Flashcards in Acid/Base/Buffers Deck (16)
The modified H-H equation for the bicarbonate system
pH = 6.1 + log ( [HCO3-] mM ) / (.03 x Pco2 mmHg)
What is [HCO3-] in the blood under normal conditions?
What is PCO2 in the blood under normal conditions?
What is [CO2] dissolved in the blood under normal conditions?
Normal arterial blood pH:
Normal venous blood ph:
Normal venous blood ph: 7.28-7.42 (lower due to higher [CO2])
Describe the law of mass action [le Chatelier's principle]:
For any reversible reaction, the forward and reverse rates of the reaction are directly dependent on the concentrations of the reactants and the products respectively.
ie: in A B, if you increase the concentration of A, the rate of A -> B goes up. If you increase the concentration of B, the rate of B -> A goes up instead.
Equilibrium constant (Keq) = [products] / [reactants].
pH is the: (formula and written description)
negative log of the proton concentration in a solution.
pH = -log[H+]
In neutral solutions, [H+] = 1 x 10-7; log [H+] = -7, negative log = 7. So a small change in pH means a big chance in H+, which is tough for our bodies to manage.
Ka measures the tendency of a weak acid to dissociate in water.
pKa is the negative log of Ka for a given weak acid.
The lower the pKa, the_____ the acid
The higher the pKa, the ___ the acid
stronger (more proton donation in water)
weaker (more proton acceptance in water)
Write the Henderson-Hasselbalch (H-H) equation for any given weak acid or base:
pH = pKa + log ([A-]/[HA]).
When pH = pKa, what is true?
when pH = pKa, the concentrations of deprotonated and protonated acid are equal.
(ie: when pH = pKa, the acid is half deprotonated and half protonated.)
In what range does maximum buffering occur?
Plus or minus 1 pH unit from the pKa of the acid/base.
_____ is the only amino acid side chain that protonates or deprotonates at physiological pHs- thus important for acid-base balance in body.
Higher levels of CO2 in the blood ____ the blood's pH. This is because you make more _____, which drives the______ of carbonic acid to form ______.
lower; carbonic acid; deprotonization; bicarbonate + a proton (These extra protons float around in the blood and lower the pH.)