Absorbtion and secretion of materials

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Anonymous
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92303
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Absorbtion and secretion of materials
Updated:
2011-06-28 16:15:22
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Absorbtion secretion materials Biology
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Higher Biology - Absorbtion and secretion of materials
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  1. The plasma membrane is said to be _______ permeable?
    selectively
  2. How can moleclues be moved across a membrane?
    • By:
    • diffusion and osmosis
    • active transport
    • endocytosis and exocytosis
  3. Define diffusion
    Diffusion is the movement of molecules or ions from a region of high concentration to a reagion of low concentration down a concentration gradient.
  4. Name three substances that diffuse easily across the plasma membrane
    Oxygen, water and carbon dioxide
  5. Name three substances that diffuse more slowly across the plasma membrane
    Glucose, amino acids and urea
  6. Name a substance that cannot diffuse across the plasma membrane
    Starch
  7. The diffusion of large molecules, such as sugars and amino acids across the plasma membrane involves membrane....?
    proteins
  8. The membrane proteins are _________ for the molecules that they recognise and transport?
    specific
  9. Define osmosis
    Osmosis is the movement of water molecules from a region of high concentration to a region of low concentration down a concentration gradient across a selectively permeable membrane
  10. Why are osmosis and diffusion known as passive processes?
    As they do not require energy
  11. Define hypotonic
    A solution is hypotonic if it has a higher water concentration than the other solution it is being compared to
  12. Define hypertonic
    A solution is hypertonic if it has a lower water concentration than the other solution it is being compared to
  13. Define isotonic
    A solution is isotonic if it has the same water concentration as the solution it is being compared to
  14. What is active transport?
    Active transport is the movement of molecules or ions from a region of low concenration to a region of high concentration ie against a concentration gradient
  15. What type of energy is needed for active transport?
    ATP (adenosine triphosphate)
  16. Active transport requires membrane _______ for the passage of molecules and ions?
    proteins
  17. Give an example of a membrane protein involved in active transport
    The sodium/potassium pump is an example of a membrane protein involved in active transport
  18. What three conditions are required for active transport?
    • Oxygen
    • Temperature
    • Level of respiratory substrate (glucose)
  19. How will these three conditions directly affect the rate of active transport?
    They will affect the rate of respiration which will affect how much ATP is made and therefore affect the rate of active transport
  20. Describe endocytosis
    To absorb very large molecules or particles across the plasma membrane, eg proteins or bacteria, the plasma membrane folds around a substance and encloses it, bringing it into the cell. When this "pouch" becomes detatched from the membrane it is called a vesicle
  21. Describe exocytosis
    To excrete large molecules synthesised by the cell, vesicles from the Golgi apparatus, they move to fuse with the plasma membrane, releasing their contents outside the cell eg proteins such as digestice enzymes or hormones

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