Bio-Tech-lect #3 Flashcards
pKa
represents the pH where an weak acid:conjugate base pair is at equilibrium ([HA] = [A-])
When is it appropriate to use the Henderson-Hasselbalch (H-H) Equation?
Mixtures of weak acids and their conjugate bases (salt).
Titration of weak acid solutions with strong base, or vice versa.
Buffers!
Biological Environments!!!
ampholyte
a molecule with both acidic and basic groups
The isoelectric point (pl)
the pH
at which average charge, for all forms of the molecule, is zero.
when pH < pI
a molecule
will be positively charged.
when pH > pI
the molecule will be negatively charged.
use of Thermodynamics
allows us to determine whether chemical processes and reactions occur spontaneously.
2nd law of thermo
“The universe tends toward maximum disorder”
doesnt tell us about a rate (thats kinetics) just that it willor wont happen given enough time.
how is a spontaneous process characterized?
by the conversion of order to chaos.
does enthalpy tell us about spontaneity?
no
1st law of thermos
Energy can be neither created or destroyed!
Or, more specifically: “the total energy of an isolated system is conserved
system
portion of the universe with which we’re concerned:
- mixture of chemical in a test tube
- single cell, perhaps entire organism
surroundings
everything else in the universe thats not the system
3 systems
isolated, closed, open
isolated system
no exchange of matter or energy
closed system
exchange of energy may occur
open system
Energy and/or matter exchange may occur.
What kind of systems are living things?
Mostly open
exchanging matter: nutrients, waste products
exchanging energy: heat from metabolism
internal energy examples and symbol
“U”
rotational, vibrational, translation energies of molecules, energy stored in covalent and noncovalent bonds
thermodynamic state
defined by describing the amounts of all substances present and any two of the following three variables:
The temperature (T).
The pressure on the system (P).
the volume of the system (V).
The internal energy (U) of a system
Includes all forms of energy that can be exchanged via simple (nonnuclear) physical processes or chemical reactions.
when can a system can exchange energy with its surroundings?
as long as its not isolated.
what happens in terms of energy when the system is not isolated system?
the internal energy can change (delta U)
how does internal energy exchange take place for a closed system?
- ) Heat (q) may be transferred to or from the system.
2. ) The system may do work (w) on its surroundings or have work done on it.
Exothermic
deltaH < 0
endothermic
deltaH > 0
