The spatial conformation of proteins mainly depends on
Correct answer: A. the sequence of amino acids in the polypeptide chain
Proteins are large biological molecules formed by many amino acids linked through peptide bonds. The primary structure of a protein refers to the sequence of amino acids from N-terminus to C-terminus, i.e., the amino acid sequence. Secondary structure refers to the local spatial arrangement of the main chain, mainly including α-helices and β-sheets. Tertiary structure involves the overall spatial arrangement of all atoms in the polypeptide chain and its side chains. Quaternary structure concerns the aggregation of protein subunits. The first three structures are collectively known as the spatial structure of proteins. The primary structure is the foundation for spatial conformation, meaning that the spatial conformation of proteins mainly depends on the sequence of amino acids in the polypeptide chain.