Do Now!! 1. What happens to your body when you get a cut? 2. Explain in your own words what happens when you get cut and the healing process

Chapter 9 Cellular Division

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 o Why must cells divide? o Take a look at the following cells… o Which cell do you think will work most efficiently?

Surface Area vs. Volume Surface Area (length x width) x 6 sides Volume length x width x height

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

Do Now!! 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)2 X 2 X 2 2) 8 x 8 X 8 3) 4 X 4 X 4

Cellular Division  Cell division occurs in all organisms:  Performs different functions  Unicellular organisms (ex: bacteria):  Binary fission: division into 2 identical cells (clone)  Multicellular organisms (ex: US!):  Mitosis Binary fission Mitosis

Cell Cycle Purposes  Growth  Cells are limited in size  Development (specialized cells)  Repair Specialized Cells Repair

The Cell Cycle  2 main phases: 1. Interphase 2. M Phase o Cells vary in cell cycle times

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

Do Now!!

Mitosis/Cytokinesis Mitosis: Nuclear Division Cytokinesis: Cytoplasm division

Mitosis Prophase Metaphase Anaphase Telophase 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase + Cytokinesis Cytokinesis

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-  Move to poles of cell  Attach to the spindle fibers

Prophase  The cell’s chromatin condenses  Sister chromatids are attached at the centromere  Spindle apparatus* forms in the cytoplasm:  Attach to sister chromatids  The nuclear envelope and nucleolus disappears  *Spindle apparatus:  Centrioles (centrosome)  Aster  Spindle fibers

Metaphase  Sister chromatids 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 of the spindle apparatus begin to shorten  The sister chromatids separate (pulled 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 Cleavage Furrow

Do Now!!  If a cell has 40 chromosomes in G1 phase, how many chromosomes will the daughter cells have?  How many chromosomes will that cell have in G2 phase?  Draw a cell with 4 chromosomes in metaphase!

Cytokinesis  In animal cells, microfilaments constrict, or pinch, the cytoplasm  They create a “cleavage furrow”  2 new and identical cells are formed!

Cytokinesis  In plant cells, a new structure, called a cell plate, forms:  Will become the cell wall  Divides the cells  2 new and identical cells are formed!

Let’s Review !  hill.com/sites/ /student_view0/chapter11/ animations.html hill.com/sites/ /student_view0/chapter11/ animations.html

Do Now!!  Label the parts of the cell.  What phases of mitosis are they in?

Cell Cycle Regulation  Normal Cell Cycle:  Different cyclin / CDK (cyclin dependent kinases) combinations signal other activities  These include:  DNA replication  Protein synthesis  Nuclear division (mitosis)

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, division will stop

Cell Cycle Checkpoints  *If G 1 checkpoint shows cell is not ready for DNA replication, it enters G 0 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 (cont.)  UV Light  Causes skin cancer (most common type of cancer)  Tanning beds linked to “melanoma”- deadliest type of skin cancer.

Carcinogens (cont.)  Pesticides  Overexposure has been known to cause leukemia and lymphoma.

Inherited cancers  Some cancers are inherited through mutated genes that “turn on” the cancer  Ex: BRCA1 gene (mutation can cause breast cancer)  Most cancers are sporadic: genetic changes over time

Cancer Cells vs. Normal Cells  Cancer cells lack density-dependent inhibition, causing cells to pile up on top of each other  They are “immortal”:  divide an infinite number of times

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