The Plasma Membrane and Cell Transport

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The Plasma Membrane and Cell Transport

• Biology
• Sections 7.2 and 8.1

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Plasma Membrane

• Plasma membrane - flexible boundary between a
  cell and its environment.

Outside Cell
Inside Cell
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What is the nickname of the Plasma Membrane?

• The Gate Keeper

Because it maintains homeostasis by controlling
what enters and leaves the cell.
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What does selectively permeable mean?

• Membrane allows some molecules to pass while
  keeping others out.
• Kind of like the screen on your window.

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Structure of the Plasma Membrane.

• Made of phospholipids like the one below

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Phospholipid

• Phospholipid is made of glycerol backbone, two
  fatty acid tails and a phosphate group.

Polar head (includes phosphate group)
Glycerol Backbone
Nonpolar tails (fatty acids)
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Phosholipid Bilayer

• There are two layers of phospholipids back to
  back, making the plasma membrane a phospholipid
  bilayer.

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Model of the Plasma Membrane

• Fluid Mosaic Model

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What can be found in the Plasma Membrane

• Proteins (Transport Proteins)
• Cholesterol - for stabilizing the phospholipids.
• Carbohydrates - identify chemical signals.

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Transport Proteins
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Cholesterol
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Carbohydrates
Carbohydrates
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• Plasma Membrane Activity
• Color/draw the plasma membrane.

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Transport Across the Plasma Membrane

• 2 Main Types
• Passive Transport -
• Moves things with their concentration gradient.
• No energy needed!
• Active Transport -
• Moves things against their concentration
  gradient.
• Requires energy!

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What is a concentration gradient?
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Passive TransportMoves things from high to low
concentration.

• Diffusion - simple movement from high to low
  concentration. No ENERGY required!
• Osmosis - diffusion of water across a selectively
  permeable membrane. (No ENERGY required!)
• Facilitated Diffusion - passive transport using a
  channel or carrier protein. (still does not
  require energy)

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Diffusion
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Osmosis
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Osmotic Pressure
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Turgor Pressure - pressure of the water in a full
vacuole of a plant cell against the cell wall.
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Active Transport

• Protein pump used to move particles from low to
  high concentration.

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Na K
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Transport of Large Particles

• Endocytosis - process by which a cell surrounds
  and takes in material. (Requires ENERGY)
• Exocytosis - the explusion or secretion of a
  material from a cell. (Requires ENERGY)

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Endocytosis
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Exocytosis