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Name ____________________________________ Date ____________ Period _____ METABOLISM AND ENZYMES Raven Ch. 8 Big Idea 2: BIOLOGICAL SYSTEMS UTILIZE FREE ENERGY AND MOLECULAR BUILDING BLOCKS TO GROW, TO REPRODUCE AND TO MAINTAIN HOMEOSTASIS. Essential Knowledge: Cell membranes are selectively permeable due to their structure. Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy. Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. Flow of energy through life Life is built on chemical reactions transforming energy from one form to another Metabolism Chemical reactions of life ___________________ between molecules dehydration synthesis synthesis _________________ reactions ___________________ between molecules hydrolysis digestion _________________ reactions Chemical reactions & energy Some chemical reactions _________________ _________________ digesting polymers hydrolysis = catabolism Some chemical reactions require _________________ _________________ building polymers dehydration synthesis = anabolism 1 Exergonic _______________ _______________ vs. Endergonic _______________ _______________ G = ______________________________________________________________________ Organisms require energy to live Where does that energy come from? coupling exergonic reactions (_______________ energy) with endergonic reactions (_________________ energy) ___________________ ___________________ What drives reactions? If reactions are “downhill”, why don’t they just happen spontaneously? _______________________________________ Activation energy Breaking down large molecules requires an initial input of energy _________________________ large biomolecules are stable must absorb energy to break bonds 2 Too much activation energy for life Activation energy amount of energy needed to destabilize the bonds of a molecule moves the reaction over an “energy hill” Reducing Activation energy __________________ reducing the amount of energy to start a reaction Enzymes vocabulary: So what’s a cell got to do to reduce activation energy? get help! … chemical help…______________ Enzymes __________________________ proteins (& RNA) facilitate chemical reactions ______________ rate of reaction without being consumed ______________ activation energy don’t change ___________________ released or required required for most biological reactions •highly _____________________ thousands of different enzymes in cells •______________ reactions of life ______________________ reactant which binds to enzyme enzyme-substrate complex: temporary association _____________________ end result of reaction _____________________ enzyme’s catalytic site; substrate fits into active site Properties of enzymes _____________________ each enzyme works with a specific substrate chemical fit between active site & substrate H bonds & ionic bonds _____________________ single enzyme molecule can catalyze thousands or more reactions per second enzymes unaffected by the reaction Affected by _____________________ any condition that affects protein structure temperature, pH, salinity 3 Naming conventions Enzymes named for reaction they catalyze ____________ breaks down sucrose ____________ break down proteins ____________ break down lipids DNA ____________ builds DNA adds nucleotides to DNA strand ____________ breaks down proteins (polypeptides) Lock and Key model __________________ model of enzyme action substrate fits into 3-D structure of enzyme’ active site H bonds between substrate & enzyme like “key fits into lock” Induced fit model __________________ model of enzyme action 3-D structure of enzyme fits substrate substrate binding cause enzyme to change shape leading to a tighter fit “_____________________________” bring chemical groups in position to catalyze reaction How does it work? Variety of mechanisms to lower activation energy & speed up reaction ____________________________ active site orients substrates in correct position for reaction enzyme brings substrate closer together ____________________________ active site binds substrate & puts stress on bonds that must be broken, making it easier to separate molecules 4