3.1 Food supply, plant growth, and productivity

• What happens to light as it comes into contact with the surface of a leaf?

  -Absorbed

  -Reflected

  -Transmitted
• What is a pigment? What happens to the light it does not absorb?

  A pigment is a substance that absorbs visible light, but displays the colour of light it does not absorb (ie light that is reflected or transmitted)
• Name the two main pigments and what wavelengths of light do they absorb?

  The two main pigments are chlorophyll and carotenoids. Chlorophyll absorbs red and blue light, while carotenoids absorb blue and green light.
• What is chromatography used for? describe the process

  •Chromatography is used to separate the photosynthetic pigments.

  -You grind leaves with sand and propanone. This is then filtered to give a mixture of pigments. You then repeatedly spit the pigment mixture on chromatography paper above an origin line.
• What does an action spectra show?

  The rate of photosynthesis carried out in different wavelengths of light.
• What does an absorption spectra show?

  The quantity of light taken in by a pigment at different wavelengths.
• Describe what happens in the Light dependent stage.

  Light energy absorbed by the photosynthetic pigments is used for exciting electrons and transferring them through the electron transport chain, causing the release of energy to pump the hydrogen ions against a concentration gradient. The high concentration of hydrogen ions flow through ATP synthase to generate ATP.

  water is split into oxygen and hydrogen ions. Oxygen is release and the hydrogen ions are transferred to the coenzyme NADP to form NADPH which is used in the Calvyn cycle.
• What can glucose be used for?

  1. respiratory substrate
  2. Synthesised into starch
  3. synthesised into cellulose
  4. passed to other biosynthetic pathways
• What is food security?

  Food security is the ability of the human population to access food of sufficient quality and quantity.
• What is photosynthesis?

  Photosynthesis is the process by which plants convert sunlight, carbon dioxide, and water into glucose and oxygen.
• What is a photosynthetic pigment?

  a photosynthetic pigment is a substance that absorbs light energy and uses it to generate ATP and for photolysis. Each pigment absorbs a different wavelength of light.
• What is the role of an accessory pigment?

  Extend the range of wavelengths of light absorbed and pass the energy onto chlorophyll a