Cellular Organelle Function

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Cellular Organelle Function

• The Cell Membrane
• how does it work?

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SELECTIVELY PERMEABLE

• What does that mean?
• It doesnt just let anything through.
• Why is this important?
• How does it work?

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What does it look like?

• The cell membrane has two layers
• One layer faces outside the cell
• One layer faces toward the cytoplasm
• The two layers are made up of heads tails

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Heads and Tails

• Scary Molecular Picture!

• Not so scary!

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Hydrophilic Head

• I love the water
• Its my friend
• I can be in the water
• I face the water and the cytoplasm

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Hydrophobic Tail

• I hate the water!
• I face away from the water and the cytoplasm
• The outside tails face the inside tails
• We are hydrocarbons, like oil, we dont mix well
  with water.

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What does it look like?

• Notice the top and bottom, bumpy looking things?
• Those are the hydrophilic head
• Notice they face the outside of the cell and the
  inside.

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What does it look like?

• Notice the squiggly lines inside the hydrophilic
  heads?
• Those are the hydrophobic tails.
• They face away from the water and towards each
  other

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So what can get in?

• Passive Transport
• requires no energy to pass through the cell
• Diffusion
• Osmosis

• Active Transport
• requires cell energy in the form of ATP, which
  it gets from the mitochondria
• Endocytosis
• Exocytosis

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Passive Transport

• Diffusion
• The process by which molecules move from an
  areas of greater concentration to an area of
  lower concentration.

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Passive Transport

• Osmosis
• The diffusion of water
• across a semi permeable
• Membrane

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Molecules of Biology

• Comparison of large and small molecules

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Molecules that easily pass the membrane

• Water Oxygen CO2

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Glucose - Sugar

• Three pictures of the same molecule glucose
• Glucose is a carbohydrate (which means it has H,
  C and O)
• Pure glucose is made by plants in photosynthesis
• It is used for energy

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Compare Sizes of Molecules
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Remember this picture?

• Chemical illustration of the membranes heads and
  tails
• Hydrophilic head
• Has the element Phosphorus
• Hydrophobic tails
• lipids

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Small Molecules May Pass

• Water
• Carbon Dioxide
• Oxygen
• Easily pass because of size and polarity
• These substances do not interfere with the snooty
  lipid layer

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Passive Transport

• Passive transport needs no energy output
• Moves with concentration gradient
• High concentration pushes to low concentrations
• From concentrations that are high to low

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Hydrophilic Molecules

• Need help passing
• When concentration gradient is present they can
  move passively
• Need a port to pass that special only to glucose

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Facilitated Diffusion

• Still passive transport
• Needs no energy
• When high to low
• Needs a special site so lipid layer does not
  reject it
• Site special only to glucose

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Energy Required Transport

• Active Transport
• Uses energy in the form of ATP molecule

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Active Transport

• Endocytosis
• A process by which a
• cell surrounds and
• engulfs substances
• Pinocytosis-large substances
• Phagocytosis-entire cells

• Exocytosis
• The process by which
• wastes are packaged in
• vesicles and vacuoles
• and leave the cell

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Exocytosis
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Pinocytosis
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Phagocytosis
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More Phagocytosis
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Active Transport

• Transport in
• Endocytosis
• Three forms
• One molecule one direction
• Two different molecules-same direction
• Two different molecules-two different directions

• Endocytosis
• Requires special ports or doors called symports
• One molecule
• Uniport
• Two Molecules same direction
• Multiport
• Two molecules different directions
• Anitport

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Symports

• Endocytosis
• Active Transport
• Requires energy to open door

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Uniports

• One molecule
• Against concentration gradient
• From concentrations that are low to high
• Special portal that uses energy

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Symports - Multiports

• Two molecules
• i.e. Na and glucose
• Coming together (especially in liver cells)
• Against concentration gradient
• Need a special port for 2 objects going in same
  direction
• Need ATP to carry out transport

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Antiport

• Two different molecules
• Sodium (Na) and potassium (K)
• Sometimes referred to as Na/K Pump (especially in
  kidney cells)
• Two different directions
• One in
• One out
• Requires special port, uses ATP