1. ACID-BASE BALANCE  AIMS:  What are acids and bases?  What is pH?  Why does pH vary?  How do you regulate pH?

2. ACIDS & BASES  Acids- release H + ions  Bases- release OH - ions  In body fluids at low concentrations  thus pH scale (1-14) to represent [H + ] and [OH - ]  pH scale  used to represent [H + ] in body,  = - log10 [H + ]  blood= 7.4  0.02  gastric acid= 1, urine= 6  pH>7 is basic, pH<7 is acidic

3. VARIATION OF pH  IMPORTANCE  Death if pH remains 8 for less than a day  Metabolic enzymes stop working, depression of CNS  Changes in pH  due mainly to [ H + ] produced by the body  Acid production- H 2 CO 3, H 2 PO 4, H 2 SO 4, Lactic, Pyruvic acids  Vomiting, diarrhoea, dehydration

4. REGULATION OF ACID BASE  DIRECT BUFFERING IN BLOOD  seconds  proteins, phosphates, Hb, HCO 3 -  INDIRECT BY LUNGS  minutes  increase or decrease breathing  INDIRECT BY KIDNEYS  slow, hours & days  excreting excess base or acid  HENDERSON-HASSELBALCH EQUATION  defines the relationship between pH and the concentration of a salt and its corresponding acid

5. CONCLUSIONS  1. Acids are substances release H + ions, Bases release OH - ions  2.pH scale (1-14) is a measure of the acidity and alkalinity  3. pH varies due to internal & external changes of acids & bases (range=7.35-7.45)  4. pH regulated by, blood buffering, lungs & kidney

7. O 2 TRANSPORT  Solubility- small (0.3 ml O 2 /100 ml blood),bound to Haemoglobin (Hb)  Hb ( heme + globin)  each Hb can bind 4 O 2  15g of Hb/100 ml blood  1.34ml O 2 /g Hb  SaO 2 = 97%  Oxygen dissociation curve  sigmoid, plateau at 100 mmHg  steep at 50 mmHg (in the tissues),thus unloading of O 2,  curve shift to the right (Bohr shift) CO 2, T, 2,3 DPG, pH  shift to left, Hb more saturated

8. CO 2 TRANSPORT  1/ PHYSICALLY DISSOLVED - (5% )  20x >soluble than O 2  2/ BICARBONATE (HCO 3 - )- 70%  Small amount produced in plasma  Maj. prod. in RBC  Requires carbonic anhydrase,  CO 2 +H 2 O H 2 CO 3 H + + HCO 3 -  Chloride shift  3/ Carbamino compounds - 5-10%; amine groups in Hb combine with CO 2  CO2 dissociation curve  Almost linear in physiological range  Haldane effect, shift to the right, easier to lose CO 2 at lungs, and release O 2 to tissues