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Starter. Fill in the blanks: Pure water has the highest possible water potential, which is 0 kPa . Solutions always have a lower water potential than pure water, so they have negative water potentials.

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  1. Starter Fill in the blanks: • Pure water has the highest possible water potential, which is 0kPa. • Solutions always have a lower water potential than pure water, so they have negative water potentials. • water always moves from a region of higher water potential to a region of lowerwater potential. (more negative) • If one cell has a water potential of -6kPa and the next one has a water potential of -4kPa, water will move from the cell at -4kPa to the cell at -6kPa. i.e. from higher water potential to lower water potential.

  2. Transport Across a Cell Membrane 1.1.2,i,j,m

  3. Learning Objectives • explain the mechanisms of diffusion, facilitated diffusion (to include channel and carrier proteins). (i) • describe the mechanism of active transport, with reference to the structure of the red blood cell membrane; (j) • explain, in terms of water potential, why the concentration of plasma proteins, glucose and electrolytes will affect the water potential of blood; (m)

  4. Facilitated Diffusion Molecules that are soluble in water or charged particles such as ions, can not diffuse through the phospholipid bilayer. So they diffuse through the plasma membrane with the help of proteins. This type of diffusion is called facilitated difusion

  5. Facilitated Diffusion Some of these proteins are protein channels that are permanently open. They are lined with hydrophilic amino acids and water Molecules can also diffuse through the membrane by binding to carrier proteins. When the molecule binds to the carrier protein, it causes the protein to change shape and release the molecule on the other side of the membrane. Give an example of facilitated diffusion.

  6. Keeping the Osmotic Balance What happens to the water potential in blood plasma if glucose concentration increases? What is going to happen to the red blood cells?

  7. Electrolytes The concentration of electrolytes in plasma and in cells that is responsible for maintaining a water potential balance. What are electrolytes?

  8. Electrolytes are ions with positive or negative charge.

  9. Why is it important to keep normal osmotic balance • Potassium plasma levels should be between 3.5-5.0 mmol dm⁻³. • If levels fall below 3.0 mmol dm⁻³, this can lead to tachycardia and cardiac arrest. • If levels above 6.0 mmol dm⁻³, this is associated with bradycardia and heart failure.

  10. Na⁺ is the major extracellular ion. While K⁺ is a major intracellular ion.

  11. Active Transport Define active transport

  12. Comparing methods of transport

  13. Task In group of three, produce an animation to show active transport, facilitated transport, diffusion, osmosis

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