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Chapter 5 Homeostasis and Transport

Chapter 5 Homeostasis and Transport. Section 5.1. Passive Transport. The movement of substances across a cell membrane without any input of energy from the cell. Diffusion. Simplest type of passive transport

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Chapter 5 Homeostasis and Transport

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  1. Chapter 5Homeostasis and Transport Section 5.1

  2. Passive Transport • The movement of substances across a cell membrane without any input of energy from the cell

  3. Diffusion • Simplest type of passive transport • Molecules move from an area of higher concentration to an area of lower concentration • Driven by kinetic energy

  4. Equilibrium • When the concentration of the molecules of a substance are the same throughout a space

  5. Diffusion Across Membranes • Cell membranes allow some molecules to pass through, but not others • Depends on size and type of molecule • Also depends on the chemical nature of the membrane

  6. Osmosis • Water molecules diffuse across a cell membrane from an area of higher concentration of H2O to an area of lower concentration

  7. Direction of Osmosis • Hypotonic- the concentration of solute molecules outside the cell is LOWER than the inside of the cell • Water moves INTO the cell

  8. Hypertonic- the concentration of solute molecules outside the cell is HIGHER than the inside of the cell • Water moves OUT OF the cell

  9. Isotonic- the concentrations of solutes outside and inside the cell are equal • No movement of water occurs

  10. How Cells Deal with Osmosis • Contractile vacuole- organelles to remove water • Turgor pressure- pressure of water against the cell wall • Plasmolysis- cells shrink away from cell walls

  11. Facilitated Diffusion • The movement of molecules across a cell membrane through the use of carrier proteins • First, a carrier protein binds to a molecule on one side of the cell membrane

  12. Second, the carrier protein changes shape shielding the molecule from the interior of the membrane • Finally, the molecule is released on the other side of the membrane

  13. Diffusion Through Ion Channels • Ion channels provide small passages for ions to diffuse across the cell membrane • Channels may have “gates” that respond to stretching of the cell membrane, electrical signals, or chemicals in the cytosol

  14. Ions such as Na+, K+, Ca2+, and Cl- are important for a variety of cell functions

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