Cell Differentiation and Cell Growth Regulators

Chapter 10

Why did we use Onion Root Tip Cells?

Why did we use Onion Root Tip Cells?

Roots grow deep into the dirt and some surface cells are“scratched” away

So… Root Tip Cells must divide rapidly = MITOSIS!

Why do cells divide?

Cell division allows organisms to grow and reproduce.

Also, cells cannot function effectively if they are too large. Compare the surface area to volume ratio.

Why do cells divide?

Cell Differentiation

Cell differentiation: when cells take on specific structures and functions Different organisms may have different

types of cells (e.g. bacterium) There may be many different types of

cells in the SAME organism (e.g. human)

Examples of Slow Dividing Cells Neurons (top)

Conduct impulses throughout our body so that we can move, think, feel, etc

Some NEVER divide

Muscle cells (bottom) Used for movement Works like a spring

Examples of Fast Dividing Cells

Cheek cells (top) Divide approximately

every three days because food scrapes off surface layers

Intestinal cells (bottom) Divides quickly because

food and bile scrape off surface layers

Frequently have cilia (hair-like projections) to help “move” food down the digestive tract

How is cell growth regulated? Proteins called cyclins control parts of the

cell cycle.

Internal regulators are cyclins that control events INSIDE the cell. For example, some cyclins pause mitosis until

chromosomes are copied. Once this occurs, then it resumes mitosis.

External regulators are cyclins that control events OUTSIDE of the cell. For example, cells grow until they reach other

cells (e.g. healing a wound). Some cyclins tell the cells to stop dividing so that it won’t interfere with other tissues.

What is cancer?

Cancer is uncontrolled cell division.

Since cancerous cells belong to the organism itself, the organism’s body has difficulty detecting and fighting the cancerous cells. Glycoproteins on cell

membrane are “self markers”

What is cancer?

Cancerous cells tend to form a clump called a tumor, but sometimes in later stages of cancer, the cancerous cells metastasize. Metastasize means that

they move to other parts of the body. For example, a cancerous lung cell might migrate to the brain and spread the cancer.

Causes

Inherited Genetic Mutation Carcinogens (e.g. certain

chemicals in cigarettes) Overexposure to

radiation (e.g. sunlight) Diet / Exercise Other

Treatments

Surgery

Radiation

Chemotherapy

Magnets???

Alternative Options