Photosynthesis

Question 1

Who all carries out photosynthesis?

Answer 1

• cyanobacteria
• algae
• all land plants

Question 2

Anatomy of chloroplasts

Answer 2

• thylakoid - a sac that contains the pigment chlorophyll
• grana - a stack of thylakoids
• stroma - liquid-filled space between grana

Question 3

Two stages of photosynthesis

Answer 3

1. Light dependent reactions
   
   • captures sunlight to produce ATP and NADPH
2. Light independent reactions (Calvin cycle)
   
   • uses ATP and NADPH to synthesize organic molecules from CO2

Question 4

Light - electromagnetic spectrum

Answer 4

ROYGBIV - energy contained by photons increases from red to violet, while wavelength decreases

Question 5

Pigments

Answer 5

Types
- chlorophyll a & b (green) - absorb all colors except green
- carotenoids (yellow/orange)
absorb all colors but ROY

Question 6

Light dependent reaction

Answer 6

• occurs in the thylakoid lumen
  1. Photosystem II -
  Antenna complex absorbs photons; electron from reaction center is excited; electron is replaced by oxidizing water to produce O2.
  2. ETC -
  excited electron passes through plastoquinone, cytochrome complex, and plastocyanin; transfer causes ATP production that is used to pump protons uphill inside the lumen.
  3. Photosystem I -
  electron loses energy; PS I uses energy from sunlight to excite it again
  4. NADP+ reductase -
  uses excited electron to reduce NADP+ to NADPH
  5. ATP synthase -
  pumps protons downhill out of the lumen and phosphorylates ADP to form ATP.

Question 7

Light independent reaction (Calvin cycle)

Answer 7

1. Carbon fixation
   5RuBP + 3CO2 –> 6x3-PGA
   enzyme - RuBisCO
2. Reduction
   6x3-PGA –> 6xG3P
   Both ATP and NADPH are oxidized in this reaction
3. Regeneration
   5xG3P –> 3xRuBP
   ATP is oxidized

Question 8

Photorespiration

Answer 8

When C3 plants close their stoma to conserve water, O2 gets trapped, causing the activation of the oxygenase function of RuBisCO.