Outline of Last LectureOutline of Current LectureCurrent LectureCellular RespirationGlycolysisKrebs CycleElectron Transport and Oxidative PhosphorylationSummaryBIO SCI 150 1st Edition Lecture 7Outline of Last Lecture 1. Endocrine Systema. Propertiesb. Types per Locationc. Regulation2. Energy and Reactionsa. Key termsb. Thermodynamicsi. Bond Energiesii. Reactions and EnzymesOutline of Current Lecture 1. Cellular Respirationa. Oxidation-Reduction i. Glycolysisii. Krebs Cycleiii. Electron Transportb. SummaryCurrent LectureCellular RespirationIn respiration the conversion of carbohydrate to CO, and water proceedsthrough numerous steps. The process can be divided into three stages:GlycolysisThe large glucose molecule is phosphorylated and split into two 3-carbonmolecules (pyruvate). Some energy is invested (in the form of ATP) andsome energy is recovered (inthe form of ATP and NADH). This processtakes place in the cytoplasm.- Glucose + Pyruvate + ATP + NADHKrebs CycleThis reaction series occurs in the mitochondrion, within the mitochondrialmatrix. The 3-carbon pyruvate molecules are broken down in a series ofreactions. Pyruvate is transported into the mitochondrion and oxidized to a2-carbon acetyl group. The 2-carbon acetyl group is added to a 4-carbonmolecule (oxaloacetate) to form a 6-carbonmolecule (citrate). In theKrebs cycle citrate is oxidized to CO, and the 4-carbon oxaloacetatemolecule. Energy is recovered in the form of ATP and electrons asNADH andFADH2 (another electron carrier).- Pyruvate + Acetate + CO, + NADH + FADH + ATPElectron Transport and Oxidative PhosphorylationIn this stage electrons derived from the oxidation steps are used to moveprotons H+ across the inner mitochondrial membrane. The electrons ofNADH are passed to electrontransport proteins. Electrons are passedalong a series of proteins until they finally reach oxygen and form water.The electron transport system uses the flow of electrons to moveprotons(H’) across the inner mitochondrial membrane into the inter-membranespace. The high concentration of protons in the space between the innerand outer mitochondrial membranes provides a concentration gradient(proton-motive force). Protons are allowed to return to the mitochondrialmatrix by passing through the ATP synthase complex. This movement isused to power the addition of a phosphate to form ATP.- NADH + FADH + O2 + ATP + H2OSummaryCellular respiration is one half of the energy cycle on which life as we know it depends. Lightenergy from the sun is trapped by photosynthesis and converted to chemical energy in the formof complex carbohydrates. Living systems depend upon this trapped energy and use respiration to regenerate the pool of ATP that serves as the energy currency of living cells.Essential to both halves of the energy cycle is oxygen. Some living systems can exist in theabsence of free oxygen (0,). For most living systems oxygen and its need for electrons tocomplete its valence shell play a vital role. Oxygen wants electrons. In the early earthenvironment oxygen existed as covalent molecules with carbon and hydrogen. In thisarrangement, oxygen holds the lion’s share of electrons, and is quite happy. Living systemsevolved chlorophyll, a molecule capable of using light energy to become more electronegativethan oxygen, and take electrons from water. The oxygen atoms, deprived of the “easy electrons”of hydrogen, are forced to share electrons with each other. Molecular oxygen (0,) is a veryrestless molecule, anxious to regain those electrons. Cellular respiration uses oxygen and itsgreed for electrons to drive a set of physical-chemical reactions that produce the energy-rich ATPmolecule. Thereactions of respiration including glycolysis, the Krebs Cycle, electron transportand oxidative phosphorylation are all employed to obtain electrons from the carbohydrateglucose and ultimately give them to oxygen. The power of the flow of electrons is harnessed toproduce ATP. In the absence of free oxygen, only a little ATP canbe