Chapter 5: Microbial Metabolism Flashcards
Metabolism:
o The sum of all chemical reactions.
• Catabolism – BREAK down.
• Anabolism – BUILD up.
Catabolism:
o Breakdown of complex molecules into simpler molecules.
o Provides energy and building blocks for anabolism.
o ATP turns into ADP and P and Energy.
Anabolism:
o Build complex molecules out of simpler molecules.
o Uses energy and building blocks from catabolic reactions.
o ADP and P and Energy turn into ATP.
Microbial Metabolism:
o Although microbial metabolism can cause disease and food spoilage, many pathways are beneficial rather than pathogenic.
• Enzymes facilitate metabolic reactions.
• ATP is used by microbes and other cells to manage energy needs.
• Catabbolic reactions couple with ATP synthesis.
• Anabolic reactions couple with ATP breakdown.
Metabolic Pathways:
o A METABOLIC PATHWAY is a sequence of enzymatically catalyzed chemical reactions in a cell.
• They are determined by enzymes.
• Enzymes are encoded by genes.
Enzymes:
o Proteins.
o Catalyze chemical reactions.
o 3D globular shape.
Catalysts:
o Speed up a chemical reaction.
• Not permanently altered themselves.
Substrate:
o The substance that the enzyme acts on.
Active Site:
o The location upon the cell in which the substrate would act upon.
Coenzymes and Cofactors:
o Important Coenzymes:
• NAD, NADP, FAD, Coenzyme A.
o Cofacters can be metal ions:
• Zinc, copper, magnesium, manganese, calcium, cobalt.
Six Enzyme Classes Based on Type of Reaction they Catalyze:
o Oxidoreductase. o Transferase. o Hydrolase. o Lyase. o Isomerase. o Ligase.
Factors Influencing Enzyme Activity:
o Temperature (denature proteins when high).
• If temperature increases, rate of reaction increases until the enzyme (protein) id denatured by heat and inactivated.
• This causes the reaction rate to fall steeply.
o pH (denature proteins when high).
o Substrate Concentration.
• Increasing concentration of substrate molecule causes rate of reaction to increase until the active sites on all the enzyme molecules are filled.
• At this point the max rate of reaction is reached.
o Inhibitors.
• Competitive Inhibition: substrate and and competitive inhibitors compete for the active site of an enzyme.
• Noncompetitive inhibition: act on other parts of the apoenzymes or on the cofactor and decrease the enzymes ability to combine with the normal substrate.
Steps of Feedback Inhibition:
o 1. Substrate Binds.
o 2. Product Produced.
o 3. End-product binds to enzyme.
o 4. Pathway shuts down.
Testing for an Enzyme:
o Control:
• Urease Negative.
o Test:
• Bacterial urease hydrolyzes urea, producing ammonia.
• Raises the pH and indicator in medium turns fuchsia.
Ribozymes:
o RNA that function as catalysts by cutting and splicing RNA.
What is a coenzyme?
o Many Coenzymes are derived from B vitamins – nonprotein – associated with and activates an enzyme.
Why is enzyme specificity important?
o Allows the enzyme to find the correct substrate in a vast sea of molecules.
What happens to an enzyme below its optimal temperature?
Slow Reaction
What happens to an enzyme above its optimal temperature?
Denatures
Why is feedback inhibition noncompetitive inhibition?
Product binds to an allosteric site
What is a ribozyme?
o RNA that acts as a catalyst specifically on strands of RNA.
Oxidation-Reduction Reactions:
o OXIDATION: Removal of electrons.
o REDUCTION: Gain of electrons.
o REDOX REACTION: Paired reaction.
The Generation of ATP:
o ATP is generated by the phosphorylation of ADP.
o Organisms use 3 different mechanisms of phosphorylation to generate ATP from ADP:
• SUBSTRATE-LEVEL PHOSPHORYLATION: ATP generated when high-energy PO4– added to ADP generates ATP - Occurs in glycolysis.
• OXIDATIVE PHOSPHORYLATION: Generate ATP in the ELECTRON TRANSPORT CHAIN.
• PHOTO-PHOSPHORYLATION: Occurs only in light-trapping photosynthetic cells. Light energy is converted to ATP when the transfer of electrons (oxidation) from chlorophyll pass through a system of carrier molecules.
Metabolic Pathways of Energy Production:
o Store energy in and release energy from organic molecules. o Breakdown of Carbs to release energy. • Glycolysis. • Krebs cycle. • Electron transport chain.
Glycolysis:
o First step is catabolism of glucose for both respiration and fermentation.
o Glucose in and 2 pyruvate (pyruvic acid) out.
o 4 total ATP, but 2 are consumed for a net gain of 2 ATP.
Additional Pathways of Glycolysis:
o PENTOSE PHOSPHATE PATHWAY:
• Uses pentoses and produces NADPH.
• Operates simultaneously with glycolysis.
o ENTNER-DOUDOROFF PATHWAY:
• Produces NADPH and ATP.
• Does not involve glycolysis.
• Occurs in Pseudomonas, Rhizobium, and Agrobacterium.
Krebs Cycle:
o The KREBS CYCLE, or citric acid cycle, is a part of cellular respiration.
o It is a series of chemical reactions used by all aerobic organisms to generate energy.
o PYRUVATE from GLYCOLYSIS is reconfigured to ACETYL CO-A.
o Produces CO2 and many ELECTRONS in the form on FADH2 and NADH that move on to the ELECTRON TRANSPORT CHAIN.
Electron Transport System:
o MOST ATP PRODUCTION OCCURS BY OXIDATIVE PHOSPHORYLATION (ELECTRON TRANSPORT CHAIN).
o In bacteria, the electron transport chain is located on the cytoplasmic membrane. In Eukaryotes in the mitochondrial membrane.
o The chain consists of a series of electron carriers.
o Electrons are transferred from one electron carrier to the next in the electron transport chain.
o As electrons move along each step of the chain, they give up a bit of energy.
o At the end of the chain, the electrons are transferred to oxygen, and water is formed as a by-product.
Cellular Respiration:
o Series of Redox Reactions that Generate ATP: • Way for Cells to Gain Energy. o AEROBIC RESPIRATION: • With Oxygen. • Final Electron Acceptor IS OXYGEN. • GLYCOLYSIS, KREBS CYCLE and ETS. o ANAEROBIC RESPIRATION: • Without Oxygen. • Final Electron Acceptor IS NOT OXYGEN. • GLYCOLYSIS, Part of the KREBS CYCLE.
Aerobic Resiration Yield:
o AEROBIC RESPIRATION:
• Final electron acceptor in ETS is O2.
• Total 36-38 ATP per glucose.
o ANAEROBIC RESPIRATION:
• Final electron acceptor in ETS is not O2.
• Yields much less energy than aerobic respiration.
Fermentation:
o AFTER GLYCOLYSIS, Pyruvic Acid is converted to an organic product.
o DOES NOT REQUIRE OXYGEN, BUT MAY OCCUR IN ITS PRESENCE.
o Pyruvic acid and the electrons carried by NADH from glycolysis are incorporated into fermentation end-products.
o FERMENTATION IS IMPORTANT IN:
• Spoilage of food by microorganisms.
• Production of alcoholic beverages.
• Production of acidic dairy products.
• Identification of bacterial organisms.
o ALCOHOL FERMENTATION:
• Glycolysis.
• 2 Pyruvic acid become:
• Produces ethanol + CO2.
o LACTIC ACID FERMENTATION:
• Glycolysis.
• 2 Pyruvic acid become:
• Homolactic fermentation:
• Produces lactic acid only.
• Heterolactic fermentation:
• Produces lactic acid and other compounds.
o RELEASES ENERGY FROM OXIDATION OF ORGANIC MOLECULES
• DOES use GLYCOLYSIS.
• DOES NOT require oxygen, but may occur in its presence.
• DOES NOT use the KREBS cycle or ETC.
• Uses an organic molecule as the final electron acceptor.
Catabolism of Organic Food Molecules:
o Proteins, Carbohydrates, and Lipids can all be sources of electrons and protons for respiration.
o Each type enter Glycolysis or the Krebs Cycle at various points.
Protein Catabolism:
o Peptone Iron Agar.
o Detects H2S production.
o H2S precipitates with iron in the medium.
o CONTROL:
• Urease Negative
o TEST:
• Bacterial urease hydrolyzes urea, producing ammonia.
• Raises the pH and indicator in medium turns fuchsia.
Overview of Metabolism:
o Metabolism is the basis of all life.
o Metabolism often forms the basis of antibiotic therapy because some antibiotics interfere with metabolic reactions.
o Glycolysis is a preparatory stage for other processes, like the anaerobic process.
o The Krebs cycle generates energy-carriers.
o The electron transport system produces a lot of ATP either by aerobic or anaerobic conditions.
o Fermentation pathways follow glycolysis.
Nutritional Classification of Organisms:
o Organisms can be classified based on their energy source.
• Phototrophs use Light.
• Chemotrophs use Chemicals.
Photoautotroph:
o Energy source: Light
o Carbon Source: CO2
o Example: Oxygenic: cyanobacteria plants Anoxygenic: green, purple bacteria.
Photoheterotroph:
o Energy Source: light
o Carbon source: organic compounds.
o Example: green, purple nonsulfur bacteria.
Chemoautotroph:
o Energy source: chemical
o Carbon source: CO2.
o Example: Iron-oxidizing bacteria.
Chemoheterotroph:
o Energy source: chemical
o Carbon source: Organic Compounds.
o Example: Fermentative bacteria. Animals, protozoa, fungi, bacteria.
Polysaccharide Biosynthesis:
o Glucose-6-phosphate, an intermediate of Glycolysis produces Glycogen.
o Fructose-6-phosphate, an intermediate of Glycolysis produces Peptidoglycan in bacteria.
Lipid Biosynthesis:
o Intermediates of Glycolysis produces Glycerol.
o Acetyl CoA produces Fatty Acids.
o And the two of them together form Simple Lipids.
Pathways of Amino Acid Biosynthesis:
o Adding or transferring amino groups of intermediate products from each of these pathways form Amino Acid.
o Pentose Phosphate Pathway.
o Krebs Cycle.
o Entner-Doudoroff Pathway.
Amino Acid Biosynthesis:
o TRANSAMINATION is making new amino acids with the amino group of old amino acids.
o Glutamic Acid and Aspartic acid are both amino acids.
o Oxaloacetic acid and alpha-ketoglutaric acid are intermediated in the Krebs cycle.
Amphibolic Pathways:
o Metabolic pathways that have both catabolic and anabolic functions.
Glycolysis Summary:
o One glucose is used. o Partial oxidation of the sugar. • Two NADH are reduced. o 2 ATP are consumed. o 4 ATP total are made. o Net of 2 ATP produced. o 2 pyruvates are end products.
Kreb’s Cycle Summary:
o Each pyruvate molecules (2) breaks down into 3 CO2, 4 NADH, 1 FADH2, and 1 ATP.
o Each glucose now completely oxidized to CO2.
o Electrons are temporarily on carrier molecules.
o 4 ATP total made by substrate level phosphorylation.
