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Lecture 9

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BIOL 1000
Michael Gadsden

Lecture 9 DNA Repair  May happen because of UV light or a Cytisine becoming Uracil by spontaneous de-amination) o CNH 2 COOH o Another way is that DNA Polymerase accidentally inserts U into DNA (as DUTP [instead of DTTP])  Note: Many chemotherapeutic drugs affect the cell so that it increases the amount of DUTP  WHY? If DUTP [] is increased by drugs, increase level of U in DNA there is a high degree of repair  The repair system is then overwhelmed and this leads to DNA fragmentation and then death of the cell  This process targets fast dividing cells (Cancer, hair etc.) and that’s why cancer patients are bald  Excision Repair o Remove misinserted base  I.E. via Uracil-DNA-glycosylase o Enzyme removes a small gap of nucleotides  This is like when RNA Primase is has to be removed o Fill in gap by DNA Poly  Proofreading by DNA Polymerase o Enzyme will notice that there is not good H bonding and it will reverse, splice and repair the base o Note: Retrovirus polymerases are highly mutagenic  Repair Mechanisms: o DNA Polmerases  Mismatch Repair o Repair enzymes recognise mispaired base o Enzymes remove multiple bases o DNA Poly repairs bases o Ligase combines two sets together Eukarya  DNA contained in nucleus... etc.  Organelles: o Generally something that is membrane encased and has a particular function  Ribosome is NOT and organelle because it is not membrane bound o Compartments in a cell with a specific function (usually metabolic) o With a degree of permanence  Endomembrane Nucleus o Connection found in the ER membrane (pores) and many folds  Plant Vs. Animal Cells o Generally same thing o Vacuole and Cell wall in Plant  Rough and Smooth ER o Rough – covered in Ribosomes so that the RNA can be quickly translated into prioteins o Smooth – synthesize fatty acids and alcohol  Liver cells have many of these because detoxification occurs in the liver  Golgi Apparatus o Processes and packages proteins, lipids and other molecules  Vacuole o Stores nutrients o Retains and degrades waste o Provides support  Lysosomes o Where particles are degraded in the cell o Degrade and recycle materials o Very acidic and thus if it bursts, the enzymes won’t work  Note: acid helps degrade Disorders  Tay-Sachs Disease o Untreatable genetic disorder  Cannot degrade gangliosides  Lipids + sugars  See Sheet  Ganglioside is found in high [] on nervous tissue membranes Endosymbiosis  All DNA in nucleoid  Essentially the ideology is that the nuclear envelope got two very similar membranes  Mitochondria came in (aerobic bacteria) and they became part of the cell o For some reason, the mitochondria wasn’t eaten and it gained an evolutionary advantage o Host cell offers protection, and the mitochondria provides ability to aerobically respire  Photosynthetic Bacteria followed the same process and became chloroplasts  Viewing some cells allow us to believe this process Plant Cell Wall  Provides strength and increased water resistance  Provides protection because it cannot be digested by humans  Between cells, Plasmodesmata allow water and other molecules to pass between neighboring cells o Plasmodismota allows cell to cell communication o A direct connection between two cells Extra Cellular Matrix  Surface layer that surrounds cells o i.e. Glycocalyx o Differences are what they are made out of o Large polysaccharides, proteins, proteoglycans (large protein – sugar molecules) o Allow cells to move past each other or have flexibility (cartilage)  Also helps protect cell from external acids etc. Cytoskeleton  Dynamic structure (3D) that fills the cytoplasm  Anchors organelles and proteins and membrane prioteins in place  Involved in the transmission of signals from the surface or Extracellular space and matrix to inside the cell  Signal Transduction o External Signal  i.e. hormone or a cytokine o Binds to plasma membrane receptor that then induces a molecular cytoplasmic signal to be made to affect the inside of the cell  i.e. turn proteins or genes on/off o Turns an external signal to an internal signal  Involved in cell movement and mobility  Three types: o Microtubule o Intermidiate Filament o Microfilament  Microtubules o Inside cell, radiate from nucleus to cell periphery  Actin o Periphery of animal cell  Intermediate Filament o Made from many different protein subunits o Often cell specific o One can ID the origin of a cancer cell by the Intermediate Filament it contains  M
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