Chapter 8
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8.1 The laws of thermodynamics describe how energy changes.


  Energy is the capacity to bring about change, to provide motion against a force, or to do work.
Kinetic energy is actively engaged in doing work, while potential energy has the capacity to do so.
An oxidation-reduction (redox) reaction is one in which an electron is taken from one atom or molecule (oxidation) and donated to another (reduction).
The First Law of Thermodynamics states that the amount of energy in the universe is constant; energy is neither lost nor created.
The Second Law of Thermodynamics states that disorder in the universe (entropy) tends to increase.
Any chemical reaction whose products contain less free energy than the original reactants can proceed spontaneously. However, the difference in free energy does not determine the rate of the reaction.
The rate of a reaction depends on the amount of activation energy required to break existing bonds.
Catalysis is the process of lowering activation energies by stressing chemical bonds.

1.  Define oxidation and reduction. Why must these two reactions always occur in concert?
2. State the First and Second Laws of Thermodynamics.
3. What is heat? What is entropy? What is free energy?
4. What is the difference between an exergonic and an endergonic reaction? Which type of reaction tends to proceed spontaneously?
5. Define activation energy. How does a catalyst affect the final proportion of reactant converted into product?

Energy Conversion
Catalysis

Thermodynamics
Coupled Reactions

Potential and Kinetic Energy
Endergonic and Exergonic Reactions

 
8.2 Enzymes are biological catalysts.


Enzymes are the major catalysts of cells; they affect the rate of a reaction but not the ultimate balance between reactants and products.
Cells contain many different enzymes, each of which catalyzes a specific reaction.
The specificity of an enzyme is due to its active site, which fits only one or a few types of substrate molecules.

6. How are the rates of enzyme-catalyzed reactions affected by temperature? What is the molecular basis for the effect on reaction rate?
7. What is the difference between the active site and an allosteric site on an enzyme?

Thermodynamics
Kinetics

Enzymes
Activity: Factors Affecting Enzyme Activity

Ribozymes

Enzyme Catalytic Cycle

 
8.3 ATP is the energy currency of life.


 Cells obtain energy from photosynthesis and the oxidation of organic molecules and use it to manufacture ATP from ADP and phosphate.
The energy stored in ATP is then used to drive endergonic reactions.

8. What part of the ATP molecule contains the bond that is employed to provide energy for most of the endergonic reactions in cells?

ATP

 
8.4 Metabolism is the chemical life of a cell. .


 Generally, the final reactions of a biochemical pathway evolved first; preceding reactions in the pathway were added later, one step at a time.

9. What is a biochemical pathway? How does feedback inhibition regulate the activity of a biochemical pathway?

Feedback Inhibition

Pathways
Activity: Biochemical Pathways: The Organizational Units of Metabolism

Science in Industry

Biochemical Pathway
Feedback Inhibition
Catabolic vs. Anabolic Pathways

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  How Scientists Think
  Student Papers

  Bioethics Case Studies
  General Biology Weblinks

Essential Study Partner
Multiple Choice Quiz