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2. Outline
Energy Flow in Living Things
Laws of Thermodynamics
Free Energy
Activation Energy

3. Energy Flow in Living Things
Energy - Capacity to perform work.
Kinetic Energy - Energy of motion.
Potential Energy - Stored energy due to an object’s relative position.
Thermodynamics - Study of energy.
Kilocalorie (1,000 calories)
Calorie - Heat required to raise temperature of one gram of water one degree Celsius.

4. Energy Flow in Living Things
Oxidation-Reduction
During a chemical reaction, the energy stored in chemical bonds may transfer to new bonds.
Oxidation - Atom or molecule loses an electron.
Reduction - Atom or molecule gains an electron.
Always take place together.

6. Laws of Thermodynamics
First Law - Energy is neither created nor destroyed; it can only change from one form to another.
Total amount of energy in the universe remains constant.
During energy conversion, some energy dissipates into the environment as heat.
Energy flows one-way from the sun through the environment.

7. Laws of Thermodynamics
Second Law - Entropy in the universe is continuously increasing.
Entropy increases continuously.

8. Free Energy
Free Energy of a molecule is the amount of energy actually available to break and subsequently form other chemical bonds.
the energy available to do work.

9. Endergonic Reaction - Requires energy input.
Free Energy
Endergonic Reaction - Requires energy input.
Exergonic Reaction - Occurs spontaneously and releases excess free energy.
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10. Activation Energy
Activation Energy is the energy required to destabilize existing chemical bonds and initiate a chemical reaction.
Most reactions require energy to get started
Catalysis - Process of lowering necessary activation energy.

11. Activation Energy and Catalysis
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12. Enzymes
Enzymes carry out most catalysis in living organisms.
Unique three-dimensional shape of an enzyme enables it to stabilize a temporary association between substrates.
Lowers activation energy necessary for new bonds to form.
(stop here for now!)

13. Enzymes (continued from last week)
How Enzymes Work
Most enzymes are globular proteins with one or more active sites for substrates to bind.
Substrate binding induces enzyme to adjust its shaped for an induced fit.

14. Enzyme Catalytic Cycle
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15. Enzymes
Enzyme Forms
Multienzyme Complexes
Enzymes catalyzing different steps of a sequence are loosely associated with one another.
Increase catalytic efficiency.
Not all Biological Catalysts are Proteins.

16. Factors Affecting Enzyme Activity
Temperature
Rate increase with temperature up to temperature optimum. pH
Changing concentration of hydrogen ions shifts the balance between positively and negatively charged amino acid residues.
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17. Factors Affecting Enzyme Activity
Inhibitors and Activators
Inhibitors - Decrease enzyme activity.
Competitive - Compete with substrate for same binding site.
Noncompetitive - Bind to enzyme in other location, altering shape.
Allosteric Site
Activators - Bind to allosteric sites and keep enzymes in active configurations.
Increase enzyme activity.
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18. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

19. Factors Affecting Enzyme Activity
Enzyme Cofactors - Enzyme function assisted by additional chemical components.
Coenzyme - Nonprotein organic molecule serves as cofactor.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

20. Adenosine triphosphate (energy currency) Composed of:
ATP
Adenosine triphosphate (energy currency)
Composed of:
Five-carbon sugar (ribose)
Adenine
Triphosphate group
Energy Storage
Phosphate groups are highly negatively charged.
Unstable bonds easily broken.
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21. Cells use ATP to drive endergonic reactions.
Instability makes ATP ideal for short-term energy source, but a poor candidate for long-term energy storage.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

22. Anabolism - Expend energy to make chemical bonds.
Biochemical Pathways
Metabolism - Total of all chemical reactions carried out by an organism.
Anabolism - Expend energy to make chemical bonds.
Catabolism - Harvest energy when chemical bonds are broken.
Biochemical Pathways - Products of one reaction becomes substrate for the next.
Regulated by feedback inhibition.
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23. Biochemical Pathways
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24. Evolution of Metabolism
Degradation
Glycolysis
Anaerobic Photosynthesis
Nitrogen Fixation
Oxygen-Forming Photosynthesis
Aerobic Photosynthesis
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25. Energy Flow in Living Things Laws of Thermodynamics Free Energy
Review
Energy Flow in Living Things
Laws of Thermodynamics
Free Energy
Activation Energy
Enzymes
Factors Affecting Enzyme Activity
ATP
Biochemical Pathways
Evolution of Metabolism
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26. Copyright © McGraw-Hill Companies Permission required for reproduction or display
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