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CHAPTER 6 - CELLS Section 6.1 & 6.2 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 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 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) 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 Gives electron microscope (SEM) a 3D image of the surface of the specimen Transmission Used electron microscope (TEM) to study internal stux – gives a cross section 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) 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 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 Similarities & Differences All Cells contain: Plasma membrane made up of a __________ Phospholipid Cytosol bilayer (cytoplasm) DNA Ribosomes Differences: Eukaryotic cells contain membrane bound organelles and the DNA is contained in the nucleus. 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 Prokaryotic cells 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!) Surface area to volume ratio Plasma membrane 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