Photosynthesis

1
Photosynthesis

• Defined as the process of transferring light
  energy into chemical energy.
• Chloroplasts part of the plant cell were
  photosynthesis occurs. Pg. 112 (green dots)
• Thylakoid a membrane disc that hold chlorophyll
  in the chloroplast.
• Granum a stack of thylakoids.
• Stroma fluid that surrounds the thylakoids in
  the chloroplast.

2
The 3 reactions of photosynthesis

• 1. Light absorption by chlorophyll
• 2. Light Reaction
• 3. Calvin Cycle (dark reaction)
• So, what happens when light strikes a chlorophyll
  molecule?
• 1. Light is given off
• 2. Heat is given off
• 3. It is used to create energy

3

• The light causes the chlorophyll molecules to
  vibrate and release electrons, which is
  electrical energy. Then in the second phase the
  electrical energy is converted to chemical
  energy.
• The transport of these electrons occurs in the
  photosystems of the light reaction.

4

• Photosystem II is where electrons are used as
  electrical energy.
• Photosystem I is where electrons are used as
  chemical energy.
• The energy produced from both photosystems is
  stored as ATP NADPH ? Stored Energy.
• Pg. 114 115 ? Steps

5
Calvin Cycle

• The stored energy in the light reaction (ATP
  NADPH) is used in the Calvin cycle. Also called
  Dark Reaction or Light-independent Reaction.
• CO2 is used to start the cycle. Hydrogen is then
  added with the help of ATP NADPH to complete
  the cycle, in which sugars are produced and
  oxygen is released.
• It stores sugars starches in the leaves.
• Plants stay alive for weeks without light because
  of the stored sugars starches.

6

• Water Carbon Dioxide ? Glucose Oxygen as a
  by-product
• Glucose (C6H12O6) is produced in the Calvin cycle
  (Dark Reaction).
• Pg. 117 ? Steps
• Plants are autotrophs not mobile
• Animals are heterotrophs mobile
• All of the reactions take place in the
  chloroplast of a plant cell (contains
  chlorophyll)
• Calvin Cycle ? stroma
• Light reactions ? thylakoid membrane

7
C4 vs. C3 Plants

• C4 plants are adapted to environments with high
  temperatures and dry conditions. Produce more
  sugars.
• Produce a 4-carbon compound of PGA
• They have enzymes that enable this.
• Ex. Corn, crabgrass, buffalo grass, sugar cane
• Warm Season Plants
• C3 plants are adapted to cooler climates.
• Produce a 3-carbon compound of PGA
• Ex. Wheat, blue-grass, fescue
• Cool Season Plants

8

• CAM plants undergo a process where their stomata
  are open at night closed during the day. Why
  would they do this? Examples?
• This occurs in very hot dry climates.
• Cactuses Pineapples
• Where does the energy come from in plants?
• What are the colors of visible light?
• ROYGBIV
• What color is most absorbed by plants?

9

• Plants use all the colors of the spectrum except
  green. It reflects green the most.
• Two types of chlorophyll ? A B.
• Chlorophyll A does photosynthesis, while
  chlorophyll B helps. Chlorophyll A prefers the
  red wavelength of visible light, which means most
  plants should grow better with that wavelength.
  Pg. 113
• During the fall plants start to lose their
  chlorophyll and other accessory pigments are now
  displayed.
• Carotenoids, xanthophylls, anthocyanins