Biol 118 1st Edition Lecture 8 Outline of Last Lecture I. Introduction to Metabolisma. Two types of energyb. First Law of Thermodynamicsc. Seconds Law of Thermodynamicsd. What is Free Energy?e. Some Important Energy Changes in Chem Reactionsf. Gibbs Free Energy Changeg. What Drives Nonspontaneous, Endergonic Reactionsh. Energetic Couplingi. Role of Redox Reactions in Metabolismj. What is a Redox Reaction?k. Electrons Are Usually Accompanied by Protonsl. Role of ATP in Metabolismm. ATP Hydrolysis & Protein Phosphorylationn. How Does ATP Drive Endergonic Reactions?Outline of Current Lecture I. Energy TransformationsII. Role of ElectronsIII. DefinitionsIV. Oxidation-ReductionV. Phosphorylation: 3 TypesVI. Ways ATP is Produced VII. Key Players in the Processing of GlucoseVIII. Cellular Respiration has 4 StepsIX. FermentationCurrent LectureThese 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 ATPo Take place in mitochondria of plant & animal cellso Allows for cellular work- e.g. muscle contraction (kinetic energy), digestion etc.- Photosynthesis: converts light energy into chemical potential energyo Takes place in chloroplasts of plantso 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 hydrogenso Helps to follow the hydrogens and their electrons as you follow the transfer of energyDefinitions- Oxidation: loss of electrons from atoms during chemical reactionso Molecules losing electrons lose energyo Say that these are oxidized- Reduction: Gain of electrons by atoms during chemical reactions o Molecules gaining electrons gain energyo Say these molecules are reduced- LEO the lion says GER: Lose Electron Oxidation; Gain Electron ReductionReduction 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 energyPhosphorylation: 3 Types- Substrate level phosphorylationo High energy phosphate added to molecules o Occurs in glycolysis and citric acid cycle- Oxidative Phosphorylationo Production of ATP via redox reactions in electron transport chaino Respiration in mitochondria when oxygen present- Photophosphorylationo Production of ATP using light energy passed through ETCo Photosynthesis in chloroplasts- Oxidative & Photo both depend on ETC & chemiosmosis (proton-motive force_Chap 9. Cellular Respiration and FermentationWays ATP is Produced- Respirationo Involves the transfer of electrons from high potential energy compounds (such asglucose) to low potential energy compoundso Ultimately to an electron acceptor such as oxygen o MANY ATP produced per glucose- Fermentationo Involves the transfer of electrons from glucose to electron acceptor other than oxygeno Allows glycolysis to continue in absence of Oxygeno Less ATP producedKey Players in the Processing of Glucose- ATPo Needed to get the reaction goingo Many ATP are produced- Nicotinamide adenine dinucleotide (NAD+)o Is reduced to NADHo NADH is an electron carrier- has reducing power and can donate electrons to reduce other molecules- FAD &FADHo Plays role later on as another electron carrierCellular Respiration has 4 Steps- Glycolysiso The processing (oxidation) of glucoseo 10 chemical reactionso Glucose is broken down into Two 3-carbon molecules of pyruvate Potential energy released is used to phosphorylate ADPo Occurs in the cytosolo Energy of 2 ATPs is added o Glucose gets phosphorylated 2 timesGives the activation energyo 6 carbon sugar is broken into two 3 carbon sugarso An inorganic phosphate is added to both 3 carbon sugars o Step 6 gives 2 NADHo Step 7 gives 2 ATPo Step 10 gives 2 ATPo Net yield: 2 ATP 2 NADH 2 pyruvateo Regulated by feedback inhibition: high levels of the products of a reaction inhibitthe function of the first enzyme High levels of ATP inhibit the enzyme phosphofructokinase- Pyruvate Processingo Pyruvate reacts with Coenzyme A (CoA) to produce acetyl CoAo Coenzyme A: enzyme cofactoro NAD+ reduced to NADHo One of pyruvate’s carbons oxidized to CO2o Two remaining carbons are transferred to CoAo 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 recycledo 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 CO2o 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 ATPo The 10 NADH & 2 FADH2 are used to make more ATP- Electron Transport & Chemiosmosiso Organized into 4 complexes Coenzyme Q & cytochrome c transfer electrons between complexes o NADH gives electrons to Complex 1 A proton is transported across the inner membraneo Q takes the electron from Complex 1o Q picks up a protono Q diffuses across the membrane and transfers its electrons to Complex 3o Its protons are released into the intermembrane spaceo Complex 3 gives electrons to cytochrome co Cytochrome transports electron to Complex 4o Complex 4 transports protons across the inner membraneo Complexes 1 & 4 transport protons directly o Final electron acceptor at the end is O2o 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 gradiento How to make ATP from the Proton-Motive Force: The ATP synthase enzyme uses the proton gradient energy to phosphorylate ADP as protons move
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