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Chapter 4

Biology 1000 textbook note (chapter 4)

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BIOL 1000
Paula Wilson

Chapter 4 Energy and Enzymes Chapter 40 y Life relies on a group of catalysts called enzymes that speed up the rates of a reaction without the need for an increase in temperaturey In a cell a group of enzymes called phosphatases catalyze the removal of phosphate groups from a range of molecules Ex Proteinsy The rapid reversible phosphorylation of particular proteins is a central mechanism of intracellular communications in almost all cells y The dephosphorylation reaction within a cell using a phosphatase enzyme is completed in approximately 10 milliseconds y Wolfendens group calculated that in an aqueous environment such as a cell without an enzyme the dephosphorylation reaction would take over 1 trillion years to occurChapter 41 y energy cannot be measured or weighed directly y can be detect it only through its ability to do work to move objects against opposing forces such as friction gravity or pressure or to push chemical reactions toward completion y energy is most conveniently defined as the capacity to do work y Ex energy to move a car on a highway energy to climb a mountain energy to build a protein from a group of amino acids or pump sucrose across a cell membraneChapter 41 ay Energy can exist in many different forms including heat chemical electrical and mechanical energy y Electromagnetic radiation including visible infrared and ultraviolet light is also a type of energy y can be converted readily from one form to anothery For example the chemical energy present in a flashlight battery is converted into electrical energy that passes through the flashlight bulb where it is transformed into light and heat y Ex 2 Through the process of photosynthesis the energy of light is converted into chemical energy in the form of complex sugars and other organic molecules y Kinetic energy is the energy possessed by an object because it is in motion y The movement present in kinetic energy is of use because it can perform work by making other objects move y Obvious examples of objects that possess kinetic energy include waves in the ocean a falling rock or a kicked football y Less obvious examples include the kinetic energy of electricity which is a flow of electrons and heat y Photons of light are also a form of kinetic energy y Potential energychemical potential energy is stored energy the energy an object has because of its location or chemical structure y Ex A boulder at the top of a cliff has potential energy because of its position in the gravitational field of Earth y Ex2 The arrangement of atoms in a molecule of glucose or gasoline has potential energy stored in the specific arrangement of atoms Chapter 41 b y The study of energy and its transformations is called thermodynamics y System the object being studiedcan be anythinga single molecule one cell or a planet y Everything outside the system is called the surroundings y The universe in this context is the total of the system and the surroundings y 3 types of systems isolated open and closed 1 an isolated system is one that does not exchange matter or energy with its surroundings Ex a perfectly insulated Thermos bottle 2 A closed system can exchange energy but not matter with its surroundings
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