IB Biology HL C1.1 Enzymes and Metabolism

Practice vocabulary flashcards covering the core and AHL concepts of enzymes, metabolism, and inhibition based on the IB Biology HL C1.1 curriculum.

Catalyst

A substance that increases the rate of a chemical reaction without being used up or permanently changed.

Enzyme

A biological catalyst; most enzymes are globular proteins.

Substrate

The reactant molecule on which an enzyme acts.

Product

A molecule formed by the enzyme-catalysed reaction.

Metabolism

The complex network of interacting and interdependent chemical reactions occurring in a living organism.

Metabolic pathways

A sequence of reactions where the product of one enzyme-catalysed reaction often becomes the substrate for the next reaction.

Specificity

The property where an enzyme catalyses one reaction or a narrow group of closely related reactions because its active site has particular chemical and physical properties.

Anabolic reactions

Reactions that build larger, more complex molecules from smaller molecules and require an input of energy, such as protein synthesis.

Catabolic reactions

Reactions that break larger molecules into smaller molecules and often release energy, such as the digestion of macromolecules.

Active site

A small region within the folded protein formed by a few amino acid residues where the substrate binds and catalysis occurs.

Induced-fit binding

A model where binding causes small conformational changes in both the enzyme and the substrate to improve binding and place reacting groups correctly.

Denaturation

A change in protein conformation caused by disruption of interactions that maintain higher levels of structure, leading to a loss of catalytic activity.

Optimum

The value of a factor (such as temperature or pH) at which the measured enzyme-catalysed reaction rate is highest.

Initial rate

The gradient measured near the start of an enzyme-catalysed reaction before substrate depletion or product accumulation changes the rate.

Activation energy

The minimum energy needed to reach the transition state and begin a reaction, including the energy required to weaken or break bonds in substrates.

Intracellular reactions

Enzyme-catalysed reactions occurring inside cells, in the cytosol or within organelles like the Krebs cycle in the mitochondrial matrix.

Extracellular reactions

Enzyme-catalysed reactions occurring outside the cell that produced the enzyme, such as chemical digestion in the gut lumen.

Endotherms

Animals such as mammals and birds that use metabolic heat to maintain a relatively constant body temperature above environmental temperature.

Linear pathway

A metabolic organisation where a starting substrate passes through a sequence to a different final product, such as glycolysis.

Cyclical pathway

A sequence of reactions that regenerates a molecule used at the start of the cycle while additional inputs enter and products leave, such as the Krebs cycle.

Allosteric site

A specific binding site on an enzyme separate from the active site.

Non-competitive inhibition

A type of inhibition where an inhibitor binds to an allosteric site, altering the active site conformation and reducing the maximum achievable reaction rate.

Competitive inhibition

A type of inhibition where the inhibitor and substrate compete for the same active site, though the maximum rate can still be reached if substrate concentration is increased.

Statins

Molecules that bind reversibly to the active site of HMG-CoA reductase to compete with its normal substrate and reduce cholesterol synthesis.

Feedback inhibition

A regulatory process where the end product of a pathway (such as isoleucine) binds to an allosteric site on an enzyme near the start of the pathway (such as threonine deaminase).

Mechanism-based inhibition

A type of inhibition where a molecule is processed by the enzyme and then reacts with and irreversibly changes the active site.

Penicillin

A mechanism-based inhibitor that reacts with the bacterial transpeptidase active site to prevent cross-linking of peptidoglycan in the cell wall.