Chapter 6 lecture notes
1. Cells need energy to perfom work.
a. What are some of the types of work that cells perform______________________?
b. What is the name of the processes by which cells gain and use energy? Metabolism!
2. What is a good definition for metabolism? Totality of chemical Rxns
3. Who performs metabolism? Everyone! Evidence of common ancestry and evolution
a. Catabolic pathways: processes which USE energy ..Examples?
b. Anabolic: processes which BUILD energy…Examples?
4. What is energy?  capacity to cause change
a. Kinetic: Energy associated with motion. Examples?
b. Potential: Energy associated with structure or location
i. Chemical: PE of chemical bonds
5. Laws of Thermodynamics: Open vs. Closed Systems
a. Energy can be transformed or transferred but not created or destroyed
i. In living systems, energy always enters as light and leaves as heat
b. Every energy transfer increases entropy
i. Entropy is a measure of disorder or randomness
c. Living organisms both increase order _________________ and decrease
order_____________
d. So why does life not violate the 2nd law of thermodynamics?
i. As entropy in organisms decreases (becomes more ordered) universal entrpy
increases (becomes more random)
ii. Organisms are islands of low entropy (high order)
e. Where do biological systems get E, What is the flow of energy? In any ecosystem,
energy enters as light and exits as heat
6. Free Energy (G): measure of a systems instability or tendency of a system to move to a more
stable state. It’s the energy available to do work. (a type of potential energy)
a. ΔG is the difference between Gfinal and Ginitial (Gfinal –Ginitial)
b. Spontaneous processes: occur without input of energy
i. Always increase entropy
c. Spontaneous processes have a negative ΔG
d. In spontaneous processes G decreases and stability increases.
e. They move towards equilibrium where no work can be done (Rxns go back and forth at
same rate)
i. Living things harness spontaneous processes to do work.
ii. Why is free energy important to understanding biological functions? It explains
and predicts how chemical processes will happen in cell
7. Exergonic Rxn: net release of energy
a. Is ΔG negative or positive?
b. Is processes spontaneous or not?
c. The magnitutude of ΔG represents the ability of the reaction to do work
d. Releases free energy (G) to do work elsewhere
8. Endergonic Rxn: net gain of G. Absorbs G
a. Is ΔG negative or positive?
b. Is a process spontaneous?
c. Uses energy produced in exergonic rxns
9. What happens when systems reaches equilibrium NO WORK can be done!
a. Defining feature of life= metabolism is never at equilibrium!
i. Always an input and output
ii. Equilibrium=death
10. How do cells gain Free Energy?
a. Convert light energy to ATP and
b. use ATP to power exergonic rxns to power endergonic rxns
c. Review: Three types of work: chemical, Transport, mechanical
d. Image: h2o is exergonic, light bulb is endergonic
e. ATP releases energy (exergonic) and becomes ADP
f. ADP has lower free energy
g. Available energy powers endergonic rxs
i. Exaxmple: glutamine
Key Terms
Metabolism/Metabolic pathways
Catabolic/Anabolic pathways
Kinetic/ Potential/Chemical
1st law of thermodynamics
2nd law of thermodynamics
Entropy
Spontaneous processes
Free energy/ ΔG
Exergonic/Endergonic
ATP/ADP