Practice question

Protein biosynthesis proceeds strictly from amino terminus to carboxyl terminus, meaning first residue Met retains free alpha-amino group and subsequent residues are added sequentially at C-terminal end, becoming new C-terminus. This vectorial N to C growth corresponds to mRNA being read 5' to 3', with ribosome adding amino acids while moving downstream. N to C polarity enables co-translational folding where N-terminal domains emerge first from exit tunnel and begin folding or targeting via signal sequences before synthesis completes, influencing folding pathways.