BIO 2 Exam 2: Bioenergetics

Question 1

Bio-Energetics Def and Two Laws

Answer 1

Energy is the ability to do work

First Law of Thermodynamics – Energy is neither created nor destroyed, but it can be transferred

Second Law of Thermodynamics – Entropy increases systems tend to become more disordered with each energy transfer

Question 2

Gibb’s Free Energy

Answer 2

G final – G initial = Delta G

Endergonic reactions G > 0 (energy is being stored)

Exergonic reactions G < 0 (energy is being released)

Question 3

Changes in Free Energy

Answer 3

Delta G of chemical reactions:

Making covalent bonds tends to be endergonic

Delta G can be affected by:

-Relative energy levels of reactants and products
-Concentration of reactants and products
-Temperature and pressure

Question 4

How to Assess Energy change

Answer 4

To just look at the energy levels, we usually look at the standard free energy change: Delta G degree

1 M each, 1 atmosphere, 25C

Biologists prefer Delta G’s as above, but also pH7

Question 5

Delta G (Degree) and Equilibrium

Answer 5

Delta G (Degree) shows that the products of this reaction are much more stable

At equilibrium, there will be more productsthan reactants

Question 6

Example: What if Delta G (degree) is less than on e?

Answer 6

Delta G (degree) < 0 there will be more products than reactants when we reach equilibrium

concentrations don’t change anymore

Question 7

Relations of Keq and Delta G (degree)

Answer 7

Keq = [Products]/[Reactants]

If Delta G (degree)’ = Keq = 1

If Delta G (degree)’ < 0 :

Exergonic or Spontaneous = Keq > 1

If Delta G (degree)’ > 0 :

Endergonic or Nonspontaneous Keq < 1

Question 8

Activation Energy

Answer 8

The reaction rate is controlled by the energetic path from reactants to products.

Activation energy is the input energy needed to reach the transition state