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Chapter 5: Ground Rules of Metabolism – Energy Flow, Metabolic Pathways, Enzymes.

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Presentation on theme: "Chapter 5: Ground Rules of Metabolism – Energy Flow, Metabolic Pathways, Enzymes."— Presentation transcript:

1 Chapter 5: Ground Rules of Metabolism – Energy Flow, Metabolic Pathways, Enzymes

2 globalchange.umich.edu

3 What Is Energy? Energy is the capacity to do work Work is a force acting on an object that causes the object to move

4 What Is Energy? Chemical energy –The energy that powers life –The objects that move are electrons, which reposition during chemical reactions

5 Laws of Thermodynamics 2 fundamental types of energy –Kinetic energy the energy of movement –e.g. light, heat, electricity, moving objects –Potential energy stored energy –e.g. chemical energy in bonds, electrical charge in a battery, a rock at the top of a hill

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7 The Laws of Thermodynamics describe the availability and usefulness of energy

8 First Law of Thermodynamics Energy can neither be created nor destroyed –Total amount of energy within a system remains constant unless energy is added or removed from system

9 Second Law of Thermodynamics Amount of useful energy decreases when energy is converted from one form to another Ex. When glucose is broken down in the body to get energy, not all of the stored energy in that molecule is used. Some of the energy is lost in the form of heat, which is not a usable form of energy for the organism. –As energy is converted from one form to another, Entropy (disorder) increases

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11 Entropy

12 Energy of Sunlight freefoto.com picturesindia.com

13 Chemical Reactions Processes that form or break chemical bonds between atoms Chemical reactions convert reactants to products Reactants Products

14 Chemical Reactions Reactions can be categorized as exergonic or endergonic based on energy gain or loss

15 Exergonic Reactions Release energy Reactants contain more energy than products

16 Exergonic Reactions Ex: the burning of glucose

17 Activation Energy All chemical rxns require an initial energy input (activation energy) to get started –Electrons of an atom repel other atoms and inhibit bond formation

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19 Endergonic Reactions Require an input of energy Products contain more energy than reactants

20 Endergonic Reactions Ex: photosynthesis

21 Coupled Reactions Exergonic rxns drive endergonic rxns Energy-carrier molecules –used to transfer energy within cells

22 Energy Carrier Molecules Energy carrier molecules are only used within cells because they are unstable motherearthnews.com newgeology.us

23 ATP Adenosine triphosphate (ATP) –most common energy carrying molecule Composed of an adenosine molecule and 3 phosphates

24 ATP Energy stored in high-energy bond extending to last phosphate Heat is given off when ATP breaks into ADP (adenosine diphosphate) and P (phosphate)

25 ATP – Coupled Reactions Energy released when ATP is broken down into ADP + P is transferred to endergonic rxns through coupling

26 Electron Carriers Energy can be transferred to electrons in glucose metabolism and photosynthesis Electron carriers transport high-energy electrons 2 common e- carriers: 1.Nicotinamide adenine dinucleotide (NAD + ) 2.Flavin adenine dinucleotide (FAD+)

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28 Metabolism Sum of all chemical rxns in a cell Many cellular reactions are linked through metabolic pathways

29 Metabolic Pathways 1.Endergonic rxns are coupled with exergonic rxns 2. Energy-carrier molecules capture energy and transfer it between rxns 3. Chemical rxns are regulated through enzymes

30 Spontaneous Reactions Spontaneous rxns proceed too slowly to sustain life Rxn speed is generally determined by the activation energy required –Rxns with low activation energies proceed rapidly at body temperature –Rxns with high activation energies (e.g. sugar breakdown) move very slowly at body temperature

31 Enzymes Proteins that catalyze (speed up) chemical rxns in cells

32 Catalysts Reduce Activation Energy Catalysts speed up rate of a chemical rxn without themselves being used up Catalysts speed up spontaneous rxns by reducing activation energy

33 Catalytic Converters Catalytic converters in cars facilitate the conversion of carbon monoxide to carbon dioxide Octane + oxygen carbon dioxide + water + energy + carbon monoxide (poisonous)

34 Catalytic Converters Catalyst in catalytic converter speeds carbon monoxide conversion Carbon monoxide + oxygen carbon dioxide + energy

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36 Enzymes Are Biological Catalysts Enzymes orient, distort, and reconfigure molecules in process of lowering activation energy Enzymes differ from non-biological catalysts b/c: 1.Are specific for molecules they catalyze 2.Activity is often enhanced or suppressed by their reactants or products

37 Enzyme Structure Have a pocket called an active site Reactants (substrates) bind to active site –Distinctive shape of active site is complementary and specific to substrate –Active site amino acids bind to substrate and distort bonds to facilitate a reaction

38 Enzyme Structure Three steps of an enzyme catalyst 1.Substrates enter active site in a specific orientation 2. Upon binding, substrates and enzyme change shape to promote a rxn 3. Products of rxn leave the active site - leave enzyme ready for another catalysis

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40 Cells Regulate Metabolism One enzyme usually catalyzes a single step in a chain of metabolic rxns

41 Control of Metabolic Pathways 1.Control of enzyme synthesis regulates availability –Enzyme synthesized only when needed 2. Some enzymes are inactive when synthesized and must be “turned on” to be active –Enzyme pepsin – found in stomach – only activated when stomach acid increases –Made in the inactive form to prevent self-digesting 3. Small organic molecules can bind to enzymes and enhance/inhibit activity (allosteric regulation)

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43 Control of Metabolic Pathways 4.Adequate amounts of formed product inhibit enzyme activity (feedback inhibition)

44 Drugs and Poisons Drugs and poisons often inhibit enzymes by competing w/natural substrate for active site Known as competitive inhibition

45 Environmental Conditions Most enzymes function optimally only within a very narrow range of conditions 3D structure of an enzyme is sensitive to pH, salts, temperature, and presence of coenzymes

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48 The End


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