Chapter 8 Metabolism

Slide 2 of 23 Overview  Cell is a CHM factory  Macromolecules are made and broken down  Cellular Respiration powers the factory  Extracts Energy stored in sugars (& other fuels)  Cells use the Energy from cellular respiration to perform various types of work  Active transport of solutes into the cell  Bioluminescence

Slide 3 of 23 Metabolism  Metabolism – Totality of an organism’s chm reactions  Consists of 2 types of pathways  Catabolic Pathway  Breakdown of complex molecules into simpler compounds  Release of energy  Digestion  Anabolic Pathway  Simpler molecules  Complicated molecules  Consumes energy  Polymerization

Slide 4 of 23 Metabolic Pathways  Begin with a specific molecule  Altered in a series of defined steps  Each step is catalyzed by an enzyme  Mechanisms regulate enzymes  Prevents molecular deficits & surpluses  Creates a specific product Enzyme 1Enzyme 2Enzyme 3 A B C D Reaction 1Reaction 2Reaction 3

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Slide 8 of 23 Enzymes  Enzymes are biological catalysts  Proteins  Catalyst  Lower activation energy  Increases the rate of the reaction  Affects nothing other than the reaction rate  Does NOT affect the free energy of the reaction

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Slide 10 of 23 Enzyme Activity is affected by…  Metabolism – Totality of an organism’s chm reactions  Concentration of substrate  Concentration of enzyme  If enzyme is saturated, then rate is determined by enzyme’s rate for substrate  product

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Slide 12 of 23 Enzymatic Regulation  Enzymes = proteins  Proteins have 3D structure  Affected by pH and Temperature  Structure & function relationship

Slide 13 of 23 Enzyme Assistants  Cofactors  Nonprotein molecules that enzymes require for catalytic activity  Typically, inorganic  Such as zinc, iron, and copper  Coenzymes  Organic cofactor (what does organic mean?)  Vitamins

Slide 14 of 23 Competitive Inhibition

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Slide 17 of 23 Pathway Regulation  2 main ways to regulate metabolic pathways:  1. Switching on/off genes  2. Regulating enzyme activity

Slide 18 of 23 Allosteric Regulation  Allosteric – specific binding site  NOT the active site!!  Can be inhibition or activation  Allosteric molecule binds to a site other than the active site  Allosteric molecule binding  enzyme shape change  Change in enzyme shape  active site shape change  Structural change = Functional change

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Slide 20 of 23 Allosteric Regulation  Enzyme units oscillate between two conformational sites  One is catalytically active, the other is inactive  Regulatory site  Called allosteric site  Activator or inhibitor binds and stabilizes the conformational form  Usually an activator or inhibitor affects all active sites

Slide 21 of 23 Cooperativity  When a substrate molecule causes an induced fit in one active site triggers the same change in all subunits of the enzyme  Amplifies the response of enzymes to substrates  Primes the enzyme to accept more substrate

Slide 22 of 23 Feedback Inhibition  A metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway

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