Ducts

Answer 21

• H ATPase
• Carbonic Anhydrase (I Cells)
• Cl-/HCO3- Exchanger
• 5%-10% HCO3- reabsorption
• Low capacity, high gradient system for H+ secretion
• Achieve urine pH = 4.5
  – Main determinant of urinary pH

Question 22

Proximal Tubules

Bicarbonate Buffering

Answer 22

Apical membranes of tubules are IMPERMEABLE to HCO3- (bicarbonate)
- Carbonic anhydrase catalyzes formation of H2CO3 from H2O and CO2 (use bicarbonate CO2)
– As CO2 increases in filtrate, CO2 diffuses into tubule cells and form H2CO3
—H2CO3 dissociate to HCO3- and H+

H+ secretion. HCO3- & Na+ reasorption (NBCe1)

Question 23

Distal Tubule & Ducts

Bicarbonate Buffering

Answer 23

Type A Intercalated Cells
- CO2 + H2O with CAll => H2CO3
- H2CO3 => HCO3- + H+
– The H+ will get secreted with the help of an ATP
– HCO3- will get reabsorbed through AE1 ( Exchanger with HCO3-/CI-)

Question 24

Ammonium/Ammonia Buffering

Proximal Tubule Cells

Answer 24

Cleaves Glutamine in the Proximal Tubule Cells
Glu => 2NH4+ and 2HCO3-

2NH4+
- 2 NH4+ => NH4+
– Get secreted (in an exchanger with Na+)
— Binded by CI- lumen and get excreted

2 HCO3-
- 2HCO3- => 3HCO3-
– Gets reabsorbed with Na+ in a symport channel

Production and secretion of NH4+ (ammonium) in proximal tubule, thick ascending loop and distal tublule

Question 25

Ammonium/Ammonia Buffering

Type A Intercalated Cells

Answer 25

NH3 (ammonia) offer an Na+ to NHE3 for reabsorption
- This happen through NHE3 (Na+/H+ exchanger)
– The H+ rxr to NH3 => NH4+
— NH4+ bind with Cl- and gets excreted

NH3 is permeable; NH4+ is poorly permeable

Question 26

Phosphate Buffering System

Answer 26

One of the instantaneous buffers
Uses H2PO4- and HPO4-
- HCl + Na2HPO4 = NaH2PO4 + NaCl
- NaOH + NaH2PO4 = Na2HPO4 + H2O

Low concentration in blood
- Better buffer in ICF, Kidney, and bones

Question 27

Phosphate Buffering System

NaHPO4

Answer 27

Happens in Proximal Tubule
- NaHPO4- + H+ (comes from vH+ ATPase and NHE3 Na+/H+ exchanger)
- Turns into NaH2PO4
– Gets secreted

Buffering of secreted H+ with filtered phospahte