1. Topic 3: The Energy of Life
Free energy
AP Framework: 2.A.1
Topic 3: The Energy of Life
Holtzclaw: (8.1 – 8.4)

2. All living systems require constant input of free energy
AP Framework: 2.A.1
Topic 3: The Energy of Life
Holtzclaw: (8.1 – 8.4)

3. Be able to
2.1 Explain how biological systems use free energy based on empirical data that all organisms require constant energy input to maintain organization, to grow and to reproduce. 2.2 Justify a scientific claim that free energy is required for living systems to maintain organization, to grow or to reproduce, but that multiple strategies exist in different living systems. 2.3 Predict how changes in free energy availability affect organisms, populations and ecosystems.

4. Life requires a highly ordered system
Order is maintained by constant free energy input into the system.
Loss of order or free energy flow results in death.

5. Life requires a highly ordered system (cont)
Increased disorder and entropy are offset by biological processes that maintain or increase order.
Energy
Photosynthesis
Cell respiration
Disorder 
Matter

6. Living systems do not violate the second law of thermodynamics
entropy increases over time, but:
Order is maintained by coupling cellular processes that increase entropy with those that decrease entropy
Energy input must exceed free energy lost to entropy to maintain order and power cellular processes.

7. Living systems do not violate the second law of thermodynamics (cont.)
Energetically favorable exergonic reactions can be coupled with reactions that have a positive free energy change
Example: ATP→ADP,
used to maintain or increase order in a system

8. Energy-related pathways in biological systems are sequential and may be entered at multiple points in the pathway
Examples:
Glycolysis and the Citric acid cycle

9. Organisms use free energy to maintain organization, grow and reproduce.

10. Organisms use various strategies to regulate body temperature and metabolism
Endothermy
thermal energy generated by metabolism
maintain homeostatic body temperature
Ectothermy
external thermal energy to regulate and maintain body temperature
Sustained energy output of a warm-blooded (mammal) and a cold-blooded (reptile) animal as a function of core temperature

11. Reproduction and rearing of offspring requires even more free energy
Different organisms use various reproductive strategies in response to energy availability
Ex. Seasonal reproduction
Arctic foxes have their litters in the early summer

12. Metabolic rate and size
generally, the smaller the organism, the higher the metabolic rate (watts/kg).
Why do you think this is?
Max Kleiber - Kleiber M. (1947). Body size and metabolic rate. Physiological Reviews 27:
Higher percentage of tissues for support and structure

13. If an organism acquires more energy than is required to maintain homeostasis, that energy will be stored or used for growth
The hormone insulin causes glucose in the blood to be absorbed into the cell and converted into fatty acids

14. If an organism requires more energy than it is able to acquire stored energy will be used
Fats are first broken down into glycerol and fatty acids. The glycerol molecule enters directly into the glycolysis pathway, and the fatty acid is taken into the mitochondria. 

15. Changes in free energy availability
can result in:
changes in population size
disruptions to an ecosystem
How could a change in the number of producers affect an ecosystem. Give an example

16. Gibbs free energy

17. catabolism + anabolism = metabolism
Catabolism – pathways that break down (catabolic)
Break bigger molecules into smaller units
Release energy
Increase entropy in the cell
Anabolism – pathways that build (anabolic)
construct bigger molecules from smaller units
Require energy
Decrease entropy in the cell
Metabolism
All of the biochemical pathways used in a cell

18. Organisms are open systems

19. Enzymes catalyze reactions

20. ∆G=∆H-T∆S
Refer to the Gibbs equation and state what combination of ∆S and ∆H
must produce a negative ∆G
must produce a positive ∆G
tends to produce a negative ∆G at low temperatures
tends to produce a negative ∆G at high temperatures.

21. Determine the free energy change for the reduction of CuO with hydrogen. Products and reactants are at 25oC. CuO (s) + H2 (g)  Cu (s) + H2O (l) ∆H = kJ; ∆S = J/ K