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Movement of substances across the plasma membrane

Movement of substances across the plasma membrane. Metabolism : all the chemical activities taking place in the cell Consists of two processes: Anabolism Catabolism. Anabolism : the building up of molecules E.g. : synthesis of protein and ATPs, which a cell needs Catabolism :

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Movement of substances across the plasma membrane

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  1. Movement of substances across the plasma membrane

  2. Metabolism : • all the chemical activities taking place in the cell • Consists of two processes: • Anabolism • Catabolism Tr.Rez@SB2013

  3. Anabolism : • the building up of molecules • E.g. : synthesis of protein and ATPs, which a cell needs • Catabolism : • breaking down of large molecules to smaller simpler molecules. • E.g. : oxidation of glucose in cell respiration Tr.Rez@SB2013

  4. Substances that leave the cell Tr.Rez@SB2013

  5. Substances that enter the cell Tr.Rez@SB2013

  6. The structure of plasma membrane

  7. Phospholipid bilayer consists of: • A polar phosphate molecule head which is hydrophilic • Two non-polar fatty acid tails which are hydrophobic Tr.Rez@SB2013

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  9. Permeability of the plasma membrane

  10. Permeability of the phospholipids bilayer • Plasma membrane : • semi-permeable • Allows only certain substances to pass through but not other Tr.Rez@SB2013

  11. Permeability of the phospholipids bilayer • Phospholipid bilayer is permeable to: • Small non-polar (hydrophobic) molecules that are lipid soluble, such as : fatty acids, glycerol, steroids, vitamin A, D, E and K • Small uncharged molecules, such as: water, oxygen and carbon dioxide Tr.Rez@SB2013

  12. Phospholipidbilayer is not permeable to: • Large polar molecules that are not soluble in lipid, such as glucose amino acids, nucleic acids and polysaccharides • Ions (charged), regardless of size, such as: H+, Na+ Tr.Rez@SB2013

  13. Types of transport across the plasma membrane

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  15. Passive transport

  16. Simple Diffusion • Random movement of ions/molecules from a region of their high concentration to a region of their low concentration down a concentration gradient until an equilibrium is achieved • Molecules that can cross are • Small non-polar (hydrophobic) molecules • Small uncharged molecules Tr.Rez@SB2013

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  19. Factors affecting the rate of diffusion: • Diffusion gradient • Size of molecules or ions • Temperature • Diffusion medium • Surface area Tr.Rez@SB2013

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  21. Facilitated diffusion

  22. Facilitated diffusion • Movement of specific molecules (or ions) across the plasma membrane • Assisted by pore proteins / carrier proteins Tr.Rez@SB2013

  23. Pore protein (channel protein) • Charged ions • Open up pore / channels across the membrane to allow entry or exit • Specific Tr.Rez@SB2013

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  25. Carrier proteins • Allow larger polar molecules (such as sugar & amino acids) to cross • A particular protein attaches itself to the binding site of a carrier protein • Then, the carrier protein changes shape and delivers the molecule across the plasma membrane Tr.Rez@SB2013

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  28. Osmosis • movement of water molecules from a region of low solute concentration (high water concentration) to a region of high solute concentration (low water concentration) through semi-permeable membrane Tr.Rez@SB2013

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  30. Examples of osmosis: • Absorption of water by root hairs • Movement of water from one cell to another • Absorption of water in the alimentary canal-stomach, small intestine and colon Tr.Rez@SB2013

  31. Active Transport • Uses carrier proteins and energy to move molecules or ions across the plasma membrane against the concentration gradient Tr.Rez@SB2013

  32. Example of active transport: • Absorption of mineral salts by roots hairs • Absorption of glucose and amino acids by cells in the small intestine Tr.Rez@SB2013

  33. The processes of passive transport and active transport in living organisms

  34. Gaseous exchange in the alveoli and blood capillaries by simple diffusion Tr.Rez@SB2013

  35. Absorption of digested food in the villi Tr.Rez@SB2013

  36. Absorption of water in root hairs of plants by osmosis Tr.Rez@SB2013

  37. 3.2 movement of substances across the plasma membrane in everyday life

  38. Hypotonic, hypertonic and isotonic solution • Isotonic solution : • Solution A and Solution B have the same solute concentration • Hypertonic solution : • Solution A is hypertonic to solution B if solution A has a higher solute concentration • Hypotonic solution: • Solution A is hypotonic to solution B if solution A has lower solute concentration than solution B Tr.Rez@SB2013

  39. Effects of hypotonic, hypertonic and isotonic solutions on plant cell

  40. crenation haemolysis Tr.Rez@SB2013

  41. Plasmolysed (flaccid) turgid Tr.Rez@SB2013

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  43. Phenomenon of wilting in plants

  44. Excessive use of chemical fertilizers release huge amount of ions, such as phosphates, nitrates, calcium, magnesium, and sulphur into soil • Increase solute concentration but decrease water molecules concentration in soil • Water molecules diffuse from the cell sap into soil water by osmosis • Cell plasmolysed, lose turgidity & support = WILT Tr.Rez@SB2013

  45. Preservation of food • Concentrated salt solution has a high concentration of solute (Na+ and Cl- ions) and very low concentration of water molecules • All water molecules inside drawn out by osmosis • Without water, bacteria and water cannot survive Tr.Rez@SB2013

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