Unit 6

• All living organisms whether plant, mammal, or bacteria, they need energy to survive
• Photosynthesis


  Plants use it to use the energy from light to be used as a store of energy in their own bodies
• ATP (adenosine triphosphate)


  A molecule which provides energy
• Producers/Autotrophs


  Photosynthetic organisms - plants - can be described as the producers or autotrophs (an organism which produces its own food) of the food chain
• Photosynthesis


  1. Energy from sunlight gets transferred

  2. Carbon Dioxide + Water → Glucose + Oxygen + (Energy [ATP])

  3. Via Chlorophyll
• The balanced formula equation for photosynthesis is: 6CO2 + 6H2O → C6H12O6 + 6O2
• The reverse reaction, oxygen + glucose → water + carbon dioxide, is the equation for aerobic respiration
• Monomer


  Glucose is formed as a product of photosynthesis
• Polymer


  Many glucose monomers chemically bonded together
• Starch


  When many glucose monomers are joined together
• Sucrose


  Plants can convert glucose into a "double unit"
• Glucose


  Soluble (dissolves in water)
• Starch


  Insoluble (does not dissolve in water)
• Glucose is a sugar molecule, also called a saccharide
• Starch


  A polysaccharide
• Glucose


  A monosaccharide
• Sucrose


  A disaccharide
• Chloroplast


  The site for photosynthesis to occur, contains chlorophyll
• As sunlight hits the plant cells and light energy is transferred to the chloroplasts, the surrounding energy is entering into the reaction therefore we call this an endothermic reaction
• An exothermic reaction would be the opposite, so heat being released to the surroundings
• Factors affecting the rate of photosynthesis

  • Light intensity
  • Temperature
  • Carbon dioxide concentration
• If one factor is not fully optimised to produce the highest rate of photosynthesis, then that factor is called the limiting factor and it is restricting the rate of reaction
• Light intensity and the rate of photosynthesis

  Directly proportional, but if the distance increases, the rate of photosynthesis would decrease
• Inverse square law


  Describes the relationship between light intensity and the rate of photosynthesis
• Calculating new light intensity when distance changes

  Inew = (dorig^2 / dnew^2) x Iorig
• Leaf adaptations for photosynthesis

  • Broad and flat to give a large surface area
  • Thin to reduce the distance gas molecules have to travel
  • Microscopic pores (stomata) allow water vapour and carbon dioxide to diffuse in and out
• Guard cells


  • Become turgid/rigid when water is present, opening the stomata
  • Become flaccid when lacking water, closing the stomata
• Adaptations of plants in hot climates

  • Needles/spines instead of leaves to minimise surface area for water loss
  • Hair to trap escaping water vapour
  • Thick cuticle to reduce water loss from transpiration
• Transpiration


  Movement of water and mineral ions through the leaves, often from the root hair cells up through the xylem vessel
• Translocation


  Movement of sugar/glucose from the companion cells to the phloem vessels bidirectionally, up or down, the body of the plant
• Functions of water in plants

  • Carry mineral ions
  • Keep cells turgid
  • Cool the leaves
  • Used in photosynthesis
• Movement of water in plants

  1. Enters root hair cells via osmosis

  2. Travels through cytoplasm to xylem vessel (passive process)

  3. Mineral ions enter root hair cells via active transport
• Xylem vessel


  Consists of cells which have died, stacked on top of each other with disintegrated top and bottom cell walls
• Molecules enter the cell membrane

  1. Osmosis

  2. Diffusion through cell walls

  3. Travel through cytoplasm

  4. Reach xylem vessel
• Passive process


  Molecules enter cell membrane
• Mineral ions enter root hair cell

  1. Active transport from low to high concentration

  2. Proteins in cell membrane actively pump ions into cell
• Active process


  Mineral ions enter root hair cell
• Xylem vessel


  • Consists of stacked dead cells with disintegrated top and bottom walls
  • Sides of walls contain hard lignin
  • Rigid system supports high-pressure water evaporation
• More water evaporates from plant


  More water diffuses up the leaves
• Transpiration occurs


  Water moves up the xylem vessel