Acid and base Flashcards
Define an acid? reaction?
Proton/H+ donor
HA (acid) <-> H+ + A- (conjugate base)
Define a base? reaction?
Proton/H+ acceptor
B (base) + H+ <-> BH+ (conjugate acid)
What is the Bronstead-Lawry Theory?
Protons can’t exist alone in solution as possess high charge density so bind to water molecule
H2O + H+ <-> H3O+
What can water dissociate into?
H2O <-> OH- + H+
In pure water what is [H+]?
pH 7
10^-7
Define strong acid?
Compound ionizes completely in solution to form hydrogen ions and a base
Define a weak acid and bases?
Compounds that only partially ionize in solution
H2CO3 <-> H+ + HCO3-
Resulting anion (bicarbonate) referred to as conjugate base of carbonic acid
Define base excess?
Quantity of acid required to return plasma pH to normal
Define standard base excess?
Quantity of acid required to return extracellular fluid to normal
Define buffers?
Weak acids/bases with conjugate base or acid Solution resists changes in pH when small quantities of strong acids or base are added.
How to calculate pH?
pH= -log10[H+]
What is normal range of pH?
7.35-7.45
Define:
Acidosis
Alkalosis
Acidaemia
Alkalemia
Acidosis: blood more acidic than normal
Alkalosis: blood more alkaline than normal
Acidaemia: low blood pH
Alkalaemia: high blood pH
How are H+ ions produced?
Generated by metabolism
Small quant- oxidation aa
- anaerobic met glucose to
lactic and pyretic acid
Main- CO2 release from oxidative (aer) met
- CO2 react water form carbonic acid
(H2CO3)
- H2CO3 dissociates int hydrogen and HCO3-
Write the equation for H+ production?
Enzyme?
Carbonic anhydrase
What speeds up the reaction of CO2 and H2O?
Carbonic anhydrase
What is the most important buffering system and what catalyses it?
Carbonic anhydrase
State the Henderson-Hasselbach equation?
pH = pK + log10 ([Base]/[Acid])
What is the value of CO2 constant?
What is equation for carbonic acid/bicarbonate?
0.03
pH = 6.1 + log10 (25mM / (0.03 x 40 mmHg))
What is the value of CO2 constant?
What is equation for carbonic acid/bicarbonate?
0.03
pH = 6.1 + log10 (25mM / (0.03 x 40 mmHg))
Define the anion gap?
Difference in serum concentration of cations (positive) and anions (negative)
e.g Cl-, HCO3-, Na+, K+
NOT- K+, PO4-, SO4
Define cations and anions?
Cations- positive
Anions- negative
What is normal anion gap numebr?
3-11 mEq/mol
What does a wide anion gap indicate?
Lactic acidosis
Ketoacidosis
Ingestion acid
Renal failure
What does a narrow anion gap indicate?
Alkalosis
Note diff types of body buffer symptoms?
Bicarbonate
Proteins
Haemoglobin
Explain the bicarbonate buffer?
Most imp
Not eff
CO2 removed lungs
Bicarb regenerate kidneys
Explain proteins buffer? Examples?
Albumin
Contain weak acidic and basic groups
Plasma and proteins imp buffer
E.g. Intracellular proteins limit pH change in
cells
Protein matrix bone buffer H+ ion in case
of chronic acidosis
Explain haemoglobin buffer? Function?
Carry oxygen to tissues
Transport CO2 and buffer H+
Hb binds both CO2 and H+
Powerful buffer
Why is deoxygenated Hb important? Process? Lungs? Tissues?
Strongest affinity CO2 and H+
Buffering effect strongest in tissues
- Little CO2 produced in red cells means CO2 produced by tissues passes into cell, down concentration gradient.
CO2 combines directly reversibly with terminal amine groups on haemoglobin molecule to form carbominohaemoglobin.
In lungs- CO2 released
- passes down concentration gradient
to alveoli – buffering of CO2
In tissues- dissolved CO2 passes into RBCs,
combine carbonic acid
- catalysed by carbonic anhydrase
- carbonic acid dissociates into
bicarbonate and H+ ions
- H+ ions bind to reduced
haemoglobin to form HHb
- HCO3- pass back into plasma in
exchange for Cl-
