Ch 3: Biochemistry Basics (Princeton Review)

Question 1

What is the first law of thermodynamics?
What is it also known as?

Answer 1

Energy can neither be created nor destroyed. The energy of the universe is constant. When the energy of a system decreases, the energy of the surroundings must increase (and vice versa).

A.k.a. the law of conservation of energy

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Question 2

What is the second law of thermodynamics?

Answer 2

The disorder, or entropy, of the universe tends to increase. In other words, spontaneous reactions tend to increase the disorder of the universe.

Question 3

What is the formula which describes the mathematical notion of free energy? (Gibbs free energy)

Answer 3

ΔG = ΔH - TΔS

(H denotes enthalpy, T denotes temperature, and S denotes entropy)

Question 4

What equation defines ΔH?

Answer 4

ΔH = ΔE + PΔV

H is enthalpy, E is bond energy, P is pressure, and V is volume

Question 5

If ΔS is negative, did the system entropy decrease or increase?

Answer 5

If ΔS is negative, then the system lost entropy, which means disorder decreased.

Question 6

ATP stores energy in the _____ bonds between its ________ groups.

Answer 6

ester
phosphate

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Question 7

Endergonic reactions only occur if…

Answer 7

…energy is added.

p. 40

Question 8

The signs of thermodynamic quantities are assigned from the point of view of….

Answer 8

….the system, not the surroundings.

Question 9

A nonspontaneous reaction is considered ___________, and has a _ ΔG.

Answer 9

unfavorable
+ΔG

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Question 10

If the products in a reaction have more entropy than the reactants and the enthalpy (H) of the reactants and the products are the same, can the reaction occur spontaneously?

Answer 10

Yes. If ΔS > 0 and ΔH = 0, then according to the second law of thermodynamics, the reaction is spontaneous.

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Question 11

What equation links ΔG°’ to the equilibrium constant for a reaction?

Answer 11

ΔG°’ = -RT ln K_eq’

Question 12

What is the study of reaction rates called?

Answer 12

chemical kinetics

Question 13

What is activation energy?

Answer 13

The energy required to produce the transition state.

The activation energy determines the kinetics of a reaction.

Question 14

A catalyst lowers the E_a of a reaction without changing the . The catalyst lowers the E_a by stabilizing the _______ state, making its existence less thermodynamically unfavorable. The second important characteristic of a catalyst is that it is not consumed in the reaction; it is regenerated with each reaction cycle.

Answer 14

ΔG

transition

Question 15

What are the 3 common changes you’ll see to help you identify oxidation reactions on the MCAT?

Answer 15

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

Question 16

What are the 3 common things you’ll see to help you identify reduction reactions on the MCAT?

Answer 16

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

Question 17

In the reaction for glucose oxidation, what are the two members of the redox pair?

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O

Answer 17

The carbons in the glucose are oxidized to CO₂, and oxygen is reduced to H₂O.

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Question 18

Which definition of acid/base is most important for the MCAT?

Answer 18

the Bronsted-Lowry definition:

Acids are proton donors.

Bases are proton acceptors (any anion or any neutral species with a lone pair of electrons can function as a base).