Ch.9/Section 3. Cell Cycle Regulation

Cell Cycle Regulation

Ms. Karen

Vocabulary

• Cancer

• Carcinogerns

• Apoptosis

• Stem cell

• Embionic stem cells

• Adult stem cells

Normal cell cycle

The rate of cell division varies depending on the type of cell. A mechanism involving proteins and enzymes controls the cell cycle.

The role of the cyclins

• The cell cycle in eukaryotic cells is driven by a combination of two substances that signal the cellular reproduction process.
• Proteins called cyclins bind to enzymes called cyclin-dependent kinases(CDKs) in the stages of interphase and mitosis to start the various activities that take place in the cell cycle.
• The combination of cyclin with CDK signals the start and the end of the cell cycle. Also, different cyclin/CDK combinations signals start other activities, including DNA replication, protein synthesis, and nuclear division.

Quality control checkpoints

The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong

G2

G1

Checkpoint: monitors for DNA damage and can stop the cycle before entering the S stage.

Mitosis

Synthesis

Abnormal cell cycle: Cancer

Cancer can lead to death

Checkpoint Fail

What is Cancer?

Although the cell cycle has a system of quality control checkpoints, it is a complex process that sometimes fails.

When cells do not respond to the normal cell cycle control mechanisms, a condition called cancer can result. Cancer is the uncontrolled growth and division of cells.

When unchecked, cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.

Causes of cancer

The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations or changes in the segments of DNA that control the production of proteins, including proteins that regulate the cell cycle.

Cancer does not only occurs in a weak organism. Cancer occurs in many healthy, active, and young organisms.

Often, the genetic change or damage that occurs is repaired by various repair systems. But if the repair system fail, cancer can result.

Substances and agents that are known to cause cancer are called carcinogens.

Causes of cancer

Substances and agents that are known to cause cancer are called carcinogens.

Avoiding known carcinogens can help reduce the risk of cancer.

Governmental agencies work to make sure that the things you eat and drink are safe.

Avoiding tobacco can reduce the risk of cancer. Some radiation, such as ultraviolet radiation from the Sun, and X-rays can lead to skin cancer.

Cancer genetics

More than one change in DNA is required to change an abnormal cell into a cancer cell. Over time, there might be many changes in DNA. This might explain why the risk of cancer increases with age. An individual who inherits one or more changes from a parent is at highest risk for developing cancer than someone who does not inherit these changes.

Apoptosis

Is the programmed cell death, for those cells that are not destined to survive.Cells going through apoptosis shrink and shrivel in a controlled process.

This occurs in cells that are damaged beyond repair, including cells with DNA damage that could lead to cancer. Apoptosis can help o protect organisms from developing cancerous growths.

Stem cells

Are unspecialized cells that can develop into specialized cells under the right conditions. This cells can remain in an organism for many years while undergoing cell division.

Embryonic stem cells

Adult stem cells

There are two basic types of stem cells

Adult stem cells

Embryonic stem cells

VS

1. They are found in various tissues in the body and might be used to maintain and repair the same kind of tissue in which they are found.
2. Even newborn has adult stem cells.
3. Certain kinds of adult stem cells also might be able to develop into different kinds of cells, providing new treatments for many diseases and conditions.

1. After a sperm fertilizes an egg, the resulting mass of cells divides repeatedly until there are about 100-150 cells.
2. These cells have not been specialized.
3. If separated, each of these cells has the capability of developing into a wide variety of specialized cells.

Thank you!