Biochemistry for nurses

1. Biochemistry for nurses
Acid-Base Regulation
 The regulation of acid-base balance is concerning the proper balance
between chemical acids and bases in the extracellular fluids (which includes
the blood plasma). Acid-Base regulation is also called Body Ph
 The body is very sensitive to its extracellular pH level otherwise outside the
acceptable range of pH, proteins are denatured and digested, enzymes lose
their ability to function, and death may occur.
 The body's acid–base balance is normally tightly regulated by buffering
agents, the respiratory system, and the renal system, keeping the blood pH
between 7.35 and 7.45.
 Nurses require a good knowledge of the normal body mechanisms which
regulate the Acid-Base balance because many ill patients have damaged
respiratory, renal and/or metabolic functions.

2. Biochemistry for nurses
Definitions
Acid: Acid is a substance which can donate a H+ or dissociate a H+
 Base: Base is a substance which can accept a H+
Water (H2O) can be an acid or a base in same time
2 H2O H3O+ + OH-
Acid/Base pair:
 HCl / Cl-
 NH4
+ / NH3
 H2O / OH-
 H3O+ / H2O

3. Biochemistry for nurses
pH: The term pH refers to the concentration of hydrogen ions (H+).
pH [H3O+]
[H3O+]pH
pH= - log [H3O+]
In water, the hydrogen ion (H+) is never free but always combined to
H2O to form H3O+
[H3O+] = [H+]

4. Biochemistry for nurses
 Buffer: Buffer is a mixture of weak acids and their conjugate bases.
The buffer has the ability to oppose changes (stabilize)
in pH when acid or base are added to a solution.
As example: Buffer in Saliva HCO3
- + H+
(conjugate base)
H2CO3
(weak acid)
 Bicarbonate (HCO3
- )/Carbonic acid (H2CO3) acid buffer system
 Salivary pH= 5.6 to 7.9
 Below pH= 5.5 demineralization occurs (destruction of the tooth enamel)
 Carbonic anhydrase is present in saliva
 After diet, bacteria produce lactic acid which increases [H+] (pH decreases)
and attack teeth by producing caries (cavities).

5. Biochemistry for nurses
Human blood pH is 7.4
 In normal conditions, blood pH is between 7.35 and 7.45.
 To maintain constant the blood pH, two organs play an essential role:
1) LUNGS: breathing in removing carbon dioxide (CO2) has an effect on the
blood pH
2) KIDNEYS: eliminating protons (H+) and retaining bicarbonate (HCO3
-) has
an effect on the blood pH
Kidneys and Lungs contribute to the maintenance of acid-base balance of the body,
but for various reasons, this balance can be broken (ACIDOSIS and ALKALOSIS).

6. Biochemistry for nurses
 An increased acidity in the blood and the other
tissues.
 The blood pH decreases below 7.35
 MAJOR CAUSES:
 Diabete 1 (accumulation of ketoacids)
 Prolonged fasting (ketosis)
 Overdose of drugs and substances such as alcohols
and aspirin
 Lactic acidosis (accumulation of lactic acid as occurs
as a result of shock or use of certain drugs)
 Severe kidney disease
 Poisons such as ethylene glycol and methanol
 Lung disorders, severe asthma, pneumonia, or
pulmonary edema
Acidosis

7. Biochemistry for nurses
 A decreased acidity in the blood and the other
tissues.
 The blood pH increase above 7.45
 MAJOR CAUSES:
 Anxiety or panic attacks
 Aspirin overdose
 Fever or infection
 Low levels of oxygen in the blood
 Loss of acid due to vomiting or drainage of the
stomach
 Overactive adrenal gland (due to Cushing syndrome
(excess secretion of cortisol) and some adrenal
tumors)
 Use of diuretics which increase production of urine
(for example, thiazides, furosemide, ethacrynic acid)
for treatment of high blood pressure, heart failure…
Alkalosis

8. Biochemistry for nurses
Response to metabolic acidosis
Interactions among the carbonic
acid/bicarbonate buffer system
and compensatory mechanisms
in the regulation of plasma pH

9. Biochemistry for nurses
Response to metabolic alkalosis
 Pulmonary ventilation is slow and shallow
allowing carbon dioxide to accumulate in
the blood
 Kidneys generate H+ and eliminate
bicarbonate from the body by urine