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Cellular Reproduction Chapter 9

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Why do cells need to reproduce?

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Why are cells so small?

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What is Surface Area? How is the surface area represented in a cell?

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What is Volume? What happens when the volume of a cell increases?

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Mini-Lab 9.1 Investigate Cell Size CellCell SizeCell Surface Area (L x W x 6) Cell Volume (L x W x H) Cell 10.00002 m Cell 20.001 m Cell 32.5 cm (0.025 m) Cell 430 cm (0.3 m) Cell 515 m

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CellCell SizeCell Surface Area (L x W x 6) Cell Volume (L x W x H) SA : V Cell 10.00002 m0.00000000240.000000000000008300, 000 : 1 Cell 20.001 m0.0000060.0000000016000 : 1 Cell 32.5 cm (0.025 m) 0.003750.000015625240 : 1 Cell 430 cm (0.30 m) 0.540.02720 : 1 Cell 515 m135033751 : 2.5

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Limits to Cell Size Smaller cells can better: 1. exchange nutrients and expel wastes across the plasma membrane. higher surface area to volume ratio (SA:V) 2. transport substances within the cell. diffusion motor proteins 3. communicate instructions for cellular functions. signal proteins

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Cell Cycle Events of the Cell Cycle

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Cell Division When a cell reaches its maximum size, the nucleus initiates cell division. Cell division the splitting of a single cell into two cells. Big Bang by M. Ormestad 2006 All rights reserved

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Cell Division Cells divide so that an organism can grow. increases mass of organism changes organism - differentiation can repair damaged cells and tissues. regeneration maintenance can reproduce.

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The Cell Cycle process of growing and dividing repeated continuously creates two cells from one cell normal animal cells - takes 12-24 hours 3 main stages interphase mitosis cytokinesis

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Interphase period of time during which the cell grows, carries out cellular functions, and makes copies of its DNA in preparation for cell division 3 parts (substages) G1 gap 1 S synthesis G2 gap 2

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Chapter 9.2 Mitosis and Cytokinesis

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Mitosis & Cytokinesis Mitosis the cells nuclear material divides 4 parts (substages) Cytokinesis the cell cytoplasm is divided into two daughter cells

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Chromosomes structures that contain the genetic material of an organism only visible during mitosis formed when chromatin is wound tightly around proteins called histones

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Why Chromosomes? Cell must insure that each new daughter cell gets a complete copy of the cells DNA. Accomplished by: 1. Duplicating each chromosome during the S-phase of the cell cycle. 2. Holding these two copies (sister chromatids) together by a ring of proteins called cohesins. 3. Condensing the chromosomes into a compact form. 4. Separating the sister chromatids and 5. Distributing these equally between the two daughter cells. Inage courtesy of J. R. Paulson and U. C. Laemmli

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Chromosome Structure sister chromatids identical copies copies created during synthesis of interphase attached at beginning of mitosis centromere Structure where the sister chromatids are attached telomeres associated with programmed cell death

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Stages of Mitosis Prophase Metaphase Anaphase Telophase Human cell undergoing cytokinesis from M. Pines, Inside the Cell: The New Frontier of Medical Science. U.S. Dept. of Health, Education, and Welfare, 1978.

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Prophase 1 st stage longest Chromosomes condense Spindle apparatus forms mitotic spindle centrosome centrioles Nuclear membrane disintegrates Nucleolus disappears Chromosomes attach to spindle apparatus

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Metaphase 2 nd stage shortest sister chromatids pulled by motor proteins along the spindle apparatus toward the center of the cell line up along the middle, or equator

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Anaphase 3 rd stage sister chromatids are pulled apart spindle apparatus microtubules shorten separates chromatids into two identical sets

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Telophase 4 th & last stage opposite of prophase Chromosomes arrive at poles of spindle apparatus decondense Nuclear membrane and nucleolus reform Spindle apparatus is broken down or recycled May occur simultaneously with cytokinesis

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Another Look at Mitosis

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Cytokinesis division of the cytoplasm into two daughter cells Animal cells microfilaments constrict cell membrane pinches cell in two cleavage furrow Plant cells construct a cell plate new cell wall forms on either side of cell plate Prokaryotic cells DNA copies attach to plasma membrane plasma membrane grows and pulls DNA copies apart cell membrane pinches into two cells

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Mitosis in Motion http://www.johnkyrk.com/mitosis.html http://www.cellsalive.com/mitosis.htm http://www.sci.sdsu.edu/multimedia/mitosis/navigator.html http://www.sumanasinc.com/webcontent/animations/content/ mitosis.html http://www.sumanasinc.com/webcontent/animations/content/ mitosis.html