b
(b) : Post translational modification \((PTM)\) is a step in protein biosynthesis. Proteins are created on ribosomes translating \(mRNA\) into polypeptide chains. These polypeptide chains undergo \(PTM\), such as folding, cutting and other processes, before becoming the mature protein product. Proteins synthesized by the rough endoplasmic reticulum and lipids synthesized by smooth endoplasmic reticulum reach the cisternae of the Golgi apparatus. Here, they combine with carbohydrates to form glycoproteins and glycolipids. This process is called glycosylation.