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Week/Lecture 5: Acids and Bases.pdf

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BIOL 171

Acids and Bases pH the measure of acidity physiologic pH: 7.35-7.45 Acid: dissociates to form H+ ion; a compound (electrolyte) that ionizes in water and releases hydrogen ions (H+); a proton donor Base: a compound that binds H+ (usually forms in water); a proton acceptor Strong vs. Weak Strong Acids: HCl---> H+ Cl - stays in ionic form; lots of H+ ions Weak Acid: H C2 --3>H+ HCO - 3 stays associated; few H+ ions Strong Base: NaOH--->Na+ OH - fully ionic; completely dissociates in water Weak Base: NaHCO ---3Na+ HCO - 3 do not fully dissociate Sources of H+ cellular metabolism of carbohydrates, proteins and fats 2 types of acids produced: volatile acid carbonic acid (H CO ) 2 3 easily becomes a gas results from combination of CO 2ith H O2 eliminated via lungs as CO 2 acid dissociates into H+ and HCO -3 reassociates into H2CO ,3then turns into gas CO 2 non-volatile (metabolic) acids kidney metabolizes acids, and sends them out through urine phosphoric and sulphuric acid (from protein metabolism) lactic acid (from anaerobic metabolism) leto acids (from protein and lipid metabolism) Regulation of Acid-Base Balance homeostasis of H+ concentration is necessary for normal cellular function 3 major mechanisms to regulate pH Buffers (immediate) substance that control H+ concentration by absorbing H+ from acids and releasing H+ to bases found in body fluids prevent rapid, drastic changes in pH consist of a weak acid and the salt of that acid convert strong acids to weaker acids and strong bases to weaker bases 3 major buffer systems protein slight negative charge, so absorb H+ phosphate absorb some H+ carbonic acid-bicarbonate CO2 + H2O H2CO3 H+ +HCO3- most important buffer in ECF because it can be regulated by both the lungs and the kidneys acts in ECF and ICF (everywhere in body) function: strong acids are neutralized by bicarbonate resulting in more carbonic acid produced ex: hydrochloric acid HCl + NaHCO --3H CO2+ Na3l strong acid buffer weak acid salt strong bases are neutralized by carbonic acid resulting in more bicarbonate being produced ex: sodium hydroxide NaOH + H C2 -->3NaHCO + H O3 2 strong base buffer weak base water mixture of carbonic acid and sodium bicarbonate in ratio of 1:20 maintains blood pH at 7.40 The Respiratory System Exhale CO (2ver secs-mins) blood pH modified by eliminating CO 2rom the blood blood pH modified by changing rate, depth of breathing increased breathing rate/depth results in increased blood pH decreased breathing rate/depth results in decreased blood pH The Kidneys Excrete H+ (over mins-hrs) metabolic reactions produce nonvolatile acids at rate of 1mEq/L of H+ per day, per Kg body weight kidneys also control pH by synthesizing new bicarbonate and reclaim filtered bicarbonate renal failure can result in rapid death Acid-Base Imbalances Acidosis: blood pH <7 abnormal increase in H+ in the body due to accumulation of acid or loss of base results in…. depression of CNS ---> coma, death Alkalosis: blood pH >7 abnormal decrease in H+ in the body due to accumulation of base or loss of acid results in …. excitability of nervous tissue ---> spasms, tetanus, convulsions, death Acidosis and alkalosis can be either respiratory or metabolic in origin. If the cause is not respiratory, it is metabolic. Respiratory Di
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