Centrosomes are the proteins that form spindle fibers. These fibers are called microtubules and are like railways on which motor proteins walk. Centrosomes double during S phase of interphase because the process of mitosis will give one centrosome to each daughter cell. But before mitosis is complete, the job of centrosomes is to form a north pole and a south pole across the dividing cell. These poles are connected by spindle fibers that start at one centrosome and reach across to the other side. The spindle fibers help pull DNA apart as the cell divides into two.
Protein synthesis begins with DNA. The DNA in an organism creates the RNA that then codes for and synthesizes the proteins. DNA is found in the cell’s nucleus and makes the RNA in the nucleus as well. The RNA then exits the nucleus and is translated by the cell’s organelles into amino acids. These small subunits are then put together in the ribosomes that are attached to the membrane of the rough endoplasmic reticulum. Then, the proteins exit the ribosomes and exit the rough endoplasmic reticulum to enter the Golgi apparatus. The Golgi apparatus packages the proteins and sends them out of the cell.