1. ATP & Thermodynamics
AP Biology
Chapter 8

2. Section 8.1
An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics

3. Metabolism All of an organism’s chemical reactions
Catabolic – breaking down molecules, releases energy
Anabolic – building molecules, requires energy

4. Laws of Thermodynamics
1st: energy can be transferred or transformed but not created nor destroyed
2nd: energy transfer or transformation increases entropy (disorder, randomness) of the universe

5. (a) First law of thermodynamics
(b) Second law of thermodynamics
Chemical energy

6. Focus: 2nd Law of Thermodynamics

7. Section 8.2
The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously

8. Gibbs Free Energy Free energy is energy available to do work
Gibbs free energy – the amount of energy a system has available to do useful work
ΔG = ΔH – TΔS
G = change in free energy
ΔH = change in total energy
TΔS = temperature x change in entropy
Spontaneous reactions – ΔG is always negative
Non-spontaneous reactions – ΔG is positive or zero

9. Endergonic reactions Exergonic reactions
Absorbs free energy from surroundings
G is positive (energy is being stored)
Non-spontaneous
Photosynthesis
Exergonic reactions
Releases free energy to surroundings
G is negative (energy is being lost)
Spontaneous
Cellular Respiration

10. Section 8.3
ATP powers cellular work by coupling exergonic reactions to endergonic reactions

11. ATP Adenosine triphosphate Has unstable phosphate bonds
Release of phosphate groups = release of energy for cellular work

12. ATP Powers Cellular Work
Cells need energy to do chemical, transport and/or mechanical work
ATP is usable, free energy for the cell
Chemical energy from food  ATP for cells

13. ATP Cycle