10-3 Regulating the Cell...

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Copyright Pearson Prentice Hall

10-3 Regulating the Cell

Cycle

10-3 Regulating the Cell Cycle

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Controls on Cell Division

Controls of Cell Division

Experiments show that normal cells will reproduce

until they come into contact with other cells.

When cells come into contact with other cells, they

respond by not growing.

* We call this behavior contact inhibition

This demonstrates that controls on cell growth and

division can be turned on and off.

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Controls on Cell Division

Contact Inhibition

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Cell Cycle Regulators


The cell cycle is regulated by a specific protein called cyclin.

The amount of this protein in the cell rises and falls in time with the cell cycle.

Scientists called this protein cyclin because it seemed to regulate the cell cycle.

Cyclins regulate the timing of the cell cycle in eukaryotic cells.

regulate.wav

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A sample of cytoplasm

is removed from a cell

in mitosis.

The sample is injected

into a second cell in

G2 of interphase.

As a result, the

second

cell enters mitosis.

Cyclins were discovered during a similar

experiment to this one.


*Cyclin is just one of many types of

regulatory proteins

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Internal Regulators

Proteins that respond to events inside the cell are called internal regulators.

Internal regulators allow the cell cycle to proceed only when certain processes have happened inside the cell.

External Regulators

Proteins that respond to events outside the cell are called external regulators.

External regulators direct cells to speed up or slow down the cell cycle.



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Uncontrolled Cell Growth


Cancer is a disorder in which some of the

body's own cells lose the ability to control

growth.

How are cancer cells different from other

cells?

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Cancer cells do not respond to the signals that regulate the growth of most cells.

Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues.

Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death.

•Tumors can be benign (fixable) or malignant (bad)

• Many cancers lack the p53 gene, which halts growth until chromosomes are all replicated.

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A benign tumor is a tumor that lacks all three of the

malignant properties of a cancer. Thus, by definition, a benign

tumor does not grow in an unlimited, aggressive manner, does

not invade surrounding tissues, and does not metastasize.

Common examples of benign tumors include moles and

uterine fibroids, lipomas (fat cells), chondromas (cartilage).

Malignant (from the Latin roots mal- = "bad" and -genus =

"born") is a medical term used to describe a severe and

progressively worsening disease. A malignant tumor is not

self-limited in its growth, is capable of invading into adjacent

tissues, and may be capable of spreading to distant tissues

(metastasizing).

* Malignant tumors are synonymous with cancer.

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Types of Malignant Cancers

Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs.

Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.

Leukemia - cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.

Lymphoma and myeloma - cancers that begin in the cells of the immune system.

Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord.

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What causes cancer/tumors?

• Exposure to harmful toxins/chemicals known as

carcinogens.

– like asbestos, smoke, Aflotoxin B1, and

formaldehyde.

• Exposure to harmful radiation

– like gamma or UV radiation

• Natural Mutations in genes

• Chromosomal issues in cell division

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Benign Tumor Example

Dermatofibroma (firbrous tumor in the dermis)

http://search.mywebsearch.com/mywebsearch/redirect.jhtml?qid=4C6ACEED2D71ED291465DD925E20ED72&searchfor=dermatofibroma&action=pick&pn=1&ptnrS=&ss=sub&st=site&cb=ZZ&pg=GGimage&ord=2&redirect=mPWsrdz9heamc8iHEhldEa94xJ%2BIq9TDqc5bdRI7I%2BIyO9GbQt9hAvVnZioBaKgkFY1GmyNKOYVQoLXDZirUVqVrxximcKtxeIDyjXa05QYHL4mJdqNeRtXBwbt8IRTm&ct=AR

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Malignant Cancer Examples

• Lung cancer

• Pancreatic Cancer

• Breast Cancer

• Prostate Cancer

• Brain tumors

• Melanoma (cancer of melanin, most often in skin)

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10-3

Resources/ch10_sectn03_quiz.qtb

Resources/ch10_sectn03_quiz.qtb

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10-3

The timing of the cell cycle is believed to be

controlled by proteins called

a. spindles.

b. cyclins.

c. regulators.

d. centrosomes.

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10-3

Proteins that respond to events inside the cell

are called

a. internal regulators.

b. external regulators.

c. cyclins.

d. growth factors.

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10-3

Once a multicellular organism reaches adult

size, the cells in its body

a. stop dividing.

b. grow and divide at different rates, depending

on the type.

c. have the same life span between cell

divisions.

d. undergo cell division randomly.

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10-3

One effect of an internal regulator is that a cell

will not begin mitosis until

a. it becomes too large.

b. the cell’s growth is stimulated.

c. it is in physical contact with other cells.

d. all its chromosomes have been replicated.

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10-3

One factor common to almost all cancer cells is

a. a lack of cyclin.

b. a defect in gene p53.

c. exposure to tobacco smoke.

d. exposure to radiation.

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Resources

http://en.wikipedia.org/wiki/Benign_tumor

http://en.wikipedia.org/wiki/Malignant

http://en.wikipedia.org/wiki/Benign_tumor

http://en.wikipedia.org/wiki/Malignant

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