Stem Cells

Cancer

How cells know when to divide. The body releases growth factors which are a lipid based hormone. The growth factor diffuses through your blood stream and spreads throughout your body. The growth factor binds to any cells that have a growth factor receptor protein in their cell membrane. The receptor protein releases cyclin. The cyclin binds to cyclin dependent kinases (CDK). The CDK phosphorylates the proteins involved in mitosis. Phosphorylation means adding a phosphate group to a protein which is the way you activate proteins.

There are three major checkpoints for mitosis or cell division. These checkpoints are in place to make sure everything goes right. If something were to go wrong with cell division it could lead to cancer or other problems. There is a checkpoint between G1 and the S phase. If the cell is not ready to replicate its DNA it will not be allowed to enter the S phase. There is another checkpoint after G2 to make sure the cell is ready for mitosis. At this checkpoint the cell makes sure that the DNA was replicated properly. The last major checkpoint is after metaphase to make sure all the chromosomes lined up properly before they enter anaphase and are separated. Each one of these checkpoints requires phosphorylation by CDK's to move on.

Cancer

Cancer is caused by unregulated cell division. It is basically mitosis gone wrong.

There are many tumor suppressors inside our cells that help us fight against cancer. There are many ways that cancer can happen. Many of the ways that cancer is formed happens when one of our tumor suppressors breaks or mutates. This happens from damaged DNA.

Here are the normal working tumor suppressors

And here is what happens when these suppressors break or mutate