Metabolism is the totality of an organism ’ s chemical reactions including matter and energy.

1. Concept 8.1: An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics • Metabolism is the totality of an organism’s chemical reactions including matter and energy.

2. Organization of the Chemistry of Life into Metabolic Pathways • A metabolic pathway is a series of chemical reactions that begins with a specific molecule and ends with a product • Each step is catalyzed by a specific enzyme • http://www.youtube.com/watch?v=QJzAvTAL9WI Enzyme 1 Enzyme 2 Enzyme 3 A B C D Reaction 1 Reaction 2 Reaction 3 Starting molecule Product

3. Metabolic Pathways: Catabolic and Anabolic Pathways • 1- Catabolic pathways breakdown complex molecules to form simpler molecules & liberate energy that is available to the cell. • e.g: in cellular respiration: Glucose breaks down to CO2 and H2O & energy is released. • some of the released energy is saved as ATP and used by the cell as energy currency. • most of the energy is released as heat energy

4. Metabolic Pathways: Catabolic and Anabolic Pathways • 2- Anabolic pathways consume energy to build complex molecules from simpler ones • Examples: • making sugars from CO2 and H2O • making starch from glucose • making proteins from amino acids. • making fats from fatty acids and glycerol

5. Forms of Energy • Energy is the capacity to cause change. • Energy exists in various forms.

6. Forms of Energy • Kinetic energy is energy associated with motion. • Potential energy is: • energy that matter possesses because of its location or structure. • It’s energy at rest, but has the potential to do work.

7. Energy can be converted from one form to another Energy conversion!!!! Wait, I can explain that. http://www.youtube.com/watch?v=vl4g7T5gw1M

8. Energy can be converted from one form to another Energy conversion!!!! What’s going on up there?

9. On the platform, the diver has more potential energy. Diving converts potential energy to kinetic energy. Energy can be converted from one form to another Climbing up converts kinetic energy of muscle movement to potential energy. In the water, the diver has less potential energy.

10. The First Law of Thermodynamics • Thermodynamics is the study of energy transformations • According to the first law of thermodynamics, the energy of the universe is constant • Energy can be transferred and transformed • Energy cannot be created or destroyed • The first law is also called the principle of conservation of energy.

11. The Second Law of Thermodynamics • During every energy transfer or transformation, some energy is unusable, often lost as heat • According to the second law of thermodynamics, every energy transfer or transformation increases the entropy (disorder) of the universe. • Living cells unavoidably convert organized forms of energy to heat CO2 Heat Chemical energy H2O First law of thermodynamics Second law of thermodynamics

12. Enzymes speed up metabolic reactions by lowering energy barriers • A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction • An enzyme is a catalytic protein

13. Enzymes

14. The Activation Energy Barrier • Every chemical reaction between molecules involves bond breaking and bond forming • The initial energy needed to start a chemical reaction is called the free energy of activation, or activation energy (EA) • Activation energy is often supplied in the form of heat from the surroundings

15. LE 8-14 B A C D Transition state EA B A Free energy D C Reactants B A DG < O C D Products Progress of the reaction

16. Enzymes lower the activation energy of a reaction • Enzymes lower the activation energy of a reaction, increase the speed of a reaction (millions of reactions per minute!) Enzymes do not affect the change in free-energy (∆G). http://www.youtube.com/watch?v=Dd1yi2aVoOc

17. Enzymes lower the activation energy of a reaction Course of reaction without enzyme EA without enzyme EA with enzyme is lower Reactants Free energy Course of reaction with enzyme DG is unaffected by enzyme Products Progress of the reaction

18. Figure 3.12 Activation Energy Initiates Reactions

19. Substrate Specificity of Enzymes • The reactant that an enzyme acts on is called the enzyme’s substrate • The enzyme binds to its substrate, forming an enzyme-substrate complex • The active site is the region on the enzyme where the substrate binds • Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction. • http://www.youtube.com/watch?v=V4OPO6JQLOE&feature=related

20. LE 8-16 Substrate Active site Enzyme-substrate complex Enzyme