The%20Plasma%20(Cell)%20Membrane%20and%20Cellular%20Transport

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The Plasma (Cell) Membrane and Cellular Transport
How cells get the materials they need to grow,
develop, and reproduce
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What do all cells have in common?

• In order to grow, develop, and reproduce all
  cells must be able to
• remove waste
• bring in nutrients/water
• bring in oxygen
• What structure allows them to do this?

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The Plasma(Cell) Membrane

• All cells have a cell membrane
• Cell Membrane Functions
• Controls what enters and exits the cell
• Maintains an internal balance called
  HOMEOSTASIS
• Provides protection and support for the cell

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Structure of the Cell Membrane

• How do you build a barrier that keeps the watery
  contents of the cell separate from the watery
  environment?

• ? FATS ?
• ? LIPIDS ?
• Remember oil water dont mix!!

What substance do you know that doesnt mix with
water?
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Structure of the Cell Membrane

• Lipid Bilayer- 2 layers of phospholipids
• phosphate head is polar (water loving)
• fatty acid tails are non-polar (water fearing)
• proteins embedded in the membrane

attracted to water
phosphate head
fatty acid tails
repelled by water
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Cell Membrane Structure continued...

• Cell membranes have pores (holes) in them
• Selectively permeable Allows some molecules in
  and keeps other molecules out

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Cell Membrane Structure continued...
So what needs to get transported across the
membrane?
aa
H2O
lipids
salt
O2
sugar
waste
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2 Types of Cellular Transport

• Passive Transport
• Cell uses NO energy
• Goes WITH the concentration gradient
• Active Transport
• Cell uses energy
• Goes AGAINST the concentration gradient

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Types of Passive Transport Diffusion

• Diffusion the movement of molecules from an
  area of high concentration to an area of low
  concentration
• Occurs until equilibrium is reached
• HIGH ? LOW

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Types of Passive Transport Diffusion

• What molecules can get through the cell membrane
  directly through simple diffusion?
• fats and oils
• gases such as oxygen and carbon dioxide

O2
lipid
salt
waste
but what about other stuff?
aa
H2O
sugar
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Types of Passive Transport Facilitated Diffusion

• Facilitated Diffusion type of passive transport
  that allows substances to cross membranes with
  assistance from special transport proteins
• specific channels allow specific material in out

inside cell
sugar
aa
H2O
salt
outside cell
waste
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Types of Passive Transport Diffusion

• Move from HIGH to LOW

fat
fat
fat
Which way will fat move?
inside cell
fat
fat
fat
LOW
HIGH
fat
outside cell
fat
fat
fat
fat
fat
fat
fat
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Types of Passive Transport Facilitated Diffusion

• Move from HIGH to LOW through a channel

sugar
sugar
sugar
sugar
inside cell
sugar
sugar
LOW
Which way will sugar move?
HIGH
outside cell
sugar
sugar
sugar
sugar
sugar
sugar
sugar
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Types of Passive Transport Osmosis

• Osmosis diffusion of water across a membrane
  both simple diffusion and facilitated diffusion

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Isotonic (Iso Same)

• The concentration of water molecules is the
  same inside and outside the cell.
• Water molecules will move across the membrane
  at the same rate in both directions
• NO NET MOVEMENT

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Hypertonic (Hyper Above)

• Hypertonic solution high solute/ lower water
  on outside
• Water molecules will move out of the cell and
  the cell shrivels
• Plant cells will lose Turgor Pressure ( the
  pressure water molecules exert on the cell wall)
• Called plasmolysis

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Hypotonic (Hypo Below)

• Hypotonic solution low solute/ high water on
  outside
• Water molecules will move IN the cell and the
  cell will swell or possibly burst (cytolysis)
• Plant cells will gain Turgor Pressure ( the
  pressure water molecules exert on the cell wall)
• Called deplasmolysis

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What type of solution are these cells in?
C
B
A
Hypertonic
Isotonic
Hypotonic
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Passive Transport Summary

• No energy required
• Molecules move from HIGH --gt LOW concentration
• Types of Passive Transport
• Diffusion
• Facilitated diffusion
• Osmosis
• isotonic vs hypertonic vs hypotonic

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Cellular Transporta reminder

• Passive Transport
• Cell doesnt use energy
• Goes WITH the concentration gradient
• Active Transport
• Cell does use energy
• Goes AGAINST the concentration gradient

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Active transport

• Cells may need molecules to move against
  concentration hill
• from LOW to HIGH using energy
• uses protein pump

energy
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Transport summary
simplediffusion
facilitateddiffusion
energy
activetransport