Microbial Metabolism Lecture Flashcards

This set of 40 vocabulary flashcards covers the fundamental concepts of microbial metabolism, including enzyme structure, metabolic pathways, and energy production strategies as detailed in the lecture.

Metabolism

The sum of all chemical and physical workings of a cell.

Catabolism

A degradative process that breaks the bonds of larger molecules to form smaller molecules, resulting in the release of energy.

Anabolism

Also called biosynthesis; a process that forms larger macromolecules from smaller molecules and requires an input of energy.

Enzymes

Biological catalysts that increase the rate of a chemical reaction by lowering the energy of activation.

Energy of activation

The resistance to a reaction that must be overcome for the reaction to proceed.

Simple enzymes

Enzymes that consist of protein alone.

Holoenzyme

A conjugated enzyme containing both a protein portion (apoenzyme) and a nonprotein portion (cofactor).

Apoenzyme

The protein portion of a conjugated enzyme, which exhibits primary, secondary, and tertiary organization.

Cofactors

The nonprotein portion of an enzyme that can be either inorganic elements (metal ions) or organic molecules (coenzymes).

Coenzymes

Organic molecules, often derived from vitamins, that serve as temporary carriers for specific chemical groups during enzymatic reactions.

Catalase

An enzyme that breaks down hydrogen peroxide and requires an iron ($Fe$) cofactor.

Hexokinase

An enzyme that transfers phosphate to glucose and requires a magnesium ($Mg$) cofactor.

Active site

Also known as the catalytic site; the specific region of an apoenzyme where the substrate binds.

Induced fit

A temporary enzyme-substrate union that occurs when the substrate moves into the active site and the enzyme adjusts to fit.

Metallic Cofactors

Metal ions that activate enzymes, help bring the active site and substrate together, and participate in the chemical reaction.

Exoenzymes

Enzymes transported extracellularly to break down large food molecules or harmful chemicals, such as cellulase or penicillinase.

Endoenzymes

Enzymes that are retained and function intracellularly; most metabolic enzymes fall into this category.

Constitutive enzymes

Enzymes that are always present and produced in equal amounts or rates regardless of the substrate concentration.

Regulated enzymes

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

Condensation reaction

An anabolic reaction that synthesizes large substrates from smaller molecules by releasing one water molecule per bond made.

Hydrolysis reaction

A catabolic reaction that breaks down large substrates into smaller molecules and requires the input of water to break the bonds.

Labile

A term describing enzymes that have become chemically unstable due to changes in environmental conditions.

Denaturation

The breaking of weak bonds that maintain the shape of an apoenzyme, rendering the enzyme nonfunctional.

Competitive inhibition

A control mechanism where a substance resembling the normal substrate competes for the active site of an enzyme.

Allosteric inhibition

Inhibiting an enzyme via a regulatory site (allosteric site) that is separate from the active site, often through negative feedback.

Noncompetitive inhibition

When an inhibitor binds to the entire enzyme-substrate complex, preventing the enzyme from completing its action.

Enzyme repression

A mechanism that automatically suppresses enzyme synthesis when the end product of a pathway reaches excess.

Enzyme induction

The process where enzymes are produced only when suitable substrates are present to avoid wasting energy.

Exergonic reactions

Chemical reactions that release energy as they proceed.

Endergonic reactions

Chemical reactions that consume energy to proceed.

Redox reactions

Paired reactions involving an electron donor and an electron acceptor which constitute a redox pair.

ATP (Adenosine Triphosphate)

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

Substrate-level phosphorylation

The synthesis of $ATP$ by the direct transfer of a phosphate group from a phosphorylated substrate to $ADP$.

Oxidative phosphorylation

The synthesis of $ATP$ through a series of redox reactions occurring during the respiratory pathway.

Bioenergetics

The study of the mechanisms of cellular energy release, encompassing both catabolic and anabolic pathways.

Glycolysis

The oxidation and splitting of a glucose ($6C$) molecule into two molecules of pyruvic acid ($3C$).

Aerobic respiration

A series of reactions that use glycolysis, the Krebs cycle, and the respiratory chain with molecular oxygen as the final electron acceptor.

Anaerobic respiration

A metabolic strategy using the same pathways as aerobic respiration but employing oxygen-containing ions (like $NO_3^-$ or $SO_4^{2-}$) as final electron acceptors.

Fermentation

The incomplete oxidation of glucose in the absence of oxygen, yielding a small amount of $ATP$ and using organic compounds as final electron acceptors.

Amphibolic

The property of metabolic pathways that can proceed bi-directionally, integrating both catabolic and anabolic functions.