test 7 body fluids and systems regulating H+ concentration

Question 1

[H+] and pH of the venous blood and interstitial fluid

Answer 1

• They are the exact same
  [H+]: 4.5 x 10^-5
  pH: 7.35

Question 2

Intracellular fluid [H+] and pH

Answer 2

• Higher [H+] (because of metabolic wastes

- lower pH

Question 3

Normal pH:
Acidosis pH:
Alkalosis pH:
Lowest limit for life:
Highest limit for life:

Answer 3

Normal pH: 7.35 - 7.45
Acidosis pH: anything less than 7.35
Alkalosis pH: anything more than 7.45
Lowest limit for life: 6.8 (Patient can live for several hours)
Highest limit for life: 8.0 (Patient can live for several hours)

Question 4

Systems regulating H+ concentration

Answer 4

1. Chemical acid-base buffers of body fluids
   • Do not eliminate H+ – Keep them tied up until balance re-established
   • Immediate
2. Respiratory center
   • Regulates the removal of CO2
   • Acts within minutes
3. Kidneys
   • Eliminate excess acid or base from the body
   • Several hours to days

Question 5

Buffering in body fluids

Answer 5

• Buffer: any substance that can reversibly bind H+
  1. Bicarbonate buffer system (role = extracellular)
  2. Phosphate buffer system (role = extracellular and intracellular)
  3. Proteins as buffers (role = intracellular)
• If one changes, they all change since they are in equilibrium

Question 6

bicarbonate buffer system

Answer 6

• 2 components
  - A weak acid: H2CO3
  - A bicarbonate salt: NaHCO3
• Carbonic anhydrase (enzyme) helps convert back and forth in the reaction

Question 7

Carbonic anhydrase abundant in

Answer 7

• Red blood cells
• Walls of lung alveoli
• Epithelial cells of renal tubules

Question 8

Addition of a strong acid (HCl) to the bicarbonate buffer system

Answer 8

• Increased H+ released from the acid is buffered by H2CO3
• Pushes equation toward CO2 + H2O
  • More carbonic acid formation causes increased CO2 and water
  production
  • The excess CO2
  greatly stimulates respiration, which eliminates CO2 from the ECF

Question 9

Addition of a strong base (NaOH) to the bicarbonate buffer system

Answer 9

• increases [bicarb] (The OH- combines with carbonic acid to form additional HCO3-)
• [H+] decreases as you add the base
  • More CO2
  combines with water to replace the carbonic acid
  • The decreased CO2
  inhibits respiration and decreases the rate of CO2 expiration
  • The rise in blood HCO3-
  is compensated for by increased renal excretion of HCO3-

Question 10

Hendrson-Hasselbalch equation

Answer 10

pH = pK + log ( [base] / [acid])
OR
pH = pK + log ([HCO3-] / pCO2dissolved)
OR
pH = pK + log ([HCO3-] / (0.0301)(pCO2))
- as pCO2 increases => amount of acid increases because amount that is being dissolved increases
- pK = equilibrium constant for the equation
- pH where concentration of acid equals concentration of base
- Measure of the strength of the acid / base
- Changes as the temperature of the solution changes
- as temperature increases => dissociates => increase [H+] => pK decreases

Question 11

pK for bicarbonate buffer system @ 37 degrees

Answer 11

6.1

Question 12

Phosphate buffer system

Answer 12

• Hydrogen phosphate accepts hydrogen ions
• Dihydrogen phosphate releases hydrogen ions
• Tubular fluid (phosphate major in kidneys) & Intracellular fluid
  - Very small concentration in extracellular fluid

Question 13

pK for phosphate buffer system @ 37 degrees

Answer 13

6.8

Question 14

Proteins as buffers

Answer 14

• Play an important role because they are plentiful in the body
  - Especially within the cells-RBCs and amino acids
  - 60-70% of total chemical buffering of body fluids is within cells