Transcript Do Now
Do Now 1. What happens to your body when you get a cut? 2. Make a drawing illustrating 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 *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) LxWxH 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 1) 3 X 2 X 2 2) 6 x 1 X 1 3) 3 X 6 X 1 • 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? 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? 2x3x2 OR 4x1x1 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.mcgrawhill.com/sites/0072437316/student_vie w0/chapter11/animations.html Do Now • Label the parts of the cell. • What phases of mitosis? Do Now- Read Article on Cancer • What was the most common type of cancer in the US in 2010? • What is the 2nd most common and what is the major factor for development of this cancer? • What is the most common in women? • In men? • What type of cancer is almost always fatal and is difficult to diagnose and treat? 9.3 Cell Cylce 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) Homework! • Cancer research – Doesn’t have to be in complete sentences – If there are more than 5 answers for a section, pick only 5 – Be ready to share your information! (very brief description) Do Now • Take out your cancer worksheet that you did for homework. Be ready to present your information! • 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