Biochemistry Basics

Question 1

Relationship b/w spontaneous/nonspontaneous reactions and entropy/energy

Answer 1

• *Spontaneous reactions**
• occurs without outside intervention
• increase disorder of the universe
• ΔG = negative
• *Nonspontaneous reactions**
• a process that requires input of energy to occur
• cannot be made spontaneous through the use of a catlayst
• ΔG = positive

Question 2

Determining total energy change for a system under any given set of conditions

Answer 2

ΔG = change in free energy for a system

ΔG = ΔH - TΔS

units: kJ mol^-1

Question 3

Enthalpy

Answer 3

a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.

ΔH = ΔE + PΔV

ΔH= change in enthalpy
ΔE= change in bond energy of products and reactions
ΔV= change in volume
P= pressure

Question 4

postive/negative gibbs and enthalpy

Answer 4

ΔG positive = nonspontaneous; endergonic

Δ G negative= spontaneous; exergonic

ΔH positive = exothermic (heat given off)

ΔH negative = endothermic (heat absorbed)

Question 5

A system will always move in direction of the ___

Answer 5

lowest free energy

Question 6

negative ΔG means that a goes to a lower __

Answer 6

free energy state

Question 7

ΔG^o’ and the equiibirum constant

Answer 7

ΔG^o’ = -RTlnK’_eq

R = gas constant (given on MCAT, pay attention to units)
T = Temperature (K)
K’_eq = ratio of products to reactions at equilibirum

K_eq = [Products]^y
[Reactants]^x

Question 8

Calculating change in free energy under physiological conditions

Answer 8

ΔG = ΔG^o’ + RT lnQ

Question 9

relationship between Q and Keq

Answer 9

Q is the ratio of products to reactions in any given set-up. Keq is ratio at equilibirum. When we disturb an equilbiirum mixture, this causes a change in Q but not in Keq, and the reaction will proceed in the direction necessary to re-establish equilbrium.

Question 10

Does Q or Keq descrive the properties of the reaction.

Answer 10

The size of Q says nothing about the properties of the reactants and products. Q is calculated from whatever the initial concentrations happens to be. It is Keq that says something about the nature of products and reactions, since it describes their concentrations after =libirum has been reached

Question 11

what is the value of ΔG at eqilibirum?

Answer 11

ΔG=0

Question 12

Factors determining spontaneity (negative ΔG)

Answer 12

1. intrinsic properties of the reactants and products (Keq)
2. concentrations of reactants and products (RTlnQ)
3. Temperature
   - if the lnQ is negative and the temp is high enough, ΔG will be negative, regardless of the value of ΔG^o’

Question 13

How is Spontaneity related to thermodynamics and kinetics related?

Answer 13

Spontaneity means that a reaction is energetically favorable, but it stays nothing about the rate of the reactions. Thermodynamics will tell you where a system starts and finished but NOTHING about the path traveled to get there. Thus ΔG does not depend on the pathway a reaction takes or the rate of a reaction; it is only a measure of the difference in free energy b/w reactants and products

Question 14

What do catalysts do?

Answer 14

• only make reaction go faster; NOT changing the free energy
• ONLY deals with kinetics
• increases rate of reactions by
  
  • STABILIZING T.S.
  • REDUCING E_A

Question 15

Explain components of reaction coordinate graoh

Question 16

Components of oxidations reactions

Answer 16

1. gain of oxygen atoms
2. loss of hydrogen atoms
3. loss of electrons

Question 17

components of reduction reactions

Answer 17

1. loss of oxygen atoms
2. gain of hydrogen atoms
3. gain of electrons

Question 18

Catabolism

Answer 18

process of breaking down molecules

Question 19

Anabolism

Answer 19

“building-up” metabolism

Question 20

How do harvest energy from glucose

Answer 20

oxidative catabolism via glycolysis and then through cellular respiration

Question 21

Bronsted-Lowry Acids and Bases

Answer 21

Acids are proton (H+) donors

Bases are proton (H+) acceptors

Question 22

Lewis Acids and Bases

Answer 22

Lewis Acids are electron-pair acceptors

Lewis Bases are electron-pair donors

Question 23

Coordinate covalent bonds

Answer 23

when one atom donates both electrons in a covalent bons

Question 24

Ka values and strength of an acid

Answer 24

higher Ka = stronger acid

lower Ka = weaker acid

Question 25

Kb and strength of a base

Answer 25

higher Kb = strong base

lower Kb = weaker base

Question 26

What are amphoteric substances?

Answer 26

amphoteric can act either as an acid or base

ALL AMINO ACIDS are examples

Question 27

what does pH measure

Answer 27

H⁺ ions in solution

Question 28

What does pOH measure

Answer 28

hydroxide (OH-) ions concentration in a solution

Question 29

calculating pH and pOH

Answer 29

pH = -log[H⁺]

pOH = -log[OH^-]

Question 30

calculating pOH from pH and vice versa

Answer 30

pOH + pH = 14

Question 31

calculating pKa and pKb

Answer 31

pKa = -log Ka

pKb = -log Kb

Question 32

strength of an acid and its pKA

Answer 32

lower pKa = stronger acid (higher Ka) = weaker base

higher pKa = weaker acid (lower Ka) = stronger base

Question 33

blood buffer system