Short Review– All organisms start life as a single cell.-like begets like

These two phrases are the basis for CELLULAR REPRODUCTION(Cell Division)

What do you think would happen if cells didn’t look exactly like the one

they were replacing????

Cells have a life cycle much like the organisms they compose.Millions of cells die or a digested by your body everyday.Cellular Reproduction helps replace them so you don’t run out of cells.

Prokaryotic cells rely on cell division for reproduction only.They use a process called: BINARY FISSION

-they literally “split into two”-must duplicate all cytoplasm, cell membrane, DNA material and ribosomes before they do.

Eukaryotic cells don’t rely on cell division for reproduction. They use itfor other purposes:

1. Growth—from infant to child to adult, seed to seedling to plant-hormones involved in this process-can be made in lab now and injected to help avoid midget

http://www.popularmechanics.co.za/wp-content/uploads/2012/11/Early-human-embryo.jpg

http://www.nobelprize.org/nobel_prizes/medicine/laureates/2010/early_human_embryos_photo.jpg

http://tfloto.files.wordpress.com/2010/04/apoptosis.jpg

http://1.bp.blogspot.com/LMyk8uUjo8c/Tk9vibMiKeI/AAAAAAAAAEA/i4rSNRK8XaA/s1600/Apoptosis.gif

2. Replacement—of worn out cells.

-cells have life times just like we do. When they get worn out, they need to be replaced with an exact copy to make sure the same job continues to be done.

3. Repair—healing of wounds, broken bones-cell division helps rejoin the skin or bone ends-wound healing starts on outside and progresses inward-bone healing begins with broken pieces and new cells “fill in” the gap created by the break-what purpose do stitches and pins have??

http://guineapigmall.com/files/broken-bones.jpg

http://images.ddccdn.com/enc/images/images/en/stitches-19630.jpg

Eukaryotic cells have many parts in them that must be duplicated inorder to ensure each cell is identical.

One of those parts is the Chromosome…which carries the DNA insidethe nucleus of the cell.

A single chromosome must copy it’s entire network of information and pass it onto a newChromosome for the new cell.

The new copy of the chromosome will remain attached to the old onefor most of the division process.

http://www.clt.astate.edu/mhuss/chromosome.jpg

The two copies of the chromosome are called “SISTER CHROMATIDS”

They are joined at the CENTROMERE, or the “middle” of the “X”During division, they will separate at the centromere and information

will be the same in each new cell.

Centromere

Sister Chromatids

DNA is replicated in the first stage of cell division…INTERPHASE.

Scientists once believed that interphase was a resting stage for the cell,but have since found out that it is actually a very busy stage.

Interphase has 3 steps:G1—cell organelles, such as ribosomes and mitochondria, willdouble in content. Cytoplasm will double, cell membrane willdoubleS—this is the stage where the DNA will double. At the end of the “S” stage, the sister chromatids will be formed.

G2—the cell prepares for division here by increasing the membrane proteins, increasing the energy supply andanything else it needs to do to divide.At the end of Interphase, the cell is ready to begin the actual act of dividing the cell into two new ones.

Cells spend the majority of their time in interphase.

(approximately 90% of their lifecycle)

Division of the nucleus is called MITOSISRequires 4 steps to happen:

1. Prophase—the nuclear membrane begins to disintegrate toallow the chromosomes to move outside of it into thecytoplasm. The chromosomes also shorten and thicken and are finally visible under a microscope. Themitotic spindle also begins formation during prophase.

2. Metaphase—chromosomes will move to the cell equator andline up. Spindle fibers, formed in the spindle region, will attach to the chromosome centromeres from each end.

3. Anaphase—the spindle fibers begin to shorten, pulling thesister chromosomes apart and in opposite directions.

4. Telophase—chromosomes finally reach opposite poles of thecell and a new nuclear membrane forms.

At this point, we have divided the nucleus but still have just one cell.

CYTOKINESIS will complete the division process.-is the division of the cytoplasm and other organelles besides the

nucleus-happens two different ways in plants and animals-Plants have the formation of a new cell wall from inside to out…

vesicles inside the cytoplasm join to form a new cell wall-Animal cells have cytoplasmic cleavage from outside to in

microfibers in the cell membrane help constrict the cell like astring around a balloon creates two ends

-Why can’t plants have cytoplasmic cleavage???New cell wall forming

Cells cannot just divide whenever they want.There is a special unit of control mechanisms that help signal cells to

start and stop division.

1. The growth hormones present in cells trigger cell growth. Withoutthe hormones present, the cell will not start the mitosis process. These are chemical messengers in the cells produced by thebody. Each cell type has a specific growth hormone for it. What class of macromolecules do hormones belong to?

2. Cells must be touching other cells in order for division to start.

3. When the cell division process has completed it’s job, Contact Inhibition will signal a stop to the division. This is triggered by one cell touching another cell.

When Cell Cycle control mechanisms are not obeyed…CANCER…occurs.

Cancer cells are no different than other cells in your body, they just Don’t pay any attention to directions to stop dividing.

Therefore, cancercells will continuethe division processeven after healing orreplacement hasoccurred and theextra cells willstack up on one another causing theformation of a tumor.

Two types of tumors can form:

Benign—these are localized tumors and will not spread. They stay in the area they were started in. This does not make them a“safe” cancer…if they are in an area where the tumor can blockthe function of a vital organ they can cause death.

Malignant—these tumors will spread away from the point of origin and can start new tumors in other parts of the organism.They are not always fatal, but can be more difficult to attack insome instances than benign tumors are. Malignant tumors metastize…meaning they can spread to other parts of the organism and continue the division process producing more tumors far away from the point of origin.

There are 4 different types of cancer:

1. Carcinoma—cancer of the skin or external or internal coveringsof the body…like the intestinal lining.

2. Sarcoma—cancer of the muscles and bones (body support system) Does not include the bone marrow.

3. Lymphoma—cancer of the lymph nodes, glands and lymph system

4. Leukemia—cancer of the blood and blood forming tissues such as bone marrow

Types of Cancer:Carcinoma—

Sarcomas– of the upper palate (human mouth) and a cat femur

Basal cell carcinoma

Malignant melanoma

Sarcoma--

Lymphomas—

http://cancertreatment-wecareindia.com/lymphoma/images/_41381321_lymphoma.gif

Lukemias—

http://www.inflammation-information.com/images/hodgkinslymphoma.jpg

Hodgkin’s Lymphoma

http://disability-claims.net/images/leukaemia.gif

Abnormal leukemia cell

http://www.medindia.net/patients/calculators/images/most-common-cancers.jpg

Skin cancer is the most common of all cancers.--accounts for nearly half of all cancers in the United States-- More than 2 million cases of basal and squamous cell skin cancer are found in U.S. each year. --Melanoma, the most serious type of skin cancer, will account for more than 75,000 cases of skin cancer in 2012.

From--http://www.cancer.org/cancer/cancercauses/sunanduvexposure/skin-cancer-facts

--Melanoma is the fifth most common cancer for males and seventh most common for females.2

--The number of women under age 40 diagnosed with basal cell carcinoma has more than doubled in the last 30 years; the incidence of squamous cell carcinoma among women under age 40 has increased almost 700 percent.22

 An estimated 45,060 new cases of invasive melanoma in men and 31,630 in women will be diagnosed in the US in 2013.2

 http://www.skincancer.org/skin-cancer-information/skin-cancer-facts#men/women

Cancer treatments vary according to type…Surgery will cure some cancers. Benign tumors can, in someinstances, be cut away and not return.

Radiation—”burn” cancer cells using targeted beams of high energylight. Generally only attacks actively dividing cancer cells.However, may target actively dividing “good” cells as well.Can cause nausea and hair loss among other side effects.

Chemotherapy—”poisons” cells using drugs to target actively dividingcells. Target cell in different stages of division. Why target thestages of cell division??

Drug Action SourceVinblastin Prevents spindle formation Periwinkle/Madagascar

Taxol Freezes spindle after forms Bark of Pacific Yewto prevent function

Bryostatin 1 no effect on normal cells Bugula neritina only cancer (ocean invert)

Esteinascidin 743promising with difficult cancers Esteinascidia turbinata

(sea squirt)

Side effects of chemo differ from drug to drug as does effectiveness ondifferent types of cancer.

Best type of cancer treatment is PREVENTION.

Eat a diet high in fiber and low in fats.

Exercise regularly.

Don’t worship the sun or tanning beds.

If you must be outside, wear protective creams and clothing.

Be tested for cancer regularly and/or be aware of signs of cancer.