Microbial Metabolism and Energy Production

Comprehensive vocabulary flashcards covering metabolic pathways, enzyme mechanics, redox reactions, cellular respiration, fermentation, and phototrophic mechanisms based on lecture notes.

Metabolism

The sum total of all chemical reactions occurring in a cell.

Metabolic Pathway

A sequence of enzyme-catalyzed chemical reactions.

Catabolic

A breaking down, energy-producing pathway typically involving hydrolysis reactions (e.g., salivary amylase catalyzing the breakdown of bread into simple sugars like glucose).

Anabolic

The synthesis of complex organic molecules from simpler subunits, requiring an input of energy and typically involving dehydration reactions.

Amphibolic

A metabolic pathway that is simultaneously catabolic and anabolic.

Enzymes

Biological catalysts that speed up chemical reactions by reducing activation energy without being consumed; each enzyme is specific to only one type of substrate.

Cofactors

Non-protein components (vitamins and minerals such as magnesium, zinc, and iron) that assist enzyme function.

Coenzymes

Loosely attached carriers that transport substances within the cell (e.g., $NAD^+$, $FAD$, coenzyme A, and ATP).

Denaturation

A change in temperature or pH that alters the 3D shape of a protein so that it no longer functions.

Saturation

A condition determining the rate of catalyzed reactions; increases as substrate concentration increases until all enzymes are bound with substrates and the reaction rate levels off.

Ribozymes

Non-protein enzymes composed of RNA molecules with catalytic activities that form part of the ribosome structure.

Oxidation

The loss of electrons ($\text{e}^-$) by a molecule, atom, or ion.

Reduction

The gain of electrons ($\text{e}^-$) by a molecule, atom, or ion.

Half Reaction

Either the oxidation or reduction reaction component of a paired redox reaction.

Electron Donor

A highly reduced molecule with the capacity to give up electrons and become oxidized.

Terminal Electron Acceptor

A highly oxidized molecule with the capacity to accept electrons and become reduced.

Respiration

A metabolic process that oxidizes organic molecules to produce energy.

Aerobic Respiration

Respiration in which electrons travel down an electron transport chain (ETC) and protons are pumped across the membrane to create a proton motive force used for ATP synthesis, using oxygen as the terminal electron acceptor.

Anaerobic Respiration

Respiration that still utilizes an electron transport chain (ETC) but uses an inorganic molecule other than oxygen as the terminal electron acceptor (e.g., sulfate $SO_4^{2-}$, nitrate $NO_3^-$, or carbonate $CO_3^{2-}$).

Fermentation

An inefficient energy-producing process that extracts energy from organic compounds using an endogenous electron acceptor and substrate-level phosphorylation, without an ETC or proton motive force.

Substrate-Level Phosphorylation

The enzymatic transfer of a high-energy phosphate group from an organic substrate to ADP to form ATP.

Endogenous Electron Acceptor

An electron acceptor created by and commonly found within the cell, usually an intermediate in the pathway used for oxidizing the energy source (e.g., pyruvate).

Embden-Meyerhof Pathway

The standard metabolic pathway for converting glucose into pyruvate during glycolysis.

Pentose Phosphate Pathway

An amphibolic pathway (hexose monophosphate pathway) involving the oxidation of glucose to synthesize 5-carbon pentose sugars used as intermediaries for making molecules like DNA and RNA.

Glycolysis

An anaerobic metabolic pathway occurring in the cytoplasmic matrix that converts a 6-carbon glucose molecule into two 3-carbon pyruvates, yielding a net of $2\,\text{ATP}$, $2\,\text{NADH}$, and $2\,\text{pyruvate}$.

Krebs Cycle

A cyclic metabolic pathway (tricarboxylic acid / TCA cycle) in which acetyl-CoA is oxidized, yielding $3\,\text{NADH}$, $1\,\text{FADH}_2$, $1\,\text{ATP}$, and $2\,CO_2$ per molecule of acetyl-CoA.

Oxidative Phosphorylation

The creation of ATP from scratch using the reducing power of $NADH$ and $FADH_2$ along with a proton motive force generated by the electron transport chain.

Chemiosmosis

The process or hypothesis explaining oxidative phosphorylation, in which the proton motive force established by the ETC is used to phosphorylate ADP into ATP.

ATP Synthase

A turbine-like enzyme that allows protons to diffuse down their concentration gradient back into the mitochondrial matrix, harnessing their kinetic energy to phosphorylate ADP to ATP.

Beta Oxidation

A stage in lipid catabolism in which fatty acids are broken down into two-carbon fragments that are converted into acetyl-CoA to enter the Krebs cycle.

Deamination

The enzymatic removal of the amine group from amino acid monomers, allowing the remaining carbon skeletons to be converted into acetyl-CoA or intermediates for glycolysis or the Krebs cycle.

Lactic Acid Fermentation

A fermentation reaction in which pyruvate and $NADH$ react to yield lactate and $NAD^+$.

Alcoholic Fermentation

A fermentation reaction in which pyruvate and $NADH$ react to yield ethanol, $CO_2$, and $NAD^+$.

Photosynthesis

An anabolic pathway occurring in prokaryotes and eukaryotes in which light energy is converted into chemical energy stored in the chemical bonds of organic molecules such as glucose.

Oxygenic Photosynthesis

A form of photosynthesis that produces oxygen as a byproduct, occurring in eukaryotes and cyanobacteria.

Anoxygenic Photosynthesis

A form of photosynthesis that does not produce oxygen, occurring in other photosynthetic bacteria and archaea.

Phototrophs

Organisms that obtain their energy from sunlight.

Chemotrophs

Organisms that obtain energy from the oxidation of organic or inorganic chemicals.

Autotrophs

Organisms that use carbon dioxide ($CO_2$) as their principal carbon source.

Heterotrophs

Organisms that obtain their carbon from reduced, pre-formed organic molecules produced by other organisms.

Photoautotrophs

Primary producers that use light for energy and $CO_2$ for carbon (fixing carbon into sugar via the Calvin-Benson cycle), such as cyanobacteria and plants.

Photoheterotrophs

Organisms that obtain energy from light while depending on organic compounds as their source of carbon.