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Published byRoger Moody Modified over 9 years ago
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CHAPTER 10 CELL GROWTH & DIVISION
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10-1 Cell Growth How do we grow? Our cells divide!
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WHY our cells divide… Why don’t our cells just get bigger? 1. increased demands on DNA Like a library… 2. harder to move nutrients/wastes in/out Surface area to volume ratio Volume increases faster Like a street… vs.
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What do we call this? Cell division: the process by which a cell divides into 2 daughter cells First, must copy DNA Why? So each daughter cell gets their own set Smaller size cells = better surface area to volume ratio
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10-2 Cell Division Two main parts: Mitosis- division of nucleus Cytokinesis- division of the cytoplasm
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Mitosis Can be… Reproduction (asexual)- unicellular organisms Growth + development- multicellular organisms Occurs right after egg is fertilized (embryo)
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Chromosomes Chromosomes- carry genetic information (DNA) Condense at the beginning of cell division Chromosomes replicate forming sister chromatids Centromere- area where chromatids attach Organisms have a specific # of chromosomes Humans = 46
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The Cell Cycle Series of events cells go thru as they grow + divide Grow, prepare for division, divide, grow again…
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Cell Cycle Phases 4 phases: 1. M phase- mitosis and cytokinesis 2. G1 phase- most of growing 3. S phase- chromosome replication 4. G2 phase- prepare for mitosis G1, S and G2 = “interphase”
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Mitosis Division of nucleus Major part of M phase of cell cycle 4 parts (PMAT) 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase
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Prophase Longest Chromosomes condense Centrioles move to opposite sides of cell form spindles Nucleolus gone/ nuclear envelope disappears
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Metaphase Chromosomes line up on metaphase plate Centromeres attach to the spindle
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Anaphase Centromeres split- 2 sister chromatids become individual chromosomes Move along spindle to opposite ends of cell
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Telophase Nuclear envelope forms at each end Spindle disappears Nucleolus forms
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Cytokinesis Division of the cytoplasm Usually occurs at the same time as telophase Animals- cell membrane draws in + pinches off Plants- cell plate forms Followed by cell membrane then cell wall
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10-3 Regulating the Cell Cycle Specific cell types are highly controlled Muscle + nerve cells- don’t divide once fully developed Skin cells + bone marrow- constantly divide to replace old cells
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Controls on Cell Division Can be turned on/off
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Cell Cycle Regulators Cyclin- protein that regulates timing of cell cycle When injected into non-dividing cell, cell would then divide Cyclin protein family- several proteins
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Cyclins 2 main types: 1. internal regulators- respond to events inside cell Ex: cell wont enter mitosis if all DNA is not copied 2. external regulators- respond to events outside cell Direct cell to speed up/slow down division Ex: growth factors- speed up during embryo development/ slow down when they contact another cell
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Uncontrolled Cell Growth Can have severe/deadly consequences Cancer- when cells do not respond to signals to regulate growth and division Cause masses (tumors)
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Causes of uncontrolled cell growth: Failure to respond to internal or external regulators (cyclins) Ex: P53- gene that normally stops cell cycle until all DNA is copied Defect causes uncontrolled cell division
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