IB Biology Topic C1.1: Enzymes and Metabolism Key Definitions

Activation energy is the minimum amount of energy required to start a chemical reaction.

The active site is a small region on an enzyme where the substrate binds. It is formed by a specific sequence of amino acids within the enzyme's overall three-dimensional structure.

A site on an enzyme other than the active site, where specific molecules can bind to regulate enzyme activity.

Anabolic reactions are metabolic processes in which smaller molecules are built into larger, more complex molecules using energy.

Catabolic reactions are metabolic processes in which larger molecules are broken down into smaller molecules, releasing energy in the process.

Collision theory states that in order for a reaction to occur, the reacting molecules must collide with sufficient energy and in the correct orientation.

Competitive inhibition is a regulatory mechanism in enzyme-catalyzed reactions where an inhibitor molecule competes with the substrate for binding to the enzyme’s active site.

1. Competitive inhibitors are molecules that resemble the substrate of an enzyme.
2. They bind to the enzyme’s active site, blocking the actual substrate from binding.

Condensation is a reaction where two molecules combine, releasing water.

A closed loop of reactions where intermediates are regenerated, allowing the cycle to repeat continuously as long as substrates are available.

The cytoplasm is the jelly-like substance inside a cell, excluding the nucleus, where various cellular activities occur.

Denaturation is the process by which the three-dimensional structure of an enzyme is altered, leading to the loss of its function.

Organisms that rely on external environmental conditions to regulate their body temperature.

Organisms that maintain a constant internal body temperature through metabolic heat production.

The temporary structure formed when a substrate binds to the active site of an enzyme, allowing the catalysed reaction to take place.

Extracellular enzymes work outside cells to break down large molecules into smaller, absorbable units.

Feedback inhibition is a process where the end product of a metabolic pathway inhibits an enzyme involved in its own synthesis.

Globular proteins are compact, spherical proteins that are typically soluble in water. Their structure results from the folding of the polypeptide chain into a tightly packed three-dimensional shape.

Glycolysis is the first step in cellular respiration, where glucose is broken down into pyruvate, releasing energy in the form of ATP.

A model of enzyme action in which the active site changes shape (undergoes a conformational change) when the substrate binds, moulding around the substrate to form a tighter enzyme-substrate complex.

Intracellular enzymes operate within cells, driving critical metabolic pathways such as glycolysis and the Krebs cycle.

Definition:
Ionic bonds form between R-groups that carry opposite charges.

A straight sequence of reactions where each product becomes the substrate for the next step, moving in one direction without looping back.

Mechanism-based inhibition, also called suicide inhibition, occurs when an inhibitor binds irreversibly to the active site of an enzyme and causes chemical changes that permanently deactivate the enzyme