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CHAPTER FIVE

This chapter explores the fundamental concepts of energy, including conservation, conversion, and cellular work. Topics covered include heat, chemical energy, ATP, enzymes, passive transport, osmosis, and active transport.

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CHAPTER FIVE

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  1. CHAPTER FIVE • About 75% of the energy generated by a car’s engineis lost as heat • You’d have to run 14 miles to burn the calories from one large pepperoni pizza

  2. SOME BASIC ENERGY CONCEPTS • Energy makes the world go around • what is energy? • Energy is the capacity to perform work

  3. Conservation of Energy • Kinetic energy is energy in motion • Potential energy is energy in storage 2 High potential energy 1 Conversion of kinetic energy to potential energy 3 Conversion of potential energy to kinetic energy 4 Low potential energy

  4. Conservation of Energy • Energy can be converted from one form toanother but it cannot be created or destroyed

  5. Heat • Heat is • a type of kinetic energy • randomized energy

  6. Chemical Energy • Chemical energy • is a form of potential energy • is found in food, gas, and other fuels

  7. Waste products poor in chemical energy Fuel rich in chemical energy Heat energy Carbon dioxide Gasoline Combustion Kinetic energy of movement Oxygen Water (a) Energy conversion in a car

  8. Heat energy Cell respiration Carbon dioxide Food Oxygen Water Energy for cellular work (b) Energy conversion in a cell

  9. Cell respiration • is the energy-releasing chemicalbreakdown of fuel molecules

  10. Food Calories • A calorie is the amount of energy that raises the temperature of 1 gram of water by 1 degree Celsius

  11. 1 Calorie = 1,000 calories • the unit used to measure the energy in food

  12. ATP AND CELLULAR WORK • The chemical energy of organic molecules is released in cell respiration to make ATP • This release occurs in the mitochondria

  13. The Structure of ATP • ATP (Adenosine TriPhosphate) • adenosine plus three phosphate groups Energy Adenosine Adenosine Phosphate transferred to other molecules

  14. ENZYMES • Metabolism is defined as all of thechemical reactions that occur in organisms; rate? • Few metabolic reactions occurwithout the assistance of enzymes

  15. Activation Energy • Activation energy • the minimum energy required to activate the reaction

  16. Enzymes • lower the activation energy for chemical reactions Activation energy barrier Enzyme Reactants Products (a) Without enzyme (b) With enzyme

  17. Selective • Each enzyme is very selective • Each enzyme fits to one specific substrate • the active site fits to the substrate and theenzyme changes shape slightly; induced fit

  18. Enzymes are reusable Substrate (sucrose) Enzyme available with empty active site 1 2 Substrate binds to enzyme Active site Enzyme (sucrase) Fructose Glucose Substrate is converted to products 4 3 Products are released

  19. Enzyme Inhibitors • Enzyme inhibitors • inhibit a metabolic reaction • bind to the active site, as substrate impostors Inhibitor Substrate Substrate Active site Active site Enzyme Enzyme (b) Enzyme inhibition by a substrate imposter (a) Normal enzyme action

  20. Passive Transport: Diffusion Across Membranes • Molecules contain heat energy • they vibrate and wander randomly • Diffusion is one result of themovement of molecules • molecules tend to spread into the available space • diffusion is passive transport; no energy is needed

  21. Molecules of dye Membrane Equilibrium (a) Passive transport of one type of molecule Equilibrium (b) Passive transport of two types of molecules

  22. Osmosis and Water Balance in Cells • Osmosis is the passive transport of wateracross a selectively permeable membrane Hypotonic solution Hypertonic solution Isotonic solutions Sugar molecule (solute) Selectively permeable membrane Osmosis (net movement of water)

  23. Water Balance in Cells • The survival of a cell depends on itsability to balance water uptake and loss Animal cell Normal Lysing Shriveled Plasma membrane Plant cell Shriveled Flaccid (wilts) Turgid (a) Isotonic solution (b) Hypotonic solution (c) Hypertonic solution

  24. Active Transport • Active transport requires energy tomove molecules across a membrane Lower solute concentration Solute Higher solute concentration

  25. Exocytosis and Endocytosis:Traffic of Large Molecules • Exocytosis • secretes substances outside of the cell Outside cell Plasma membrane Cytoplasm (a) Exocytosis

  26. Endocytosis • takes material into the cell (b) Endocytosis

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