3.1 - food supply, plant growth and productivity

• What 4 qualities do breeders seek in developing crops?

  • Higher nutritional values
  • resistance to pests and disease
  • physical characteristics suited to rearing and harvesting
  • ability to thrive in particular environmental conditions
• Advantage of livestock production?

  Possible in managed/wild habitats unsuitable for cultivation of crops
• Disadvantage of livestock production?

  Produce less food per unit area than plant crops due to loss of energy between trophic levels
• What are the 3 fates of light energy when light from the sun strikes a leaf?

  • Absorbed
  • reflected
  • transmitted
• What kind of light can be used for photosynthesis?

  Absorbed light
• What are the 3 photosynthetic pigments?

  • Chlorophyll a
  • chlorophyll b
  • carotenoids
• What photosynthetic pigment is a main pigment?

  Chlorophyll a
• what photosynthetic pigments are accessory pigments?

  • Chlorophyll b
  • carotenoids
• What colours of light does chlorophyll a absorb

  • red
  • blue
• What colours of light does chlorophyll b absorb?

  • Red
  • blue
• What colours of light do carotenoids absorb?

  Colours other than red and blue
• Why do plants appear green?

  They reflect light of the green wavelengths
• Why are other pigments than chlorophyll a important ?

  Accessory pigments extend the range of wavelengths where light can be absorbed and pass the energy to chlorophyll a for photosynthesis
• What is the first stage of photosynthesis?

  light dependent stage
• where does the light dependent stage take place in a plant cell?

  granum of chloroplast
• where does stage 2 of photosynthesis take place?

  stroma of chloroplast
• what is the second stage of photosynthesis?

  carbon fixation
• Label this chloroplast

  A) Stroma

  B) Inner membrane

  C) Outer membrane

  D) Stack of granum

  
• how do electrons travel through the membrane?

  they are excited by light energy which gives them energy to travel
• what is the enzyme that generates ATP?

  ATP synthase
• what is the splitting of water called?

  photolysis
• what is the coenzyme which carries hydrogen to the carbon fixation stage?

  NADP becomes NADPH
• what 3 reactants are required for the carbon fixation stage?

  • ATP
  • NADPH
  • carbon dioxide
• what is the word equation for photosynthesis?

  Carbon dioxide + water - sunlight -> glucose + oxygen
• what enzyme is used to fix carbon dioxide?

  RuBisCO
• how does RuBisCO fix carbon dioxide?

  attaches carbon dioxide to ribulose biphosphate ( RuBP ), producing 3-phosphoglycerate ( 3PG )
• how does 3-phosphoglycerate form glyceraldehyde-3-phosphate ( G3P )?

  Phosphorylated by ATP from stage 1 and combined with hydrogen from NADPH
• what is glyceraldehyde-3-phosphate used for?

  • regeneration of ribulose biphosphate ( RuBP )
  • synthesis of glucose
• what are the 3 fates of glucose?

  • used in respiration as a respiratory substrate
  • used in other anabolic reactions to make starch for storage or cellulose for cell wall
  • passed to other biosynthetic pathways to form a variety of metabolites such as DNA/protein/fat
• Label this image (full names)

  A) RuBisCO

  B) 3-phosphoglycerate

  C) Glyceraldehyde-3-phosphate

  D) Ribulose biphosphate

  E) Carbon dioxide

  F) Glucose

  
• why can glucose not be produced from photosynthesis in the absence of light?

  ATP and NADPH would not be generated
• what is the effect of lower carbon dioxide concentration on carbon fixation?

  RuBP accumulated as it cannot be fixed to carbon dioxide
• Describe the effect of absorbed light energy on the pigment molecules?

  Releases high energy electrons to form ATP by ATP synthase