Cytology Notes Cytology: the study of cells

A short history of cells 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 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.

Microscopes opened up the world of cells Robert Hooke (1665) –the 1st cytologist How do we study cells? Drawings by Hooke flea cork

The cell theory All living things are made of cells Cells are the basic units of life Cell only come from other cells

–0.2µm resolution –~size of a bacterium –visible light passes through specimen –can be used to study live cells Light microscopes

Transmission electron microscopes TEM –used mainly to study internal structure of cells aims an electron beam through thin section of specimen cucumber seed leafrabbit trachea

Scanning electron microscopes SEM –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 CB HypertonicIsotonicHypotonic