Biochemical Buffers And Regulation Of Body PH Flashcards
Tissue pH
7.40
Organs that have role in regulating pH
Lungs and kidneys
PH equation
pH = -log10 [H+]
Change in one pH unit represents _____ change in [H+]
10-fold change
T/f strong acids and bases ionize completely in dilute aqueous solutions
T
Degree of dissociation of weak acid depends on ____
Value for Ka
Weak acids in body
. Amino acids
. Fatty acids
. Lactic acid
. Ammonium
Weak bases in body
. Lactate
. Acetate
. Ammonia
Henderson-Hasselbalch equation
pH = pKa + log ([A-]/[HA])
What is a buffer
. Solution that resists a change in pH when either acid or base is added
. Mixture of weak acid and conjugate base
When does a buffer work best and why?
. Composed of equal amts of HA and A-
. Any added strong base can combine w/ weak acid and be neutralized and vice versa
When do you lose buffering power?
. Depleted conjugate acid or conjugate base
Smallest changes in pH occur with a buffer when ___
Addition of acid/base to a buffer whose pH is in the region of the pK
When [HA] = [A-] then pH = ____
pK
Best buffering range for conjugate pair
.pK +/- 1pH unit
Why is pH regulation important to our health
. Enzymes and proteins function in specific pH ranges
Acceptable range pH for arterial plasma pH and consistent range w/ life
. Acceptable: 7.40 +/- 0.05
. Life: 6.8-7.8
Sources of acids and bases in body
. Glucose and fatty acid oxidation generate CO2 and H2O
. Metabolism generates organic acids
Primary buffer system in body
Bicarbonate
Bicarbonate equation
CO2 (gas) -> CO2 (dissolved) + H2O H2CO3 H + HCO3
Important players in bicarbonate buffer system
. carbonic acid (H2CO3)
. Bicarbonate/base (HCO3-)
. CO2 acid
K1 in bicarbonate rxn
[H2CO3]/[CO2][H2O}
K2 in bicarbonate rxn
[H+][HCO3-]/[H2CO3]
How is bicarbonate rxn K1 equilibrium maintained?
Carbonic anhydrase
WHen bicarbonate rxn K1 lies to the left there’s more ___
CO2 than H20 (400 times more)
When K2 lies to the right in bicarbonate rxn there mor e____
HCO3, not much H2CO3
Final equation for find bicarbonate pH
pH = 6.1 + log ([HCO3]/[CO2])
How does buffer w/ pK of 6.1 act as effective buffer at pH 7.4?
Open system and acid and base can be added/substrate as needed
Why does [HCOs]/[CO2] ratio not change much?
Human body secretes CO2 as gas in lungs but then is replenished by metabolism of fuels in tissues
. CO2 dissolved is in equilibrium w/ CO2 gas
. Kidneys can retain or excrete base HCO3 as needed
Does carbonate buffer system have more conjugate base or acid and what does this mean?
Base, it can buffer additions of acid better than additions of base
Conversion factor of CO2 anew hy is it needed
[CO2] in mmol/L = 0.03 [CO2 mmHg]
Needed to do Henderson-Hasselbalch so CP2 is in same units as bicarbonate
T/F CO2 is not soluble in aqueous environments?
T
How is CO2 transported from tissues to lungs?
. Generated in tissues during catabolism of fuels to generate ATP
. Converted to very soluble bicarbonate (HCO3) that is carried to lungs
What occurs w/ CO2 in tissues
. CO2 diffuses into erythrocyte
. Carbonic anhydrase catalyzes hydration of CO2 and H2O which dissociates to release H+ and HCO3-
. Cl-HCO3 exchanges (band 3 antiport transporter) exports HCO3 while importing CL to maintain electrical neutrality
CO2 in the lung
.dissolved CO2 exhaled
. Law of mass action moves carbonic anhydrase in opposite direction
. Brings HCO3 into erythrocyte to form CO2 which can cross membrane to be exhaled
Respiratory acidosis
. Lungs aren’t excreting enough acid as CO2
. Acid accumulates in blood and pH drops
. Ex: blocked airway, emphysema, COPD
Respiratory alkalosis
. Lungs excrete too much acid as CO2 causing inc. in blood pH
. Ex: hyperventilation
Metabolic acidosis
. Body generates too much acid that can’t be excreted by lungs
. ex:lactic acid, diabetic ketoacidosis, oral ingestion of acid
Metabolic alkalosis
. Someone has alkaline blood and it not result of respiratory imbalance
. Ex: excess vomiting of stomach contents, ingestion of antacids
Compensation for pH
. Involves changes in lung and kidney
. Metabolic imbalance compensated w/ respiratory and vice versa
Body pH regulators and how quickly they can mediate
. Buffers: accommodate acid/ base additions almost immediately
. Lungs: respiratory rate via loss/retention of CO2 in minutes
. Kidneys: regulates loss of H, ammonia, bicarbonate, and others in matter of minutes to hours
Serum EBAL
. Anion gap
. EBAL = [Na] - ([Cl] + [HCO3])
. Represents differences btw total primary cations and anions measured in blood
. Sometimes K included
high anion gap is typical of ____
Metabolic acidosis
Stomach pH
1-3
Small intestine pH
6-8
Where are drugs absorbed best across membranes?
. At pH where dissociation of side chain results in neutral molecule since drugs go through protein transporters or hydrophobic nature of neutral molecule allows it to pass through membrane
Acidic amino acid (aspartic acid) side chain pK value
3.9
Basic amino acids (arginine) pK value
6.0
Insulin characteristics
. Small protein, net charge -1.8
. Naturally water soluble
. Degraded rapidly in body
Insulin glargine characteristics
. Less water soluble due to charge closer to 0 (+0.2)
. Injected subcutaneously and precipitates at pH of body
. Dissolves slowly over time causing better long term glycemic control and fewer injections
How to distinguish btw respiratory and metabolic acidosis
. If respiratory, CO2 and [HCO3] will also be high
. If metabolic then [HCO3] will be low and [CO2] will be low
How to distinguish btw respiratory and metabolic alkalosis
. Respiratory then [CO2] and [HCO3] will be low
. Metabolic only through consumption of base of vomiting a ton
What if pH is normal but [CO2] and [HCO3] are not w/in normal range?
. Underlying pH disorder that is being compensated
. High edge of normal pH is alkalosis
. Low edge of normal pH is acidosis
