The nucleus stores the DNA (codes for the production of proteins) and also contains the nucleolus, which manufactures ribosomes
The DNA from the nucleus is copied into a molecule of mRNA via a process known as transcription
The mRNA strand leaves the nucleus through a nuclear pore and attaches to a ribosome on the rough endoplasmic reticulum
The ribosome 'reads' the genetic instructions contained within the mRNA and uses this code to synthesise a protein via a process known as translation
Protein synthesis part 2
protein then passes into the lumen (the inside space) of the rough endoplasmic reticulum to be folded and processed
Cells that produce a large number of proteins, e.g. enzyme- or hormone-producing cells have an extensive rough endoplasmic reticulum
The processed proteins are then transported to the Golgi apparatus (also known as the Golgi body or Golgi complex) in vesicles which fuse with the Golgi apparatus, releasing the proteins
Protein synthesis part 3
The Golgi apparatus modifies the proteins, preparing them for secretion
Proteins that go through the Golgi apparatus are usually exported (e.g. hormones such as insulin), put into lysosomes (e.g. hydrolytic enzymes) or delivered to other organelles
The modified proteins then leave the Golgi apparatus in vesicles
Finally, these vesicles (containing the final proteins) fuse with the cell surface membrane, releasing the proteins by the process of exocytosis
Proteinsynthesis
Proteinsynthesis
Glycoprotein
-protein with a glycocalyx (carbohydrate side chain) attached
Glycoprotein formation
formation of the glycoprotein is the result of reactions that are catalysed by the glycosylation enzymes contained within the Golgi apparatus which attach various sugar monomers to the proteins as they move through the compartments
gp120
-found on the viral coat of HIV and this virus uses this structure to attach to the CD4 receptor that is found on the outside of T-helper cells, an immune system cell. The result is a cascade of conformational changes
in the glycoproteins that leads to the fusion of the viral membrane with the host cell membrane and a subsequent infection