Homeostasis

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Homeostasis Transport

• Ch.5

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(5-1) Homeostasis

• Cell membranes control what goes in out

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(No Transcript)
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Passive Transport

• Movement of materials across a cell membrane
  without the use of E (ATP)
• 4 Types
• Diffusion
• Osmosis
• Facilitated Diffusion
• Ion Channels

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Diffusion

• Movement of molecules from an area of high
  concentration to low conc.

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Concentration Gradient

• Difference in conc. of molecules across a
  membrane
• Down the gradient
• Move from high to low conc.

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Equilibrium

• Conc. is equal on both sides of the membrane
• Diffusion ends

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Diffusion Across a Membrane

• Depends upon size, shape, chemical makeup
• Easy to diffuse
• Small
• Nonpolar
• (dissolve in
• lipids)

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Osmosis

• Water diffusion across a membrane

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Hypotonic Solution

• Solute conc. is higher inside water conc. is
  higher outside the cell
• Water moves into the cell
• May cause cytolysis
• (cells burst)

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Hypertonic Solution

• Solute conc. is higher outside water conc. is
  higher inside the cell
• Water moves out of the cell
• May cause plasmolysis
• (cells shrink)

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Isotonic Solution

• Solute water conc.s are equal on both sides of
  the membrane
• Equilibrium

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Isotonic
Hypertonic
Hypotonic
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How Cells Deal with Osmosis

• Contractile vacuoles collect
• excess water pump it out of
• the cell
• Requires E
• Turgor pressure P that water exerts against the
  cell wall

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Facilitated Diffusion

• Carrier proteins assist diffusion across a
  membrane
• Specific to certain molecules (glucose)

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Diffusion via Ion Channels

• Ion channels assist diffusion across a membrane
• Some always open, others gated
• Common ions
• Na
• K
• Cl-
• Ca2

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(No Transcript)
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(5-2) Active Transport

• Movement of a substance across a cell membrane
  against a conc. gradient
• Requires E

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Na-K Pump

• Carrier protein that transports K into Na out
  of the cells
• Helps conduction of electrical impulses in nerve
  cells

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Endocytosis

• Cell surrounds engulfs substances
• 2 Types
• Pinocytosis fluids or solutes
• Phagocytosis large particles

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Exocytosis

• Vesicle inside a cell fuses w/ the cell membrane
  releases contents outside of cell
• Proteins, waste, toxins