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Transcript
```Lecture 6 Notes – Metabolism: Energy and Enzymes Questions • What forms of energy are used by a cell? • How is energy used to drive biological processes within cells? • What might happen if insufficient energy is available for cells to function? Intro – chapter focuses on how cells perform work: energy, enzymes, membranes 6.1 Energy and the Cell Energy = the capacity to perform work Two types: 1. Kinetic energy = energy of motion a. Heat is kinetic energy – random movement of particles b. Light is kinetic energy 2. Potential energy = stored capacity to perform work as a result of location or structure a. Chemical energy – energy stored in arrangement of atoms in molecules b. Cell converts potential energy to kinetic energy to perform work Thermodynamics = study of energy transformations that occur in a collection of matter, or system 1. First Law of Thermodynamics = total amount of energy in universe is constant, energy can be transferred or transformed but not created nor destroyed 2. Second Law of Thermodynamics = every energy change results in increased disorder, or entropy, unusable energy is lost to surroundings as heat 6. 2 Chemical reactions store or release energy 1. Reactants vs. products: A + B  C + D 2. Free Energy – ∆G – amount of energy left to do work after a chemical reaction has occurred. 3. Endergonic reactions – require an input of energy equal to the difference in potential energy of reactants and products • Example = photosynthesis – uses energy of sunlight to form organic compounds • ∆G > 0 (draw picture) 4. Exergonic reactions – result in an output of energy equal to the difference in the potential energy of the reactants and products • Example = burning and cellular respiration – chemical energy of reactants is released to form energy-­‐poor products • Cellular respiration: glucose is burned to produce ATP, heat, CO2 and water • ∆G < 0 and reaction is spontaneous (draw picture) 5. Cellular metabolism = sum of endergonic reactions and exergonic reactions in cells 6. Energy coupling = the use of energy released from exergonic reactions to drive endergonic reactions ATP = adenosine triphosphate • Powers all forms of cellular work • Glucose contains too much energy – like using a \$100 bill to buy a soda in a vending machine • Adenine (nitrogenous base) + ribose (5 carbon sugar) + three phosphate groups (all negatively charged) • Mutual repulsion of phosphate groups contributes to potential energy stored in ATP (like a compressed spring) • Energy stored in bonds between phosphate groups – bonds broken by hydrolysis • ATP + H2O  ADP + P + energy (exergenic reaction) • ADP = Adenosine diphosphate •
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