Absorption & Secretion of Materials Higher Biology Unit 1
<ul><li>Why do cells need to transport? </li></ul>
<ul><li>What are the different mechanisms of transport? </li></ul>
Key Terms <ul><li>Find definitions for: </li></ul><ul><ul><li>Absorption </li></ul></ul><ul><ul><li>Secretion </li></ul></...
Cell Boundaries <ul><li>What surrounds cells? </li></ul><ul><li>Make notes on the plant cell wall. </li></ul><ul><ul><li>W...
Structure of plasma membrane
Structure of plasma membrane <ul><li>Cell membranes have a structure involving phospholipids, proteins and carbohydrates. ...
Phospholipids
Phospholipids <ul><li>The phospholipids spontaneously form a bilayer due to their hydrophilic phosphate heads and hydropho...
Proteins <ul><li>Protein revision </li></ul><ul><ul><li>What are the monomers? </li></ul></ul><ul><ul><li>What are the bon...
Proteins <ul><li>Transport </li></ul><ul><ul><li>Intrinsic proteins span the membrane and are used by the cell in the tran...
Proteins <ul><li>Enzymes </li></ul><ul><ul><li>Membrane proteins may also act as enzymes. </li></ul></ul><ul><ul><li>E.g. ...
Proteins <ul><li>Receptors </li></ul><ul><ul><li>Proteins have very specific shapes. </li></ul></ul><ul><ul><li>What gives...
Proteins <ul><li>Antigens </li></ul><ul><ul><li>Antigens act as cell identity markers. </li></ul></ul><ul><ul><li>These an...
Glycolipids <ul><li>What are glycolipids? </li></ul><ul><ul><li>Glycolipids are also involved in cell-cell recognition. </...
Diffusion <ul><li>What is diffusion? Can you define it? </li></ul><ul><ul><li>Diffusion is due to the kinetic energy of mo...
Diffusion
Diffusion <ul><li>But how can polar molecules diffuse across membranes? </li></ul><ul><ul><li>Facilitated Diffusion  </li>...
Facilitated Diffusion <ul><li>There are two models for the mechanisms of facilitated diffusion. </li></ul><ul><li>Carrier ...
Facilitated Diffusion
Facilitated Diffusion <ul><li>Channel proteins   </li></ul><ul><ul><li>simply provide selective corridors allowing ions to...
Facilitated Diffusion <ul><li>Facilitated diffusion occurs because of the kinetic energy of the molecules involved. </li><...
Active Transport   <ul><li>Some transport proteins can move solutes against their concentration gradients. </li></ul><ul><...
 
Osmosis <ul><li>Osmosis is a special case of diffusion across a selectively permeable membrane.  </li></ul>What do you rem...
Osmosis <ul><li>Consider two cells separated by a partially permeable membrane:   </li></ul><ul><li>In which direction wil...
Osmosis <ul><li>Effect on cells </li></ul><ul><li>Use the information on p9-11 to explain what happens to plant cells and ...
Bulk Transport <ul><li>How are large molecules transported across the membrane? </li></ul><ul><ul><li>Use p15 to draw diag...
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2. Absorption & Secretion Of Materials

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2. Absorption & Secretion Of Materials

  1. 1. Absorption & Secretion of Materials Higher Biology Unit 1
  2. 2. <ul><li>Why do cells need to transport? </li></ul>
  3. 3. <ul><li>What are the different mechanisms of transport? </li></ul>
  4. 4. Key Terms <ul><li>Find definitions for: </li></ul><ul><ul><li>Absorption </li></ul></ul><ul><ul><li>Secretion </li></ul></ul><ul><ul><li>Diffusion </li></ul></ul><ul><ul><li>Osmosis </li></ul></ul><ul><ul><li>Active transport </li></ul></ul>
  5. 5. Cell Boundaries <ul><li>What surrounds cells? </li></ul><ul><li>Make notes on the plant cell wall. </li></ul><ul><ul><li>What is its structure? </li></ul></ul><ul><ul><li>What role does it play in the movement of substances in and out of plant cells? </li></ul></ul><ul><li>Describe how the chemical nature of cell membranes has been investigated. </li></ul><ul><ul><li>What were the conclusions of this work? </li></ul></ul>
  6. 6. Structure of plasma membrane
  7. 7. Structure of plasma membrane <ul><li>Cell membranes have a structure involving phospholipids, proteins and carbohydrates. </li></ul><ul><li>The model of this structure is described as the fluid mosaic model. </li></ul><ul><ul><li>Why? </li></ul></ul><ul><ul><li>Sketch a 2-D diagram showing the fluid mosaic structure of the cell membrane. </li></ul></ul>
  8. 8. Phospholipids
  9. 9. Phospholipids <ul><li>The phospholipids spontaneously form a bilayer due to their hydrophilic phosphate heads and hydrophobic fatty acid tails. </li></ul><ul><li>The interaction between the phospholipids provide the membrane with stability. </li></ul><ul><li>The structure of phospholipids also provide the membrane with selective permeability. </li></ul><ul><ul><li>What molecules will be able to pass through the phospholipid bilayer? </li></ul></ul>
  10. 10. Proteins <ul><li>Protein revision </li></ul><ul><ul><li>What are the monomers? </li></ul></ul><ul><ul><li>What are the bonds between the monomers? </li></ul></ul><ul><ul><li>Proteins are said to be specific, what does this mean? </li></ul></ul><ul><ul><li>What gives them this specificity? </li></ul></ul><ul><ul><li>How can their function be altered? </li></ul></ul>
  11. 11. Proteins <ul><li>Transport </li></ul><ul><ul><li>Intrinsic proteins span the membrane and are used by the cell in the transport of specific, small, water-soluble substances such as glucose: carrier proteins. </li></ul></ul><ul><ul><li>Specific proteins called channel proteins allow ions to pass through the membrane. Channel proteins are specific and can open & close and are therefore described as gated. </li></ul></ul>
  12. 12. Proteins <ul><li>Enzymes </li></ul><ul><ul><li>Membrane proteins may also act as enzymes. </li></ul></ul><ul><ul><li>E.g. microvilli on epithelial cells lining some parts of the gut contain digestive enzymes in their cell surface membranes. </li></ul></ul><ul><ul><li>Another example of a membrane enzyme is ATPase </li></ul></ul><ul><ul><ul><li>link to photosynthesis & respiration. </li></ul></ul></ul>
  13. 13. Proteins <ul><li>Receptors </li></ul><ul><ul><li>Proteins have very specific shapes. </li></ul></ul><ul><ul><li>What gives them this shape? </li></ul></ul><ul><ul><li>What type of bonds hold it together? </li></ul></ul><ul><ul><li>This makes them ideal as receptor molecules for chemical signalling between cells. </li></ul></ul><ul><ul><li>Can you think of some examples of this? </li></ul></ul>
  14. 14. Proteins <ul><li>Antigens </li></ul><ul><ul><li>Antigens act as cell identity markers. </li></ul></ul><ul><ul><li>These antigens are glycoproteins. </li></ul></ul><ul><ul><li>What are glycoproteins? </li></ul></ul><ul><ul><li>There are numerous possible shapes to the glycoprotein. </li></ul></ul><ul><ul><ul><li>Describe how this feature allows glycoproteins to act as antigens. </li></ul></ul></ul><ul><ul><ul><li>What advantage does this ‘name-tagging’ convey to the organism? </li></ul></ul></ul>
  15. 15. Glycolipids <ul><li>What are glycolipids? </li></ul><ul><ul><li>Glycolipids are also involved in cell-cell recognition. </li></ul></ul><ul><ul><li>With glycoproteins, they are also involved in sticking cells together in tissues. </li></ul></ul>
  16. 16. Diffusion <ul><li>What is diffusion? Can you define it? </li></ul><ul><ul><li>Diffusion is due to the kinetic energy of molecules and occurs because particles of liquids and gases undergo continuous random movements. </li></ul></ul><ul><ul><li>Diffusion occurs across cell membranes through the phospholipid bilayer where concentration differences arise provided the molecules are small or non-polar. </li></ul></ul>
  17. 17. Diffusion
  18. 18. Diffusion <ul><li>But how can polar molecules diffuse across membranes? </li></ul><ul><ul><li>Facilitated Diffusion </li></ul></ul><ul><li>Transport proteins have many of the properties of enzymes: </li></ul><ul><ul><li>they are specialised for the solute they transport </li></ul></ul><ul><ul><li>they can become saturated </li></ul></ul><ul><ul><li>they can become inhibited </li></ul></ul><ul><li>Unlike enzymes, they do not catalyse chemical reactions. Instead they catalyse the physical process of transporting molecules across the membrane. </li></ul>
  19. 19. Facilitated Diffusion <ul><li>There are two models for the mechanisms of facilitated diffusion. </li></ul><ul><li>Carrier proteins </li></ul><ul><ul><li>bind to the molecule to be transported and a change in the shape of the protein results in the molecule being transported across the membrane. </li></ul></ul>
  20. 20. Facilitated Diffusion
  21. 21. Facilitated Diffusion <ul><li>Channel proteins </li></ul><ul><ul><li>simply provide selective corridors allowing ions to cross the membrane, some of which are gated. </li></ul></ul>
  22. 22. Facilitated Diffusion <ul><li>Facilitated diffusion occurs because of the kinetic energy of the molecules involved. </li></ul><ul><li>Energy from metabolism is not required. </li></ul><ul><li>The rate of diffusion is affected by: </li></ul><ul><ul><li>gradient </li></ul></ul><ul><ul><li>surface area </li></ul></ul><ul><ul><li>distance </li></ul></ul><ul><ul><li>temperature </li></ul></ul><ul><ul><li>molecule size & polarity </li></ul></ul>
  23. 23. Active Transport <ul><li>Some transport proteins can move solutes against their concentration gradients. </li></ul><ul><li>To move a molecule across a membrane against its gradient the cell must expend its own metabolic energy. </li></ul><ul><li>ATP supplies the energy for active transport. </li></ul>
  24. 25. Osmosis <ul><li>Osmosis is a special case of diffusion across a selectively permeable membrane. </li></ul>What do you remember about osmosis from SG?
  25. 26. Osmosis <ul><li>Consider two cells separated by a partially permeable membrane: </li></ul><ul><li>In which direction will the net movement of water be? </li></ul>
  26. 27. Osmosis <ul><li>Effect on cells </li></ul><ul><li>Use the information on p9-11 to explain what happens to plant cells and animal cells when they are placed in each of the following solutions: </li></ul><ul><ul><li>Isotonic to the cell cytoplasm </li></ul></ul><ul><ul><li>Hypertonic to the cell cytoplasm </li></ul></ul><ul><ul><li>Hypotonic to the cell cytoplasm </li></ul></ul>
  27. 28. Bulk Transport <ul><li>How are large molecules transported across the membrane? </li></ul><ul><ul><li>Use p15 to draw diagrams and make notes on Endocytosis & Exocytosis . </li></ul></ul><ul><li>Answer the testing your knowledge questions for chapter 2. </li></ul>

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