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U-M BIOLOGY 207 - Cell Structure and Function
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BIOLOGY 207 1st Edition Lecture 4 Outline of Previous Lecture I. Thermodynamics of Redox ReactionsII. Characterization of Energy MetabolismOutline of Current Lecture I. RespirationII. Cytoplasmic Membrane Current LectureCell Structure and FunctionI. Respirationa. Chemoorganotrophic Respirationi. Breaking up organic compounds through glucolysis and the Citric Acid Cycle to create energyii. There is a directed flow of electrons during glycolysis (breaking up of glucose)iii. Glucose is oxidized to pyruvate/NAD+ is reduced to NADHiv. Pyruvate then goes to the Citric Acid Cycle 1. Here, it is oxidized to CO2 2. NAD+ is reduced to NADH againv. NADH is used in the electron transport chain (ETC) as a carrier of electrons1. These electrons then go through different electron acceptors until it reaches the terminal electron acceptor, creating a Proton Motive Force (PMF)a. The ETC generates the PMF by acting as a proton pump by using electron energy from electron carriers to more protons/Hydrogen ions out of the membraneb. Thus, more protons are outside than inside, creating a gradientc. ATPase lets the protons pass through the membrane and phosphorylates ADP to synthesize ATP through oxidative phosphorylationb. Chemolithotrophic Respiration 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.i. The main difference is that the energy created is taken from the oxidation of inorganic compounds; otherwise, the mechanisms are generally the same1. The only main difference is the source of electrons is from inorganic substances such as H2S, and the electron acceptors are anything with higher redox potentials, which can be seen and interpreted via the redox towerii. The PMF is used to reverse natural flwo of electrons against the natural gradient1. The protons are pumped out, reversing electron transport 2. This reduces the NADP+ to NADPH, since no NADH or NADPH is made on its own as in chemoorganotrophic respirationc. Fermentationi. Metabolic process converting sugars to acids, gases or alcoholsii. No ETC is involved in the production of energyiii. In the case of glycolysis, two end products of fermentation are lactate and ethanol1. ATP is produced along the way with substrate level phosphorilation iv. PMF in fermentative organisms still occurs for transport and motility1. ATPase reversala. Pumps out protons from the cell b. This allows the cell to move Summary of different chemotroph respirationsElectron donor(organic compound)Organic e–acceptorsElectronacceptorsElectronacceptorsFermentationChemotrophsAerobicrespirationAnaerobic respiration ChemoorganotrophyAnaerobic respiration Aerobic respirationChemolithotrophyElectron transport/generation of pmfElectron transport/generation of pmfd. Reducing Poweri. NADPH provides the electrons needed for reducing power1. NADPH + H+  NADP+ + 2e- + 2H+2. NADPH is a biosynthesis compound which provides powerii. Chemoorganotrophs already have a ready source, so it is easier for them to supply the NADPHiii. In other cases, such as for chemolithotrophs, the NADP+ is reduced via PMF pumping out protons to reduce it to NADPHiv. Examples of reduction:1. Nitrogen Fixationa. N2 + 8H+ + 8e-  2NH3 + H2i. The N is reduced- it goes from a charge of 0 to a chargeof -32. Autotrophic carbon fixationa. CO2 + 4e- + 4H+ → CH2O + H2O i. The C is reduced- it goes from a charge of +4 to a charge of 0II. Cytoplasmic Membranea. Phospholipid bilayer that distinguishes the cell from its environmentb. Three main functions:i. Permeability barrier1. Nothing leaks out that shouldn’t; waste is excreted via transportation gateway, utilizing energy2. Conversely, nothing gets, including nutrients, in without a mechanism using energy as wellii. Protein anchor1. Since it is not open to nutrients and waste entering and exiting at will,there are many proteins along the membrane which communicate with the cell to bring things in and outiii. Energy conservation1. Site of the PMFc. Bacterial Cytoplasmic i. High protein content and ii. Hydrophobic (anti-water) middle areaiii. Fluid, free-moving 1. Structurally weak2. Need other things to help keep structureBacterial Cytoplastic Membraneiv. Bacteria/Eukarya Cytoplasmic membrane (Figure A)1. Glycerol phosphates serve as the hydrophilic head region 2. An ester link connects to fatty acids (R)v. Archaea membrane (Figure B)1. Glycerol phosphates serve as the hydrophilic head region 2. An ether link connects other hydrophobic units with the same base unit (R is isoprene, Figure C)vi. Even though archaea and bacteria/eukarya both have bilayer membranes, they are composed of different thingsd. Protein in membranei. Used to communicate with environmentii. Transport protein1. Features of transportersa. Simple transport: driven by the energy in the PMFb. Group translocation: chemical modification of the transported substance driven by phosphoenolpyruvatei. The substance transported in (eg. glucose) is phosphorilated upon entrance- a phosphate group is added; now it is charged and modifiedHydrophobic region; fatty acidsHydrophilic regionGlycerophosphatesc. ATP Binding Cassette (ABC) transporter: periplasmic binding proteins are involved, and energy comes from ATPi. Many ABCs that work when compounds are at very lowconcentrationsii. Extra energy2. Allow accumulation of compounds in cytoplasm3. Highly specific-each protein only transports certain molecules in/out4. Synthesis of transporters is highly


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U-M BIOLOGY 207 - Cell Structure and Function

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