Week 6 Life102 Notes
Week 6 Life102 Notes Life 102
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This 7 page Class Notes was uploaded by Sydney Dingman on Sunday February 28, 2016. The Class Notes belongs to Life 102 at Colorado State University taught by Erik N Arthun in Winter 2016. Since its upload, it has received 31 views. For similar materials see Attributes of Living Systems in Biology at Colorado State University.
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Date Created: 02/28/16
Week 6 LIFE 102 Notes 2/22/16, Chapter 8 cont. ATP and Metabolism o ATP is needed for most endergonic (energy in) processes Created constantly through respiration Organization of the Chemistry of Life into Metabolic Pathways o Metabolic pathway: begins with a specific molecules and ends with a product o Each step is catalyzed by a specific enzyme o ABCD (A starting molecule, D is product) Enzymes needed for each arrow/transformation Enzymes o Speed up metabolic reactions by lowering energy barriers o Catalyst: chemical agent that speeds up a reaction without being consumed by the reaction o Enzyme: catalytic protein o Hydrolysis of sucrose by the enzyme sucrase is an example of an enzyme-catalyzed reaction Enzyme Activity o Most exergonic reactions have to be activated before they proceed spontaneously o Activation Energy; initial energy needed to start a reaction Ways to overcome the activation barrier: o Heating: bonds loosened o Enzymes: proteins that speed up reactionsbiological catalysts o Enzymes are very specific: they accelerate one particular reaction o Reactants that the enzyme uses: substrate o Enzymes lower the activation energy required which is why the reaction is much faster Activation energy is lowered by enzymes o Enzymes promote reactions by serving as a physical site upon which the reactant molecules (substrate) can be positioned for various interactions Enzyme-Substrate Interactions o Active Site: the actual site on the enzyme where the substrate binds for the reaction to proceed o “Lock-and-key” fit: the active site is very specific in its shape and chemistry for the substrate o The enzyme Is not used up in the reaction Is not part of the final products Can be re-used again How do enzymes lower activation energy? o Enzyme could use one or more of the following: o Enzyme binds substrates in right position for reaction o Enzyme binding of substrates stressed atomic bonds, so they break easily o Active site may have properties that facilitate reaction (acid/basic, hydrophobic) o Side groups of amino acids may participate in reaction and be restored o Overall: reaction is facilitated! Influences on Enzymatic Reaction Rate o Environmental conditions: Temperature When heated up to an extreme amount, the enzyme would denature pH o Each enzyme has a temperature optimum and pH optimum Enzymatic reaction rate is influenced by: o Activation/ Inhibition by other molecules: Cofactors 2 Cofactor: non-protein molecule/atom required for enzyme activity Like metals and coenzymes Inhibitors Activators Regulation of Enzyme Activity o Cofactors Non-protein molecule or atom that is required for enzyme activity Many are metals o Inhibitors Competitive: binds in active site Non-competitive: binds in allosteric site o Activators Activate enzymes through binding at allosteric (other) site Can’t compete in the active site because it would be blocking the active site, doing its opposite function Why have inhibitors and activators? o To regulate enzyme activity Regulate how much of a product is formed (too much or too little) Multimeric Enzymes: o Have multiple active sites which can be controlled with just one activator or inhibitor Metabolic Pathway: series of enzymes that work together Feed-back inhibition: o An enzyme is inhibited by its product o Less product more made o More product less made o No need for inhibitors or activators with this feedback Strategy of Metabolism o Use catabolism to: 3 Release energy Capture electrons Liberate building blocks o Drive anabolism by Spending energy Using electrons Using building blocks 2/24/16, Chapter 9, Cellular Respiration and Fermentation Energy Movement through Ecosystems o Energy flows into an ecosystem as sunlight and leaves as heat Photosynthesis- chloroplasts Respiration- mitochondria Steal electrons from our food for use and high energy molecules Uses for ATP: o Transport work o Mechanical work o Chemical work Catabolic pathways yield energy by oxidizing organic fuels o The breakdown of organic molecules is exergonic o Cellular Respiration: C6H12O6+O2 o Oxidation and Reduction: CO2+H2O+Energy o The transfer of electrons during chemical reactions releases energy stored in organic molecules o The released energy is ultimately used to make ATP Principle of Redox o Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions o In oxidation, a substance loses electrons, or is oxidized o In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) 4 OIL RIG Oxidation Is Lost Reduction Is Gained o Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds o Oxygen is VERY electronegative: It attracts electrons It pulls electrons closer to its nucleus As electrons are pulled closer to oxygen, there is a release of energy Oxidation of organic fuel molecules during cellular respiration o During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced o Electrons from organic compounds are usually first transferred to NAD+, a coenzyme (electron shuttle) o Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP Dropped off at the top of the stairwell and is pulled down Cellular respiration o Electrons are H+ are transferred from glucose to oxygen o High-energy electrons in glucose become low-energy electrons in H20 and CO2 o This reaction releases energy that is used to make ATP Breakdown of Glucose Overview o Glucose is broken down in little steps o A little energy is released per step: Small enough for a cell to handle Large enough to drive ATP production Respiration uses intermediate molecules to transfer electrons o NADH and FADH2 serve as intermediate molecules that carry electrons o NADH passes the electrons to the electron transport chain 5 o Unlike uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction o O2 pulls electrons down the chain in an energy-yielding tumble The energy yielded is used to regenerate ATP Electron transport chain and Oxidative Phosphorylation First Step in Breakdown of Glucose: Glycolysis o Oxidized during Glycolysis and Citric Acid Cycle o Electrons are gradually transferred from glucose to NAD to ETC to Oxygen o “Glycolysis”—Sugar splitting o Glucose is broken from 6 carbons to 2 sets of 3 forming 2 chains of pyruvate o Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration Adding a phosphate group using oxidative power to ADP to create ATP o A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation o For each molecule of glucolse degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP Substrate-level Phophorylation o All ATP created in Glycolysis Citric Acid Cycle STEP 1: GLYCOLYSIS o Breaks down glucose into two molecules of pyruvate o Occurs in the cytoplasm o Glycolysis occurs whether or not O2 is present o Energy can be broken down into an Energy Investment Phase or Energy Payoff Phase Energy investment phase: 2 sites where 1 ATP is used= -2ATP Energy payoff phase: 2 sites where 2 ATP are gained= +4ATP Glycolysis summary 6 o One glucose is used o Partial oxidation of the sugar (loss of electrons Two NAD+ are reduced (gain of electrons) o 4 ATP total are made o 2 ATP are consumed Net of 2 ATP produced o 2 pyruvates are end products Serve as starting substrates for the citric acid cycle Before the citric acid cycle can begin: o Pyruvate must be converted to acetyl Coenzyme A, which links glycolysis to the citric acid cycle 7