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5.1 The Flow of Energy in Living Things • Energy is the ability to do work • Energy is considered to exist in two states kinetic energy • the energy of motion potential energy • stored energy that can be used for motion • All the work carried out by living organisms involves the transformation of potential energy to kinetic energy Figure 5.1 Potential and kinetic energy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Potential energy (b) Potential energy (c) Kinetic energy a: © Nice One Productions/Corbis RF Water Gradient of a Dam 5.1 The Flow of Energy in Living Things • There are many forms of energy but all of them can be converted to heat • Heat energy is the most convenient form of energy to measure • Thermodynamics is the study of energy or heat changes 5.2 The Laws of Thermodynamics • Laws of thermodynamics govern the energy changes of the universe, including those involved with any activity of an organism • 1st Law of Thermodynamics the total amount of energy in the universe remains constant energy can change from one state to another but it can never be created nor destroyed during the energy conversions, some of the energy is lost as heat energy • 2nd Law of Thermodynamics the amount of disorder, or entropy, in the universe is increasing Figure 5.3 Entropy in action Figure 5.4 Chemical reactions and catalysis 5.4 How Enzymes Work • Enzymes are the catalysts used by cells to perform particular reactions enzymes bind specifically to a molecule and stress the bonds to make the reaction more likely to proceed the active site is the site on the enzyme that binds to a reactant the site on the reactant where the enzyme binds is called the binding site Figure 5.5 An enzyme’s shape determines its activity Essential Biological Process 5A: How Enzymes Work 5.4 How Enzymes Work • Catalyzed reactions may occur together in sequence the product of one reaction is the substrate for the next reaction until a final product is made the series of reactions is called a biochemical pathway Figure 5.6 A biochemical pathway 5.4 How Enzymes Work • Temperature and pH affect enzyme activity Enzymes function within an optimum temperature range Enzymes function within an optimal pH range Figure 5.7 Enzymes are sensitive to their environment Essential Biological Process 5B: Regulating Enzyme Activity Figure 5.8 How enzymes can be inhibited 5.6 ATP: The Energy Currency of the Cell • The energy from the sun or from food sources must be converted to a form that cells can use adenosine triphosphate (ATP) is the energy currency of the cell 5.6 ATP: The Energy Currency of the Cell • The structure of ATP suits it as an energy carrier each ATP molecule has three parts 1. a sugar 2. an adenine nucleotide 3. a chain of three phosphate groups the phosphates are negatively charged and it takes a lot of chemical energy to hold them together the phosphates are poised to come apart Figure 5.9 The parts of an ATP molecule Photosynthesis and Cellular Respiration Complementary Processes High Energy Electrons Release Energy to make ATP e– ATP e– e– e– e– NADPH e– Mill makes ATP e– Photosystem II Photosystem I Location of Photosynthesis (a) Leaves Copyright © 2011 Pearson Education, Inc. Location of Photosynthesis cuticle upper epidermis mesophyll cells (a) Leaves lower epidermis (b) Internal leaf structure Copyright © 2011 Pearson Education, Inc. Location of Photosynthesis cuticle upper epidermis mesophyll cells (a) Leaves lower epidermis (b) Internal leaf structure (c) Mesophyll cell containing chloroplasts Copyright © 2011 Pearson Education, Inc. Location of Photosynthesis cuticle upper epidermis mesophyll cells (a) Leaves lower epidermis outer membrane inner membrane thylakoid (b) Internal leaf structure stroma (d) Chloroplast (c) Mesophyll cell containing chloroplasts Copyright © 2011 Pearson Education, Inc. A Chloroplast outer membrane inner membrane thylakoid stroma How do Gases Get In and Out of Leaf? How is Light Captured by Leaf? Figure 6.2 How a photosystem works Figure 6.3 Plants use two photosystems in the lightdependent reactions Figure 6.5 The photosynthetic electrons are used to produce ATP and NADPH The Light-Independent Reactions (Calvin Cycle) Input CO2 ATP NADPH CALVIN CYCLE Output: G3P Photosynthesis Overview - Simplified Light H2O Chloroplast CO2 Stroma NADP+ ADP P Thylakoid membranes Light reactions Calvin cycle ATP NADPH O2 Sugar Photosynthesis Overview - Detailed H2O CO2 Chloroplast Light NADP+ ADP + P Photosystem II Thylakoid membranes RuBP CALVIN CYCLE 3-PGA (in stroma) Electron transport chains Photosystem I ATP NADPH Stroma G3P O2 Sugars LIGHT REACTIONS CALVIN CYCLE Cellular respiration Cellulose Starch Other organic compounds Figure 7.3 An overview of cellular respiration https://www.youtube.com/watch?v=joZ1Es A5_NY https://www.youtube.com/watch?v=Gb2EzF_XqA