1. Chapter 8~ An Introduction to Metabolism

2. Metabolism Metabolism Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell Catabolic pathways: degradative (break down) process such as cellular respiration; net release of energy from molecules Anabolic pathways: building process such as protein synthesis; photosynthesis; net gain of energy in molecules

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

4. Thermodynamics Energy (E)~ capacity to do work; –Kinetic energy~ energy of motion –Potential energy~ stored energy Chemical energy~ potential energy of molecules Thermodynamics~ study of E transformations 1st Law: conservation of energy; E transferred/transformed, not created/destroyed 2nd Law: transformations increase entropy (disorder, randomness)

5. An example of energy conversion First law of thermodynamics: Energy can be transferred or transformed but neither created nor destroyed. For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement in (b). (a) Chemical energy

6. The Second Law of Thermodynamics Spontaneous changes that do not require outside energy increase the entropy, or disorder, of the universe Second law of thermodynamics: Every energy transfer or transformation increases the disorder (entropy) of the universe. For example, disorder is added to the cheetah’s surroundings in the form of heat and the small molecules that are the by-products of metabolism. (b) Heat co 2 H2OH2O +

7. Energy Changes Free energy: portion of system’s E that can perform work Exergonic reaction: net release of free E to surroundings Endergonic reaction: absorbs free E from surroundings

8. The Structure and Hydrolysis of ATP ATP (adenosine triphosphate) –Is the cell’s energy shuttle –Provides energy for cellular functions O O O O CH 2 H OH H N HH O N C HC N C C N NH 2 Adenine Ribose Phosphate groups O O O O O O - --- CH

9. Energy is released from ATP When the terminal phosphate bond is broken P Adenosine triphosphate (ATP) H2OH2O + Energy Inorganic phosphate Adenosine diphosphate (ADP) PP PPP i

10. How ATP Performs Work ATP drives endergonic reactions –By phosphorylation, transferring a phosphate to other molecules

11. The three types of cellular work (c) Chemical work: ATP phosphorylates key reactants P Membrane protein Motor protein P i Protein moved (a) Mechanical work: ATP phosphorylates motor proteins ATP (b) Transport work: ATP phosphorylates transport proteins Solute PP i transportedSolute Glu NH 3 NH 2 P i + + Reactants: Glutamic acid and ammonia Product (glutamine) made ADP + P

12. Energy & ATP Exergonic processes drive endergonic ones (ATP) Adenosine triphosphate ATP tail: high negative charge ATP hydrolysis: release of free E Phosphorylation- phosphate group transferred to a molecule

13. ATP ADP + P i Energy for cellular work (endergonic, energy-consuming processes) Energy from catabolism (exergonic, energy yielding processes) ATP/ADP cycle Catabolic pathways –Drive the regeneration of ATP from ADP and phosphate ATP synthesis from ADP + P i requires energy ATP hydrolysis to ADP + P i yields energy

14. Directional chemical reactions Chemical reactions start with reactants and end with products. –Most reactions can proceed in both directions A + B C (starting)(product) Equilibrium is met when the reaction proceeds equally in either direction

15. Chemistry of Life during Metabolic Activity A metabolic pathway has many steps –That begin with a specific molecule and end with a product –That are each catalyzed by a specific enzyme Enzyme 1Enzyme 2Enzyme 3 A B C D Reaction 1Reaction 2Reaction 3 Starting molecule Product

16. Catabolic pathways (degradative) –Break down complex molecules into simpler compounds –Release energy Anabolic pathways (biosynthetic) –Build complicated molecules from simpler ones –Consume energy Chemistry of Life during Metabolic Activity

17. Enzymes Catalytic proteins: speed up the rate of reactions w/o being consumed Activation Energy: the E required to break or form bonds Substrate: enzyme reactant Active site: pocket or groove on enzyme that binds to substrate Induced fit model- strained reactants more readily react

18. The active site Is the region on the enzyme where the substrate binds Substrate Active site Enzyme

19. Induced fit of a substrate Brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction Enzyme- substrate complex

20. How Enzymes Work Progress of the reaction Products Reactants Course of reaction with enzyme Course of reaction without enzyme EAEA without enzyme E A with enzyme is lower ∆G is unaffected by enzyme Free energy

21. How Enzymes Work 1.Enzyme attaches to the substrate during the chemical reaction and slightly changes its shape so the substrate fits tightly 2.At the active site, the activation energy is reduced making the substrate more likely to react 3.When the reaction is complete, products leave the enzyme and it can catalyze other reactions

23. Effects of Local Conditions on Enzyme Activity The activity of an enzyme –Is affected by general environmental factors

24. Effects on Enzyme Activity Temperature pH Allosteric control- substances can bind and affect enzymes. Cofactors: –inorganic, nonprotein helpers; ex.: zinc, iron, copper Coenzymes: –organic helpers; ex.: vitamins