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Cell Biology

Cell Biology. Honors CS2 Ms. Levensailor. The Cell Theory. All living things are made of cells! Lowest level of structure. Cells are the basic unit of structure and function in living things! Capable of performing all the activities of life. All cells come from pre-existing cells.

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Cell Biology

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  1. Cell Biology Honors CS2 Ms. Levensailor

  2. The Cell Theory • All living things are made of cells! • Lowest level of structure. • Cells are the basic unit of structure and function in living things! • Capable of performing all the activities of life. • All cells come from pre-existing cells.

  3. Two Major Classes of Cells • Prokaryotic Cells: lacks a nucleus and other organelles. • Bacteria • Archaea • Eukaryotic Cells: has a nucleus and organelles surrounded by membranes. • Protists, fungi, plants and animals

  4. Eukaryotic • Greek meaning “true kernel” • Kernel refers to the nucleus • 10 to 100 micrometers

  5. Prokaryotic • Much simpler in structure • Smaller in size (1 to 10 micrometers in diameter)

  6. Cell Size • Size directly relates to function! • Logistics of carrying out metabolism sets limits to cell size. • Lower limits: Mycoplasmas (bacteria) • Smallest packages with enough DNA to program metabolism • Also enough enzymes to sustain itself and reproduce.

  7. Cell Size Continued • Upper limits: as a object increases in size, its volume grows proportionately more than its surface area. • Area is proportional to a linear dimension squared • cm2 • Volume is proportional to the linear dimension cubed. • cm3

  8. Surface-to-Volume Ratio • The smaller the object, the greater its ratio of surface area to volume. • Area / Volume

  9. Cell shape and rates of diffusion • With your face partner do pre-lab 6 • www.biology.com • A high surface-to-volume ratio facilitates the exchange of materials between a cell and its environment.

  10. Cell shape and rates of diffusion • Plasma membranes function as a selective barrier that allows sufficient passage of: • Oxygen, nutrients, and wastes • For each square micrometer of membrane, only so much of a particular substance can cross per second.

  11. Cell shape and rates of diffusion • If a cell were very large, rates of chemical exchange would be inadequate to maintain the cell. • This explains the microscopic size of most cells. • Larger organisms don’t have larger cells, just more cells.

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