Power Lecture Chapter 6 Ground Rules of Metabolism

Power. Lecture: Chapter 6 Ground Rules of Metabolism

Impacts, Issues: Alcohol, Enzymes, and Your Liver Catalase is an enzyme that helps the body break down toxic substances in alcoholic drinks

Impacts, Issues: Alcohol, Enzymes, and Your Liver The liver plays a central role in alcohol metabolism Consumption of too much alcohol, as in binge drinking, can lead to alcoholic hepatitis or alcoholic cirrhosis

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6. 1 First Law of Thermodynamics The total amount of energy in the universe remains constant Energy can undergo conversions from one form to another, but it cannot be created or destroyed

Second Law of Thermodynamics No energy conversion is ever 100 percent efficient The total amount of energy is flowing from high-energy forms to forms lower in energy

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Entropy Measure of degree of disorder in a system Free energy – amount of energy available to break and make bonds

One-Way Flow of Energy The sun is life’s primary energy source Producers trap energy from the sun and convert it into chemical bond energy All organisms use the energy stored in the bonds of organic compounds to do work

Section 6. 2: Participants in Metabolic Reactions Energy carriers Enzymes Cofactors Transport proteins Reactants Intermediates Products

Endergonic Reactions Energy input required Product has more energy than starting substances http: //bp 3. blogger. com/_6 ZOUx. Sfm. Ye. A/R 19 Pgp. ZQIj. I/AAAAABc/jla. Gr. T 4 -W 3 Y/s 320/bio 4. jpg

Exergonic Reactions Energy is released Products have less energy than starting substance http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/exergonic. gif

The Role of ATP Cells “earn” ATP in exergonic reactions Cells “spend” ATP in endergonic reactions base three phosphate groups sugar Fig. 6 -6 a, p. 96

ATP/ADP Cycle http: //www. accessexcellence. org/RC/VL/GG/ecb_images/03_32_ATP_and_ADP_cycle. jpg

Section 6. 3: Enzyme Structure and Function Enzymes are catalytic molecules Used again Specific Nearly all proteins Active Sites

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Four Features of Enzymes 1) Enzymes do not make anything happen that could not happen on its own. They just make it happen much faster. 2) Reactions do not alter or use up enzyme molecules.

Four Features of Enzymes 3) The same enzyme usually works for both the forward and reverse reactions. 4) Each type of enzyme recognizes and binds to only certain substrates.

Activation Energy For a reaction to occur, an energy barrier must be surmounted Enzymes make the energy barrier smaller http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/catreact. gif

More Features Enzyme stabilizes transition state Help substrates get together Orientate subtrates Shut out water Induced-fit model

Section 6. 4: Allosteric Activation allosteric activator vacant allosteric binding site active site altered, can bind substrate enzyme active site cannot bind substrate

Specific Irreversible Forms strong covalent bonds at active site React with -SH, OH, or acid groups Ex: Ag, Hg, Pb Noncompetitive Reversible Changes shape, thus changing active site

Competitive Example: Ethanol to acetaldehyde to acetic acid 2 nd rxn fast but Anatabuse block causing side effects Stop drinking

Allosteric Inhibition

Negative Feedback http: //www. steve. gb. com/images/science/negative_feedback. pn g

Positive Feedback http: //www. steve. gb. com/images/science/positive_feedforward. png

Nonspecific Effect of Temperature Small increase in temperature increases molecular collisions, reaction rates High temperatures disrupt bonds and destroy the shape of active site (denature)

Effect of Temperature Fig. 6 -13, p. 81

Effect of p. H

Enzyme Helpers Cofactors Coenzymes • NAD+, NADP+, FAD • Accept electrons and hydrogen ions; transfer them within cell • Derived from vitamins Metal ions • Ferrous iron in cytochromes

Section 6. 5: Metabolic Pathways Enzyme-mediated sequences of reactions in cells Biosynthetic (anabolic) – ex: photosynthesis Degradative (catabolic) – ex: aerobic respiration

Chemical Equilibrium At equilibrium, the energy in the reactants equals that in the products Product and reactant molecules usually differ in energy content Therefore, at equilibrium, the amount of reactant almost never equals the amount of product

Redox Reactions Cells release energy efficiently by electron transfers, or oxidation-reduction reactions (“redox” reactions) One molecule gives up electrons (is oxidized) and another gains them (is reduced) Hydrogen atoms are commonly released at the same time, thus becoming H+

Electron Transfer Chains Arrangement of enzymes, coenzymes, cell membrane As one molecule is oxidized, next is reduced Function in aerobic respiration and photosynthesis at

Uncontrolled vs. Controlled Energy Release H 2 1/2 O 2 Explosive release of energy as heat that cannot be harnessed for cellular work H 2 O

Section 6. 6: Bioluminescence An outcome of enzyme-mediated reactions that release energy as fluorescent light Used to indicate evidence of metabolism or successful gene transfer.

Bioluminescent Organism North American Firefly flashes to help find mates. Fig. 6 -18 b, p. 102

Bioluminescent Bacteria Daylight Night Fig. 6 -19, p. 103

Bioluminescent Bacteria Using glowing bacteria to chart the location of infectious bacteria inside living mice and the spread through body tissues. Bottom shows how antibiotics have killed most of the infection. Fig. 6 -20, p. 103