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Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
Chapter 8
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Chapter 8

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    1. <ul><li>Chapter 8 </li></ul><ul><li>An Introduction to Metabolism </li></ul>
    2. <ul><li>I. Energy: The capacity to do work. The ability to change matter </li></ul><ul><li>Can exist in two forms: </li></ul><ul><ul><li>1. Kinetic energy : Energy of motion. Energy that is actively performing work. Examples: </li></ul></ul><ul><ul><ul><li>Heat : Energy of particles in motion. </li></ul></ul></ul><ul><ul><ul><li>Light : Energy of photons of light </li></ul></ul></ul><ul><ul><li>2. Potential energy : Stored energy due to position or arrangement of matter. Examples: </li></ul></ul><ul><ul><ul><li>Chemical energy : Potential energy of molecules due to the arrangement of atoms. The most important type of energy for living organisms. </li></ul></ul></ul><ul><ul><ul><li>Position : Bicycle at the top of a hill. </li></ul></ul></ul>
    3. <ul><li>Kinds of Energy </li></ul><ul><ul><li>Electromagnetic </li></ul></ul><ul><ul><li>Chemical </li></ul></ul><ul><ul><li>Nuclear </li></ul></ul><ul><ul><li>Light </li></ul></ul><ul><ul><li>Mechanical </li></ul></ul><ul><ul><li>Electrical </li></ul></ul><ul><ul><li>Heat </li></ul></ul><ul><ul><li>Sound </li></ul></ul>
    4. <ul><li>II. Energy Transformation </li></ul><ul><li>Energy can be converted from one kind to another. Transformations are inefficient , generating heat. </li></ul><ul><li>Examples : </li></ul><ul><ul><li>Light energy -------- --> Chemical energy (sugar) + Heat </li></ul></ul><ul><ul><li>Chemical energy -- ---> Mechanical energy + Heat </li></ul></ul><ul><ul><li>Electrical energy --- --> Light energy + Heat </li></ul></ul><ul><ul><li>Chemical energy --- --> Biological work + Heat </li></ul></ul><ul><li>Heat is easily measured energy, because all other forms of energy can be converted to heat. </li></ul><ul><li>From a biological standpoint, heat is a poor kind of energy which is not very useful to do work. </li></ul><ul><li>Why? Because heat is lost to the environment. </li></ul>
    5. <ul><li>III. All energy transformations are subject to the First and Second Laws of Thermodynamics </li></ul><ul><ul><li>1. First Law of Thermodynamics : Energy can be transformed (e.g.: chemical to mechanical), but cannot be created nor destroyed. The total amount of energy in the universe is constant . </li></ul></ul><ul><ul><li>Biological Consequence : Living organisms cannot create the energy they need to live. They must capture it from their environment. </li></ul></ul><ul><ul><li>Sources of energy used by living organisms : Sun and chemical energy. </li></ul></ul>
    6. <ul><li>2. Second Law of Thermodynamics </li></ul><ul><li>ENERGY CONVERSIONS ARE INEFFICIENT </li></ul><ul><li>In any energy transformation, a certain amount of energy is lost as heat. </li></ul><ul><li>By comparison, living organisms are relatively efficient. </li></ul><ul><li>Electrical Energy -------> ---------> 5% Light + 95% Heat </li></ul><ul><li>Chemical Energy --> ----------------> 25% Mechanical </li></ul><ul><li>(Gasoline) 75% Heat </li></ul><ul><li>Chemical Energy --------> -----------> 40% ATP + 60% Heat </li></ul><ul><li>(Glucose) </li></ul>
    7. <ul><li>III. Laws of Thermodynamics (Cont.) </li></ul><ul><ul><li>2. Second Law of Thermodynamics : Energy conversions reduce the order of the universe, because heat is dispersed into the environment. </li></ul></ul><ul><ul><li>As a result, the universe inevitably tends toward a state of increased disorder or chaos ( entropy ). Entropy (S) : Measure of disorder. </li></ul></ul><ul><ul><li>Disorganized, less usable energy (heat). </li></ul></ul><ul><ul><li>Heat is random molecular motion, a form of entropy. </li></ul></ul><ul><ul><li>Biological Consequences : Living organisms must constantly take in energy to avoid entropy (disintegration, death and decay). </li></ul></ul><ul><ul><li>High quality energy is a limited resource, because usable energy, decreases over time. </li></ul></ul>
    8. <ul><li>IV. Chemical Reactions Either Store or Release Energy : </li></ul><ul><li>I. Exergonic Reactions : </li></ul><ul><li>Release free energy. </li></ul><ul><li>Also exothermic (release heat). </li></ul><ul><li>Products have less energy than the reactants. </li></ul><ul><li>Example : </li></ul><ul><li>Cellular respiration is an exergonic process: </li></ul><ul><li>C 6 H 12 O 6 + 6 O 2 ----> 6 CO 2 + 6 H 2 O + Energy </li></ul><ul><li>Sugar Oxygen Carbon Water </li></ul><ul><li>Dioxide </li></ul><ul><li>High Energy Reactants Low Energy Products </li></ul>
    9. Change in Free Energy of a System: <ul><li> G =  H - T  S </li></ul><ul><li> G is Gibb’s Free Energy or the energy available to do work. </li></ul><ul><li> H is the total energy. </li></ul><ul><li>T is the temperature in Kelvin. </li></ul><ul><li> S is entropy </li></ul><ul><li>Exergonic Reactions,  G - </li></ul><ul><li>Endergonic Reaction,  G + </li></ul>
    10. <ul><li>IV. Chemical Reactions Store or Release Energy : </li></ul><ul><li>II. Endergonic Reactions : </li></ul><ul><li>Require net input of free energy. </li></ul><ul><li>Also endothermic (absorb heat). </li></ul><ul><li>Products have more energy than the reactants. </li></ul><ul><li>Create products that are rich in potential energy. </li></ul><ul><li>Example : </li></ul><ul><li>Photosynthesis is an endergonic process: </li></ul><ul><li>6 CO 2 + 6 H 2 O + Sunlight ----> C 6 H 12 O 6 + 6 O 2 </li></ul><ul><li>Carbon Water Energy Sugar Oxygen </li></ul><ul><li>Dioxide </li></ul><ul><li>Low Energy Reactants High Energy Products </li></ul>
    11. Chemical Reactions Either Store or Release Energy Endergonic Reactions Exergonic Reactions Require Energy Release Energy Higher Energy Products Lower Energy Products
    12. <ul><li>Metabolism : All chemical processes that occur within a living organism. Either catabolic or anabolic reactions. </li></ul><ul><li>I. Catabolic Reactions : </li></ul><ul><ul><li>Release energy ( exergonic ). </li></ul></ul><ul><ul><li>Break down large molecules (proteins, polysaccharides) into their building blocks (amino acids, simple sugars). </li></ul></ul><ul><ul><li>Often coupled to the endergonic synthesis of ATP. </li></ul></ul><ul><ul><li>Examples : </li></ul></ul><ul><ul><li>1. Cellular respiration is a catabolic process: </li></ul></ul><ul><ul><li>C 6 H 12 O 6 + 6 O 2 -------> 6 CO 2 + 6 H 2 O + Energy </li></ul></ul><ul><ul><li>Sugar Oxygen Carbon dioxide Water </li></ul></ul><ul><ul><li>2. The digestion of sucrose is a catabolic process: </li></ul></ul><ul><ul><li>Sucrose + Water -------> Glucose + Fructose + Energy </li></ul></ul><ul><ul><li>Disaccharide Monosaccharides </li></ul></ul>
    13. <ul><li>Metabolism: Catabolism + Anabolism </li></ul><ul><li>II. Anabolic Reactions : </li></ul><ul><ul><li>Require energy ( endergonic ). </li></ul></ul><ul><ul><li>Build large molecules (proteins, polysaccharides) from their building blocks (amino acids, simple sugars). </li></ul></ul><ul><ul><li>Often coupled to the exergonic breakdown or hydrolysis of ATP. </li></ul></ul><ul><ul><li>Examples : </li></ul></ul><ul><ul><li>1. Photosynthesis is an anabolic process: </li></ul></ul><ul><ul><li>6 CO 2 + 6 H 2 O + Sunlight ----> C 6 H 12 O 6 + 6 O 2 </li></ul></ul><ul><ul><li>Carbon Water Sugar Oxygen </li></ul></ul><ul><ul><li>Dioxide </li></ul></ul><ul><ul><li>2. Synthesis of sucrose is an anabolic process: </li></ul></ul><ul><ul><li>Glucose + Fructose + Energy -------> Sucrose + H 2 O </li></ul></ul><ul><ul><li>Monosaccharides Disaccharide </li></ul></ul>
    14.  
    15. <ul><li>V. ATP: Shuttles Chemical Energy in the Cell </li></ul><ul><ul><li>Coupled Reactions : </li></ul></ul><ul><ul><ul><li>Endergonic and exergonic reactions are often coupled to each other in living organisms. </li></ul></ul></ul><ul><ul><ul><li>The energy released by exergonic reactions is used to fuel endergonic reactions. </li></ul></ul></ul><ul><ul><li>ATP “shuttles” energy around the cell from exergonic reactions to endergonic reactions . </li></ul></ul><ul><ul><ul><li>One cell makes and hydrolyzes about 10 million ATPs/second. </li></ul></ul></ul><ul><ul><ul><li>Cells contain a small supply of ATP molecules (1-5 seconds ). </li></ul></ul></ul><ul><ul><li>ATP powers nearly all forms of cellular work: </li></ul></ul><ul><ul><ul><li>1. Mechanical work : Muscle contraction, beating of flagella and cilia, cell movement, movement of organelles, cell division. </li></ul></ul></ul><ul><ul><ul><li>2. Transport work: Moving things in & out of cells. </li></ul></ul></ul><ul><ul><ul><li>3. Chemical work : All endergonic reactions. </li></ul></ul></ul>
    16. <ul><ul><li>A. Structure of ATP (Adenosine triphosphate) </li></ul></ul><ul><ul><ul><li>Adenine : Nitrogenous base. </li></ul></ul></ul><ul><ul><ul><li>Ribose : Pentose sugar, same ribose of RNA. </li></ul></ul></ul><ul><ul><ul><li>Three Phosphate groups: High energy bonds . </li></ul></ul></ul><ul><ul><li>B. ATP Releases Energy When Phosphates Are Removed: </li></ul></ul><ul><ul><li>Phosphate bonds are rich in chemical energy and easily broken by hydrolysis : </li></ul></ul><ul><ul><li>ATP + H 2 O ----> ADP + Energy + P i </li></ul></ul><ul><ul><li>ADP + H 2 O ----> AMP + Energy + P i </li></ul></ul>
    17. Structure and Hydrolysis of ATP
    18. <ul><ul><li>C. Regeneration of ATP : </li></ul></ul><ul><ul><li>ATP can be regenerated through dehydration synthesis : </li></ul></ul><ul><ul><li>ADP + Energy + P i ----> ATP + H 2 O </li></ul></ul><ul><ul><li>Phosphorylation : Transfer of a phosphate group to a molecule. Requires energy. </li></ul></ul><ul><ul><li>The energy required for this endergonic reaction is obtained by trapping energy released by other exergonic reactions </li></ul></ul><ul><ul><li>(E.g.: Cellular respiration). </li></ul></ul>
    19. ATP Shuttles Energy From Exergonic Reactions to Endergonic Reactions

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