Acids & Bases Flashcards
4 Properties of Water
Polar Universal Solvent High Heat Capacity High Heat of Vaporization High Dielectric Constant
What shape is water molecule?
Tetrahedal
How can water molecules H-bond?
Partial + of H and partial - of O allow it to H-bond and thus be a good solvent (good for hydrophilic molecules)
What attraction can O have?
Electrostatic attraction with positively charged atoms
Why are H-bonds important?
Hold proteins together (alpha-Helix & beta-sheet) Nucleic acid structure Enzyme binding mechanisms Ligand binding DNA double helix Water-sugar bonding
Hydrophobic interaction?
Important hydrophobic interactions
Non-polar greasy molecules clump together to exclude water
Proteins, nucleic acids, lipid micelles, polysaccharides, membranes, lipoproteins
Amphipathic
Molecules that are hydrophobic on one end and hydrophilic on another end (detergent or fatty acid)
Micelle
hydrophilic exterior interacts with h=water around it, hydrophobic core
Ionic bond
F = e1e2/Dr^2, attractive or repulsive force btw like or unlike charges
van Der waals
weak interactions that act only at a specific region (sinusoidal short curve)
Strong interactions vs. weak interactions
Strong: covalent bonding (C-H, C-C) [100 kcal/mole]
Weak: H-bond, ionic bond, van der waals, hydrophobic (<10 kcal/mol)
What are some body buffers?
Phosphate, bicarbonate, hemoglobin
Acid
Proton donor HA
Base
Proton acceptor A-
Strong acid dissociation
completely
What does the strength of the weak acid depend upon?
pK value
What is Kd?
Kw?
Dissociation constant of water, or Kw
Kw = [H+][OH-] = 10^-14
What is relationship between Kd and acid strength?
Kd is a measure of how much an acid will dissociate. Therefore if the Kd is high, then the acid will be a strong acid.
Define pK mathematically
pK = -log[K]
Buffer, it’s composition
Solution that resists change in pH. Contains acid and conjugate base
Where on a titration curve is a buffer shown?
Where pH change is small when strong A or strong B is added
What is buffer capacity?
Total concentration of acid and base in solution. Higher the concentration of buffer, the more effective it acts as a buffer
What is bodily blood pH?
7.4
What can pH affect?
Protein conformation, enzyme function, solubility, transport of compounds
When does pH = pK
HA = A-
What range does the buffering range sit?
+- 1 pH unit of pK of reactive group, whether acid or amine
Polyprotic
Use Ka values in between to calculate relative to Henderson-Hasselbach
Henderson-Hasselbach
pH = pK +log[A-/HA]
Law of electroneutrality
sum of + charges = sum of - charges
pKa of bicarbonate
6.1
What buffers blood at 7.4?
Largely bicarbonate
Small phosphate
Very small protein
What enzyme works in the bicarbonate buffer system?
Carbonic anhydrase
Explain bicarbonate buffer system
Carbonic anhydrase converts CO2 and water to carbonic acid. Carbonic acid then dissociates to from bicarbonate and H+
