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What is energy?

Cell. Energetics 1. What is energy?. Energy. Energy is the ability to do work. Energy is a phenomenon, not a material. Two broad categories of energy: Potential Kinetic. Potential Energy. Potential energy is stored energy. Examples: coiled spring, bonds between atoms. Kinetic Energy.

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What is energy?

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  1. Cell Energetics 1 • What is energy?

  2. Energy • Energy is the ability to do work. • Energy is a phenomenon, not a material. • Two broad categories of energy: • Potential • Kinetic

  3. Potential Energy • Potential energy is stored energy. • Examples: coiled spring, bonds between atoms

  4. Kinetic Energy • Kinetic energy is energy that has been released to do work. • Examples: car in motion, heat, light.

  5. Potential Kinetic Magnetic Radiant (Light) Gravity Electrical Chemical Sound Nuclear Motion Stored mechanical Thermal (heat) Examples of Energy

  6. First Law of Thermodynamics • Assuming there is no input of energy, the total energy within a given system remains constant. Energy is conserved. • Energy can change form (example: chemical energy in cells may be converted to heat, motion, etc.)

  7. Potential Kinetic Chemical: Energy stored in chemical bonds in food. Motion: Muscles in motion Chemical: Energy stored by photosynthesis. Radiant: Sunlight Electrical: Current used by an electric heater. Thermal: Heat produced by the heater. Chemical: Gasoline Motion: Car powered by burning gasoline. Energy Transformations

  8. Second Law of Thermodynamics • Assuming there is no input of energy (closed system), when energy is converted from one form to another, the amount of useful energy in the system decreases. • Entropy is the tendency toward an increase in randomness and disorder in a closed system.

  9. Thinking Question • Write out an answer to this question: • Do living systems violate the second law of thermodynamics? Why or why not? • Share your response with a partner and discuss what you have written.

  10. Exergonic Reactions • Exergonic (exothermic) reactions release energy. • In exergonic reactions, the reactants have more energy than the products. • However, all chemical reactions require an input of energy to get them started.

  11. Exergonic Reaction

  12. Exergonic Reactions: Living systems • In living systems, exergonic reactions are carried out by enzymes. • Enzymes lower the activation energy required to get these reactions started, so there is more net energy at the end. • Enzymes also control the rate of the reaction so that heat is controlled.

  13. Endergonic Reactions • Endergonic (endothermic) reactions require an input of energy. • Products of the reactions have more energy than the reactants.

  14. Endergonic Reaction Ammonium thiocyanate + Barium hydroxide

  15. Coupled Reactions • Living organisms use energy from exergonic reactions to drive endergonic reactions. • The reactions may occur in different places. Energy may be transferred by energy-carrier molecules such as ATP.

  16. ATP • Adenosine triphosphate (ATP) is the universal energy molecule. • ATP is made up of adenine, a ribose sugar, and three phosphate groups.

  17. ATP and Energy • ATP is synthesized from ADP (Adenosine diphosphate) and a phosphate group, using energy released from the breakdown of glucose, fats, and amino acids. • When the terminal phosphate bond in ATP is broken, energy is released. • ATP is a very unstable molecule.

  18. ATP and Living Organisms • ATP is used by all living organisms. • In plants, the chloroplasts harvest light to make ATP and use it to make glucose and other carbon compounds. • Plants, animals, and all other eukaryotes break down glucose and other compounds to make ATP for their metabolic needs.

  19. Thinking Question • Think about all the things going on in your cells right now. • List as many things as you can think of that probably require ATP to run them.

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