Chapter 5- Microbial Metabolism Flashcards
Properties of a metabolic pathway
determined by enzymes, and allows organisms to release and store energy in a series of controlled reactions as opposed to a single burst that would be very inefficient (much of the energy would be lost in the form of heat).
What determines whether a chemical rxn will occur from the collision?
speed of the particles, orientation of the particles, and the activation energy required for the rxn.
How can you increase non-biological reaction rates?
increasing temperature, concentration, or the pressure.
Activation energy
the amount of collision energy needed for a chemical rxn.
Reaction rate
how fast or slow a rxn takes place determined by the frequency of collisions containing sufficient energy to bring about a rxn.
enzyme characteristics?
generally globular, acts on a specific substance(s), and its substrate(s), catalyzes only one reaction, can operate at physiological temperatures, subject to various cellular controls, and does not always bind just one substrate.
how do enzymes lower the activation energy?
proximity and orientation: enzyme orients substrate into position that increases the probability of a successful rxn.
What allows the release of an enzyme’s products?
upon completion of the rxn, the products no longer fit in the active site, so they are then released.
Effects of pH on enzyme?
extreme pH changes the enzyme’s 3D structure, because H+ and OH- compete with its hydrogen and ionic bonds
Example of a competitive inhibitor?
Sulfanilamide; PABA is needed to synthesize to produce folic acid and sulfanilamide competes with PABA. Sulfanilamide isn’t toxic to mammals because they get their folic acid in the form of a B vitamin. And bacterial cells cannot use folic acid from their environment because they cannot transport it across the cell.
Examples of enzyme poisons
Cyanide: binds the iron in iron-containing enzymes cytochrome).
Fluoride: binds Ca2+ or Mg2+
3 Mechanisms to generate ATP?
Substrate-level phosphorylation: a high-energy phosphate from a catabolic intermediate is transferred to ADP or GDP.
Oxidative phosphorylation: e-‘s from molecules are used to reduce e- carriers such as NAD+ and FAD that pass their e-‘s to the ETC. This carries protons and e-‘s, which results in e-‘s going to acceptors and the transportation of protons across a membrane to establish a proton gradient.
photophosphorylation: occurs only in photosynthesis, and light energy is converted to ATP and NADPH.
Glycolysis
AKA EMP pathway, the breakdown of 1 glucose molecule into 2 NADH and 2 ATP molecules and 2 pyruvates; consists of a preparatory stage and an energy conserving stage.
Prep stage of glycolysis
2 ATP are used; glucose is phosphorylated, isomerized, phosphorylated and then split into 2 glyceraldehyde-3-phosphate molecules.
Energy-conserving stage of glycolysis
2 G3Ps are oxidized to 2 pyruvates with a yield of 4 ATPS (remember: 2 ATP NET), and 2 NADH produced.
Other pathways for prokaryotes to oxidize glucose?
Pentose phosphate pathway and ED pathway.
Pentose phosphate pathway
Can be used with glycolysis or ED pathway, breaks down 5-C sugars/glucose to produce 2 mol of NADPH for each glucose; has intermediates that can be used to synthesize amino acids, nucleic acids and other macromolecules.
ED pathway
catabolize glucose to pyruvate without glucose or pentose phosphate pathway. produces 1 ATP, 1 NADPH and 1 NADH for each mol of glucose; present in some gram - bacteria.
Krebs cycle
oxidation/reduction rxns that transfer the PE of acetyl-CoA to e- carrier coenzymes (NADH mainly, and FADH2); ATP is also produced via substrate-level phosphorylation. For every 2 mol of acetyl CoA=> 4 mol of CO2, 2 mol ATP, 6 mol of NADH and 2 mol of FADH2.
Carriers in ETC
Flavoproteins: flavin mononucleotide (FMN>FMNH>FMNH2)
Cytochromes: proteins with heme.
Complexes in ETC
1- pumps H+'s 2- transfers e-'s to ubiquinone 3- pumps H+'s 4- pumps H+'s 5- ATP synthase
Fermentation
anaerobic process where an organic molecule can be oxidized using an organic molecule as an e- acceptor to produce small amounts of ATP.
Lactic acid fermentation
Homolactic- only lactic acid
heterolactic- produces lactic acid and other compounds.
lipid catabolism
Lipids are broken down in the extracellular space by lipases to break down triacylglycerol into fatty acids and glycerol.
