Microbial Growth & Metabolism - Vocabulary Flashcards

Vocabulary flashcards covering key concepts from the lecture notes on microbial growth, enzymes, metabolism, and environmental factors.

Microbial Growth

Increase in the number of microbial cells in a population (growth through cell division).

Enzymes

Proteins that act as catalysts to speed up chemical reactions in the cell; work at a specific active site and have a 3D shape that is not permanently altered by the reactions they catalyze.

Metabolism

All chemical reactions occurring within a cell.

Catabolism

Metabolic pathways that break down molecules to release energy (e.g., glycolysis, Krebs cycle).

Anabolism

Metabolic pathways that build macromolecules from smaller precursors, using energy.

Substrate

A molecule that binds to an enzyme’s active site and is transformed during the reaction.

Active Site

The region of an enzyme where the substrate binds and the chemical reaction occurs.

Substrate Concentration

Amount of substrate available, which can affect the rate of enzyme activity.

Inhibitors

Substances that decrease or block enzyme activity.

Temperature (Enzyme Activity)

Environmental temperature with optimum, minimum, and maximum ranges; temperatures outside the optimum can stop or denature enzymes.

pH

A measure of acidity/alkalinity; most microbes have an optimum near neutral pH; deviations can damage enzymes, DNA, and membranes.

Water Availability

Cytoplasm is ~70-80% water; dehydration reduces chemical reactions and can render cells dormant or dead.

Isotonic Environment

Solute concentrations are equal inside and outside the cell; balanced water movement; most microbes thrive here.

Hypotonic Environment

Lower external solute concentration; water enters the cell; cells with walls are protected from lysis, bacteria grow well here.

Hypertonic Environment

Higher external solute concentration; water leaves the cell; plasmolysis can occur; halophiles tolerate high salt.

Halophiles

Microbes that grow optimally in high salt concentrations.

Halotolerant

Organisms that tolerate high salt and can grow in isotonic or hypotonic conditions but grow slowly at high salt.

Neutrophiles

Microbes that grow best near neutral pH (~7).

Acidophiles

Organisms that grow optimally in acidic environments (low pH, typically below pH 5).

Alkaliphiles

Organisms that grow optimally in alkaline environments (high pH, typically above pH 8).

Acid-Tolerant

Organisms that can tolerate acidic environments and often grow best near neutral pH; example includes some stomach-associated bacteria.

Alkaline-Tolerant

Organisms that tolerate alkaline environments and can grow near neutral pH, but prefer conditions above neutral when possible.

Oxygen (O2) Requirements

Microbes can be aerobic (use O2) or anaerobic (no O2); O2 availability influences energy yield and growth rate.

Reactive Oxygen Species (ROS)

Toxic byproducts of oxygen metabolism that can damage cells unless detoxified by enzymes.

Catalase

Enzyme that decomposes hydrogen peroxide (H2O2) into water and oxygen, protecting cells from ROS.

Hydrogen Peroxide (H2O2)

Reactive oxygen species harmful to cells; detoxified by catalase and other enzymes.

Obligate Aerobe

O2-required organism; cannot live without oxygen and has enzymes to degrade ROS.

Microaerophile

Organism that requires low levels of O2 for growth and has limited ROS-degrading enzymes.

Obligate Anaerobe

Organisms that require no O2 and are killed by ROS due to lack of detoxifying enzymes.

Aerotolerant Anaerobe

Anaerobic organisms that tolerate O2 but do not use it for energy; possess ROS-detoxifying enzymes.

Facultative Anaerobe

Can use O2 if present (aerobic respiration) but can grow by fermentation in its absence.

ROS-Degrading Enzymes

Enzymes (e.g., catalase, superoxide dismutase) that neutralize ROS to protect cells.

Glycolysis

Metabolic pathway that breaks down glucose to pyruvate, producing ATP and NADH.

Krebs Cycle (Citric Acid Cycle)

Central metabolic pathway generating NADH, FADH2, and ATP from acetyl-CoA; part of aerobic respiration.

Fermentation

Anaerobic energy-production pathway producing ATP with organic molecules as electron acceptors.

Respiratory Chain / Electron Transport Chain

Series of membrane-bound carriers that transfer electrons to generate ATP (oxidative phosphorylation).

Pyruvate

End product of glycolysis; can be oxidized to acetyl-CoA or reduced in fermentation.}

Acetyl-CoA

Key metabolic intermediate that enters the Krebs cycle to release energy.

Glucose

A monosaccharide and primary energy source for many microbes; substrate for glycolysis.

Precursor Molecules

Small molecules used to synthesize macromolecules (nucleotides, amino acids, sugars, fatty acids).

Building Blocks

Molecules like amino acids, nucleotides, sugars, and fatty acids used to assemble macromolecules.

Macromolecules

Large biological polymers such as proteins, peptidoglycan, RNA/DNA, and complex lipids.

Generation Time

Time required for a microbial population to double; varies by species and environmental conditions.