A Level Biology Practice Exam

What are proteins primarily made up of?

1. Fatty acids

2. Amino acids

3. Glycerol

4. Nucleotide sequences

The correct answer is: Amino acids

Proteins are primarily made up of amino acids, which are organic compounds composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. There are 20 standard amino acids that combine in various sequences to form proteins, each with a unique side chain that determines its characteristics and functions. The specific sequence of amino acids in a protein dictates its structure and ultimately its function within the organism, whether it's acting as an enzyme, hormone, structural component, or antibody. In contrast, fatty acids are the building blocks of lipids, glycerol is part of triglycerides and phospholipids, and nucleotide sequences make up nucleic acids like DNA and RNA. These components do not contribute to the structure or formation of proteins, thereby reinforcing that amino acids are the correct answer to this question.