Regulating the Cell Cycle

The cell cycle is controlled by regulatory proteins both inside and outside the cell.

Cyclins proteins that regulate the timing of the cell

cycle in eukaryotic cells.

Internal regulators proteins that respond to events

inside a cell. They allow the cell cycle to proceed only

once certain processes have happened inside the cell.

External regulators proteins that respond to events

outside the cell. They direct cells to speed up or slow

down the cell cycle.

Growth factors are external regulators that stimulate the

growth and division of cells. They are important during

embryonic development and wound healing.

• When an injury such as a broken bone occurs, cells are stimulated to divide rapidly and start the healing process.

• The rate of cell division slows when the healing process nears completion. These are all controlled by regulatory proteins.

Cells end their lives in one of 2 ways

By accident due to damage or injury

Apoptosis

A process of programmed cell death. Plays a key role in development by

shaping the structures of tissues & organs in plants & animals.

Cell growth has to be regulated carefully because uncontrolled cell growth can be severe. Ex. Cancer

Disorder in which body cells lose the ability to control growth.

Cancer cells do not

respond to the signals that

regulate the growth of

most cells. As a result, the

cells divide uncontrollably.

Cancer cells form a mass

of cells called a tumor.

Cancer:

http://www.youtube.com/watch?v=LEpTTolebqo&feature=related

Oral Cancer

Adisease characterized by uncontrolled cell division & growth.

Tumors are of 2 types:

1. Benign Tumor: stays in one place, usually harmless.

2. Malignant Tumor: cells move around in the body. Results in CANCER.

The spread of cancer cells is called metastasis.

Cancer cells absorb nutrients needed by other cells,

block nerve connections,

prevent organs from functioning.

Chen Zongtao with 154 LB.

tumor on his right leg.

Caused by defects in genes that regulate cell growth & cell division.

A damaged or defective p53 gene is common in cancer cells.

The damage causes cells to lose the information needed to respond to growth signals.

Some sources of gene defects are:

smoking tobacco,

radiation exposure,

defective genes,

viral infection.

Lung Cancer- smoking

UV exposure

Karposi Sarcoma

Some localized tumors can be removed by surgery.

Ex. Melanomas most serious form of skin cancer. (Early detection)

Lai Thi Dao , a 15 year old Vietnamese girl, endured a huge facial tumor called a Schwannoma for most of her life

300 lbs Tumor Removed Video

http://www.youtube.com/watch?v=dvDUX

KegwZw

Many tumors can be treated with targeted radiation. Ex. Cancer cells that

growth rapidly

Chemotherapy is the use of compounds that kill or slow the growth of cancer cells. Problems with the

fact it kills normal cells.

Cell Differentiation

The human body contains ~100,000,000,000,000 (100 trillion) cells. All produced from 47

cell cycles.

We all started life as one cell

We all pass through an early stage of development stage called an embryo.

During development, an organism’s cells become

more differentiated and specialized for particular

functions.

For example, a plant has specialized cells in its roots,

stems, and leaves.

• The process by which

cells become specialized

is known as

differentiation.

• During the development

of an organism, cells

differentiate into many

types of cells.

• Ex. Nerve, skin, cardiac

cells, etc.

Important because it helps to determine the cell’s ultimate identity.

Ex. Will the cell spend its life as a nerve cell or a muscle cell.

•The unspecialized

cells from which

differentiated cells

develop are known

as stem cells.

• There are two types of stem cells: embryonic and

adult stem cells.

All the cells in the body formed from a fertilized egg cell

Totipotent cell,

• able to form all the

tissues of the body. • Fertilized egg and the cells

produced by the first few

cell divisions of embryonic

development are truly

totipotent.

•

After about four days of development,

a human embryo forms into a blastocyst,

Blastocyst:

a hollow ball of cells with a cluster of cells inside known as the inner cell mass.

The cells of the blastocyst have started to specialize:

Outer cells form the tissue that attach the embryo to its mother.

Inner cell mass form the embryo Inner cell mass is called

pluripotent cells

Cells capable of developing into many, but not all, of the body's cell types.

•Embryonic stem cells

are pluripotent.

•embryonic stem

cells have the

capacity to produce

most cell types in the

human body.

•Adult stem cells are

multipotent

They can produce

many types of

differentiated cells.

•Adult stem cells of a

given organ or tissue

typically produce only

the types of cells that are

unique to that tissue.

• Stem cell research may lead to new ways to repair

the cellular damage that results from heart attack,

stroke, and spinal cord injuries.

One example is the approach to reversing heart

attack damage illustrated below.

Finger regrown video: http://www.youtube.com/watch?v=u3nI__psfBA

Ethical Issue:

•Harvesting, or gathering, embryonic stem cells cause destruction of the embryo.

Political Issue:

•Government funding of embryonic stem cell research is an important political issue.

VIDEO: http://www.teachersdomain.org/asset/nsn08_vid_stemcell2/

OR http://www.pbs.org/wgbh/nova/teachers/body/stem-cells-breakthrough.html

•Groups seeking to protect embryos oppose such research as unethical.

•Other groups support this research as essential to saving human lives and so view it as unethical to restrict the research.