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Lecture 5

BSC 108 Lecture 5: Biology Chapter 5 Notes
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Department
Biological Sciences
Course
BSC 108
Professor
Christina Yates
Semester
Fall

Description
Biology Chapter 5 Notes Energy • Energy can be changed from one form to another ➢ However it cannot be created or destroyed ➢ This is the conversion of energy principle or the first law of thermal dynamics Entropy • Heat ➢ Is a type of kinetic energy ➢ Is a product of all energy conversions • Scientists use the term entropy as a measure of disorder or randomness ➢ All energy conversions increase the entropy of the universe Chemical Energy • Chemical energy ➢ Is a form of potential energy ➢ Is found in food, gasoline, and other fuels • Living cells and automobile engines use the same basic process to make chemical energy do work Food Calories • A calories is the amount of energy that raises the temperature of one gram of water by one degree Celsius • Calories are very small units of energy ➢ Not practical for measuring the energy in food • A food calories (capitol C) is actually a kilocalorie ➢ 1,00 calories The Calories in Food • Foods with the most c-h bonds • Stores the most potential energy • Have the most calories • Make the most ATP Cellular respiration • It is the energy-releasing chemical breakdown of fuel molecules • Provides energy for the cell to do work • A series of energy transferring chemical reactions • The chemical bonds in food are broken down • The energy in those bonds is shifted to the bonds in ATP ➢ ATP is the energy currency in all cells • About 40% of the energy in food is transferred to ATP ➢ The remainder becomes heat • ATP: adenosine triphosphate • ADP: adenosine diphosphate • Examples: ➢ Motor protein performing mechanical work ➢ Transport protein performing transport work ➢ Chemical reactants performing chemical work The ATP Cycle • Cellular work spends on ATP • ATP is recycled from ADP and phosphate through cellular respiration • ATP functions is what is called energy coupling, or the ATP cycle Enzymes • Metabolism is the sum total of all chemical reactions that occur in organisms • Few metabolic reactions occur without the assistance of enzymes Activation energy • Activation energy: ➢ Is the energy that activates the reactants in a chemical reaction ➢ Triggers a chemical reaction to proceed • Enzymes ➢ Lower the activation energy for chemical reactions Induced Fit • Each enzyme is very selective ➢ It catalyzes specific reactions • Each enzyme recognizes a specific substrate ➢ The active site fits to the substrate and the enzyme changes shape slightly. ➢ This interaction is called induced fit ➢ They are specific to their substrate • Enzymes can function over and over again ➢ This is a key characteristic of enzymes Cells • Cells Control…. 1. The flow of energy 2. The pace of chemical reactions 3. The flow of materials to and from the environment ➢ Importing nutrients ➢ Exporting waste Enzyme Inhibitors • Enzyme inhibitors ➢ Can inhibit a metabolic reaction ➢ Some bind to the active site, as substrate imposters ➢ Bind at a remote site, changing the enzymes shape Membrane Function • Working cells must control the flow of materials to and from the environment ➢ Membrane proteins help with this task • Membrane proteins perform a variety of functions Passive Transport: Diffusion Across Membranes • Molecules contain heat energy ➢ They vibrate and wander randomly • Diffusion is one result of the movement of molecules ➢ Molecules tend to spread into the available space ➢ Diffusion is passive transport; no energy is needed • Another type of passive transport is facilitated diffusion, the transport of some substances by specific transport proteins that act as selective corridors. Osmosis and Water Balance in Cells • Osmosis is the passive transport of water across a selectively permeable membrane. Solutions • Hypertonic solution: has a higher concentration of solute • Hypotonic solution: has a lower concentration of solute • Isotonic: has an equal concentration of solute Water Balance in Animal Cells • The survival of a cell depends on its ability to balance water uptake and loss. • Isotonic: ➢ Animal cell: normal ➢ Plant: flaccid (wilts) • Hypotonic: ➢ Animal: lysing ➢ Plant: turgid • Hypertonic: ➢ Animal: shriveled ➢ Plant: shriveled Osmoregulation • Osmoregulation is the control of water balance in animals • Water balance in plant cells is different ➢ They have rigid cell walls ➢ They are at the mercy of the environment Active Transport: the Pumping of Molecules Across Membranes • Active transport requires energy to move molecules across a membrane Exocytosis and Endocytosis: Traffic of Large Molecules • Exocytosis: secretes s
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