BIOL2010 Week 3: Metabolism - University of Doha for Science & Technology PDF

www.udst.edu.qa BIOL2010 Week 3: Metabolism Metabolism Metabolism can be defined as all of the chemical reactions that occur in any living organism 1. Catabolism – catabolic reactions – Breaking down 2. Anabolism – anabolic reactions – Building up Examples include: Production of biologic...

www.udst.edu.qa BIOL2010 Week 3: Metabolism Metabolism Metabolism can be defined as all of the chemical reactions that occur in any living organism 1. Catabolism – catabolic reactions – Breaking down 2. Anabolism – anabolic reactions – Building up Examples include: Production of biological molecules – proteins, starches, DNA/RNA Cellular respiration – utilizing oxygen and sugar to make energy Digestion – breaking down larger molecules into usable molecules Muscle contraction – energy production for actin/myosin Metabolism – Carbon Sources Microbial organisms can also be described by the source that the organism uses for Carbon Autotrophs – Use carbon dioxide as their sole source of carbon. Ex: Plants, algae, cyanobacteria Heterotrophs – organisms that use organic compounds other than carbon dioxide as a source of carbon. Ex: humans, fungi, animals and protozoans. Most microorganisms are chemoheterotrophs Use nutrients obtained from hosts, living or dead. Metabolism – Energy Source Phototrophs – Use light as an energy source Energy produced through photosynthesis Chemotrophs – use organic or inorganic molecules as an energy source Two categories of chemotrophs: Chemolithotrophs – use inorganic molecules as an energy source Chemoorganotrophs – use organic molecules as an energy source.  Carbon + Energy Sources The terms relating to an energy source can be combined with the terms relating to carbon source: Photoautotrophs – organisms that use photons as an energy source and carbon dioxide as their carbon source - Plants Photoheterotrophs – organisms that use light as an energy source but other organic molecules for carbon – rare form of metabolism Chemoautotrophs – use chemicals as an energy source and carbon dioxide as their sole carbon source – rare form of metabolism Chemoheterotrophs – use chemicals as their energy source and molecules other than carbon dioxide as their source of carbon – most organisms (except plants) Metabolism The nutrients needed by Microorganisms include: Carbon, Nitrogen, Sulfur, Phosphorus & Vitamins Additional elements required include Sodium, potassium, chlorine, magnesium, calcium, iron, and iodine Organisms also require a continuous intake of essential nutrients that cannot be synthesized: Fatty acids and amino acids These combine to make the essential macromolecules of life: Carbohydrates, amino acids, lipids, proteins, and DNA/RNA Metabolism Carbon compounds are the main energy source for most microbes Generally in the form of carbohydrates Nitrogen is used in the synthesis of specific materials that include : Enzymes, proteins, nucleic acids Some bacteria are able to use chemicals as a source of energy Sulfur is used in the production of amino acids and certain co-enzymes Phosphorus is used on the production of nucleic acids and phospholipids Trace elements (Cu, Zn, Co, Fe, Mn, and Se) are used as co-factors with enzymes Growth factors: Vitamins are used as co-enzymes Also require the presence of amino acids, purines and pyrimidines Metabolism – Nutritional Requirements The nutritional requirements of a microorganism is determined by: The number and type of enzymes that it has. Microorganisms with fewer enzymes need more nutrients because they cannot synthesize needed substances. Enzymes Enzymes are proteins which speed up chemical reactions that take place inside cells Lower the activation energy of a reaction Allow the reaction to proceed using less energy Act on substrates which convert to different molecules Activation energy is the energy it takes to Start a chemical reaction Biological catalysts Enzymes Enzymes lower the activation energy A reaction can occur easily in order from #1 – #4 as shown by the red line on this graph The energy required to start the reaction, without a catalyst, would probably damage or destroy the cell Enzymes Factors Affecting Enzymes Enzyme activity can be affected by: 1. pH 2. Temperature Enzymes and pH An enzyme works best at a specific pH Referred to as the optimum pH for that enzyme A change in pH will cause the Shape of the enzyme to change This alters the enzymes active site so that the enzyme and substrate no longer fit together A protein that has changed its shape is said to be Denatured Enzymes and Temperature An enzyme works best at a specific temperature range Referred to as the optimum temperature for that enzyme A change in temperature will cause the shape of the enzyme to change: Altering its active site and ability to function Microbial Metabolism Anabolic reactions are chemical reactions that involve the synthesis of large molecules from their smaller components or from smaller molecules Anabolic reactions result in the release of larger molecules and consume energy Examples include: 2 H2(g) + O2(g)  2 H2O(g) Na(s) + Cl2(g)  NaCl(s) 6C02 + 6H20 + energy → 602 + C6H1206 Amino acid1 + amino acid2 + amino acid3  a protein made up of 3 amino acids Microbial Metabolism Catabolic reactions are chemical reactions that involve the breakdown of large molecules into their components or into smaller molecules. Catabolic reactions result in the release of smaller molecules and energy Examples include: 2 H2O(g)  2 H2(g) + O2(g) NaCl(s)  Na(s) + Cl2(g) 602 + C6H1206 → 6C02 + 6H20 + energy Microbial Metabolism Adenosine triphosphate (ATP) is the energy molecule used by cells ATP: Produced in the MITOCHONDRIA Provides the energy required for metabolism Movement such as muscle contractions Movement of chromosomes during cell division Active transport Production of proteins for enzymes, hormones etc. Microbial Metabolism Adenosine diphosphate (ADP) is the PRECUSOR to ATP ADP: A lower energy compound During cellular respiration an extra phosphate group added to it using a high energy bond When the cell needs energy this phosphate group can be removed, releasing energy for the cell to use Adenosine triphosphate (ATP) is the energy molecule used by cells Microbial Metabolism One other special molecule of interest produced: CyclicAMP (cyclic adenosine monophosphate): A molecule made from ATP that is a common signaling (or second messenger) molecule found inside cells cAMP is an INTERGRAL part of a series of reactions required for a chemical reaction to occur It RELAYS messages from molecules outside the cell telling the cell what metabolic activity to INITIATE inside the cell cAMP which will go on to catalyze a specific reaction inside the cell EPINEPHRINE (adrenaline) is an example of one compound that uses cAMP Epinephrine is used to initiate (start) the breakdown of glycogen by cells in the in liver Epinephrine increases this breakdown even though it does not enter the cells Glycolysis All living cells can convert glucose into pyruvate Process is called glycolysis Takes place in the cytoplasm Bacteria can convert specific sugars into pyruvate using the glycolytic pathway Mannitol – only a few medically significant bacteria can convert Staphylococcus aureus, Enterococcus & Enterobacter Glucose Lactose Sucrose The ability to convert those sugars forms the basis for biochemical tests to identify bacteria Mannitol Salt Agar test - looks for the evidence of mannitol fermentation and acid production The end result of each catabolic process is the production of pyruvate Krebs Cycle Krebs Cycle = Citric Acid Cycle = Tricarboxylic Acid Cycle After glycolysis: In the presence of oxygen (aerobes), pyruvate is changed to Acetyl-CoA, and can then pass through to the Krebs cycle. Occurs in the cytoplasm. The Products of the Krebs cycle include ATP, carbon dioxide gas, and electrons are transferred to molecules of NADH, and FADH2. These act as electron carriers in the next step. Electron Transport Chain (ETC) A series of proteins within the membrane of the cell (happens in the mitochondria in eukaryotic cells). These proteins accept electrons from NADH, and FADH2, and pump the H+ ions outside the membrane. This builds up a electro chemical (charge) gradient. H+ ions then flow back across the membrane through an enzyme, ATP synthase. As the ion pass through the pump Pi is added to ADP to create ATP. Proteins Proteases Deamination Protein metabolism Amino Acids Bacteria can also use proteins and fatty acids as a source of energy Can convert proteins into pyruvate which is cycled into the Krebs cycle Can also produce intermediaries from amino acids - Acetyl-CoA To use proteins, deamination must take place Remove the amine group from the AA Ammonia is produced and excreted Some bacteria convert the ammonia to urea and use that as an entry point into the TCA cycle  Fats and Lipids Metabolism Fats and Lipids Fatty Acids Glycerol Bacteria can cycle fats into the TCA cycle. Pyruvate Fats decompose to glycerol and fatty acids Acetyl-CoA Glycerol is converted to Pyruvate so enters Acetyl-CoA Acetyl-CoA through the Acetyl-CoA entry point Fatty acids are entered directly into the Krebs Acetyl-Co-A Enters directly into the Kreb’s Cycle cycle Fermentation Fermentation is a low energy anaerobic metabolic process, very little energy is created, electron acceptors and carries are generated which allows the organism to continue metabolic processes. Some bacteria reduce pyruvate to produce energy using fermentation Lactic Acid fermentation Alcohol fermentation 2,3-Butanediol fermentation Mixed acid fermentation Fermentation The fermentation is dependent upon the types of enzymes that the organisms make or possess Lactobacillus uses an enzyme that converts pyruvate to lactic acid Lactic acid is very sour and has industrial applications Humans can also convert pyruvate to lactic acid in the muscles When our muscles run out of oxygen and require energy – during a hard workout – burn Saccharomyces cerevesii– fungus makes alcohol through fermentation Enterobacter – uses fermentation to produce 2,3-butanediol Eserichia coli produces mixed acids All of these processes produce a little ATP  Metabolism Carbohydrates Fats and Lipids Proteins Acetyl-CoA NADH Glycolysis Krebs Cycle Electron Transport Chain Pyruvate FADH2 34 ATP 2 2 ATP FERMENTATION ATP