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

What are proteins primarily made of?

1. Carbohydrates

2. Amino acids

3. Fatty acids

4. Nucleotides

The correct answer is: Amino acids

Proteins are primarily made of amino acids, which are organic compounds composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Amino acids link together through peptide bonds to form long chains, which then fold into specific three-dimensional shapes to create functional proteins. Each protein’s unique sequence of amino acids determines its structure and function, enabling proteins to play various roles within the body, such as acting as enzymes, structural components, or signaling molecules. Carbohydrates, fatty acids, and nucleotides are not the building blocks of proteins. Carbohydrates serve primarily as energy sources and structural components in cells, fatty acids are the building blocks of lipids (fats), and nucleotides are the basic units of nucleic acids like DNA and RNA, which are involved in genetic information storage and transfer. Thus, the uniqueness of proteins stems from their composition of amino acids, making them essential for countless biological processes.