cells spend as much as 80% of their total energy budget on protein synthesis. That’s because cells are mostly made of proteins; about half the dry weight of a bacterium is protein. Proteins are also very costly to make – they are strings of amino acids, usually a few hundred of them linked together in a long chain by ‘peptide’ bonds. Each peptide bond requires at least 5 ATPs to seal, five times as much as is needed to polymerise nucleotides into DNA.
