1. Acid-Base Balance: introduction

pH is a measure of?

-H+

Regulation of HCO3- and CO2 in?

-HCO3- in kidneys -CO2 in lungs...

blood pH

7.4

pH values in some body fluids: gastric juices plasma pancreatic juice

gj: H+ is .01 & pH is 2.0 p: H+ .00000004 & pH 7.4 pj: H+ .00000001 & pH 8.0

Normal pH is?

- 7.4 -we can survive from 6.8 to 7.8

The Henderson-Hasselbalch equation

- It describes the relationship between pH and the mixture of an acid and its conjugate base -Using this equation we can calculate the pH of a solution if the HCO3 concentration and PCO2 are known ↑ HCO3 -----> ↑ pH --------> alkalosis ↑ PCO2 -------> ↓ pH --------> acidosis

how are pH and H+ are related?

- inversely related -pH= -log [H+]

Then the amount of CO2 in the blood is calculated using?

-PCO2 x 0.03 umol/mm Hg (solubility coefficient for CO2) -H+ = K x (PCO2 x 0.03)/ HCO3-

all acids?

-dissociative to some extent -ex. H2CO3 dissociates to H+. And HCO3- -at pH = 6.1 ...50% in associated form and 50% not disassociated

H2CO3 come from ?

-hydration reaction -aka adding CO2 and H2O together

pH

-is a measure of the proton concentration ([H+]) in a solution and both are inversely related - as pH goes down (becomes more acidic) the higher the H+ concentration

dissociation constant K

-is used to calculate the concentration of undissociated acid (H2CO3) relative to its dissociated ions (H+ and HCO3-) -K= ([H+]xHCO3-)/ [H2CO3 ]

Two organs help maintaining the physiological pH?

-lungs and kidneys

Buffer

-substances in the body are extremelly important to maintain the physiological pH of about 7.4 (blood) which is required for normal cell function -intracellular and extracellular buffer systems

Abnormal H+ concentrations have adverse effects on the function of all organ systems

-the concentration of H+ ions in the ECF has to be maintained within narrow limits by, for instance, eliminating H+ ions from the body at the same rate at which they are added to the body (= acid-base regulation)

Hydrogen ions affect the structure of proteins, and consequently?

-the functions of enzymes, receptors, transport proteins, channels, etc.

Life depends on maintaining

1. The proper amount of body water 2. The correct proportion of water and electrolytes in the water 3. The proper acid-base balance

neutral

A solution with the same pH as pure water (pH = 7)

Co2 + H20 -CA- H2CO3 - H+ + HCO3

CA: carbonic acid CO2 is in the lungs/ respiration Proton and bicarbonate is in the kidneys

Since the [H2CO3] in solution is low and difficult to measure, another close-related molecule is used?

CO2 -is directly proportional to the amount of undissociated H2CO3

The dissociation constant K can also be arranged as?

H+ = K x (H2CO3/ HCO3-)

All acids are dissociated to some extent

HA <------> H+ + A- H2CO3 <------> H+ + HCO3-

A constant pH in the body is essential for?

cell function

Solutions with a lower pH

have a high H+ concentration

Solutions with a higher pH

have a lower H+ concentration

For bicarbonate buffer pK = 6.1, then the Henderson- Hasselbalch equation is?

pH = 6.1 + log HCO3/ (0.03 x PCO2)

The Henderson-Hasselbalch equation

pH = pKa + log([base]/ [acid])

The relationship between H+ concetration and pH is

pH=log 1/([H+]) =-log[H+] H+ concentration of the blood = 0.00000004 mol/L Therefore, Blood pH = - log [0.00000004] = 7.4