26 1-5 Flashcards
List important sources of acids in the body.
Biggest source: CO2. Amino acids, fatty acids, lactic acids, acids of citric cycle, ketoacids
Four ways acids originate?
- Breakdown of phosphorus containing proteins releasing phosphoric acid into ECF
- Anaerobic respiration - lactic acid
- Fat metabolism - Ketone bodies
- Loading and transport of CO2 in the bloos HCO3- liberates H ions
List the three major chemical buffer systems
Bicarbonate buffer system, Phosphate buffer system, Protein buffer system
A chemical buffer is?
A system of one or more compounds that resist changes in pH when a strong acid or base is added.
This is done by binding to H+ when pH drops and releasing H+ when pH rises.
How does the bicarbonate buffer system resist pH changes. In what compartment?
Main and most important buffer of ECF (blood and interstitial fluid.)
Mixture of H2CO3 (carb acid) and NaHCO3 (sodium bicarbonate, a weak base).
When a strong acid is added, carbonic acid is mostly unchanged, but bicarbonate ions of the salt bind to excess H+ forming more carbonic acid.
When a strong base is added, the sodium bicarbonate remains relatively unaffected, but the carbonic acid dissociates donating more H+ to bind to excess hydroxide.
Stong acid added to bicarbonate buffer sys.
HCl + NaHCO3 – H2CO3 + NaCl
Strong acid + weak base = weak acid + salt
Strong base added to bicarbonate buffer sys.
NaOh + H2CO3 – NaHCO3 + H2O
strong base + weak acid = Weak base + water
What regulates the bicarbonate concentrations?
ECF - kidneys, Plasma - respiratory system
How does the Phosphate buffer system resist pH changes. In what compartment?
Urine and ICF.
Sodium dihydrogen is the weak acid, Monohydrogen is the weak base (operates like bicarb sys.)
How does the Protein buffer system resist pH changes. In what compartment?
Proteins in plasma and in cells.
Organic acids containing carboxyl groups can dissociate to release H+ or H+ can bind to an amino group if excess H+.
75% of buffering power of the body resides in cells/intracellular proteins.
Acids are _____________? Bases are ___________?
Proton donors, proton acceptors.
Acids dissociate from their H+. Bases tie up H+.
Lines of defense to maintain Acid-Base balance?
- Chemical buffers (act in seconds)
- Respiratory system (act in mins, 75% of capacity of acid/base balance)
- Kidney (act in hours)
Buffers can tie up acids-bases temporarily, lungs can dispose of the volatile acid, carbonic acid, by eliminating CO2, only the kidney can rid the body of other acids: phosphoric/uric/lactic/ketone.
Kidneys can also renew chem buffers used in reg H+ in ECF.
Describe the influence of the respiratory system on acid-base balance.
CO2 + H2O = H2CO3 = H+ + HCO3-.
If Pco2 rises, medullary chemoreceptors ↑ resp rate/depth.
In addition, any rise in plasma H+ excites resp ctr via peripheral chemoreceptors to ↑ resp rate/depth. (reactions to the left in the lungs, h+ turned into h2o)
When blood pH rises, the respiratory center is depressed aloowing accumulation of CO2 in the blood (pushes to the right).
Describe how the kidneys regulate hydrogen and bicarbonate ion concentrations in the blood.
Kidneys can directly excrete or reabsorb H+.
Kidneys can indirectly alter pH by changing the reabsorption or excretions of HCO3- (bicarbonate ions can be conserved from filtrate when depleted and their reabsorption is dependent on H+ secretion)
Most important renal mechanism for regulating balance
Conserving (reabsorbing) or generating HCO3- and excreting HCO3-.
Intercalated A cells of renal tubules can synthesize new bicarbonate.
When the body is in alkalosis, intercalated B cells excrete bicarbonate and reclaim H+.
Ammonium ions/weak acid can also be excreted replenishing the alkaline reserve.
