Enzymes, Metabolism, and ATP in Cellular Processes C1

Catalyst

A substance that allows a reaction to proceed at a faster rate or under different conditions than otherwise possible.

Enzymes

Biological catalysts that are not consumed by the specific reactions they catalyse, allowing chemical reactions to proceed within a biologically relevant passage of time.

DNA replication

The process of making an identical copy of a DNA strand, which would be unable to occur within the lifetime of a cell without enzymes.

Chemical digestion

The breakdown of food into smaller molecules that can be absorbed by the body, which would be unable to happen within the period of transit through the digestive tract without enzymes.

Temperature regulation

Enzymes allow chemical reactions to proceed at biologically appropriate temperatures, preventing the need for higher temperatures that could denature cell components.

Homeostasis

The ability of an organism to maintain internal stability and balance despite external changes, which would not be maintained without enzymes preventing denaturation of cell components.

Metabolism

The totality of all enzyme-catalysed reactions that occur within a living cell or organism, representing the sum total of all the chemistry happening.

Enzyme specificity

The characteristic of enzymes requiring many different types for various reactions, allowing control over metabolism through the regulation of these specific enzymes.

Anabolic Reactions

Metabolic reactions that build up complex molecules from simpler ones, involving condensation reactions and examples like glucose production in photosynthesis.

Catabolic Reactions

Metabolic reactions that break down complex molecules into simpler ones, involving hydrolysis reactions and examples like glucose breakdown in cell respiration.

Enzyme

A globular protein acting as a biological catalyst, speeding up chemical reactions without being consumed, named after the substrate it reacts with and having an active site for binding.

Active Site

The region on the enzyme's surface where the substrate binds, composed of a few amino acids and interacting with the substrate's shape and chemical properties.

Enzyme-Substrate Complex

Formed when a substrate binds to the enzyme's active site, leading to the conversion of the substrate into a product.

Induced Fit Model

Describes how the enzyme's active site undergoes a conformational change upon substrate binding to improve binding and catalysis, allowing for broad specificity.

Enzyme Catalysis

Occurs when substrate and enzyme collide in the correct orientation, influenced by molecular motion and collisions, with increased rates by higher temperatures and substrate concentrations.

Denaturation

A structural change in the enzyme due to external factors like high temperatures or extreme pH, disrupting the active site and affecting enzyme-substrate interactions.

Temperature, pH, Substrate Concentration

Factors affecting enzyme activity, with temperature affecting kinetic energy, pH altering enzyme charge and shape, and substrate concentration influencing enzyme activity up to a saturation point.

Rate of Reaction

Calculated as the inverse of the time taken for the reaction to proceed, determining the speed of the enzyme-catalyzed reaction.

Activation Energy

The energy required for a chemical reaction to proceed, lowered by enzymes to speed up reactions, with exergonic reactions releasing energy and endergonic reactions requiring energy.

Heat Generation

Occurs during metabolic reactions due to energy inefficiencies, utilized by endotherms to maintain body temperature and influenced by metabolic activity levels.

Metabolic Pathways

Organized chains or cycles of enzyme-catalyzed reactions, with linear pathways (e.g., glycolysis) and cyclical pathways (e.g., Krebs cycle), allowing for regulation through intermediates.

Non-Competitive Inhibition

Involves an inhibitor binding to an allosteric site on the enzyme, causing a conformational change that prevents substrate binding, exemplified by cyanide poisoning.

Competitive Inhibition

Occurs when an inhibitor competes with the substrate for the enzyme's active site, blocking substrate binding, with statins as an example of cholesterol-lowering drugs.

Feedback Inhibition

A negative feedback mechanism where the end product of a metabolic pathway inhibits an enzyme from an earlier step, regulating product levels.

Mechanism-Based Inhibition

Irreversible binding of an inhibitor to the active site, forming a covalent bond and permanently inhibiting the enzyme, illustrated by penicillin's action on bacterial cell wall synthesis.

ATP

Adenosine triphosphate, the cell's energy currency, containing three phosphate groups that store energy in their bonds and releasing energy when hydrolyzed.