Do Now1. What happens to your body when you get a

cut?

2. Make a drawing illustrating the healing process.

Cellular Division

Objectives1. To understand why cells divide.

2. To explain different limitations on cell size.

3. To summarize the steps of the cell cycle.

Cell Size*Take a look at the following cells…

*Which cell do you think will work most efficiently?

Surface Area vs. Volume

L x W x # of sides

L x W x H

Practice…

Find the SA:V ratio for the three cubes above.

Which cube has the higher SA:V ratio?

Size Limitations Key factor that limits cell growth is ratio of

surface area to volume

As the cell grows, its volume increases much more rapidly than the surface area.

Cell can have difficulty supplying nutrients and expelling waste products.

Transport of Substances

Substances enter membrane through diffusion

Diffusion over a large distance = slow

Smaller cells are more efficient!

Cell Communication

The need for signaling proteins to move throughout the cell also limits cell size.

Cell size affects the ability of the cell to communicate instructions for cellular functions.

Cell Cycle Varies between 8 minutes and one year Average 12-24 hours

Cell Cycle All cells start out in Interphase They then enter cell division, Mitosis &

Cytokinesis

InterphaseA. G1 Phase: First growth phase The cell is growing, carrying out

normal cell functions, and preparing to replicate DNA.

B. S Phase: DNA is copied (DNA

Replication)

C. G2 Phase: Second Growth Phase Proteins needed for cell division

are produced The cell prepares for the

division of its nucleus.

Mitosis/Cytokinesis

Mitosis: Nuclear Division Cytokinesis: Cell Division

Do Now

Do Now Please hand homework in the bin.

Grab a piece of construction paper from my desk. (Color doesn’t matter)

Then sign into Kahoot.it using the game code on the board.

This will be done individually.

Important Vocab. Chromosome-

Tightly coiled DNA

Chromatid- Half a replicated Chromosome

Chromatin- loosely coiled DNA

Centromere- Center of a chromosome- where the sister chromatids attach

Centriole- Organize the microtubules Attach to the spindle fibers

MITOSIS

Prophase Nucleolus disappears

Nuclear membrane breaks apart

The cell’s chromatin tightens making chromosomes visible!

Sister chromatids are attached at the centromere.

Spindle apparatus forms and attaches to centromeres of chromosomes.

Metaphase Sister chromatids (duplicted chromosomes) are pulled

along the spindle apparatus toward the center of the cell.

They line up in the middle of the cell at metaphase plate.

Anaphase

The microtubules (spindle fibers) of the spindle apparatus begin to shorten.

The sister chromatids separate (apart). The chromosomes move toward the poles of

the cell.

Telophase The chromosomes arrive at the poles and begin

to relax. Two new nuclear membranes begin to form and

the nucleoli reappear. The spindle apparatus disassembles.

Cytokinesis Cytoplasm will divide forming two new genetically

identical daughter cells.

In animal cells, microfilaments constrict, or pinch, the cytoplasm. They create a “cleavage furrow”

In plant cells, a new structure, called a cell plate, forms ( which will eventually become the new cell wall)

A B C

D E

Quick Review – Place Cells in Mitosis Order

Let’s Review!

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter11/animations.html

Do Now Label the parts of the cell. What phases of mitosis?

9.3 Cell Cycle Regulation

Normal Cell Cycle:Different cyclin / CDK (cyclin

dependent kinases) combinations signal other activities

These including○ DNA replication ○ Protein synthesis○ Nuclear division

Quality Control Checkpoints The cell cycle has built-in checkpoints These monitor the cycle and can stop it if

something goes wrong. Spindle checkpoints also have been identified

in mitosis.Ex. If no spindle fibers – will stop before cytokinesis

Cell Cycle Checkpoints

*If G1 checkpoint shows cell is not ready for DNA replication, it enters G0 phase and will not divide.*

When Cell Division Goes Wrong

Begins as a single cell that undergoes “transformation” (process converting a normal cell into a cancer cell)

Immune system fails to destroy cell. Cell proliferates and forms a tumor.

Transformation Transformation is caused by mutations. Mutations can result from a variety of different

“carcinogens” (things that cause cancer)

Carcinogens Tobacco

“Dip” : contains 28 known carcinogens.

Cigarettes

Carcinogens

UV LightCauses skin cancer

(most common type of cancer)

Tanning beds linked to “melanoma”- deadliest type of skin cancer.

Carcinogens Pesticides

Overexposure has been known to cause leukemia and lymphoma.

Cancer Cells vs. Normal Cells Cancer cells lack density-dependent inhibition, causing

cells to pile up on top of each other

They proceed past checkpoints

They are “immortal”, meaning they can divide an infinite number of times, whereas nomral cells divide only about 20-50 times before stopping.

Tumors Benign tumor

Abnormally growing mass of cellsCan disrupt certain organs, ex: brain, if they get too

bigCan be completely removed with surgery

Malignant tumorSpreads into neighboring tissuesCan metastasize, enter blood and lymph vessels, and

spread to other organs and parts of the body

Types of Cancer Carcinomas

Originates in external or internal “coverings” such as skin or the lining of the intestine

SarcomasIn tissues that support the body such as bone and

muscle

Leukemias and lymphomasIn blood-forming tissues such as bone marrow,

spleen, and lymph nodes.

Cancer Genetics

Multiple changes in DNA are needed to cause cancer

Cancer increase with age

Certain cancers are inherited in certain families (chances to have it)

Do Now

What is the difference between a benign tumor and a malignant tumor?What category of cancer is found on the lining of different organs?

Apoptosis Programmed cell death Cells going through apoptosis actually shrink

and shrivel in a controlled process.Ex. Leave in FallEx. Webbed Fingers/ToesDNA Damaged Cells

Stem Cells Unspecialized cells

that can develop into specialized cells when under the right conditions

Stem Cells (cont)

Embryonic Stem Cells Adult Stem Cells

•After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells.

•Found in various tissues in the body and might be used to maintain and repair the same kind of tissue

•These cells have not become specialized.

•Less controversial because the adult stem cells can be obtained with the consent of their donor

http://www.stemcellresearchfacts.com/definition.html

Stem Cell Controversy http://www.youtube.com/watch?v=27skh7prkN0

&feature=related

As a review… Draw out all of the phases of mitosis with

colored pencils. Use 4 chromosomes