Protein production begins injSp||P 
nucleus at the DNA (a). A coded 
message for a protein leaves the 
nucleus in the form of RNA (b) and 
goes to either free ribosomes (c) or to 
ribosomes bound to the endoplasmic: 
reticulum (d). ‘When released from a 
free ribosome, a protein (e) can 
become incorporated into cytoskeletal 
fibers: (f) or into sUcfitMrganelles as a 
mitochondrion (g) or a peroxisom#|h|. 
Proteins made in the endoplasmic 
reticulum leave in a vesicle (i) and 
migrate to the Golgi apparatus (j). 
Proteins are sorted in the Golgi and are 
then carried in vesicles to lysosomes (k), 
or are secreted (I) or incorporated into 
the cell's .surface membrane (m). 
20 
