Transcript Cytology Notes

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
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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
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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.
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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
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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