B4 - Transport in plants

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  • Created by: Naomi
  • Created on: 20-01-13 14:47
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  • Transport in plants
    • Diffusion
      • Random movement of particles
      • High to low concentration
      • Leaves are adapted to increase the rate of diffusion of carbon dioxide and oxygen by having:
        • (Usually) a large surface area
        • Specialised openings called stomata
        • Gaps between the spongy mesophyll cells
      • Rate of diffusion is not a fixed quantity. It can be increase by having
        • A steeper concentration gradient
        • A shorter distance for molecules to travel
        • A greater surface area for the molecules to diffuse from or into
    • Osmosis
      • Diffusion
        • Random movement of particles
        • High to low concentration
        • Leaves are adapted to increase the rate of diffusion of carbon dioxide and oxygen by having:
          • (Usually) a large surface area
          • Specialised openings called stomata
          • Gaps between the spongy mesophyll cells
        • Rate of diffusion is not a fixed quantity. It can be increase by having
          • A steeper concentration gradient
          • A shorter distance for molecules to travel
          • A greater surface area for the molecules to diffuse from or into
      • The movment of water in cells across a partially-permeable membrane
        • From an area of high WATER concentration (dilute) to an area of low WATER concentration (concentrated)
      • From an area of high WATER concentration (dilute) to an area of low WATER concentration (concentrated)
    • Water in cells
      • The entry of water into plant cells increases the pressure pushing on the cell wall
        • This turgor pressure supports the cell, stopping it, and the whole plant, from collapsing
          • When too much water leaves the cell, it loses this pressure and wilts
      • A plant cell full of water is said to be turgid
        • When the cell loses water the cell contents shrink and become pasmolysed and the cell is called flaccid
      • Animal cells will also react to intake and loss of water due to osmosis
        • They will also shrink and collapse when they lose too much water and swell up when too much water enters
          • Since animal cells lack a supposting cell wall, when too much water enters they will swell up and burst (lysis)
            • When too much water leaves an animal cell, it shows crenation by shrinking into a scalloped shape
    • Xylem and phloem cells
      • Both types of tissue are continuous from the root, through the stem and into the leaf
      • Xylem cells carry water and minerals
        • Involved in transpiration
        • Dead cells, their cellulose walls have an extra thickening of lignin for extra strength and support
      • Phloem cells carry food substances such as sugars
        • Involved in translocation
        • Living and arranged in columns
    • Transpiration
      • The evaporation and diffusion of water from inside leaves
        • This loss of water from leaves helps to create a continuous flow of water from the roots to the leaves in xylem cells
      • Transpiration ensures that plants have water for cooling by evaporation, photosynthesis, support from cells' turgor pressure and for transport of minerals
      • The rate of transpiration can be increased by:
        • An increase in temperature
          • Causing an increase in the evaporation of water
        • An increase in light intensity
          • Results in stomata being open
        • An increase in air movement
          • Blowing away air containing a lot of evaporated water
        • A decrease in humidity
          • Allowing more water to evaporate
      • The structure of a leaf is adapted to prevent too much water loss
        • There is a waxy cuticle covering the outer epidermal cells
        • Stomata only on the bottom of the leaf
        • Guard cells are able to change the size of the stomatal opening
          • The guard cells contain chloroplasts, so photosynthesis will produce sugars, increasing turgor pressuure, causing the cells to swell
            • The guard cells curve as they swell, opening the stomata
            • Photosynthesis needs water, so this only happens when water needs to exit the leaf because there is water for the guard cell to use
        • Other ways to reduce water loss:
          • Smaller stomata
          • Fewer stomata
    • Minerals
      • Plants need minerals such as:
        • Magnesium compounds
          • Involved in photosynthesis
          • Magnesium is used to make chlorophyll
          • A lack of magnesium causes yellow leaves
        • Phosphates
          • Involved in respiration and growth
          • Phosphorus is used to make DNA and cell membranes
          • A lack of phosphates causes poor root growth and discoloured leaves
        • Nitrates
          • Make proteins which plants use for cell growth
          • Nitrogen (from nitrates) is used to produce amino acids
          • A lack of nitrate causes poor growth and yellow leaves
        • Potassium compounds
          • Involved in respiration and photosynthesis
          • Potassium is used to help enzyme action in respiration and photosynthesis
          • A lack of potassium causes poor flower and root growth  and discoloured leaves
      • Active transport
        • Transport in plants
          • Osmosis
            • The movment of water in cells across a partially-permeable membrane
            • Water in cells
              • The entry of water into plant cells increases the pressure pushing on the cell wall
                • This turgor pressure supports the cell, stopping it, and the whole plant, from collapsing
                  • When too much water leaves the cell, it loses this pressure and wilts
              • A plant cell full of water is said to be turgid
                • When the cell loses water the cell contents shrink and become pasmolysed and the cell is called flaccid
              • Animal cells will also react to intake and loss of water due to osmosis
                • They will also shrink and collapse when they lose too much water and swell up when too much water enters
                  • Since animal cells lack a supposting cell wall, when too much water enters they will swell up and burst (lysis)
                    • When too much water leaves an animal cell, it shows crenation by shrinking into a scalloped shape
            • Xylem and phloem cells
              • Both types of tissue are continuous from the root, through the stem and into the leaf
              • Xylem cells carry water and minerals
                • Involved in transpiration
                • Dead cells, their cellulose walls have an extra thickening of lignin for extra strength and support
              • Phloem cells carry food substances such as sugars
                • Involved in translocation
                • Living and arranged in columns
            • Transpiration
              • The evaporation and diffusion of water from inside leaves
                • This loss of water from leaves helps to create a continuous flow of water from the roots to the leaves in xylem cells
              • Transpiration ensures that plants have water for cooling by evaporation, photosynthesis, support from cells' turgor pressure and for transport of minerals
              • The rate of transpiration can be increased by:
                • An increase in temperature
                  • Causing an increase in the evaporation of water
                • An increase in light intensity
                  • Results in stomata being open
                • An increase in air movement
                  • Blowing away air containing a lot of evaporated water
                • A decrease in humidity
                  • Allowing more water to evaporate
              • The structure of a leaf is adapted to prevent too much water loss
                • There is a waxy cuticle covering the outer epidermal cells
                • Stomata only on the bottom of the leaf
                • Guard cells are able to change the size of the stomatal opening
                  • The guard cells contain chloroplasts, so photosynthesis will produce sugars, increasing turgor pressuure, causing the cells to swell
                    • The guard cells curve as they swell, opening the stomata
                    • Photosynthesis needs water, so this only happens when water needs to exit the leaf because there is water for the guard cell to use
                • Other ways to reduce water loss:
                  • Smaller stomata
                  • Fewer stomata
            • Minerals
              • Plants need minerals such as:
                • Magnesium compounds
                  • Involved in photosynthesis
                  • Magnesium is used to make chlorophyll
                  • A lack of magnesium causes yellow leaves
                • Phosphates
                  • Involved in respiration and growth
                  • Phosphorus is used to make DNA and cell membranes
                  • A lack of phosphates causes poor root growth and discoloured leaves
                • Nitrates
                  • Make proteins which plants use for cell growth
                  • Nitrogen (from nitrates) is used to produce amino acids
                  • A lack of nitrate causes poor growth and yellow leaves
                • Potassium compounds
                  • Involved in respiration and photosynthesis
                  • Potassium is used to help enzyme action in respiration and photosynthesis
                  • A lack of potassium causes poor flower and root growth  and discoloured leaves
              • Active transport
                • Minerals are taken up by active transport rather than by diffusion or osmosis
                  • A system of carriers transport select minerals across the cell membrane
                • Moves minerals against the concentration gradient (low to high) so requires energy
          • Minerals are taken up by active transport rather than by diffusion or osmosis
            • A system of carriers transport select minerals across the cell membrane
          • Moves minerals against the concentration gradient (low to high) so requires energy

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