Lecture 4

Question 1

pH =?

Answer 1

-log[H+]

Question 2

The concentration of H+ in tomato juice (pH ~4) is
how many times its concentration in the blood
(pH ~7)?

Answer 2

1000

Question 3

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.

Answer 3

• protonated

- dissociated

Question 4

pka =?

Answer 4

-log[Ka]

Question 5

A strong acid will have a ___ Ka and a ___ pKa

Answer 5

• Large Ka

- Small pKa

Question 6

What is the Henderson-Hasselbalch eqn?

Answer 6

pH = pKa + log [A-]/[HA]

Question 7

When does ph = pka

Answer 7

When [A] = [HA]

- aka half the acid molecules are dissociated into its conjugate base

Question 8

What is a diprotic acid

Answer 8

Acid with two ionizable hydrogens

Question 9

Why is protein folding favourable

Answer 9

• forms new weak interactions which is enthalpically favourable
• releases ordered water molecules which is entropically favourable

Question 10

ΔS is positive when a system becomes more

Answer 10

disordered

Question 11

if ΔG is negative, the process is thermodynamically

Answer 11

favourable

spontaneous

Question 12

if ΔG is positive, process is

Answer 12

unfavoured

- reverse is favoured

Question 13

A large negative ΔG means that a reaction will occur

Answer 13

spontaneously

Question 14

What are the units of delta S, delta G, delta H

Answer 14

• Delta G = kJ/mol
• Delta S = kJ/mol x K
• Delta H = kJ/mol

Question 15

What is delta G influence by

Answer 15

the characteristics of the reacting molecules, temperature,
pressure, and, for biological systems, pH; it is also influenced by the concentrations
of reactants and products

Question 16

The larger the _____ of DG the further from equilibrium the reaction is.

Answer 16

absolute value

Question 17

if DG°’is negative, Keq will be ______ and the _____ reaction is favoured at standard state

Answer 17

• greater than 1 (more products than reactants)

- forward

Question 18

if DG°’is positive, Keq will be ______ and the _____ reaction is favoured at standard state

Answer 18

• less than 1 (more reactants than products_

- reverse

Question 19

What are enzymes

Answer 19

• 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

Question 20

What is turnover rate

Answer 20

the number of substrate

(reactant) molecules converted to product per enzyme molecule per unit time.
- units are per second (sec-1 )

Question 21

What is delta G cross

Answer 21

Activation energy

- difference in energy between transition state and substrate

Question 22

What is the lock and key hypothesis

Answer 22

• Substrate fits perfectly into enzyme active site

Question 23

What is the induced fit model

Answer 23

• Both substrate and active site distorted and fit conformations close to the transition state conformation

Question 24

What is substrate analog

Answer 24

• mimic of substrate

- binds to enzyme active site but not real eased