Unit 2 Review: Bacterial Metabolism

Vocabulary flashcards covering the key terms, enzymes, pathways, and concepts for bacterial metabolism and glucose catabolism from Unit 2 Review.

Adenosine triphosphate (ATP)

The primary energy currency of the cell, composed of the nitrogenous base adenine, a ribose pentose sugar, and three phosphate groups.

Pentose sugar

A five-carbon sugar molecule, such as the ribose unit present in adenosine triphosphate (ATP).

Phosphate group

A functional group consisting of phosphorus bonded to oxygen atoms; in ATP, three of these groups are linked by high-energy bonds whose hydrolysis releases energy.

ATP hydrolysis

The exergonic breakdown of ATP into ADP and an inorganic phosphate group, releasing free energy to power cellular processes.

Phosphorylation

The addition of a phosphate group to a molecule, such as the synthesis of ATP by attaching a phosphate group to ADP.

Metabolism

The total sum of all biochemical reactions and pathways occurring within a living organism or cell.

Metabolic pathways

Series of sequentially linked enzyme-catalyzed chemical reactions that convert starting substrates into final end products through a series of intermediates.

Intermediate

A chemical compound synthesized during the steps of a metabolic pathway between the initial substrate and the final end product.

End product

The final resulting substance formed at the conclusion of a metabolic pathway.

Anabolic pathways

Biosynthetic metabolic pathways that consume energy to assemble complex cellular macromolecules from simpler precursor molecules.

Catabolic pathways

Degradative metabolic pathways that break down complex molecules into simpler compounds, releasing free energy.

Endergonic reactions

Non-spontaneous chemical reactions that absorb or require an input of free energy to proceed.

Exergonic reactions

Chemical reactions that release free energy as reactants are converted into products.

Enzymes

Biological catalysts, primarily three-dimensional proteins, that accelerate the rates of specific chemical reactions by reducing activation energy without being altered.

Substrate

The specific chemical reactant molecule that binds to the active site of an enzyme to undergo a catalyzed reaction.

Substrate specificity

The property of an enzyme to selectively bind only particular reactant molecules based on complementary three-dimensional active site conformation.

Cofactor

A non-protein chemical component or metallic ion required by an enzyme to achieve its functional catalytic activity.

Denature

The loss of an enzyme's native three-dimensional tertiary structure due to environmental stress like extreme heat or pH, which destroys its catalytic function.

Temperature range

The span of temperatures between the minimum and maximum within which an enzyme remains functional and active.

Optimum temperature

The specific temperature at which an enzyme catalyzes its reaction at the maximal rate.

pH range

The interval of hydrogen ion concentrations within which an enzyme retains structural integrity and catalytic activity.

Optimum pH

The specific pH value at which an enzyme exhibits its highest catalytic activity.

Endoenzymes

Enzymes that remain inside the microbial cell to catalyze intracellular metabolic reactions.

Exoenzymes

Enzymes secreted outside the bacterial cell to break down large extracellular nutrient molecules or host tissues, frequently functioning as virulence factors in bacterial infections.

Amylase

An exoenzyme secreted by bacteria to catalyze the breakdown of starch into smaller oligosaccharides and glucose.

Cellulase

An exoenzyme that hydrolyzes cellulose into smaller carbohydrate units such as cellobiose and glucose.

Collagenase

An exoenzyme that degrades collagen in host connective tissues, facilitating tissue destruction and bacterial invasion during infection.

Lipase

An exoenzyme that breaks down lipid macromolecules into fatty acids and glycerol.

Streptokinase

An exoenzyme produced by pathogenic streptococci that dissolves host blood clots, promoting the spread of bacteria through tissues.

Glucose catabolism

The biochemical breakdown of glucose to yield energy (ATP) through pathways including aerobic respiration, anaerobic respiration, or fermentation.

Redox reactions

Coupled oxidation-reduction chemical reactions in which electrons are transferred from an electron donor to an electron acceptor.

Oxidation

The loss of electrons (or hydrogen atoms) from a substance during a chemical reaction.

Reduction

The gain of electrons (or hydrogen atoms) by a substance during a chemical reaction.

Electron donor

A compound that loses or transfers electrons to another substance in an oxidation-reduction reaction, thereby becoming oxidized.

Electron acceptor

A compound that receives electrons during an oxidation-reduction reaction, thereby becoming reduced.

Glycolysis

The catabolic metabolic pathway that oxidizes one molecule of glucose into two molecules of pyruvate, generating a net yield of ATP and $NADH$.

Pyruvate

The three-carbon intermediate produced at the end of glycolysis that can be further processed through pyruvate oxidation or fermentation.

Electron carrier molecule

A coenzyme (such as $NAD^+$ or $FAD$) capable of reversibly accepting and donating electrons during cellular metabolic reactions.

$$NAD^+/NADH$$

A primary coenzyme redox pair where $NAD^+$ accepts electrons from catabolic oxidation reactions to form $NADH$, which later donates electrons to an electron transport chain or organic intermediate.

Pyruvate oxidation

The metabolic stage converting pyruvate into acetyl-CoA ($acetyl\text{-}CoA$), producing $NADH$ and releasing carbon dioxide ($CO_2$).

Acetyl-CoA

A two-carbon acetyl unit linked to coenzyme A, produced from pyruvate oxidation, that delivers acetyl carbons into the TCA cycle.

TCA cycle

The tricarboxylic acid (Krebs) cycle; a circular metabolic pathway that completely oxidizes acetyl-CoA into $CO_2$, producing ATP, $NADH$, and $FADH_2$.

$$FAD/FADH_2$$

A redox coenzyme system where $FAD$ is reduced to $FADH_2$ in the TCA cycle by accepting electrons, later transferring them into the electron transport chain.

Carbon dioxide ($CO_2$)

The completely oxidized, one-carbon byproduct released during pyruvate oxidation and the TCA cycle.

Electron transport chain

A membrane-bound series of electron carrier proteins that transport electrons from donor coenzymes to a terminal electron acceptor while pumping protons to generate a proton motive force.

Terminal electron acceptor

The final inorganic or organic molecule that accepts electrons at the conclusion of an electron transport chain or fermentation pathway.

Proton motive force

An electrochemical proton ($H^+$) gradient established across a membrane by the electron transport chain, providing energy to drive ATP synthesis.

ATP synthase

A transmembrane enzyme complex that harnesses the potential energy of the proton motive force to synthesize ATP from ADP and inorganic phosphate.

Oxidative phosphorylation

The synthesis of ATP driven by the redox energy of the electron transport chain and chemiosmosis via ATP synthase.

Aerobic respiration

A complete metabolic oxidation of glucose via glycolysis, pyruvate oxidation, the TCA cycle, and an electron transport chain using molecular oxygen ($O_2$) as the final electron acceptor.

Anaerobic respiration

A respiratory metabolic pathway that couples an electron transport chain to generate ATP using an inorganic terminal electron acceptor other than oxygen.

Sulfate reduction ($SO_4^{2-}$ reduction)

A form of anaerobic respiration in which inorganic sulfate ($SO_4^{2-}$) functions as the terminal electron acceptor in the electron transport chain.

Iron reduction ($Fe^{3+}$ reduction)

A form of anaerobic respiration in which ferric iron ($Fe^{3+}$) serves as the terminal electron acceptor.

Nitrate reduction ($NO_3^-$ reduction)

A form of anaerobic respiration in which inorganic nitrate ($NO_3^-$) acts as the terminal electron acceptor in the electron transport chain.

Fermentation

An anaerobic catabolic pathway that generates ATP solely via substrate-level phosphorylation without an electron transport chain, using an endogenous organic intermediate as the final electron acceptor to regenerate $NAD^+$ from $NADH$.

Organic intermediate

An internal carbon compound (such as pyruvate or acetaldehyde) utilized as an electron acceptor during fermentation to regenerate oxidized $NAD^+$ from $NADH$.

Lactic acid fermentation

A fermentation pathway wherein pyruvate is reduced directly by $NADH$ to produce lactic acid (lactate) as the primary end product, regenerating $NAD^+$.

Ethanol fermentation

A fermentation pathway wherein pyruvate is decarboxylated to acetaldehyde and subsequently reduced by $NADH$ to form ethanol and $CO_2$, regenerating $NAD^+$.