Chapter 3 - Biochemistry Basics

Question 1

potential energy

Answer 1

energy stored in chemical bonds

Question 2

What is the most important potential energy storage molecule in all cells?

Answer 2

ATP, which stores energy in the ester bonds between its phosphate groups.

Question 3

e rst law of thermodynamics, also known as the law of conservation of energy, states that ______

Answer 3

the energy of the universe is constant.

It implies that when the energy of a system decreases, the energy of the rest of the universe (the surroundings) must increase, and vice versa.

Question 4

e second law of thermodynamics states that the disorder, or entropy, of the universe tends to ____

Answer 4

increase

Another way to state the second law is as follows: Spontaneous reactions tend to increase the disorder of the universe.

Question 5

If the ∆S of a system is negative, has the disorder of that system increased or decreased?

Answer 5

If ∆S is negative, then the system lost entropy, which means that disorder decreased.

Question 6

∆G = ∆H – T∆S

Answer 6

G = free energy (Gibbs free energy)
H= enthalpy
T= Temperature

Question 7

∆H = ∆E + P∆V

Answer 7

E represents the bond energy of products or reactants in a system, P is pressure, and V is volume

Question 8

Given that cellular reactions take place in the liquid phase, how is H (enthalpy) related to E (bond energy) in a cell?

Answer 8

H ≈ E, since the change in volume is negligible (∆V ≈ 0)

Question 9

∆G increases with _________ ∆H (bond energy) and ________ with increasing entropy.

Answer 9

∆G increases with increasing ∆H (bond energy) and decreases with increasing entropy.

Question 10

Given the second law of thermodynamics and the mathematical de nition of ∆G, which reac- tion will be favorable: one with a decrease in free energy (∆G 0)?

Answer 10

Favorable reactions have ∆G

Question 11

What does the change in the Gibbs free energy of a reaction determines?

Answer 11

The change in the Gibbs free energy of a reaction determines whether the reaction is favorable (spontane- ous, ∆G negative) or unfavorable (nonspontaneous, ∆G positive).

In terms of the generic reaction
A+B→C+D

the Gibbs free energy change determines whether the reactants (denoted A and B) will stay as they are or
be converted to products (C and D).

Question 12

∆G of spontaneous reaction is ____

Answer 12

Spontaneous reactions, ones that occur without a net addition of energy, have ∆G

Question 13

Endergonic reactions only occur if energy is _____.

Answer 13

Endergonic reactions only occur if energy is added.

Question 14

Most metabolic reactions are _______

Answer 14

Most metabolic reactions are exothermic

Question 15

∆G°′ =

Answer 15

∆G°′ = −RT ln K′eq