OCR GCSE Biology 2025 – 400 Free Practice Questions to Pass the Exam

The sequence of amino acids in an enzyme is determined by the instructions found in the genes. Genes are segments of DNA that encode the information necessary for synthesizing proteins, including enzymes. During the process of transcription, the DNA sequence is transcribed into messenger RNA (mRNA), which then undergoes translation at the ribosome. The specific sequence of nucleotides in the mRNA is read in sets of three, known as codons, each of which corresponds to a specific amino acid. This establishes the primary structure of the enzyme, ultimately influencing its shape and function.

While environmental conditions can affect how genes are expressed (which might influence enzyme activity), they do not change the underlying genetic instructions. Similarly, while diet can provide the necessary amino acids for protein synthesis, it does not dictate the sequence itself; that sequence is inherently determined by the organism's genetic makeup. Cellular respiration, on the other hand, is a metabolic process that generates energy for the cell and does not have a direct role in determining the amino acid sequence of proteins.