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Chapter 10 Cell Growth and Division 10-1 Cell Growth A. Limits to Cell Growth 1. Larger the cell becomes the more demands put on the cell’s DNA a. Cell cannot and does not make more DNA -computer hard drive space/program needs 2. Larger the cell the more problem the cell has in moving materials/waste through membrane a. As cell increases in size: -volume increases compared to surface area -less surface area to let things in/out -ex. balloon B. Division of the Cell 1. Cell Division a. Process by which a cell divides into 2 new identical daughter cells 2. 2 Stages a. Mitosis -division of the nucleus b. Cytokinesis -division of the cytoplasm 10-2 Cell Division A. Chromosomes 1. passes genetic info from gen. to gen. 2. composed of DNA and proteins 3. each species has specific number of chromosomes a. Fruit fly—8 chromosomes carrot—18 chromosomes humans—46 chromosomes 4. Invisible as chromatin—even under microscope 5. As compacted chromatin (chromosomes) visible under microscope 6. Replicates (make copies) and form identical “sister” chromatids (2 chromosomes) 7. Chromatids are attached at the centromere 8. human cell entering cell division has 46 chromosomes which duplicates to 92 chromos. (46 chromatids) 9. Handout of sister chromatid B. Cell Cycle 1. series of events cell goes through as it grows and divides a. Cell grows b. Prepares for division c. Divides to form 2 identical daughter cells d. cycles again 2. Handout 3. Events of cell cycle Cell cycle has 2 stages: --Interphase (G1, S, G2) --cell division (mitosis (PMAT) and cytokinesis) 4. Interphase Interphase --may last a long time --period between divisions --cell is performing normal life activities --chromatin is present --phases--Gap 1 (G1), Synthesis phase (S), Gap 2 (G2) b. Phases of interphase S phase --DNA replication --Synthesis of DNA molecules --Key proteins for DNA is synthesized c. Phases of interphase Gap 2 (G2) --Organelles required for division are produced --Shortest of interphase --Preparation for mitosis 5. M Phase M phase M phase --Prophase --Metaphase --Anaphase --Telophase --PMAT—division of nucleus --Cytokinesis— Division of cytoplasm a. Phases of interphase Gap 1 or G1—cells do most of the growing (increase in size), synthesizes proteins and organelles C. Mitosis 1. 4 Phases a. Prophase, metaphase, anaphase, telophase (PMAT) b. Phases last from a few minutes to several days depending on cell type c. Handout 10-3 Regulating the Cell Cycle A. Controls on Cell Division 1. Human Body Cells a. Muscle/nerve cells do not divide once developed --heart attacks, strokes, severed nerves/spinal cord b. Skin, digestive, bone divide rapidly --repair, healing, replacement 2. cell growth can be “turned on/off” B. a. When cells come into contact with each other they stop growing b. When nutrients are gone growth stops Cell Cycle Regulators 1. cyclin a. Protein (in the eukaryote cell) which regulates cell cycle -amount of cyclin rises and falls in cycle 2. Two types of regulatory proteins a. Internal regulators -respond to events inside the cell -examples: *ensures a cell does not enter mitosis until chromosomes are duplicated *cell does not enter anaphase until chromosomes are attached to spindles b. External regulators -responds to events outside the cell -speeds up/slows down cell cycle -examples: *growth regulators #embryonic development #wound healing #prevents excessive growth 3. Uncontrolled Cell Growth a. Cancer -cells lose their ability to control growth -cells do not respond to signals that regulate cell growth -tumor *mass of uncontrolled cells which damages surrounding tissues *cancer cells can break off and spread throughout the body -cancer cells have a defect in p53 gene *p53 gene halts cell cycle until chromosomes are duplicated *lost or defective info in p53 causes cells not to respond to info