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Chapter 3

• AP I
• The Cell pages 92-107

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Passage through membranes

• In passive movement there is no expenditure of
  energy
• This includes 4 categories
• Simple diffusion
• Filtration
• Facilitated diffusion
• Osmosis

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Simple diffusion

• The movement of materials across membranes, in
  air, or in water from areas of greater
  concentration to areas of lesser concentration
  until equilibrium is reached
• This doesnt require the cell to expend energy
• Examples are perfume diffusing through the mall,
  alka-seltzer diffusing in your glass

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Facilitated Diffusion

• Diffusion using a carrier protein
• It still does not require the cell to expend
  energy
• http//www.lionden.com/cell_animations.htm
• http//www.johnkyrk.com/index.html for animations
  of many things

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Osmosis

• Movement of water molecules from greater water
  concentration to lesser concentration (think
  about a glass of tea with a spoonful of sugar in
  it versus one with no sugar)
• One of the interesting concepts that occur with
  osmosis is tonicity. There are three types of
  solutions based on tonicity.
• Isotonic-equal solid
• Hypotonic-less solid
• Hypertonic-greater solid
• http//www.tvdsb.on.ca/westmin/science/sbi3a1/Cell
  s/Osmosis.htm

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Isotonic

• If a human blood cell is placed in an isotonic
  solution (in a test tube) the two solutions have
  equal concentrations of salt.
• Human blood is approximately 0.9 percent salt
  (saline) and the isotonic solution would also be
  0.9.
• In this environment the fluids (water) leaves the
  cell and enters it at the same rate, so the cell
  is not adversely effected.

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hypotonic

• If our human blood cell is placed in a hypotonic
  solution, the concentrations of salt are not
  equal.
• The hypotonic solution has less salt (pure water
  for example.)
• In this situation, the water will flow into the
  cell and the cell may rupture.
• A good way to remember this Where salt goes,
  water follows.

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hypertonic

• This is the opposite of hypotonic.
• This time the blood cell will lose water because
  more salt is outside the cell.
• This can cause dehydration and death.
• The scientific word for this shrinking is
  crenation.

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Active transport

• The cell has to use energy (ATP)
• This time the movement is from less concentration
  to more
• Includes the processes of endocytosis,
  exocytosis, and receptor mediated endocytosis

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Endocytosis

• This involves the movement of material into a
  cell
• There are two types pinocytosis (cell drinking)
  and phagocytosis (cell eating)
• One involves the movement of fluids into the cell
  (pinocytosis)
• The other involves the movement of solid
  particles into the cell (phagocytosis)

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Pinocytosis
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Receptor Mediated Endocytosis
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Receptor mediated endocytosis

• This is the movement of materials into the cell
• The difference between this and regular
  endocytosis is that the material (food) must
  attach to a protein receptor to enter the cell
• An interesting clinical application we have LDL
  receptors in our liver that help catch the
  cholesterol in our blood and lets the liver
  process it
• People with hypercholesterolemia have a limited
  number of LDL receptors in the liver, and have
  high cholesterol levels that usually result in
  early death due to stroke

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Exocytosis

• This involves the removal of material from a cell
• One example is products that have been packaged
  by the golgi apparatus are exported from the cell
  in this manner
• Also the cell can get rid of waste in this manner
• Transcytosis combines endocytosis and exocytosis
  to move a substance from one end of the cell to
  the other.

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Cell division

• When a human cell divides it must go through a
  series of steps
• The first step is called interphase and is
  necessary to duplicate the cell contents
  (including the DNA of the chromosomes

• The remaining steps (called mitosis) are
• Prophase
• Metaphase
• Anaphase
• Telophase
• The end result is two identical daughter cells,
  each containing 46 chromosomes

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Centrioles

• These are important in cell division
• They produce a structure called a mitotic spindle

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Interphase
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Prophase
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Metaphase
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Anaphase
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Telephase
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Terms and reading assignment
cytokinesis division of the cytoplasm karyokinse
sis-division of nuclear material Cleavage
furrow-membrane that forms during
cytokinesis Read control of cell division (p.
105-106) what is the difference between a benign
tumor and a malignant tumor? Read about stem
cells and progenitor cells. (what is the
difference?)
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Cell animations

• http//www.johnkyrk.com/
• http//vcell.ndsu.nodak.edu/animations/
• http//www.stolaf.edu/people/giannini/biological2
  0anamations.html
• Mitosis
• http//highered.mcgraw-hill.com/sites/0072437316/s
  tudent_view0/chapter11/animations.html