Cells 4-Systems & Functions

In the developing embryo elimination of larval tissues

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Unformatted text preview: its (fingers Elimination & toes) during development. toes) Elimination of excess neurons in developing Elimination nervous system (up to 50% of the total of developing embryonic neurons). developing Important in maintenance of adult tissues! Balancing cell proliferation & maintaining constant Balancing cell numbers in tissues that turnover regularly. cell Example 500 billion blood cells die daily - balancing their Example continual production in the bone marrow. continual Defense mechanism against damaged or infected cells. Example Virus-infected cells frequently undergo Example apoptosis, thereby preventing virus spreading. Example DNA damage often induces a cell into apoptosis Example thus eliminating dangerous mutations that may lead to cancer. lead Apoptosis OVERVIEW Apoptosis Caspases & Apoptosis Caspases Caspases The EXECUTIONERS of programmed cell death! (“C” + “Asp” + ase) Protease enzymes with Cysteine residues at their Protease Cysteine active sites. active Cleave substrate proteins after Aspartic acid (Asp) Cleave Aspartic residues. residues. Cleave ~100 different cell target proteins!! Caspase Example Caspase Cell Death Receptors Cell Cell death signals Polypeptides belonging to the tumor necrosis factor Polypeptides (TNF) family. (TNF) Cell death receptors TNF Receptor Family Virus infected cells, Cancerous cells, other Immune cells Ligand binding results in receptor trimerization, association Ligand with “adaptor” proteins and Caspase-8, autocleavage or activation of Caspase-8, activation of more caspases and other “enhancing” proteins “enhancing” Signaling Cell Survival Signaling Default Status of Most Cells Apoptosis unless Default actively suppressed by “survival signals.” actively .” There are many pathways that signal cell There survival and inhibition of apoptosis! survival Example Example Neurons that make the correct “connections” don’t die. They are maintained by nerve growth factors from the tissues. factors Apoptosis Summary Apoptosis Programmed cell death is “normal” and Programmed essential to balance in multicellular life forms like us! forms Caspases are a family of enzymes that cause Caspases apoptosis apoptosis Cells can be signaled to undergo apoptosis Cells Apoptosis can be avoided by survival signals Questions? Questions?...
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This note was uploaded on 09/26/2013 for the course BIO 232 taught by Professor Bradfillmore during the Fall '13 term at E. Washington.

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