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Micro ch8 Metabolism
Microbiology ch. 8 Metabolism
| Question | Answer |
|---|---|
| Anabolism | aka biosynthesis; any process that results in synthesis of cell molecules and structures. Building and bond-making process; forms larger molecules from small ones. Usually requires energy input. |
| Catabolism | degradative; break bonds of larger molecules into smaller molecules and often release energy. |
| Metabolism | linking of anabolism to catabolism ensures efficient completion of cellular processes; Assembles smaller molecules into larger macromolecules for the cell; uses ATP |
| Metabolism | Degrades macromolecules into smaller molecules and yields energy; Conserves energy in the form of ATP or heat |
| Enzymes | class of macromolecules; catalysts that increase rate of chemical reaction without becoming part of the products/being consumed in the reaction. |
| How do enzymes work? | as catalysts or substrates |
| Catalysts | enzyme that speeds up the rate of a metabolic reaction |
| Energy of activation | resistance to a reaction that must be overcome for a reaction to proceed. |
| Energy of activation Achieved by | increasing thermal energy to increase molecular velocity; increasing concentration of reactants to increase rate of collisions; adding a catalyst |
| Enzyme structure | primary structure is protein; classified as simple or conjugated |
| Simple enzymes | consist of protein alone |
| Conjugated enzymes | consist of protein and nonprotein molecules; A.K. A. Holoenzyme |
| Apoenzyme | refers to the protein of an holoenzyme (conjugated enzyme) |
| Apoenzymes | range in size; exhibit levels of molecular complexity in primary, secondary, tertiary, and sometime quaternary organization. |
| Active site | where the substrate binds; Crevice or groove on the enzyme |
| Specificity | Enzyme-substrate interaction; lock & key fit in which substrate is inserted into active site’s pocket |
| Enzyme-substrate interaction; lock & key fit | Temporary union between enzyme and substrate; Weak, reversible bonding; reaction occurs on substrate; Product is formed and released |
| Cofactors | Supporting the work of enzymes |
| Cofactors | participate in precise functions between the enzyme and its substrate |
| Metallic cofactors | activate enzymes, help bring the active site and substrate close together, participate directly in chemical reactions with the enzyme substrate complex. |
| Coenzymes | organic compunds; work with an apoenzyme to perform necessary alteration of a substrate; general function is to remove a chemical group from one substrate molecule and add it to another substrate, thereby serving as a transient carrier of this group. |
| Vitamins | important component of coenzymes; vitamin deficiency prevents the complete holoenzyme from forming; consequently both the chemical reaction and structure/function dependent upon that reaction are compromised. |
| Classification of enzyme functions | according to characteristics such as site of action, type of action, and substrate. |
| Location and regularity of enzyme action | perform tasks either inside or outside the cell in which they were produced. |
| Exoenzymes | after synthesis, transported extracellularly where they break down (hydrolyze) large food molecules or harmful chemicals. Ex. cellulose, amylase, penicillinase. |
| Endoenzymes | after synthesis are retained intracellularly and function there; most enzymes of metabolic pathways are this variety. |
| Constitutive enzymes | enzymes always present and in relatively constant amounts regardless of amount of substrate. |
| Regulated enzymes | production is either turned on (induced) or off (repressed) in response to changes in concentration of the substrate. Level of inducible/repressible enzymes controlled y degree to which the genes for these proteins are transcribed into proteins. |
| Dehydration reactions | aka synthesis reactions (formation of proteins, DNA, RNA; forming storage polymers like starch, glycogen; assembling new cell parts) typically require ATP and release one water molecule for each bond made; anabolic reaction |
| Hydrolysis reaction | catabolic reactions involving energy transaction, remodeling of cell structure, digestion of macromolecules require enzymes to break bonds, which requires input of water. |
| Oxidation and reduction | some atoms/compounds readily give or receive electrons and participate in oxidation (loss of electrons) or reduction (gain of electrons). Compound that loses = oxidized; compound that receives = reduced |
| Aminotransferases | convert one type of amino acid into antoehr by transferring an amino group |
| Phosphotransferases | participate in transfer of phosphate groups and are involved in energy transfer |
| Methyltransferases | move a methyl (CH3) group from substrate to substrate |
| Decarboxylases | catalyze removal of carbon dioxide from organic acids in several metabolic pathways. |
| The role of microbial enzymes in disease | many pathogens secrete unique exoenzymes that help them avoid host defenses or promote multiplication in tissues. Referred to as virulence factors, or toxins. |
| Streptokinase | Streptococcus pyogenes |
| Elastase and collagenase | Pseudomonas aeruginosa |
| Lecithinase C | Clostridium perfringens |
| The sensitivity of enzymes to their environments | Activity highly influenced by cell’s environment; usually enzymes operate under the natural temperature, pH, and osmotic pressure of an organism’s habitat. Changes lead to the enzyme becoming unstable or labile. |
| Labile | chemically unstable enzyme |
| Denaturation | process by which the weak bonds that maintain the native shape of the apoenzyme are broken, which in turn prevents substrate from binding to the active site. Nonfunctioning enzymes block metabolic reactions and can lead to cell death. |
| Metabolic reactions | proceed in a systematic, highly regulated manner that maximizes use of available nutrients and energy; cell responds to environmental conditions by using metabolic reactions that most favor growth and survival. |
| Regulation of metabolism | largely the regulation of enzymes by system of checks and balances. |
| Metabolic pathways | Multistep series of reactions; each step catalyzed by an enzyme; product of a reaction is often the reactant for the next, forming linear chain of reactions. Interconnected; each has pacemaker (us. First enzyme) |
| Pacemaker enzyme regulation | either enzyme itself is inhibited/activated or amount of the enzyme in the system is altered. |
| Direct controls on the actions of enzymes | competitive and noncompetitive inhibtion |
| Competitive inhibition | bacterial cell supplies molecule mimicking enzymes normal substrate; mimic occupies binding site, preventing substrate from binding. |
| Noncompetitive inhibition | negative feedback; occurs when cell has two binding sites—active and regulatory sites. |
| Regulatory binding site | receives regulatory molecule, which is usually product of enzymatic reaction itself; provides neg feedback to slow enzymatic activity once certain conc product is produced; does not bind in same site as active molecule. |
| Controls on enzyme synthesis | replacement of enzymes can be regulated according to cell demand. Mechanisms of this system are genetic, so require regulation of DNA and protein synthesis machinery. |
| Enzyme repression | stop further synthesis of an enzyme somewhere along its pathway. Response time is longer than for feedback inhibition, but its effects are more enduring. |
| Enzyme induction | enzymes are induced only when suitable substrates are present; synthesis of an enzyme is induced by its substrate. Ex. Escherichia coli |
| The Pursuit and Utilization of Energy | Energy comes directly from light or is contained in chemical bonds and released when substances are catabolized/broken down; Energy is stored in ATP |
| Energy in cells | cells manage energy in the form of chemical reactions that change molecules; some release energy, others require it. |
| Exergonic reaction | releases energy as it goes forward; free energy; available for doing cellular work |
| Endergonic reaction | energy transaction driven forward by addition of energy. |
| Redox reactions | energy extracted; usually occurs in redox pair; process saves electron along w/energy, changes energy balance, leaves previously reduced compound w/ less energy than oxidized one; Energy captured can be used to phosphorylate to ADP/some other compound |
| Redox pair | electron donor and electron acceptor |
| Phosphorylation and ATP synthesis | energy present in electron receptor is used to phosphorylate (add an inorganic phosphate) to ADP/another compound; this stores the energy in high-energy molecule—like ATP. |
| Dehydrogenation | removal of hydrogens (which contains one proton, one electron) from a compound during a redox reaction; essential supplier of electrons for the respiratory electron transport system. |
| Electron carriers | Molecular shuttles; most are coenzymes that transfer both electrons and hydrogens; some transfer electrons only. NAD and NADH |
| Adenosine triphosphate | Metabolic money |
| The molecular structure of ATP | Phosphate, sugar (ribose), and a base (adenine) |
| The metabolic role of ATP | The primary energy currency of the cell; When used, it must be replaced, so ATP utilization and replacement is an ongoing cycle. |
| Substrate-level phosphorylation | ATP is formed by transfer of a phosphate group from a phosphorylated compound directly to ADP to yield ATP |
| Oxidative phosphorylation | a series of redox reactions occurring during the final phase of the respiratory pathway |
| Photophosphorylation | ATP is formed through a series of sunlight driven reactions |
| Pathway | a series of biochemical reactions; Catabolic and anabolic pathways in a cell are interconnected and interdependent |
| Metabolism | enzymes used to catalyze reactions that break down (catabolize) organic molecules to materials (precursor molecules) that cells can then use to build (anabolize) larger, more complex molecules that are particularly suited to them |
| Metabolism Reducing power | electrons available in NADH and FADH2 needed in large quantities |
| Metabolism Energy | stored in the bonds of ATP; needed in large quantity for the anabolic parts of metabolism. |
| Catabolism | Getting materials and energy |
| Glycolysis | most common pathway to break down glucose |
| Aerobic respiration | series of reactions; convert glucose to CO2, allows cell to recover significant amt of energy; characteristic of many bacteria, fungi, protozoa, and animals; Relies on free oxygen as final acceptor for electrons & hydrogens; produces large amount of ATP |
| Anaerobic respiration | same three pathways as aerobic respiration, but does not use molecular oxygen as the final electron acceptor. Instead, NO3, So4 and other oxidized compounds are utilized. |
| Glucose | The starting compound of Aerobic respiration |
| Glycolysis | The starting lineup; enzymatically converts glucose through several steps into pyruvic acid |
| Glycolysis | Depending on the organism/conditions, may be first phase of aerobic respiration or may serve as primary metabolic pathway |
| Steps in the glycolytic pathway | Oxidation of glucose, Phosphorylation of some intermediates (used 2 ATP), Splits 6 carbon sugar into two 3 carbon molecules, Coenzyme NAD is reduced to NADH, Substrate level phosphorylation (4 ATPs synthesized) Water is generated |
| Glycolysis end products | NET ATP IS 2 because has to use 2 ATP to start; Final intermediates are two Pyruvic acid molecules. |
| Pyruvic acid | A central metabolite |
| The Krebs cycle or TCA cycle | A carbon and energy wheel |
| The processing of pyruvic acid | to connect the glycolysis pathway to the Krebs cycle, the pyruvic acid is first converted to a starting compound for that cycle |
| Role of acetyl coenzyme A | the acetyl group remains attached to coenzyme A forming acetyl coenzyme A (acetyl CoA that feeds into Krebs cycle |
| Role of NADH | NADH will be shuttled into electron transport and used to generate ATP via oxidative phosphorylation |
| Steps in the Krebs cycle/TCA cycle | the Krebs cycle serves to transfer the energy stored in acetyl Coa to NAD+ and FAD by reducing them (transferring hydrogen ions to them); so the main products are these reduced molecueles as well as 2 ATPs |
| Kreb/TCA cycle | Each pyruvic acid is processed to enter the TCA cycle (two complete cycles); CO2 is generated; Coenzymes NAD and FAD are reduced to NADH and FADH2; Net yield of 2 ATPs; Critical intermediates are synthesized |
| The respiratory chain | Electron transport and oxidative phosphorylation; Final processing mill for electrons and hydrogen ions and the major generator of ATP |
| Elements of electron transport | The energy cascade; NADH and FADH2 donate electrons to the electron carriers; Membrane bound carriers transfer electrons (redox reactions) across membrane; The final electron acceptor complete the terminal step (ex. oxygen) |
| products of fermentation in microorganisms | Alcoholic fermentation (Converting pyruvic acid to ethanol); Acidic fermentation, Homolactic fermentation, Mixed acid fermentation |
| Lipid catabolism | lipases break down lipids to fatty acids and glycerol; Fatty acids are broken down through beta oxidation |
| Protein catabolism | Proteases, Deamination |
| Amphibolic sources of cellular building blocks | Gluconeogenesis, Beta-oxidation, Amination, Transamination |
| Anabolism | Formation of macromolecules; Carbohydrate biosynthesis, amino acids, protein synthesis, and nucleic acid synthesis |
| Photosynthesis | Two phases; Light-dependent reactions require sunlight; Light-independent reactions proceed in light or dark conditions |
| Photons | energy packets from the sun |
| Photosynthetic pigments absorb energy | Chlorophylls, Carotenoids, Phycobilins |
| Light-dependent reactions | Take place in the thylakoid membranes (grana) of the chloroplast |
| Active site | specific region on an apoenzyme that binds substrate; site for reaction catalysis |
| Apoenzyme | protein part of an enzyme (as opposed to the nonprotein/inorganic cofactors) |
| Holoenzyme | enzyme complete with its apoenzyme and cofactors |
| Substrate | specific molecule upon which an enzyme acts |
| Non competitive inhibitor | enzyme inhibitor; regulatory molecule binds to a site other than the active site |
| Competitive inhibitor | bacterial cell supplies molecule mimicking enzymes normal substrate; mimic occupies binding site, preventing substrate from binding. |
| “ES” Complex | enzyme substrate complex; substrates bind with “lock-and-key” fit; once reaction is complete, the product is released and enzyme is reused. |
| Coenzyme | organic compound that works w/ apoenzyme to perform necessary alteration of substrate; general function to remove a chemical group from one substrate molecule & add it to another substrate, serving as a transient carrier of this group |
| Cofactor | other organic molecules (coenzymes) or inorganic elements (metal ions)—participate in precise functions between the enzyme and its substrate; enzyme accessory |
| Product | substance left after a reaction is complete |
| Specificity | seen in the lock & key fit in which a substrate is inserted into active site’s pocket. It is a temporary union between the enzyme and substrate, and has weak, reversible bonding |
| Induced fit | describes the interaction between the substrate and a flexible active site. The substrate changes the conformation on the enzyme, and allows better binding and catalytic effects. |
| Enzymatic activity can be regulated on several levels. What are they? | Metabolic pathways—regulated by the enzymes that catalyze the reactions; Direct control on the actions of enzymes is done via competitive and non-competitive inhibition; Genetic control via enzyme repression and induction (controls on enzyme synthesis) |
| Constitutive enzymes | enzymes always present and in relatively constant amounts regardless of amount of substrate. |
| Regulated enzymes | production is either turned on (induced) or off (repressed) in response to changes in concentration of the substrate. Level of inducible/repressible enzymes controlled by degree to which the genes for these proteins are transcribed into proteins. |
| What molecule functions as the cells “energy currency?” | Adenosine Triphosphate (ATP) |
| What is substrate level phosphorylation? How is it different than phosphorylation by ATP synthase? | Substrate-level phosphorylation--ATP is formed by transfer of a phosphate group from a phosphorylated compound directly to ADP to yield ATP. Oxidative phosphorylation |
| What is the role of NAD in respiration? | It is a carrier that transports electrons to the electron transport chain. |
| What parts of the respiratory pathway are used during fermentation? | The glycolytic pathway |
| Is the Krebs cycle used in fermentation? | No, because the Krebs cycle is an aerobic process. |
| What product of the EMP is used by the cell to produce amino acids? | (EMP |
| What biological reaction is “Fat Burning”? | Beta oxidation |
| The book lists 3 types of fermentation reactions. What are they? | Alcoholic--in yeast/bacterial species that have metabolic pathways for converting pyruvic acid to ethanol; Acidic- varied pathways; homolactic or heterolactic; Mixed acid- system converts pyruvic acid to several acids simultaneously |
Created by:
jenedws
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