Chapter 3: Cell Structure and Function

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Chapter 3 Cell Structure and Function

• Section 3-2 Part 1
• Cell Boundaries and
• Passive Transport

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Maintaining Balance

• Cells must maintain homeostasis
• Need nutrients to function and create energy
• The cell membrane is the boundary between the
  cell and it environment
• Responsible for controlling what enters and
  leaves the cell
• Selectively permeable

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Structure of the Cell Membrane

• Phospholipid bilayer (two layers of lipids back
  to back)
• Phospholipid lipid with a phosphate group
  attached (fig 3.7 p. 54)

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Phospholipid Bilayer
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Makeup of Phospholipid Bilayer

• Fatty acid tails are nonpolar (hydrophobic) and
  phosphate head is polar (hydrophilic)
• Hydrophilic head faces outside and inside of cell
• Hydrophobic tails form cushion between layers
  that keeps water out
• Fluid mosaic model

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Fluid Mosaic Model

• http//glencoe.mcgraw-hill.com/sites/0078695104/st
  udent_view0/unit2/chapter7/concepts_in_motion.html
  

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Other Components of the Cell Membrane

• Cholesterol to stabilize phospholipids
• Proteins
• Transport proteins span the membrane, control the
  movement of large molecules
• Marker proteins aid in immune recognition
• Carbohydrates

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The Cell Wall

• Found in all plant cells, also algae and some
  bacteria
• Located outside cell membrane
• Support and protect
• Made of carbohydrate and protein
• In plants, made of cellulose (carb)

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Passive Transport

• Substances move across the cell membrane without
  the cell expending energy
• Three types
• Diffusion
• Facilitated diffusion
• Osmosis

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Diffusion

• Random movement of molecules from areas of high
  concentration to areas of low concentration
• Works on alcohols, water, small lipids
• http//www.indiana.edu/phys215/lecture/lecnotes/d
  iff.html

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Facilitated Diffusion

• Diffusion of larger molecules with the help of
  transport proteins

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Passive Transport animation

• http//glencoe.mcgraw-hill.com/sites/0078695104/st
  udent_view0/unit2/chapter7/concepts_in_motion.html