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Transcript
Cytology Notes Cytology: the study of cells A short history of cells. • 1665--Robert Hooke “discovers” cells with an early microscope (30x) • 1675: Anton Von Leeuwenhoek sees microorganisms (300 x) • 1855 Theodore Schwann and Mathias Schleiden propose Cell Theory. Discover cell membrane. • 1855 Rudolf Virchow shows that cells must come from other cells. (Remember Francesco Redi disproving spontaneous generation, 1650?) • 1945 electron microscope show new cell parts • 1950’s first stem cells discovered in bone marrow. How do we study cells? • Microscopes opened up the world of cells • Robert Hooke (1665) – the 1st cytologist Drawings by Hooke cork flea The cell theory • All living things are made of cells • Cells are the basic units of life • Cell only come from other cells Light microscopes – 0.2µm resolution – ~size of a bacterium – visible light passes through specimen – can be used to study live cells • TEM Transmission electron microscopes – used mainly to study internal structure of cells • aims an electron beam through thin section of specimen rabbit trachea cucumber seed leaf • SEM Scanning electron microscopes – studying surface structures • sample surface covered with thin film of gold • beam excites electrons on surface • great depth of field = an image that seems 3-D rabbit trachea Cell size • Cells are quite uniform in size • Size is limited by the surface area to volume ratio. Cell shape • • • • • Cell shape (form) is related to function Skin cells flat Blood cells mobile Muscle cells contracting fibers Nerve cell have wire-like parts Cell types • Prokaryotic cells: (no nucleus) – Bacteria cells are really small and often have cilia or flagella for movement. You really can’t see them with our microscopes. • Eukaryotic cells: (lots of parts) – Plant cells tend to be boxy because of their rigid cell wall. – Animal cells are flexible Cell types--all have cytoplasm, ribosomes, cell membrane, DNA • Prokaryote: bacteria cells – – – – No nucleus or other membrane bound parts Cell membrane and a cell wall DNA in a loop Small and simple • Eukaryote: ALL OTHER CELLS! – plant, animal, fungi, protist – Many specialized parts--organelles – DNA in a nucleus **Plant cells have extra parts--chloroplasts, cell wall made of cellulose, large central vacuole Cell Parts: organelles • Cell Membrane/plasma membrane – All cells – Controls access • Cell wall – Plant cells and prokaryotes (bacteria) – Second layer, protective • Cytoplasm – “cell juice” – Cytosol (water and dissolved stuff/electrolytes) and organelles Vesicles: bubble like dealies • Vacuoles: storage – Large in some plant cells • Peroxisomes: detox of chemicals – Lots in liver cells • Lysosomes: digestive vesicles full of enzymes More organelles • Chloroplasts: use photosynthesis to store solar energy in glucose molecules • Centreoles: involved in mitosis (cell division) • Flagella: long swimming hairs • Cilia: short swimming hairs. Might move mucous. • • • • Now You Know HOOKE AND Leeuwenhoek Schleiden and Schwann Cell theory (3 parts) Organelles: – cell membrane – cell wall – nucleus – nucleolus – chromatin – ER – ribosomes – golgi bodies – mitochondria – vacuole – lysosome – peroxisome – centrioles – chloroplast – cytoskeleton Body types • Unicellular: single celled • Colonial: many cells, loosely connected like volvox algae • Aggregate: like slime molds • Multicelled: many cells – – – – – differentiated Specialized Division of labor Cellular communication Tissues, organs, organ systems Cell Membrane • Semi-permeable--some things can pass through • Lipid bi-layer--two layers of Phospholipids • Contains: – Phospholipids: polar head and non-polar tails – Membrane proteins: Channels for stuff, receptors for hormones and neurotransmitters, markers for immune system – Cholesterol: structure • Fluid mosaic model: all parts of the cell membrane are floating around each other. How molecules cross the plasma membrane Membrane function • Maintain homeostasis! • Passive transport: no cellular energy needed. – Diffusion: molecules move from high concentration to low concentration • How a smell spreads through the air • How ink spreads in water – Osmosis: diffusion of water • Why salt water dries things out • Why the water spray makes the produce crisp – Facilitated diffusion: diffusion through channels. • Simple diffusion goes right through the membrane Osmotic pressure • When water enters or leaves cell and inflates or deflates it • Depends on concentration of salts dissolved in the water of the cell compared to the environment. – Hypotonic: you in salt water – Hypertonic: salmon in fresh water – Isotonic: just right What type of solution are these cells in? A B C Hypertonic Isotonic Hypotonic