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Summary Biology, ISBN: 9781260169614 MLB 111
Lecture notes + summary of textbook on Unit 1.
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MLB 111 – UNIT 1 1MLB 111
Unit 1
Cell Structure and Function
Textbook: pg. 63-67
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, MLB 111 – UNIT 1 2
4.1 Cell Theory
• Cells are too small to see
• Typical eukaryotic cell = 10 – 100 µm
• Robert Hooke first to observe cells = cellulae
• Anton Van Leeuwenhoek observed living cells first
• Matthias Schleiden and Theodor Schwann first invented the cell theory
Cell theory is the unifying foundation of cell biology
1. All organisms are composed of cells and the life processes occur within these
cells
2. Cells are the smallest living things, the basic unit of organization of all
organisms
3. Cells arise only from pre-existing cells
Cell size is limited
• Most cells are relatively small – diffusion of substances in and out of them
• Diffusion is affected by variables such as:
1. Surface area available for diffusion
2. Temperature
3. Concentration gradient
4. Distance over which diffusion must occur
• As the cell size increases, length of time of diffusion from outside to inside
increases
• Larger cells need to:
- Synthesize more macromolecules
- Have correspondingly higher energy requirements
- Produce a greater quantity of waste
• Molecules used for energy and biosynthesis (and any metabolic waste
produced must be removed) must be transported through the membrane
• Rate of this transport depends on both the distance to the membrane and
the area of the membrane available
• Thus, an organism made up of many relatively small cells has an advantage
over one composed of fewer, larger cells
Surface area-to-volume ratio
• Cell size increase = volume increases much more rapidly than it’s surface
area
• Spherical cells: the surface area is proportional to the square of the radius,
whereas the volume is proportional to the cube of the radius
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