Lecture 4 Flashcards
pH =?
-log[H+]
The concentration of H+ in tomato juice (pH ~4) is
how many times its concentration in the blood
(pH ~7)?
1000
pH is less than pKa, it is going to be in the ___ form. When the pH is higher than the pKa than most of the acid is going to be ____ into the conjugate base form. When they’re equal, half molecules are protonated half are in conjugate base.
- protonated
- dissociated
pka =?
-log[Ka]
A strong acid will have a ___ Ka and a ___ pKa
- Large Ka
- Small pKa
What is the Henderson-Hasselbalch eqn?
pH = pKa + log [A-]/[HA]
When does ph = pka
When [A] = [HA]
- aka half the acid molecules are dissociated into its conjugate base
What is a diprotic acid
Acid with two ionizable hydrogens
Why is protein folding favourable
- forms new weak interactions which is enthalpically favourable
- releases ordered water molecules which is entropically favourable
ΔS is positive when a system becomes more
disordered
if ΔG is negative, the process is thermodynamically
favourable
spontaneous
if ΔG is positive, process is
unfavoured
- reverse is favoured
A large negative ΔG means that a reaction will occur
spontaneously
What are the units of delta S, delta G, delta H
- Delta G = kJ/mol
- Delta S = kJ/mol x K
- Delta H = kJ/mol
What is delta G influence by
the characteristics of the reacting molecules, temperature,
pressure, and, for biological systems, pH; it is also influenced by the concentrations
of reactants and products
The larger the _____ of DG the further from equilibrium the reaction is.
absolute value
if DG°’is negative, Keq will be ______ and the _____ reaction is favoured at standard state
- greater than 1 (more products than reactants)
- forward
if DG°’is positive, Keq will be ______ and the _____ reaction is favoured at standard state
- less than 1 (more reactants than products_
- reverse
What are enzymes
- biological catalysts that dramatically increase the rate of reactions
- do not ‘drive’ reactions; they allow a favorable reaction to reach equilibrium faster
- lower activation energy
- not consumed, catalysts
- alter rxn rate NOT RXN EQ
- DOES NOT CHANGE DELTA G
What is turnover rate
the number of substrate
(reactant) molecules converted to product per enzyme molecule per unit time.
- units are per second (sec-1 )
What is delta G cross
Activation energy
- difference in energy between transition state and substrate
What is the lock and key hypothesis
- Substrate fits perfectly into enzyme active site
What is the induced fit model
- Both substrate and active site distorted and fit conformations close to the transition state conformation
What is substrate analog
- mimic of substrate
- binds to enzyme active site but not real eased
