Do Now

1. What happens to your body when you get a cut?

2. Make a drawing illustrating the healing process.

Cellular Division

Chapter 9

Objectives

1. 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

(2 x L x W) + (2 x L x H) + (2 x H x W)

L x W x H

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!

Think-Pair-Share

• If you had 3 cells with the dimensions on the left…

• Which cell has the largest surface area to volume ratio?

• What benefit does this cell have?

1) 3 X 2 X 21) 3 X 2 X 22) 6 x 1 X 12) 6 x 1 X 13) 3 X 6 X 13) 3 X 6 X 1

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• Cell division prevents the cell from

becoming too large.

• It also is the way the cell reproduces so that you grow and heal certain injuries.

• Cells reproduce by a cycle of growing and dividing called the cell cycle

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

Interphase• A. 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.

Genetic Material = CHROMATIN

Mitosis/Cytokinesis

• Mitosis: Nuclear Division• Cytokinesis: Cell Division

Do Now

Review• Surface area : Volume :: _________ : _______

(Cell Parts)

Which cell has a bigger surface area to volume ratio?

2 x 3 x 2 OR 4 x 1 x 1

What benefit does this cell have?

MITOSIS

MITOSIS

• Label and order the cells from 1 – 5

• What are the differences between plant and animal cells during

division?

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

Prophase

• The cell’s chromatin tightens• Sister chromatids are attached

at the centromere.• Spindle fibers form in the

cytoplasm.• The nuclear envelope seems

to disappear.• Spindle fibers attach to the

sister chromatids.

Metaphase

• Sister chromatids are pulled along the spindle apparatus toward the center of the cell.

• They line up in the middle of the cell.

Anaphase

• The microtubules 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• 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.

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 Light

– Causes 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 cells– Can disrupt certain organs, ex: brain, if they get too

big– Can be completely removed with surgery

• Malignant tumor– Spreads into neighboring tissues– Can 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

• Sarcomas– In tissues that support the body such as bone and

muscle

• Leukemias and lymphomas– In 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 Fall– Ex. Webbed Fingers/Toes– DNA 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

Quiz Study Guide…

• Cell Cycle – Interphase (G1, S, G2)– Mitosis (PMAT)– Cytokinesis

• Phases of Mitosis• Cell Regulation (CDK, Checkpoints, and cyclins)• Cancer• Stem Cells• Apoptosis• Cell Volume VS. Surface Area Ratio

As a review…

• Draw out all of the phases of mitosis with colored pencils. Use 4 chromosomes