Lecture 17 -- review questions Flashcards by Jonah Chang

what is acid-base balance?

adequate levels of acid and bases in blood and body for proper cell functioning

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what is the normal pH range of the blood?

7.35-7.45

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what is a volatile acid?

acid that is produced from CO2

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what is a physiological example of a volatile acid?

carbonic acid (from CO2)

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what is a non-volatile or fixed acid?

acid that is produced form anything other than CO2

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what is a physiological example of a non-volatile or fixed acid?

lactic acid (anaerobic fermentation)

phosophoric acids (nucleic acid catabolism)

fatty acids and ketones (fat catabolism)

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what is acidosis?

blood pH below 7.4

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what is alkalosis?

blood pH above 7.4

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how is blood pH kept within a narrow range when our bodies are constantly producing acid?

buffer systems

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what buffers does the body use as a 1st line of defense in response to an increase in pH?

And as the 2nd line?

3rd line?

1st line – chemical buffers – seconds

2nd line – physiological buffer – respiratory system – min to hrs

3rd line – physiological buffer – urinary system – days to weeks

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what 2 organs play an essential role in maintaining acid-base balance? (think about physiological buffers)

lungs

kidneys

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what is a chemical buffer?

molecules that maintain pH by releasing or binding H+

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what are the 3 chemical buffer systems in the body

bicarbonate buffer system

phosphate buffer system

protein buffer system

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why is the role of chemical buffers in controlling blood pH limited?

chemical buffers guard against sudden swings in pH

don’t eliminate or add H+ to the body, only release or bind

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where is the bicarbonate buffer system more critical, in the ECF or ICF? How about the phosphate buffer system?

(tip: which anion is more abundant in the ICF?)

(phosphate is most abundant anion in ICF)

bicarbonate buffer system –> more critical in ECF

phosphate buffer system –> more critical in urine and ICF

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if the pH of a solution decreases, what happens to the concentration of H+ in the solution: increase or decrease?

pH decreases == more acidic == increased [H+]

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if the pH of a solution increases, what happens to the concentration of H+ in the solution: increase or decrease?

pH increases == more basic == decreased [H+]

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which group in a protein acts as an acid, the amino or the carboxyl group? why?

(think carboxylic acid is an acid)

carboxyl group –> COOH can become COO- and H+

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which group in a protein acts as a base, the amino or the carboxyl group? why?

amino group –> NH2 can accept a H+ to become NH3+

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when the body experiences alkalosis, how do proteins help restore the acid-base balance?

carboxyl group in amino acid releases an H+

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when the body experiences acidosis, how do proteins help restore the acid-base balance?

amino group in amino acid binds an H+

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what is the chemical formula for carbonic acid?

H2CO3

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what is the chemical formula for the bicarbonate ion?

HCO3-

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what volatile gas is carbonic acid (H2CO3) in equilibrium with?

CO2

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how is the carbonic acid created in our body?

CO2 (released from tissues) + H2O --> (carbonic anhydrase) --> H2CO3

why is CO2 elimination crucial? (which acid does it form?)

CO2 must be eliminated to form H2CO3 which can release H+

what chemical reaction is catalyzed by carbonic anhydrase?

CO2 (released from tissues) + H20 --> (carbonic anhydrase) --> H2CO3

which component acts as an acid (=H+ donor) in the carbonic acid-bicarbonate buffer system?

H2CO3 carbonic acid (weak acid)

which component acts as a base (=H+ acceptor) in the carbonic acid-bicarbonate buffer system?

HCO3- bicarbonate ion (weak conj. base)

what is the equation for the bicarbonate-carbonic acid buffering system?

CO2 + H2O --> (carbonic anhydrase) --> H2CO3 --> HCO3- + H+

suppose there is an excess of acid (H+) in the blood (=acidosis or acdiemia), and the bicarbonate ion accepts those extra H+ of the solution ("neutralize the excess of acid"). What happens to the pH of the solution, increase or decrease?

increase back to normal range (7.35-7.45)

suppose there is a deficiency of acid (H+) or excess of a base in the blood (=alkalosis or alkalemia), and the carbonic acid donates H+ to the solution (releases the H+). what happens to the pH of the solution, increase or decrease?

decrease back to normal range (7.35-7.45)

what is the way the body gets rid of volatile acid?

respiratory --> increase rate and depth of breathing --> expel CO2

what is the way the body gets rid of fixed acid?

kidneys --> increase H+ excretion by producing more bicarb (HCO3-)

which organ maintains bicarbonate levels?

kidneys

which organ maintains CO2 levels?

lungs

can the respiratory system get rid of increased fixed acids in blood?

no -- it can only directly get rid of volatile acids --> but getting rid of more CO2 helps bring H+ fixed acid levels down

why does increasing breathing rate and depth (=hyperventilation) increase pH? what happens to CO2 and H+ levels? what is the name of this disorder? (respiratory/metabolic, acidosis/alkalosis?) in which direction (to the right or the left) would the carbonic acid-bicarbonate buffer system equation move in this case?

hyperventilation == get rid of CO2 == lower H+ levels respiratory alkalosis carbonic acid-bicarbonate buffer system equation move to the left --> decrease CO2 == decrease H+

why does a decrease in breathing rate and depth decrease pH? What happens to CO2 and H+ levels? What is the name of this disorder? (respiratory/metabolic, acidosis/alkalosis?). In which direction (to the right or the left) would the carbonic acid-bicarbonate buffer system equation move in this case?

hypoventilation == more CO2 in body == higher H+ levels respiratory alkalosis carbonic acid-bicarbonate buffer system equation moves to the right --> more CO2 == more H+

reabsorption of HCO3- in the renal tubule is always tied to the secretion of which ion?

H+

what is the goal of reabsorbing H+ from the urine? (to counteract acidosis or alkalosis)

lower pH to make more acidic counteract alkalosis

what is the goal of secreting more H+ in the urine? (to counteract acidosis or alkalosis)

increase pH to make more basic counteract acidosis

what is the goal of reabsorbing more bicarbonate ions from the urine? (to counteract acidosis or alkalosis?)

reabsorb HCO3- ==> get more base secrete H+ ==> get rid of acid counteract acidosis

what is the goal of secreting bicarbonate ions in the urine? (to counteract acidosis or alkalosis?)

secrete HCO3- ==> get rid of base reabsorb H+ ==> get more acid counteract alkalosis

which 3 transport proteins of the renal tubule are related to acid-base regulation, and where are they located?

Na+ H+ exchanger --> found in PCT K+/H+ ATPase --> found in a-intercalated cells in CD H+ ATPase --> found in a-intercalated cells in CD

in order to reabsorb bicarbonate ions from the lumen of the renal tubule, this ion must be decomposed to water and CO2: why (tip: is the membrane permeable to bicarbonate ions?)

membrane is not permeable to HCO3- ions HCO3- combines with H+ to H2CO3 --> H2CO3 H2CO3 decomposes thru carbonic anhydrase to H2O + CO2

where is the H+ secreted into the renal tubule coming from? (tip: check what happens to the carbonic acid inside of the tubule cells in the PCT)

HCO3- + H+ originally in tubular fluid --> become H2CO3 --> become H2O + CO2 (via carbonic anhydrase) --> diffuse into renal tubular cell --> become H2CO3 (via CA) --> become H+ and HCO3- H+ starts at renal tubular cell and gets secreted into tubular lumen

what metabolic changes would you check to see for acid-base balance? (ie the concentration of which ion in the blood)

check HCO3- concentration when [HCO3-] is high ==> more base and less acid ==> [H+] secretion is high ==> low [H+] in blood ==> pH is high ==> alkalosis when [HCO3-] is low ==> less base and more acid ==> H+ reabsorption is high ==> high [H+] in blood ==> pH is low ==> acidosis

what is acid-base disorder developed when there is an increased PCO2?

respiratory acidosis

what is acid-base disorder developed when there is decreased PCO2?

respiratory alkalosis

what acid-base disorder is developed when there is an increased HCO3-?

metabolic alkalosis (more base == less acid == basic)

what acid-base disorder is developed when there is an decreased HCO3-?

metabolic acidosis (more acid == less base == acidic)

what are the 2 ways that metabolic acidosis can occur?

diabetic ketoacidosis ==> (increased acid production) renal failure ==> (lower acid elimiation)

what are the 2 ways that metabolic alkalosis can occur?

overuse of antacids (excess HCO3-) loss of acids H+ (vomiting)

what are the 2 ways that metabolic alkalosis can occur?

overuse of antacids (excess HCO3-) loss of acids H+ (vomiting)

which organ compensates for acid-base disorders of metabolic origin

lungs

which organ compensates for acid-base disorders of respiratory origin?

kidneys

how do the lungs compensate for metabolic alkalosis?

metabolic alkalosis == high [HCO3-] lungs increase pCO2 levels --> increase [H+] --> more acidic --> lower pH to normal levels

how do the lungs compensate for metabolic acidosis?

metabolic acidosis == low [HCO3-] lungs decrease pCO2 levels --> decrease [H+] --> more basic --> increase pH to normal levels

how do the kidneys compensate for respiratory alkalosis?

respiratory alkalosis == low pCO2 kidneys decrease [HCO3-] levels: --> less base --> more acidic --> decrease pH to normal levels

how do the kidneys compensate for respiratory acidosis?

respiratory acidosis == high pCO2 kidneys increase [HCO3-] levels: --> more base --> increase pH to normal levels

classify the following conditions as possible causes of respiratory acidosis/alkalosis or metabolic acidosis/alkalosis: - inhibition of the respiratory center - lung damage - airway obstruction - diarrhea - diabetic ketoacidosis - renal failure - high altitude (decreased O2) - anxiety - overuse of antacids (e.g. bicarbonate) - vomiting gastric contents

respiratory acidosis: - inhibition of the respiratory center - lung damage - airway obstruction - diarrhea metabolic acidosis: - diabetic ketoacidosis - renal failure respiratory alkalosis: - high altitude (decreased O2) - anxiety metabolic alkalosis: - overuse of antacids (e.g. bicarbonate) - vomiting gastric contents