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Chapter 5 Microbial Nutrition and Culture. Siti Sarah Jumali (ext 2123) Room 3/14 sarah_jumali84@hotmail.com. Groups of bugs based on energy capture and carbon source. AUTOTROPHY : Use carbon dioxide to synthesize organic molecules Two types: Photoautotrophs : obtain energy from light
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Chapter 5 Microbial Nutrition and Culture Siti Sarah Jumali (ext 2123) Room 3/14 sarah_jumali84@hotmail.com
Groups of bugs based on energy capture and carbon source • AUTOTROPHY: Use carbon dioxide to synthesize organic molecules • Two types: • Photoautotrophs: obtain energy from light • Chemoautotrophs: obtain energy from oxidizing simple inorganic substance
Groups of bugs based on energy capture and carbon source cont’d • HETEROTROPHY: Get carbon dioxide from ready made organic molecules • Two types: • Photoheterotrophs: obtain chemical energy from light • Chemoheterotrophs: obtain energy from breaking down ready-made organic compounds
Metabolism • The sum of all chemical processes carried out by living organisms • Anabolism: rxn that requires energy in order to synthesize complex molecules from the simpler ones - (use energy and building blocks to build large molecules) • Catabolism: rxn that releases energy by breaking complex molecules into simpler ones which can be reused as building blocks - (provides energy and building blocks for anabolism)
Metabolism: The sum of catabolism and anabolism Catabolism Energy Anabolism
Metabolic Pathway • Glycolisis, fermentation, aerobic respiration and photosynthesis each consists of a series of chemical reaction • The product of one reaction serves as the substrate for the next: ABCD • Such chain of reactions is called a metabolic pathway: - Anabolic pathways make the complex molecules that form structure of cells, enzymes and molecules that control cells - Catabolic pathways capture energy in a form a cell can use
Oxidation-Reduction Reactions • All catabolic reactions involve electron transfer which is directly related to oxidation and reduction (redox potential) • Redox reaction: An oxidation reaction paired with a reduction reaction - Oxidation: the loss of removal of electrons -Reduction: the gain of electrons
Representative Biological Oxidations Acronyms for oxidation and reduction: • Oxidation Is Losing Electrons, Reduction Is Gaining Electrons: OIL RIG • Losing Electrons Oxidation, Gaining Electrons Reduction: LEO the lion. GER! or LEO says GER • Electron Loss Means Oxidation: ELMO In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenation.
Energy Transfer by Carrier Molecules • Carrier molecules such as Cytochrome (cyt) and some coenzymes carry energy in the form of electrons in many biochemical reactions • Coenzymes such as FAD carry whole hydrogen atoms (electrons together with protons); NAD carries one hydrogen atom and one “naked” electron • When co-enzymes are reduced, they increase in energy, when they are oxidized, they decrease in energy.
Energy Generation of ATP • ATP is generated by the phosphorylation of ADP ADP + Pi + Energy ATP • In cells, energy is provided by the hydrolysis of ATP ATP ADP + Pi + Energy Energy Energy
Generation of ATP • Substrate level Phosphorylation: Energy from the transfer of a high energy PO4 to ADP generates ATP C-C-C-P + ADP C-C-C + ATP • Oxidative Phosphorylation: Energy relseased from transfer of electrons (oxidation) of one compound to another (reduction) is used to generate Atp in the electron transport chain • Photophosporylation: Light causes chlorophyll to give up electrons. Energy released from transfer of electrons (oxidation) of chlorophyll trough a system of carrier molecules is used to generate ATP
Carbohydrate Catabolism • The breakdown of carbohydrate to release energy involves • Glycolisis (cytoplasm) • Krebs cycle (mitochondrion) • Electron transport chain
Glycolysis • Glycolysis (Embden Meyerhof pathway) is the metabolic pathway used by most autotrophic and heterotrophic organismsm to begin breakdown of glucose • Does not require oxygen, but occur in precense or absence of oxygen • Overall chemical reaction of Glycolysis
Glycolysis: Oxidation of Glucose 2ATP 2 NAD+ 2ADP 2NADH + 2H+ 4 ADP 4 ATP Glucose two Glyceraldehyde-3-PO4 two Pyruvate
Glycolysis: Oxidation of Glucose 2 NAD+ 2 NADH + 2 H+
Glycolysis: Oxidation of Glucose Glycolysis generates 2 ATP molecules and 2 NADH + 2 H+ Two ATP used in adding phosphate groups to glucose and fructose-6-phosphate (- 2 ATP) Four ATP generated in direct transfer to ADP by two 3-C molecules (+ 4 ATP) Glucose + 2 ADP + 2 Pi + 2 NAD+ 2pyruvate + 2 ATP + 2 NADH + 2 H+
Pathways for Pyruvate Aerobic conditions O || CH3–C –COO- + NAD+ + CoA pyruvate O || CH3–C –CoA + CO2 + NADH + H+ acetyl CoA
Pathways for Pyruvate Anaerobic conditions(No O2 available) Reduce to lactate to replenish NAD+ for glycolysis O OH || | CH3–C –COO- + NADH + H+ CH3–CH –COO- + NAD+ pyruvate lactate enzyme: lactate dehydrogenase
Alternative to Glycolysis • Pentose phosphate pathway • Uses pentoses and NADPH • Operates with glycolisis • Entner-Doudoroff pathway • Produces NADPH and ATP • Does not involve glycolisis • Pseudomonas, Rhizobium, Agrobacterium
Intermediate step • Pyruvic acid (from glycolysis) is oxidized and decarboxylated
The Krebs Cycle/ The Citric acid cycle (TCA cycle) • Oxidation of acetyl Co-A produces NADH and FADH2 (mitochondrion)
The Electron Transport Chain • An electron transport chain (ETC) couples electron transfer between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer of H+ ions (protons) across a membrane. • A series of oxidation-reduction reactions, the electron transport chain (ETC) performs 2 basic functions: • Accepting electrons from an electron donor and transferring them to an electron acceptor • Conserving for ATP synthesis some of the energy released during the electron transfer • A series of carrier molecules that are, in turn oxidized and reduced as electrons are passed down the chain • Energy released can be used to produce ATP by chemiosmosis
Chemiosmosis • Electrons from the hydrogen atoms removed from the reactions of the Krebs cycle are transferred through the electron transport system • Electron transport creates the H potential across the membrane • Combination of hydrogen/electron carriers