Download Cell Cycle regulation

Cell Cycle Regulation
Observations of Cells
• A. Cells typically grow until their cell
membranes (or cell walls) come into contact with
another structure.
•
1. Cells grown in a lab grow until they touch
the edge of the petri plate or another cell.
•
2. When you cut your skin or break a bone,
the cells at the site of the injury will grow until
they fill in the empty space.
• **These two examples show that there are
controls on when cell division occurs.
Controls on the Cell Cycle
• External Regulators- proteins that respond to
events outside of the cell
•
1. Hormones (Growth factors) are an
example.
•
a. When an organism is supposed to
grow bigger, it may release growth hormone that
causes certain cells to respond by progressing
through the cell cycle.
•
2. Cells touching each other or their
surroundings is another example.
•
a. Cells will stop growing and
dividing when they contact each other or an
object in their surroundings
Other Controls on the Cell Cycle
• A. Internal Regulators- proteins that respond
to events that occur inside the cell.
•
1. One example is a protein that will not
allow the cell to enter mitosis until all the DNA
has been replicated
•
2. Another example is a protein that
prevents anaphase from occurring until all the
chromosomes have attached to a spindle.