Biology C1.1 Definitions

Metabolism

Sum of all the interdependent chemical reactions within an organism

Catalyst

Substance that increases the rate of a chemical reaction (or allows it to proceed under different conditions) but is not changed by the reaction

Enzyme

Globular protein which acts as a biological catalyst by speeding up the rate of a chemical reaction

Product

Result of an enzyme catalyzed reaction

Substrate

Specific molecule that binds to an enzyme, and it undergoes a chemical reaction to form a product

Enzyme-substrate specificity

The shape and chemical properties of an enzyme’s active site allow only the respective substrate molecule(s) to bind. So, each enzyme catalyzes only one specific reaction, or a specific group of reactions

Anabolic reactions

Reactions that require energy to build up smaller molecules into larger ones (ex. Photosynthesis)

Catabolic reactions

Reactions that release energy by breaking down larger molecules into smaller ones (ex. respiration)

Active site

Region on the surface of the enzyme to which a substrate molecule binds

Substrate complex

The temporary bond formed between the enzyme and its substrate when the substrate binds to the enzyme’s active site

Lock and key theory

Enzyme's active site is like a lock, and the substrate is like a key. The substrate fits into the active site, and this specific fit is crucial for the enzyme to catalyze the reaction

Induced fit theory

Active site of an enzyme can change its shape slightly to accommodate the substrate more effectively. Acknowledges that the enzyme and substrate undergo conformational changes upon binding, leading to a more precise fit (Explains how enzymes can catalyse reactions even if the initial fit is not perfect)

Substrate-active site collision

When a substrate and an active site come together as a result of molecular motion

Denaturation

Permanent change in an enzyme's structure (caused by temperature/pH) by disrupting the bonds and interactions that maintain its shape. Alters the enzyme's active site, making it unable to bind with its substrate effectively

Reliability

Demonstrated by repeating an experiment to show that results are consistent

Reaction rate

Speed at which substrates are converted to products. Unit = change in amount of chemical / time

Activation energy

Energy required for substrates to pass through transition stage before they’re converted into products