Lecture 1: pH, Water Flashcards
pH, Water, Buffers, H-H Equation
Why does water have elevated surface tension, viscosity, and stability?
Hydrogen Bonding
What percentage of the body is water for newborns, adults, and eldery?
Newborn - 75-80%
Adult - 60-70%
Elderly - 40ish%
How many molecules can a H2O atom bind to?
4
How does water affect proteins?
Bulk water stabilizes from outside,(keeps in native structure) and aids with solubility
What is normal biological pH?
7.35 - 7.45
What two main organs regulate water balance (pH)?
Lungs (fast!) , Kidneys (slow!)
What is the molecular weight of water?
55.6 g/mol
pH Equation
pH = -log[H+]
Define Acid/Base in Bronsted terms
Acid - Proton Donor
Base - Proton Acceptor
pKa for -COOH (carboxylic acid)
4 ~ 5
pKa for -NH3+ (amine)
9 ~ 10
pKa for H2CO3 (Carbonic Acid)
6.1
pKa for H2PO4-
7.2
What determines extent of dissociation for weak acids?
How do you use this to find pKa?
Ka
pKa = -log[Ka]
When does pH = pKa?
When [conjugate acid] and [conjugate base] are equal
What is the Henderson Hasselbalch Equation?
How is it used?
pH = pKa + log [A-] / [HA]
– Used to calculate pH or pOH of solution of weak acid using constants
Do drugs cross membranes best when neutral or charged?
Neutral
What are the pKa’s for Carbonic Acid (H2CO3)?
pKa1 = 6.1 pKa2 = 10.2
What are the pKa’s for Phosphoric Acid (H3PO4)?
pKa1 = 2.1 pKa2 = 6.8 pKa3 = 12.4
What two factors contribute to buffering capacity?
How do you select best buffer for purpose?
- Molar Conc. of buffer
- pKa
Best buffer has pKa close to pH desired (+/- 1) at highest possible concentration
What are the two most important buffers in human body?
Carbonate and phosphate
What is bicarbonate buffer equation?
https://www.scienceabc.com/wp-content/uploads/2017/03/Carbonate-buffer.jpg
How to determine CO2 in bicarbonate buffer equation?
Measure pCO2, multiply by conversion factor (0.03 mM/mm Hg)
How do the lungs control pH?
Reduce pCO2 in blood
