CIE IGCSE Biology: Enzymes

Vocabulary flashcards covering the definition, function, mechanism, and factors affecting enzymes, as well as experimental methods for investigating enzyme activity.

Enzymes

Proteins that act as biological catalysts, speeding up the rate of chemical reactions without being changed or used up in the process.

Biological Catalysts

Substances made in living cells that increase the speed of metabolic reactions without being consumed.

Metabolic Reactions

All the chemical reactions that occur within an organism to maintain life.

Substrate

The specific molecule or molecules that are broken down or joined together by an enzyme in a reaction.

Product

The molecule or molecules released from the enzyme's active site after a reaction has occurred.

Active Site

The part of an enzyme with a specific 3-D shape where the substrate attaches for a reaction to occur.

Complementary Shape

The specific fit between an enzyme's active site and its substrate, often described by the lock and key hypothesis.

Lock and Key Hypothesis

A model describing how an enzyme is specific to one particular substrate because they have complementary shapes.

Enzyme-Substrate Complex

The temporary structure formed when a substrate moves into and binds with an enzyme's active site.

Optimum Temperature

The temperature at which an enzyme works at its fastest rate; in the human body, this is typically $37^\circ C$.

Denaturation

An irreversible change in an enzyme's shape, caused by high temperatures or extreme pH, which breaks the bonds holding the protein together and prevents the substrate from fitting.

Optimum pH

The pH level at which a specific enzyme is most active; for most it is $pH\,7$, but for stomach enzymes it is around $pH\,2$.

Duodenum

A part of the digestive system where enzymes typically have a higher optimum pH of $pH\,8$ or $pH\,9$.

Amylase

An enzyme that digests the polysaccharide starch into the disaccharide maltose.

Starch

A polysaccharide made of glucose that serves as the substrate for the enzyme amylase.

Maltose

A disaccharide of glucose produced when amylase breaks down starch.

Iodine Solution

A chemical reagent used to test for starch; it turns blue-black in the presence of starch and remains orange-brown when starch is absent.

Buffer Solution

A solution used in experiments to maintain a constant pH level while testing enzyme activity.

Kinetic Energy

The energy molecules have that increases with temperature, leading to more frequent collisions between enzymes and substrates.