B3: Living Together Food and Ecosystems

  • B3: Living Together: Food and Ecosystems
  • OCR 21st Century
  • Created by: Monoruvwe
  • Created on: 17-02-19 14:48
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  • B3:Living Together (Food and Ecosystems)
    • Transport in Plants + Prokaryotes
      • Single celled organisms are only 1 cell big (which makes diffusion a lot easier)
      • in multicellular organisms, some cells are deep inside an organism
        • This makes diffusion difficult because it's a long way from them to the outside enviroment and so specialised exchange surfaces are needed.
      • Plants
        • Carbon dioxide and oxygen move in out of plant cells by diffusion
        • Lower surface of leaf is full of tiny pores called stomata
        • Stomata let carbon dioxide and oxygen diffuse in out
          • Also allow water vapour to escape
      • Roots hairs
        • Plants take both water and ions in through their roots
        • Cells on plant roots grow long 'hairs' which stick out into soil
    • Diffusion, Osmosis and Active transport
      • Diffusion
        • The net movement of particles from an area of higher concentration to an area of lower concentration
        • Happens in both liquids and gases
        • Continues until concentration of diffusing particles are EVEN in BOTH areas
      • Osmosis
        • The net movement of water molecules across a partially permeable membrane form area of higher concentration to lower concentration
        • Water Molecules actually pass through both ways
          • Happens because water molecules are moving all the time
        • Steady net flow of reigon with fewer water molecules
        • Dilutes strong sugar
        • Important because plant don't have skeletons
          • This means that the cells being the right size and shape matter
            • When plant cells take water, they stretch and bulge
    • Photosynthesis
      • What is it?
        • A series of Chemical reactions in the cells of producer.
        • Plants make their own food in the form of glucose
        • Glucose= Made from Carbon dioxide and water by photosynthesis
      • Equation Model
        • Uses words to represent the reactants and products
        • Carbon dioxide + Water ---> Glucose + Oxygen
        • CO  + H O -> C H C O  + O
      • 2 stage Model
        • Can be summarised in two main stages
      • Inside a Leaf Cell
        • Contain organelles called chloroplasts
        • Each chloroplast contains chlorophyll
        • Chloroplasts contains enzymes needed for photosynthesis
      • Energy
        • Only happens in light
        • Without the sun (or another light source)= NO PHOTOSYNTHESIS
        • An endothermic process
        • Endothermic= A process that transfers energy from its surroundings, make them cooler.
      • Rate of Photosynthesis
        • Temperature
          • Too slow= Can't photosynthesise
          • Untitled
          • Too High= Enzymes become denatured
            • Happens about 45 degrees Celsius
        • Carbon Dioxide
          • One of the substrates needed for Photosynthesis
          • More Carbon dioxide= Increased rate of photosynthesis
          • However after a certain pint, carbon dioxide is no longer a limiting factor.
        • Light
          • Light transfers energy needed for photosynthesis
          • Increased light level=  Increased rate of photo synthesis
          • Distance of Light source and light intensity are INVERSELY proportional
          • Distance increases= Light intensity decreases
          • LI  1 divide by d
    • Enzymes
      • What are they?
        • Biological Catalyst
        • Speed up chemical reactions.
        • Catalyse recations
        • Break down larger molecules into smaller ones.
        • Proteins
        • Made up of a long chain of amino acids
      • What is the use?
        • Biological temperatures are from 0 to 50 degrees Celsius
        • This WAY too slow to support life.
        • Increasing Temperature helps. but it also damages cells
        • Enzymes can increase rate of reaction by up to 10 billion times
        • IMPOSSIBLE to live without
      • Rate of reaction
        • PH
          • Too high/low = Interferes with bonds holding them together
          • Changes shape of active site and denatures enzyme.
          • All enzymes have an optimum PH (often 7, but not always)
        • Temperature
          • Higher temperature = Faster rate of reaction
          • Enzymes and substrates have more energy meaning they move about more.
          • Too Hot= Bonds will break and enzymes become denatured.
        • Substrate Concentration
          • Higher substrate concentration=Faster Reaction
          • Due to Enzyme more likely to meet up and react with a substrate molecule
          • Only true up until a point
          • After all the active sights are full, there will be no increase.
      • Lock and Key Model
        • 1) An enzyme has an active sight
        • 2) Only the correct substrate fits into the active site
        • 3) The reaction takes place in the active site
        • 4) The products molecules leave the active site.
        • The enzymes is not permanently changed can be used again
    • Xylem, Phloem and Stomata
      • Xylem
        • Plant tissue that transports water and dissolved minerals through a plant
        • Made of dead cells joined together end to end
        • Have a hole down the middle
        • Thick side walls are made of cellulose
        • Cells walls are also strengthened by lignin
        • Take water and water up the stem from the root
      • Pholem
        • A plant tissue that transports sugar through the plant
        • Made of columns of living cells called sieve tube elements
        • Sieve tubes have no nucleus
        • Pholem vessels transport food substances up and down the stem (translocation)
        • Sugars enter through active transport
      • Stomata
        • Tiny holes in the outer surface of a leaf that enable a plant to exhange gases with its surrounding
        • Open and close automatically
        • surrounded by guard cells which change shape to control size
        • Sensitive to light
    • Transpiration
      • The process of water movement through a plant and its evaporation from cells in the leaves
      • Pulls water thrugh plant
      • rate of  water uptake
        • Temperature
          • Warmer = faster
        • Light intensity
          • Brighter= greater
        • Air Movement
          • More air= faster

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