Biol 118 1st Edition Lecture 8 Outline of Last Lecture I Introduction to Metabolism a Two types of energy b First Law of Thermodynamics c Seconds Law of Thermodynamics d What is Free Energy e Some Important Energy Changes in Chem Reactions f Gibbs Free Energy Change g What Drives Nonspontaneous Endergonic Reactions h Energetic Coupling i Role of Redox Reactions in Metabolism j What is a Redox Reaction k Electrons Are Usually Accompanied by Protons l Role of ATP in Metabolism m ATP Hydrolysis Protein Phosphorylation n How Does ATP Drive Endergonic Reactions Outline of Current Lecture I Energy Transformations II Role of Electrons III Definitions IV Oxidation Reduction V Phosphorylation 3 Types VI Ways ATP is Produced VII Key Players in the Processing of Glucose VIII Cellular Respiration has 4 Steps IX Fermentation Current Lecture These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Energy Transformations Respiration convert chemical potential energy of foods into ATP o Take place in mitochondria of plant animal cells o Allows for cellular work e g muscle contraction kinetic energy digestion etc Photosynthesis converts light energy into chemical potential energy o Takes place in chloroplasts of plants o Produces foods that are then available to make ATP respiration Role of electrons Electrons are involved in the movement of energy Electron energy is transferred in chemical reactions Sometimes move along with hydrogens o Helps to follow the hydrogens and their electrons as you follow the transfer of energy Definitions Oxidation loss of electrons from atoms during chemical reactions o Molecules losing electrons lose energy o Say that these are oxidized Reduction Gain of electrons by atoms during chemical reactions o Molecules gaining electrons gain energy o Say these molecules are reduced LEO the lion says GER Lose Electron Oxidation Gain Electron Reduction Reduction of CO2 to form sugars Electrons along with H s combine with carbon to form carbohydrates CO2 is reduced Sometimes referred to as fixing C which refers to addition of H s to form energy rich molecules Oxidation Reduction Whenever something is oxidized something else is reduced electrons are accepted by something else Called Redox Reactions and are occurring throughout both respiration and photosynthesis Reduced molecules gain electrons usually an H with it Oxidized molecules tend to have lower potential energy Phosphorylation 3 Types Substrate level phosphorylation o High energy phosphate added to molecules o Occurs in glycolysis and citric acid cycle Oxidative Phosphorylation o Production of ATP via redox reactions in electron transport chain o Respiration in mitochondria when oxygen present Photophosphorylation o Production of ATP using light energy passed through ETC o Photosynthesis in chloroplasts Oxidative Photo both depend on ETC chemiosmosis proton motive force Chap 9 Cellular Respiration and Fermentation Ways ATP is Produced Respiration o Involves the transfer of electrons from high potential energy compounds such as glucose to low potential energy compounds o Ultimately to an electron acceptor such as oxygen o MANY ATP produced per glucose Fermentation o Involves the transfer of electrons from glucose to electron acceptor other than oxygen o Allows glycolysis to continue in absence of Oxygen o Less ATP produced Key Players in the Processing of Glucose ATP o Needed to get the reaction going o Many ATP are produced Nicotinamide adenine dinucleotide NAD o Is reduced to NADH o NADH is an electron carrier has reducing power and can donate electrons to reduce other molecules FAD FADH o Plays role later on as another electron carrier Cellular Respiration has 4 Steps Glycolysis o The processing oxidation of glucose o 10 chemical reactions o Glucose is broken down into Two 3 carbon molecules of pyruvate Potential energy released is used to phosphorylate ADP o Occurs in the cytosol o Energy of 2 ATPs is added o Glucose gets phosphorylated 2 times Gives the activation energy o 6 carbon sugar is broken into two 3 carbon sugars o An inorganic phosphate is added to both 3 carbon sugars o Step 6 gives 2 NADH o Step 7 gives 2 ATP o Step 10 gives 2 ATP o Net yield 2 ATP 2 NADH 2 pyruvate o Regulated by feedback inhibition high levels of the products of a reaction inhibit the function of the first enzyme High levels of ATP inhibit the enzyme phosphofructokinase Pyruvate Processing o Pyruvate reacts with Coenzyme A CoA to produce acetyl CoA o Coenzyme A enzyme cofactor o NAD reduced to NADH o One of pyruvate s carbons oxidized to CO2 o Two remaining carbons are transferred to CoA o Enzyme is pyruvate dehydrogenase Citric Acid Cycle Krebs Cycle o Eight small carboxylic acids R COOH o These molecules are not used up they are recycled o Citrate 1st molecule in the cycle formed from acetyl CoA and oxaloacetate last molecule in the cycle o In the Krebs Cycle the two remaining carbons from pyruvate are oxidized to CO2 o Regulated by Feedback Inhibition ATP NADH o Results 4 NADH 1 from pyruvate processing with CoA 3 from Krebs Cycle 1 FADH2 molecule 1 guanosine triphosphate GTP Can be easily converted to ATP o The 10 NADH 2 FADH2 are used to make more ATP Electron Transport Chemiosmosis o Organized into 4 complexes o o o o o o o o o o o o o o o Coenzyme Q cytochrome c transfer electrons between complexes NADH gives electrons to Complex 1 A proton is transported across the inner membrane Q takes the electron from Complex 1 Q picks up a proton Q diffuses across the membrane and transfers its electrons to Complex 3 Its protons are released into the intermembrane space Complex 3 gives electrons to cytochrome c Cytochrome transports electron to Complex 4 Complex 4 transports protons across the inner membrane Complexes 1 4 transport protons directly Final electron acceptor at the end is O2 Note FADH2 transfers electrons to Complex 2 no proton transport by Complex 2 So less energy is transferred to the proton motive force by FADH2 At each step of the electron transport Electrons lose potential energy Energy released is used to pump protons across the membrane Forms a strong electrochemical gradient How to make ATP from the Proton Motive Force The ATP synthase enzyme uses the proton gradient energy to phosphorylate ADP as protons move back across the membrane ATP Synthase A complex of F1 unit ATPase knob Membrane bound proton transporting base F0
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