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2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
2. Absorption & Secretion Of Materials
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2. Absorption & Secretion Of Materials

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

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