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CHAPTER 6 - CELLS Section 6.1 & 6.2
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Importance of cells An organism’s basic unit of structure & function is the cell Everything we do occurs fundamentally at the cellular level Thinking Moving Maintaining homeostasis Cells discovered by Robert Hooke in 1665
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Studying Cells How do we understand cells if we can’t see them?
Microscopes allow us to see the inner workings of cells Two main types of Microscopes Light Microscope (LM) – 1665-present Electron Microscope (EM) – 1950’s-present
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Light Microscopes Allow us to see plant & animal cells and the nucleus. Can also see bacteria cells. Light passes through the specimen and lenses, bends the light to magnify the image. Magnification: ratio of an object’s image to its real size (max. about 1,000x) Resolution: measure of the clarity of the image (max. about 200nm – size of bacteria)
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Electron Microscopes Rapidly advance our understanding of cells because we could see subcellular structures Focuses a beam of electrons through the specimen Two types: Scanning electron microscope (SEM) Gives a 3D image of the surface of the specimen Transmission electron microscope (TEM) Used to study internal stux – gives a cross section
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Advantages & Disadvantages
Light Microscopes Advantage: Can study living organisms Disadvantage: Can’t see organelles in detail Electron Microscopes Advantage: Can see organelles in detail Disadvantage: Specimens are killed in preparation process (not for living tissues)
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Cell Fractionation Goal: take cells apart and separate the major organelles from one another Process: Centrifuge spins test tubes at various speeds Cell components separate by size and density Result: Bulk quantity of cellular organelles to study composition and function
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Section 6.2 Two types of cells
Prokaryotic found in Domain _______ & _______ Eukaryotic found in Domain _______ What 4 Kingdoms contain organisms with Eukaryotic cells? 1. Animal 2. Plant 3. Protist 4. Fungi
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Similarities & Differences
All Cells contain: Plasma membrane made up of a __________ Phospholipid bilayer Cytosol (cytoplasm) DNA Ribosomes Differences: Eukaryotic cells contain membrane bound organelles and the DNA is contained in the nucleus.
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Prokaryotic cells: DNA located in nucleoid region
Prefix: pro means “before” Suffix: karyon means “kernel” (nucleus) No membrane bound organelles in cytoplasm Smaller & simpler Cilia and flagella for locomotion Some have cell wall surrounding plasma membrane
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Prokaryotic cells
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Cell Size Cellular metabolism sets a limit on how large a cell can get
The cell needs to bring in oxygen & nutrients and needs to get rid of waste Cell needs to maintain a high surface area to volume ratio to exchange the materials it needs to Larger organisms do not have larger cells just more of them (we have trillions of cells!)
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Surface area to volume ratio
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Plasma membrane
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Eukaryotic cells Contain membrane bound organelles
Larger than prokaryotic cells and more complex Animal & Plant cells Draw a diagram of an animal and a plant cell
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