CH3: BIOCHEM Basics Flashcards
First Law of Thermodynamics (AKA Law of Conservation of Energy)
The energy of the universe is constant
SO when E of a system DECR –> E of universe/surroundings INCR
Second Law of Thermodynamics
Entropy (AKA disorder) of the universe increases
Entropy symbol = S
Gibbs Free Energy
DELTA G = DELTA H -T DELTA S
H= enthalpy (potential E)
S= entropy
T= temperature in K
T and S = kinetic E
DELTA G <0 FAVORABLE
Enthalpy
Internal energy contained in a compound
DELTA H= DELTA E + P DELTA V
H= enthalpy
E= bond energy
P= pressure
V= volume
Spontaneous
Favorable
DELTA G <0
Nonspontaneous
UNfavorable
DELTA G >0
Exergonic
Energy OUT
Negative DELTA G
Endergonic
Energy IN
Positive DELTA G
Exothermic
Heat OUT
Negative DELTA H
Endothermic
Heat IN
Positive DELTA H
Equilibrium
Reaction rate forward = Reaction rate reverse
Q
Ratio products to reactants
K eq
ratio products to reactants AT EQUILIBRIUM
You’re studying a particular reaction. You find the reaction in a book and read DELTA G*’ from a table. Can you calculate DELTA G for this reaction in a living human being without any more info?
NO
Need to know concentrations of products and reactants
How can DELTA G be negative is DELTA G*’ is positive?
if RT ln Q more negative than DELTA G*’ is positive
Does K eq indicate the rate at which a reaction
No
Only the concentrations of at equilibrium
When K eq is large which has lower free energy: products or reactants
Products
More products = less free energy
When Q is large which has lower free energy
unknown
Only derived from initial concentrations
Which direction forward or backward will be favored in a reaction if DELTA G= 0
NEITHER
Reached equilibrium
Chemical kinetics
Study of reaction rates
Transition state (TS)
Unstable and takes a lot of energy to make
Only around for a short time to form products or break down into reactants
Activation Enegy (Ea)
Energy needed to make the transition state
Can be “reaction barrier” even with NEG DELTA G
Catalyst
INCR Ea by:
1. Lowers Ea of a reaction wo changing the DELTA G
2. Stabilizes the transition state so its LESS thermodynamically Unfavorable
NOT consumed in the reaction
DOESN”t change thermodynamics ONLY kinetics
Enzymes
Biological catalysts
INCREASE reaction rate by DECREASING activation energy
DO NOT affect DELTA G
Kinetic role NOT thermodynamic role
NOT used up in rxn
specific for certain rxns
Photosynthesis
Plants store light energy in bond energy of carbohydrates
Photoautotrophs
Use light energy to make their own food
Chemoheterotrophs
Use energy of chemicals made by other organisms
Oxidation
Loss of electrons
Reduction
Gain electrons
Oxidation Reactions
- Gain O atoms
- Lose H atoms
- Lose electrons
Reduction Reactions
- Lose O atoms
- Gain H atoms
- Gain electrons
Redox pair
When one atoms gets reduced another MUST be oxidized
Catabolism
Break down molecules
Anabolism
Building up molecules
Oxidative Catabolism
Extracts energy from glucose
Glucose gets oxidized AND oxygen reduced
BL Acids
MOST IMP FOR MCAT
Proton (H+) donors
BL Bases
MOST IMP FOR MCAT
Proton (H+) acceptors
Lewis Acids
Electron-pair acceptors
Lewis Bases
Electron-pair donors
BL Conjugate Acid
Has extra H+ than base
BL Conjugate base
Missing H+
Acid-ionization (or acid-dissociation) constant
Ka
Equilibrium expression for acid
LARGER Ka = STRONGER acid
SMALLER Ka = WEAKER acid
Base-ionization (or base-dissociation) constant
Kb
Equil expression for a base
LARGER Kb = STRONGER base
SMALLER Kb = WEAKER base
Polyprotic
Has more than 1 proton to donate
EX: carbonic acid
Amphoteric
A substance that can be either an acid or a base
Any conjugate base of a weak polyprotic acid is ALWAYS amphoteric
Includes amino acids
pH =
-log[H+]
[H+] = 10^-pH
LOW pH equals
HIGH [H+]
HIGH pH equals
LOW [H+]
pOH =
-log[OH-]
pKa=
-logKa
pKb=
-log Kb
The acid with the LOWER pKa is…
the STRONGER acid
The base with the LOWER pKb is…
the STRONGER base
