L6 - Microbial Metabolism and Growth Flashcards

Vocabulary flashcards covering microbial metabolism, enzymes, cellular transport, catabolism, bacterial growth phases, and environmental factors affecting factors based on lecture materials provided.

Proteins

Biological molecules serving as scaffolds and enzymes; they fold from primary polypeptide chains into secondary, tertiary, and sometimes quaternary structures.

Enzyme

A biological catalyst that speeds up the rate of a reaction without being consumed; represented by the formula $E + S \rightarrow ES \rightarrow E + P$.

Apoenzyme

The protein component of an enzyme that is inactive without its necessary cofactors or coenzymes.

Holoenzyme

A complete, functional enzyme consisting of a protein component (apoenzyme) plus a cofactor and/or coenzyme.

Cofactors

Inorganic elements such as $Fe$, $Cu$, $Mg$, $Mn$, $Zn$, $Co$, and $Se$ that participate in chemical reactions and coordinate substrates in the active site.

Coenzymes

Organic molecules used to add or transfer chemical groups from one substrate to another.

Competitive inhibitor

A molecule that mimics the substrate and competes for binding at the enzyme's active site.

Non-competitive inhibitor

A molecule that binds to an allosteric site rather than the active site, often providing substrate-level control of a reaction.

Allosteric regulation

The process where the binding of an allosteric inhibitor reduces enzyme activity, while an allosteric activator increases it.

Feedback inhibition

A mechanism where the end product of a metabolic pathway serves as a noncompetitive inhibitor to an enzyme early in the pathway.

Constitutive enzymes

Enzymes that are always present in relatively constant amounts regardless of the cellular environment.

Regulated enzymes

Enzymes whose production is turned on (induced) or off (repressed) in response to changes in substrate concentration.

Protein denaturation

The permanent inactivation of a protein when it unfolds due to temperatures above the maximum, or changes in $pH$ and salinity.

Amphipathic molecule

A molecule, such as a phospholipid, that contains both a polar (hydrophilic) side and a non-polar (hydrophobic) side.

Simple diffusion

The movement of substances down a concentration gradient directly through the cell membrane.

Facilitated Diffusion

The substrate-specific movement of substances down a concentration gradient through a receptor.

Active transport

The substrate-specific transport of substances across a membrane using $ATP$ or energy from another substance's concentration gradient.

Nucleotides

The repeating subunits of DNA and RNA, composed of a nitrogenous base, a pentose ($5$-carbon) sugar, and a phosphate group.

Purine

A nitrogenous base with a double-ring structure.

Pyrimidine

A nitrogenous base with a single-ring structure.

Adenosine Triphosphate (ATP)

The energy currency of the cell, composed of adenine, ribose, and three phosphate groups.

Aerobic Respiration

A catabolic pathway using oxygen as the terminal electron acceptor, yielding a maximum net of $36-38\,ATPs$.

Anaerobic Respiration

A catabolic pathway using non-$O_2$ compounds (such as $SO_4^{2-}$, $NO_3^-$, or $CO_3^{2-}$) as electron acceptors, yielding between $2-36\,ATPs$.

Fermentation

The incomplete oxidation of glucose using organic compounds as electron acceptors, yielding $2\,ATPs$ and regenerating $NAD^+$ for glycolysis.

Glycolysis

The enzymatic conversion of glucose to pyruvic acid (pyruvate), synthesizing a small amount of $ATP$ anaerobically.

Krebs (TCA) Cycle

A cycle that transfers energy from acetyl $CoA$ to $NAD^+$ and $FAD$, producing reduced $NADH$, $FADH_2$, and $2\,ATP$ via substrate-level phosphorylation.

Cytochromes

Chain of redox carriers in the Electron Transport System that pass electrons sequentially to allow the active transport of hydrogens out of the cell.

ATP synthase

An enzyme through which hydrogens flow back into the cell to generate $34\,ATP$ per glucose molecule.

$\beta$-oxidation

The process where long fatty acid chains are cut from a glycerol backbone and ligated to Coenzyme A ($CoA$) to form Acetyl $CoA$ for energy.

Binary Fission

The basis of bacterial population growth, requiring accurate chromosome replication and the doubling of all cytoplasmic resources.

Generation time (Doubling time)

The time required for a complete fission cycle to occur, resulting in the doubling of the population.

Lag phase

The initial stage of a bacterial growth curve where cells are adjusting to the environment and not yet increasing in number.

Exponential growth phase (log phase)

The stage in a growth curve where doubling continues at a constant rate as long as the environment remains favorable.

Stationary phase

The stage where the rate of cell birth equals the rate of cell death, causing the population size to plateau.

Death phase

The stage in a growth curve where cells die at an exponential rate due to the depletion of nutrients and buildup of waste.

Spectrophotometer

An instrument used for rapid measurement of bacterial growth by providing total cell counts (viable and non-viable) based on turbidity.

Resazurin

A metabolic indicator used to measure $NADH$ levels to distinguish between dead and alive cells.

Quorum sensing

A system where bacteria sense their own numbers and coordinate group behaviors like virulence or bioluminescence.

Psychrophiles

Organisms with optimum growth below $15\,^\circ C$ that are capable of growth below $0\,^\circ C$.

Psychrotrophs

Organisms that grow slowly in the cold but have an optimum temperature between $15\,^\circ C$ and $30\,^\circ C$, such as Listeria.

Mesophiles

The most medically significant group of organisms, with optimum growth at $20-40\,^\circ C$ (pathogens often at $37\,^\circ C$).

Thermoduric microbes

Microbes, often spore-forming, that can survive short exposures to high temperatures and contaminate pasteurized foods.

Thermophiles

Organisms that grow optimally above $45\,^\circ C$ and are found in geothermally active areas or compost piles.

Taq

A DNA polymerase derived from thermophiles used in PCR reactions.