Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Energy and Life Chapter 5 Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Outline Thermodynamics Chemical Reactions Enzymes ATP Photosynthesis  Photosystems  C 3 and C 4 Cellular Respiration

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Flow of Energy in Living Things Energy - The capacity to do work.  Kinetic - Energy in motion  Potential - Stored Energy Thermodynamics - Changes in heat Calorie - Energy required to raise the temperature of 1 gram of water 1 degree Celsius. Kilocalorie - 1,000 calories

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Oxidation - Reduction Chemical Reaction - Forming or breaking a chemical bond.  Oxidation - Process of losing an electron.  Reduction - Process of gaining an electron. Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Laws of Thermodynamics First Law - Energy can change form, but can never be created nor destroyed.  During energy conversion, some energy dissipates as heat. Second Law - Disorder in the universe is continuously increasing.  Entropy - Measure of disorder in a system.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Chemical Reactions Chemical reactions begin with reactants (substrate) and end up with products.  Exergonic - Products contain less energy than reactants.  Endergonic - Products contain more energy than reactants.  Activation Energy - Extra energy required to destabilize chemical bonds and initiate a chemical reaction. - Catalysis - Lowering activation energy.

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Enzymes Enzymes are catalysts used by cells to lower activation energy of a particular reaction.  Bind to specific molecule and stress bonds to make a particular reaction more likely. - Active Site - Site on enzyme surface where reactant fits. - Binding Site - Site on reactant that binds to enzyme. Enzyme activity is affected by any change in condition that alters the enzyme’s three dimensional shape.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Enzymes Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Regulating Enzymes Many enzymes can have their shapes altered when signal molecules bind to their surfaces. (Allosteric Enzymes)  If new shape no longer fits reactant, the signal acts as enzyme inhibitor. Coenzyme - Nonprotein organic molecule acting as a cofactor (chemical components to aid catalysis).

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies How Cells Use Energy Adenosine Triphosphate (ATP) is the molecule in the body that supplies energy.  Sugar backbone  Adenine (DNA nucleotide base)  Chain of three phosphates Most energy exchanges in cells involve cleavage of outermost bond, converting ATP into ADP and inorganic phosphate.

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Photosynthesis Photosynthesis takes place in three stages:  Light Reactions - Capturing energy from sunlight. - Using energy to make ATP.  Calvin Cycle  Using ATP to power synthesis of plant molecules from CO 2. 6CO 2 +12H 2 O + light = C 6 H 12 O 6 +6H 2 O+6O 2

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Capturing Energy From Sunlight Full range photons is known as electromagnetic spectrum.  Humans perceive photons with intermediate amounts of energy as visible light.  Plants appear green because they absorb mainly blue and red light, reflecting back what is left of the visible light. - Particular kinds of atoms absorb only photons with the appropriate amount of energy.

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Capturing Energy From Sunlight Pigments are molecules that absorb light.  Main pigment in plants that absorbs light is chlorophyll. - Chlorophyll a and b  Carotenoids capture wavelengths not efficiently absorbed by chlorophyll.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Capturing Energy From Sunlight

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Organizing Pigments Into Photosystems Light reactions takes place in three stages:  Primary photoevent  Electron transport  Chemiosmosis Light is absorbed by clusters of chlorophyll and accessory pigment molecules.  Reaction center acts as energy sink.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Photosystem Mechanics Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Converting Light to Energy Plants use a two-stage photosystem called noncyclic photophosphorylation.  High energy electrons generated by photosystem II are used to synthesize ATP and then passed to photosystem I to drive production of NADPH.

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies C 3 Photosynthesis Calvin Cycle (C 3 Photosynthesis) performs the assembly of new molecules.  Occurs in stroma of chloroplasts Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies C 4 Photosynthesis As temperatures increase, C 3 becomes inefficient because plants must close stomata to reduce water loss and as a result CO 2 and O 2 movement is restricted.  Internal CO 2 concentrations fall. C 4 plants fix carbon in mesophyll cells.  CO 2 concentrated in bundle sheath cells. - Stomata can be open shorter periods of time, thus conserving water.  High energetic costs

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Cellular Respiration Energy for living is obtained by breaking down organic molecules assembled by chloroplasts.  Cellular Respiration - oxidation of foodstuffs to obtain energy. - Aerobic Respiration (Requires oxygen) Carried out in Two Stages:  Glycolysis (Occurs in cytoplasm)  Oxidation (Occurs in mitochondria)

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Cellular Respiration

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Cellular Respiration Anaerobic Respiration  Uses different inorganic electron acceptors than oxygen. - Methanogens (heat-loving bacteria) - Sulfur Bacteria

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Fermentation Electrons that are also a product of glycolysis but are not donated to oxygen are added to organic molecules.

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Acteyl-CoA When oxygen is available, a second oxidative stage of cellular respiration takes place. Copyright © McGraw-Hill Companies Permission required for reproduction or display

Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Krebs Cycle Krebs Cycle is the next step of oxidative respiration and takes place in mitochondria. Occurs in three stages:  Acetyl Co-A binds a four-carbon molecule and produces a six-carbon molecule.  Two carbons are removed as CO 2.  Four-carbon starting material regenerated.

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Electron Transport Chain NADH molecules carry their electrons to inner mitochondrial membrane where they transfer electrons to a series of membrane- associated proteins. Copyright © McGraw-Hill Companies Permission required for reproduction or display

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Johnson - The Living World: 3rd Ed. - All Rights Reserved - McGraw Hill Companies Review Thermodynamics Chemical Reactions Enzymes ATP Photosynthesis  Photosystems  C 3 and C 4 Cellular Respiration

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