Chapter 9: Microbial Metabolism Flashcards
Metabolism
The term used to describe all of the chemical reactions inside a cell.
Metabolic Pathways
Cellular processes such as the building or breaking down of complex molecules occur through series of stepwise, interconnected chemical reactions.
Exergonic Reactions
Reactions that are spontaneous and release energy.
Endergonic Reactions
Require energy to proceed.
Anabolism
Refers to those endergonic metabolic pathways involved in biosynthesis, converting simple molecular building blocks into more complex molecules, and fueled by the use of cellular energy.
Catabolism
Refers to exergonic pathways that break down complex molecules into simpler ones.
Autotrophs
Organisms that convert inorganic carbon dioxide into organic carbon compounds (Ex. plants and cyanobacteria).
Heterotrophs
Rely on more complex organic carbon compounds as nutrients; these are provided to them initially by autotrophs (Ex. humans, E. coli).
Phototrophs
Get their energy for electron transfer from light.
Chemotrophs
Obtains energy for electron transfer by breaking chemical bonds.
Organotrophs
Chemotrophs that obtain energy from organic compounds including humans, fungi, and many prokaryotes.
Lithotrophs
Chemotrophs that get energy from inorganic compounds, including hydrogen sulfide and reduced iron.
Oxidation Reactions
Reactions that remove electrons from donor molecules, leaving them oxidized.
Reduction Reactions
Those that add electrons to acceptor molecules, leaving them reduced.
Redox Reactions
Oxidation and reduction occur in tandem.
Electron Carriers
Molecules that bind to and shuttle high-energy electrons between compounds in pathways.
NAD+/NADH
The most common mobile electron carrier used in catabolism. NAD+ is the oxidized form of the molecule; NADH is the reduced form of the molecule.
Adenosine Monophosphate (AMP)
Composed of an adenine molecule bonded to a ribose molecule and a single phosphate group.
Catalyst
A substance that helps speed up a chemical reaction and is not used up in the reaction.
Activation Energy
The energy needed to form or break chemical bonds and convert reactants to products.
Substrates
The chemical reactants to which an enzyme binds.
Active Site
The location within the enzyme where the substrate binds.
Active Site
The location within the enzyme where the substrate binds.
Induced Fit
Active-site modification in the presence of substrate, along with the simultaneous formation of the transition state.
Cofactors
Inorganic ions such as iron and magnesium that help stabilize enzyme conformation and function.
Coenzymes
Organic helper molecules that are required for enzyme action; they are not consumed and, hence, are reusable.
Coenzyme A (CoA)
Bind to the enzyme’s active site, aiding in the chemistry of the transition of a substrate to a product.
Apoenzyme
An enzyme lacking a necessary cofactor or coenzyme and is inactive.
Holoenzyme
An enzyme with the necessary associated cofactor or coenzyme and is active.
Competitive Inhibitor
A molecule similar enough to a substrate that is can compete with the substrate for binding to the active site by simply blocking the substrate from binding.
Allosteric Site
A location other than the active site.
Noncompetitive (Allosteric) Inhibitor
Binds to the enzyme at an allosteric site, and still manages to block substrate binding to the active site by inducing a conformational change that reduces the affinity of the enzyme for its substrate.
Allosteric Activators
Bind to locations on an enzyme away from the active site, inducing a conformational change that increases the affinity of the enzyme’s active site(s) for its substrate(s).
Feedback Inhibition
Involves the use of a pathway product to regulate its own further production.
Embden-Meyerhif-Parnas (EMP) Pathway (Part One)
The first part of the pathway is called the energy investment phase, uses energy from two ATP molecules to modify a glucose molecule so that the six-carbon sugar molecule can be split evenly into two phosphorylated three-carbon molecules called glyceraldehyde 3-phosphate (G3P)
Embden-Meyerhif-Parnas (EMP) Pathway (Part Two)
The second part of the pathway, called the energy payoff phase, extracts energy by oxidizing G3P to pyruvate, producing four ATP molecules and reducing two molecules of NAD+ to two molecules of NADH, using electrons that originated from glucose.
Substrate-Level Phosphorylation
A phosphate group is removed from an organic molecule and is directly transferred to an available ADP molecule, producing ATP.
Entner-Doudoroff (ED) Pathway
Glycolysis pathway used by bacteria, including Pseudomonas aeruginosa.
Phosphate Pathway (PPP)/Phosphogluconate Pathway/Hexose Monophosphate Shunt
May be the most ancient universal glycolytic pathway; is favored when the cell has need for nucleic acid and/or protein synthesis, respectively.
Transition Reaction/Bridge Reaction
When the pyruvate is decarboxylated by the enzyme complex pyruvate dehydrogenase to a two-carbon acetyl group.
Coenzyme A (CoA)
A very large carrier compound that two-carbon acetyl must be attached to to proceed in the metabolic process.
Krebs Cycle
Transfers remaining electrons from the acetyl group produced during the transition reaction to electron carrier molecules, thus reducing them.
Electron Transport System
Is the last component involved in the process of cellular respiration; it comprises a series of membrane-associated protein complexes and associated mobile accessory electron carriers.
Redox Potential
A measure of the ease with which a molecule will accept electrons.
Aerobic Respiration
The final electron acceptor at the end of the ETS is an oxygen molecule (O2) that becomes reduced to water (H2O) by the final ETS carrier.
Anaerobic Respiration
Using an inorganic molecule other than oxygen as a final electron acceptor.
Fermentation
Does not involve an electron transport system and does not directly produce any additional ATP beyond that produced during glycolysis by substrate-level phosphorylation.
Lactic Acid Fermentation
Makes yogurt and cheese, and is used by animals in muscles during oxygen depletion. Pyruvate + NADH <—> Lactic Acid + NAD+
Homolactic Fermentation
When lactic acid is the only fermentation product.
Alcohol Fermentation
Produces ethanol; is used in the production of alcoholic beverages and also makes bread products rise due to the CO2 production; also used in biofuel production.
Propionic Acid Fermentation
The propionic acid produced contributes to the distinctive flavor of Swiss cheese, for example/
Lipases
Catalyze the breaking down of triglycerides.
Phospholipaes
Catalyze the breaking down of phospholipids.
Phospholipase
Catalyze the breaking down of phospholipids.
Beta-Oxidation
Sequentially removes two-carbon acetyl groups from the ends of fatty acids chains, reducing NAD+ and FAD to produce NADH and PADH2, respectively, whose electrons can be used to make ATP by oxidative phosphorylation.
Protease
The enzymes that degrades proteins.
