Chapter 7 Lecture Outline Energy and Enzymes

Energy in Living Systems Metabolism is the sum of all chemical reactions in the body. Metabolism transfers energy and follows the laws of thermodynamics. © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 2

Laws of Thermodynamics 1st Law: Energy cannot be either created or destroyed 2nd Law: When reactions occur, they become more disordered © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 3

The Carbon Cycle and Energy Living organisms all require energy to survive Sun is source of most energy on Earth Light energy is used by producers to synthesize sugars Plants performing photosynthesis © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 4

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The Carbon Cycle and Energy For non-photosynthesizing organisms (mostly consumers), energy is acquired from food molecules. Carbon dioxide and food molecules are involved in this energy transfer. © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 6

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e The Carbon Cycle © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 7

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Using Energy from Food Energy transfer in nonliving systems can be explosive: Carbon in wood + O2  CO2 + H2O + energy Energy transfer in cells must be controlled: Carbon in food + O2  CO2 + H2O + energy © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 8

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Transfer of Electrons Capturing energy requires transfer of electrons Reactions that transfer electrons are called redox (oxidation/reduction) reactions Oxidation—loss of electrons Reduction—gain of electrons © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 9

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Metabolism All chemical reactions within living cells Anabolic Biosynthetic: create complex molecules out of smaller compounds Catabolic Break down complex molecules to release energy © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 12

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Chemical reactions and thermodynamics A + B  C + D Reactants: A + B Products: C + D Some chemical reactions need a “jump start” to proceed Activation energy: Energy needed to jump‑start a reaction © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 14

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Enzymes Speed Up Reactions Enzymes are biological catalysts Lower the energy of activation Increase the speed of reaction © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 16

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The Structure of Enzymes Very specific for reactions Three‑dimensional shape determines function Active site is region where the substrate binds Induced fit: active site molds around substrate © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 18

Enzymes as Molecular Matchmakers © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 19

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Enzymes in Metabolism Metabolic pathways in the body usually involve several reactions. There may be several intermediates. Each intermediate has its own enzyme. B A C D Enzyme 1 Enzyme 2 Enzyme 3 © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 20

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Enzyme Function Enzymes depend on random collisions. Multiple enzymes may be located close together. This maximizes molecular collisions. © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 21

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Metabolism and Life Span Slowing down metabolism increases life span Higher metabolism results in toxic by products (free radicals) Antioxidants help break down free radicals Some examples of antioxidants Vitamin E Vitamin C Beta-carotene © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 23

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© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Concept Quiz Why are high fevers dangerous and sometimes life‑threatening? Molecules move faster at higher temperatures. Enzymes may change shape at high temperatures. Invading microbes survive better and reproduce faster at high temperatures. The correct answer is B. High fevers are life-threatening for a long period of time because enzymes begin to denature at higher temperatures. Lower fevers can actually be beneficial to the body. It is the natural defense mechanism. Molecules do move faster at higher temperatures, but this answer choice does not address the question. Microbes may reproduce faster at higher temperatures, up to an optimal temperature. Higher than the optimum, microbes can be destroyed. © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 26

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Concept Quiz The loss of electrons is called Oxidation Reduction Redox The correct answer is A. Students often incorrectly think of loss of electrons as reduction. Remind them if something is being reduced, it is acquiring a negative charge and, therefore, gaining an electron. Redox refers to both oxidation and reduction. © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 27

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Concept Quiz Where a substrate binds to an enzyme is known as the Active site Activation energy Energy transfer site The correct answer is A. The active site is where a substrate binds. The shape of the active site dictates the enzyme’s activity and which substrates may bind to it. Activation energy is the energy required to start a reaction. Energy transfer site is listed as a distraction. © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 28

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Biology in the News Doctors Warned about Common Drugs for Pain; NSAIDs Tied to Risk of Heart Attack, Stroke NSAIDs: Non‑steroid anti‑inflammatory drugs Two major categories COX-1 inhibitors May result in stomach problems COX-2 inhibitors Long-term use associated with heart disease Removed from the market © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 29

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Terms Activation energy Active site Anabolic reaction Biosynthetic reaction Catabolic reaction Catalyst Coupled reaction Enzyme First law of thermodynamics Induced fit model Kinetic energy Metabolic pathway Metabolism Oxidation Potential energy © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 30

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Terms Products Redox reaction Reactants Reduction Second law of thermodynamics Substrate © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 31

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Process Animation 7.1a The Energy of Chemical Reactions Macintosh Windows © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 32

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Process Animation 7.1b Heat and Chemical Reactions Macintosh Windows © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 33

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Process Animation 7.1c Enzyme Catalysis Macintosh Windows © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 34

© 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e Process Animation 7.1d Enzymes and Activation Energy Macintosh Windows © 2009 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 35

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Additional Art from Chapter 7 All art files from the book are available in JPEG and PPT formats on the Instructor Resource Disc

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