B1- Transport in cells

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  • Created on: 18-04-22 16:18
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  • B1- Transport in cells
    • Diffusion
      • Spreading out of particles or a gas or in a solution.
        • Net movement of particles from a region of high concentration to low concentration.
          • Movement of particles is random
      • Can occur quickly in water but must be hot as hot water particles have more energy than cold water particles.
        • Substances that can diffuse across a cell membrane are: glucose, water, amino acids and oxygen.
      • Factors that affect rate of diffusion
        • Temperature, concentration gradient and surface area
          • Concentration gradient- larger CG= faster diffusion
          • Temperature- Higher temp. give particles more energy and increase rate of diffusion
          • Surface area- lager surface area= faster diffusion
      • Surface area to volume ratio
        • The surface area defines how quickly organisms can absorb substances
      • Exchange Surface
        • Alveoli: They are very thin, are moist, have large combines surface area, and covered by a network of fine capillaries.
          • Villi: Theyt are very thin, have a large combined surface are and are covered by lots of caplillaries.
    • Osmosis
      • Special type of diffusion, where water moves from an area of high water concentration to low water concentration through a PARTIALLY PERMEABLE MEMBRANE.
        • Therefore it moves from a dilute solution to a concentrated solution.
          • Dilute- Contains high concentration of water and low concentration of sugar.
            • Water- SOLVENT
            • Sugar- SOLUTE
          • Concentrated- contains low concentration of water and high concentration of sugar.
      • ISOTONIC- If trhe concentration of solute outside the cell is the same as the internal concentration.
        • HYPERTONIC- If the concentration of solute outside the cell is higher than internal concentration.
        • HYPOTONIC- If concentration of solute outside the cell is lower than the internal concentration.
    • Active Transport
      • Movement of dissolved molecules into or out of the cell through a cell membrane, from a region of low concentraion to a region of higher concentration
      • Involves the movement of substances
      • Occurs in digestion, lots of sugar already in blood and very little in gut so sugar is moved up a concentration gradient into the blood.
    • Differences between transport in cells
      • Diffusion and osmosis occur down a concentration gradient (High to low)
        • Active transport occurs up a concentration gradient (low to high)
      • Diffusion spreads its particles around an area.
      • Osmosis is specifically about water.
      • Osmosis occurs through partially permeable membrane, diffusion occurs anywhere


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