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108 Unit 2

Acid-Base Physiology

Hydrogen Ion Activity -efficient biochemical and enzymatic processes demand an exacting cellular environment -Free [H+] is measuered in plasma
Hydrogen Ions -among most important factors in the cellular environment -affect all physical and biochemical cellular phenomena -increases acidic value of solution
pH stands for -Power of hydrogen -Potential Hydrogen -Logarithmic value of the reciprocal of the [H+] -4 x 10^8 moler per liter (.00000004)
Ways to Express pH - - log (4 x 10^8) or (0.00000004) - -(-7.3979) - 7.40 (normal)
3 Descriptions of pH - [H+] -Negative log of the [H+] -Log of the reciprocal of the [H+] or inversely proportional to the [H+]
Components that affect the pH -Respiratory Component (PCO2) -Metabolic Component (HCO3-/Bicarb)
Respiratory Component (PCO2) -acid -pCO2 has an inverse affect on pH -increased pCO2 increases the acidic value of a solution [H+]
Metabolic Component (HCO3-/Bicarb) -base -HCO3- has a direct affect on pH -increased HCO3- increases alkalotic (basic) value of solution [H+] -HCO3- wants to bind to hydrogen so it eliminates free floating H+
Acids donate hydrogen ions (protons)
Bases accept hydrogen ions (protons)
Metabolism Aggregate of all chemical processes that result in: -growth -energy production -elimination of waste -other bodily functions as they relate to the distribution of nutrients in th blood after digestion
Two phases of Metabolism -Catabolism -Anabolism
Catabolism -destructive phase -larger molecules are converted to smaller molecules -decomposition reactions -breaks down nutrients -produces energy (exergonic)
Anabolism -constructive phase -smaller molecules are converted to larger molecules (synthesis) -growth and repair -consumes energy (endergonic)
What does Metabolic Rate Determine? -quantity of CO2 produced and enters the blood
What does Lung Function Determine? -quantity of CO2 excreted from the blood
Sources of Energy -Carbohydrate Metabolism: Main source of energy -Lipid/Fate Metabolism: used if carb metabolism is deficient -Protein Metabolism: "last resort energy"
Carbohydrate Metabolism -final products of digestion include glucose, fructose, and galactose
Glucose -95% of blood sugars produced -stored as glycogen or fat -converted back to glucose as needed -carried through cell membranes by proteins that are aided by insulin
Glycolysis -metabolic pathway that converts glucose to energy -aerobic metabolism -anaerobic metabolism -CO2 is a waste product
Aerobic Metabolism yields what? -pyruvic acid
What does Anaerobic Metabolism yield? -lactic acid
Incomplete oxidation of Carbohydrates -can be caused by stress & Exercise -both aerobic and anaerobic metabolism yield ATP and H+ -H+ are used in oxidative phosphorylation to produce more HTP
What can reverse Incomplete Oxidation of Carbohydrates? -increased O2 -Decreased activity -Decreased metabolism
Iipids(fats) Metabolism -fats are stored or used as energy for the body -if carbohydrate metabolism is deficient, more fat will be used -Acetoacetic Acid (typd of keto acid) is waste product
Protein Metabolism -O2 transport -Enzyme function -Aid in muscle contraction -catabolized into amino acids -used as a last resort for energy -NH3 (ammonia) is a key waste product
Respiratory Quotient (RQ) CO2 produced/O2 consumed -80% is normal
What accounts for nearly all the O2 consumption of the body? -Oxidation of carbohydrates and fats -major sources of energy for the body
Metabolism of Carbohydrates RQ -1 mole O2 consumed -1 mole CO2 produced -RQ = 100%
Metabolism of Fats RQ -1 mole of O2 consumed -0.7 moles CO2 produced -RQ = 70%
Metabolism of Proteins RQ -1 mole of O2 consumed -0.7 moles of CO2 produced -RQ = 70%
Where is CO2 carried? -plasma 5% -RBC 95%
Plasma CO2 -dissolved CO2 accounts for most CO2 carried in plasma -0.1% reacts with water for form H2CO3 (hydrolysis or hydration) -difficult to distinguish between dCO2 and H2CO3
Plasma CO2 Hydrolysis equation -very slow -carbonic anydrase (enzyme) is not present
Total dCO2 plasma PCO2 x 0.003
Solubility coefficient of CO2 0.003
Total dCO2 -value used to represent H2CO3 in Henderson-Hasselbach equation
Dissolved CO2 accounts for 8% of total CO2 released in the lungs
CO2 Transport in the RBC -80% of CO2 is transported as bicarbonate (HCO3-) -hydrolysis occurs very rapidly due to carbonic anhydrase -12% of CO2 chemically combines with amino acids contained within the hemoglobin forming carbaminohemoglobin -This process produces H+
The relationship between CO2 and hemaglobin -CO2 has a higher affinity for Hemoglobin and kicks the hydrogen off which increases the content of H+ in the blood and decreases pH
Chloride Shift -HCO3 diffuses into plasma due to concentration gradient between RBC and plasma -CL ions enter RBC to maintain electroneutrality
CO2 and Metabolism -Metabolic rate determines CO2 production -PaCO2 changes with rate of CO2 production when alveolar ventilation is constant
CO2 Elimination -Ventilation determines rate of CO2 Elimination -Hyperventilation: high rate and/or volume -Hypoventilation: low rate and/or volume
How long does it take pH to adjust in the Respiratory System? 1-3 minutes change in rate and/or volume breathing
Ventilation and Acid-Base Physiology PCO2 = 1/Alveolar ventilation
Hemoglobin -oxygen carrying protein in the RBC -each molecule contains 4 molecules of Fe+ -each Fe+ molecule can reversibly bind to 1 molecule of O2 -Major buffer due to reversible binding with H+ -also binds with CO2
Bohr Effect -Right shift in Curve -Decreased Hb affinity for oxygen -increase H+ -decrease pH -increase CO2 -Increase Temp -Increase 2-3 DPG -O2 becomes more available and is released into tissue cells
Hb in Bohr Effect -more capable of binding H+ to amio acids in Hb -slightly alters structure of Hb -Decreases ability of Hb to carry O2 -Increases blood's ability to carry CO2
Haldene Effect -addition of O2 to the blood enhances CO2 release from Hb -Left Shift in Curve -Increases Hb affinity for oxygen -decrease H+ -Decrease CO2 -Decrease Temp -Decrease 2-3 DPG
Metabolic Acid-Base Physiology -regulated by kidneys -controls excess of H+ or HCO3 through buffers
Kidneys -HCO3- is reabsorbed into the blood -H+ is excreted into urine -total amount of hydrogen ions excreted are significant to metabolic acid-base balance -cannot produce urine with a pH below 4.4
How often does Free H+ urinary acid secretion occur? less than 1% of the time
What accounts for excretion of most nonvolatile acids? phosphate and ammonium urinary buffers
Carbonic anhydrase in Renal Tubular cells -H2CO3 is rapidly dissociated into H+ and HCO3- -HCO3- must react with H+ before it can be reabsorbed as CO2
Renal Correction of Acidosis -excess H+ is excreted in urine -HCO3- binds with Na+ to form NaHCO3 -NaHCO3 is then reabsorbed into the blood
Renal Correction of Alkalosis -excess of HCO3- relative to H+ -HCO3- cannot be reabsorbed without reacting with H+ -Excess HCO3- is excreted in urine
Buffering Systems -prevents drastic changes in pH of a body fluid -converts strong acids and bases into weak acids and bases
Significant deviation from normal pH range -poorly tolerated -May be life threatening
Chemical Equilibrium -Rate of reaction of a substance in one direction is equal to the rate of reaction in the opposite direction
Isohydric Principle -any condition tha causes [H+] to change causes balance of all buffer systems to change at the same time -buffer systems buffer each other -any condition that chanegs balance of any one of the buffer systems also changes balance of all the others
Major Buffering Systems -Hb -Kidneys
Types of Buffer Systems -RBC -HCO3- -Phosphate (HPO4) -Ammonia (NH3-)
RBC Buffering -Carried out by Hb -Hb binds reversibly with H+
HCO3- Bicarb Buffer -found in plasma, RBCs, renal tubules -HCO3- binds with H+ forming H2CO3 -H2CO3 is then converted to CO2 and H20
Phosphate (HPO4) Buffer -renal buffer -sodium phosphate (Na2HPO4) is highly concentrated in tubular fluid -excess H+ takes the place of Na+ to form NaH2PO4) (sodicum acid phosphate) -NaH2PO4 is excreted in urine -Freed Na+ binds with HCO3- and is reabsorbed as NaHCO3
Ammonia (NH3-) Buffer -NH3- is located in tubular fluid -excess H+ binds wtih NH3- and a CL- ion to form NH4CL (ammonia chloride) -NH4CL is excreted in urine -HCO3- binds with Na+ and is reabsorbed
Created by: Mdarrielle09