welcome to cell biology!
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Welcome to Cell Biology!. it's alive!. Cell Theory. 2.1: Outline the Cell Theory 2.1.2: Discuss the Evidence for Cell Theory. Cell Theory. Living organisms are composed of cells Cells are the smallest unit of life - PowerPoint PPT PresentationTRANSCRIPT
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Cell Theory
• 2.1: Outline the Cell Theory• 2.1.2: Discuss the Evidence for Cell Theory
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Cell Theory
1. Living organisms are composed of cells2. Cells are the smallest unit of life3. Cells come from pre-existing cells, by division
(so that new cells cannot be constructed from non living substance)
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The History of Cell Theory
Let’s meet who discovered cells…Meet the Scientists...
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1. All living things are made of cells…
Digestive Tissue Goblet Cells http://www.olympusmicro.com/galleries/abramowitz/index.html 6.11.12
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How do we know that all living things are made of cells?
Because we can SEE them through microscopes….
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When we we first start talking about ‘Cells’?
Robert Hooke coined the term ‘cells’ since he felt that the space-filled chambers of dead cork resembled a monk’s empty cell…
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Cell Theory: Robert HookeMicrographia, 1665:
. . . I could exceedingly plainly perceive it to be all perforated
and porous, much like a Honey-comb, but that the pores of it
were not regular. . . . these pores, or cells, . . . were indeed the first microscopical pores I ever saw,
and perhaps, that were ever seen, for I had not met with any Writer
or Person, that had made any mention of them before this. . .
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The Father of Microscopy: Van Leeuwenhoek
The first man to visualise single-celled animals (he called protists animacules): 1674Microscopy bytes
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Nothing smaller can survive independently
If a cell is broken down into its individual components, its
subunits cannot survive independently
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3.All cells come from pre-existing cells: ‘Omnis Cellula e cellula ‘
• Disproving spontaneous generation
• Pasteur
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Limitations to cell theory
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Limitations 1: There are many unicellular organisms
• Mobile amoeba
Primitive unicellular organisms carry out all of the functions of life• Prostista • Paramecium• Amoebae• Giant amoebae!
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Limitations to cell theory: multinucleated cells (syncytiae)
• Skeletal and cardiac muscle
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Limitations to cell theory: multinucleated cells (syncytiae)
Fungal hyphae (phase contrast microscopy)
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How large are cells?
Let's put things into perspective....
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What units do we use to measure cells and cell components?
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Size is relative….
Organism Size
Prokaryotic cell 1 – 10 μm
Animal Cell 10 – 30 μm
Plant Cell 10 – 100 μm
Virus < 100 ηm
DNA molecule 2 ηm
Phospholipid membrane 10 ηm
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How do microscopes work?
• Anatomy of vision
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Magnification and scale bars
• You will often need to calculate the actual size of a specimen/ component of a cell from a microscope image, or a photograph/micrograph
• The first step is to ensure that all parts of your calculation have the same units!!
Magnification = size of imageactual size of
specimen