Basic Water and chemistry Flashcards
covalent bonds
sharing of electrons
What are non-covalent bonds?
much weaker than covalent bonds, reversible, repeated
What are three types of covalent bonds?
- Ionic Bonds (strongest)
- H-Bonds
- Van der Waals Interactions
- Hydrophobic interactions (weakest)
What are ionic bonds?
electrostatic interactions (“salt bridges”) - can be broken down by water
What are H-Bonds?
Bonds b/t electronegative atoms (commonly Oxygen and Nitrogen) and Hydrogens; can be disrupted by water
What are Van Der Waals Interactions?
electrostatic interactions of partial charges (random, transient asymmetry)
What are hydrophobic interactions?
hydrophobic regions of a biomolecule interacting with another hydrophobic molecule
What are functional groups?
part(s) of a molecule that can affect the properties and function of that molecule
What are the 8 functional groups?
- Hydrophobic (non-polar) -Hydrocarbon chain/aromatic
- Hydroxyl (OH)
- Aldehyde (carbonyl with H and R group attached)
- Keto (carbonyl with two R groups)
- carboxyl (carbonyl with OH and R group)
- Amino (Amine)
- Phosphate (R group with PO4)
- Sulfhydryl (R group with SH, can form compunds with other thiols(sulfhydryl bridges))
Name 5 distinct characteristics of H2O
- Polar
- Involved in H-Bonding
- Good Solvent for any charged/polar molecules
- can’t dissolve uncharged/polar molecules
- Dissociation of water: H2O H1+ + OH1-
When the charge distribution in a molecule is not uniform
Polar Molecule (i.e. O is electronegative and H is electropositive)
PH
- Measure of a free hydrogen ion (“proton”) concentration
- A log scale of proton concentration (H+)
- Importance: Affects the electrostatic interactions (bonding), which alters the structure and function of a biomolecule.
- Water/other molecules can dissociate to release H+ protons
Measures the extent to which reactants are converted to products by the rxn at equilibrium
Keq
Rxn for Keq
[H+][OH-]/[H20]
Where M of [H+] and [OH-] is 10^-7 (each)
and M of [H2O] is 55.5
What is a common misconception of equilibrium?
That the substances are present in equal amounts.
What is true when a rxn has reached equilibrium?
concentration of reactants and products are unchanging with time (forward and backward rxn have the same time).
You can relate pH to hydrogen ion concentration
using the following equation:
pH = - log10 [H+]
(Since, [H+] is 10-7 M… pH = -log10 (10-7) = 7
… which is the pH of pure H2O. )
Proton Donor
Acid
What is the result when an acid loses a Hydrogen ion?
It becomes (“unprotonated”), resulting in an ionized, conjugate base
Proton Acceptor
Base
What is the result when an base gains a Hydrogen ion?
It becomes (“protonated”), resulting in an ionized, conjugate acid
Equilibrium constant, Ka
Ka = [H+][A-] / [HA]
The Henderson-Hasselbach equation allows us to correlate ___ with ___.
pH, pKa
What is the Henderson-Hasselbach equation?
pH = pKa + log ([A-] / [HA])
What two things can you do using the Henderson-Hasselbach equation?
- Calculate relative amounts of protonation of acids and bases in a given pH.
- Calculate change in pH when acid/base is added.
What does it mean when pH=pKa?
acid and base are in equal concentrations
when acid is half-associated/dissociated/protonated/unprotonated
What is a buffer?
acid-base conjugate pairs that resist changes in pH
When are buffers most effective?
at he vicinity of its pKa
