Chapter 05 - Chapter 5 Lecture Outline Introduction

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Chapter 5 Lecture Outline Introduction Cool “Fires” Attract Mates and Meals A. Characteristics of organisms (the light of a firefly, the red pigments of a New England autumn, the trumpeting of an elk, the rank odor of mildew in a damp closet) are all the products of chemical reactions that occur in organisms and their cells. B. Organisms carry out chemical reactions for the purpose of energy transformation. In fact, all reactions involve some energy transformation. C. This chapter covers several topics involved in how cells actually perform work: energy, enzymes, and membranes. Preview: Some reactions are simply required for biosynthesis (for example, the digestion of food into smaller parts, the formation of pigments, or the release of smelly waste products). Biosynthesis is discussed further in Module 6.15. I. Energy and the Cell Module 5.1 Energy is the capacity to perform work. A. Energy can only be described and measured by how it affects matter. Energy is defined as the capacity to perform work. There are two forms of energy. B. Kinetic energy is the energy of motion (Figure 5.1A). Heat (or thermal energy) is the kinetic energy associated with randomly moving molecules. The energy in light is another form of kinetic energy (talk about capturing energy from light during photosynthesis). C. Potential energy is the stored capacity to perform work as a result of location or structure (Figure 5.1B). The most important form of potential energy in living things is the potential energy stored in the arrangement of atoms in molecules (structure). This is called chemical energy. The cell can convert the chemical energy (potential energy in the bonds) to kinetic energy and perform work. NOTE: Some everyday examples help clarify these early definitions, such as Figure 5.1C and diagrams of water flowing downhill, dammed up, and flowing through a turbine or over a waterwheel. Module 5.2 Two laws govern energy transformations. A. Thermodynamics is the study of energy transformation that occurs in matter. Preview: As discussed in Module 36.8, there is a limit to the length of a food chain. These limits are the direct result of the laws of thermodynamics. B. First law of thermodynamics (energy conservation). The total amount of energy in the universe is constant; this energy can be transferred or transformed but neither created nor destroyed. Discuss the light bulb in the classroom that converts the electricity to light energy (and some heat, which is explained in the second law). C. Second law of thermodynamics (entropy or disorder increases). Every energy change results in increased disorder, or increased entropy (when looking at the state of the energy throughout the system studied). As energy is converted from one form to another, unusable energy is lost to the surrounding environment in the form of heat (Figure 5.2A). Remind the students that this is why our body temperature is at 37 8 C and why we must sweat to stay cool when we work or play hard. D.
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Chapter 05 - Chapter 5 Lecture Outline Introduction

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