OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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What is an example of a functional protein?

Keratin
Collagen
Enzymes
Actin

The correct answer is: Enzymes

Proteins can have various functions in biological systems, and functional proteins are those that play active roles in biological processes. Enzymes are a prime example of functional proteins; they catalyze biochemical reactions, increasing the rate at which they occur. By lowering the activation energy required for reactions, enzymes allow metabolic processes to proceed under physiological conditions that would not support these reactions without their assistance. In contrast, keratin and collagen primarily serve structural roles. Keratin is a fibrous protein found in hair, nails, and the outer layer of skin, providing strength and protection, while collagen is a crucial component of connective tissues, providing structural integrity and support in various body parts. Actin, while also playing a significant role in muscle contraction and cellular processes, functions more as a structural protein that participates in the cytoskeleton's composition. Thus, the designation of enzymes as functional proteins is due to their direct involvement in facilitating and regulating countless biochemical reactions essential for life processes.