SQA National 5 Biology Practice Exam

The term used for proteins that function as catalysts in biological reactions is enzymes. Enzymes play a crucial role in facilitating and speeding up chemical reactions within the body without being consumed in the process. They lower the activation energy required for reactions, allowing metabolic processes to occur more efficiently and at lower temperatures. This characteristic is essential for sustaining life, as many biochemical reactions would proceed too slowly or not at all under normal physiological conditions without the help of enzymes.

In biological systems, enzymes are highly specific, meaning each type of enzyme typically catalyzes only one type of reaction or acts on a specific substrate. This specificity is critical for maintaining the regulation and balance of various metabolic pathways.

Antibodies, hormones, and receptors, while also important proteins in biological processes, serve different functions; antibodies are involved in the immune response, hormones act as signaling molecules to regulate physiological processes, and receptors are responsible for sensing and transmitting signals within and between cells. These roles do not involve catalyzing chemical reactions like enzymes do.