Microbiology Key Concepts: Metabolism, Growth, and Microbial Control

Enzymes are biological catalysts, specific to substrates, reusable, and sensitive to environmental conditions.

Enzymes lower activation energy by binding substrates at the active site, facilitating the reaction.

Streptokinase is an enzyme, not a living organism, so it does not cause streptococcal infection when injected.

Enzymes bind only specific substrates due to the shape and chemical properties of their active sites.

Enzymes are primarily proteins, sometimes with non-protein cofactors.

The specific molecule upon which an enzyme acts during a biochemical reaction.

Enzymes have an apoenzyme (protein part) and may require a cofactor or coenzyme to be active.

Temperature, pH, substrate concentration, and inhibitors affect enzyme function.

The removal of an amino group from an amino acid or other compound.

Competitive, noncompetitive, and feedback inhibition regulate enzyme activity.

Inhibition controls metabolic pathways and prevents overproduction of products.

Pyruvate is the end-product; fermentation regenerates NAD⁺ when respiration is unavailable.

Respiration uses an electron transport chain and oxygen or other acceptors; fermentation does not and yields less energy.

Respiration produces more ATP per glucose molecule than fermentation.

Entner-Doudoroff and pentose phosphate pathways provide alternatives to glycolysis under certain conditions.

Fats are broken into glycerol and fatty acids; proteins undergo deamination before entering metabolic pathways.

Carbohydrates are used first, then fats, then proteins.

Energy input, often from ATP, and precursor molecules to build complex molecules.

Photosynthesis uses light energy to produce glucose and oxygen.

A metabolic pathway that functions in both catabolism and anabolism.

Organic molecules contain carbon-hydrogen bonds; inorganic molecules generally do not.

Growth factors are organic compounds required in small amounts; trace elements are inorganic minerals needed for enzyme function.

Conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) usable by organisms.

Categories like obligate aerobe, facultative anaerobe, microaerophile describe oxygen requirements and tolerance.

Enzymes that detoxify reactive oxygen species; presence indicates oxygen tolerance.

Likely an obligate anaerobe sensitive to oxygen.

Psychrophiles, mesophiles, thermophiles, and hyperthermophiles differ by optimal growth temperatures.

Communities of microorganisms embedded in a matrix of polysaccharides, proteins, and DNA; important for protection and survival.

Prokaryotes grow by binary fission; eukaryotes grow by mitosis and cell enlargement.

Time required for a bacterial population to double in number.

Procedures to prevent contamination by unwanted microorganisms.

Broth is liquid for growing large numbers; plates are solid for isolating colonies.

Direct counts measure cells; indirect methods like turbidity estimate growth by optical density.

Lowest concentration of an antimicrobial that inhibits visible growth.

Time required to kill 90% of microorganisms at a given temperature.

Include heat, radiation, filtration; used based on target organism and material.

Thermal death time is time to kill all microbes at a temp; thermal death point is lowest temp to kill in 10 minutes.

Includes batch, flash, and ultra-high temperature methods to reduce pathogens without sterilization.

Disinfectants and antiseptics vary in spectrum and use; choice depends on application and target organisms.