4) Photosynthesis Cheat Cheat

Photosynthesis

Light energy from the sun is used to synthesize glucose.

• Chlorophyll A, B and carotenoids absorb energy from sun

• Photons excite electrons

• Excited electrons are unstable and re-emit energy

  • energy is Chlorophyll A has a porphyrin ring with Mg2+ atom inside

Outer membrane

Granum

Stack of Thylakoids

Thylakoid membrane

structure which absorbs light, location of the ETC (non-cyclic photophosphorylation)

Thylakoid Lumen

Location of photolysis. H+ ions accumulate due to ETC

Intermembrane Space

Inner Membrane

Stroma Lamellae

Location of Cyclic PhotophosphorylationS

Stroma

Location of the Calvin Cycle

Light Reaction

Where: Thylakoid Membrane

• The electrons from photolysis trapped by PSII are energized by light

Cyclic Phosphorylation

Where: Stroma Lamellae

• 2 e- from PSI go back through the 1st ETC and generate 1 ATP

• These 2 e- are recycled into PSI and can either go through the cyclic of non-cyclic pathway again

What: ATP

Non-Cyclic Phosphorylation

Where: Thylakoid Membrane

• 2 e- go through an ETC. PSI reduces NADP+ & H+ NADPH using to 2e-

• This NADPH is used in the Calvin Cycle to produce

What: ATP and NADPH

Light Reaction Key Products:

NADPH, O2, ATP

Action Spectrum

Chloroplasts most effective at absorbing red and blue light

Green wavelengths are reflected, making it least effective at photosynthesis

Photolysis

H2O splits into 2H+, 2e-, ½ O2.

• 2H+ is used for NADPH formation

• The 2 e- lost in PSII is replenished through this process

• ½ O2 is released as gas

Photolysis occurs at PSII

Chemiosmosis

Where: Thylakoid Membrane

Uses H+ gradient to create ATP

• H+ accumulated in the thylakoid lumen

  • H+ is released into the lumen through photolysis

  • between PSII and PSI, cytochromes bring H+ into the lumen from the stroma. This creates a pH and an electrical gradient

• ATP synthase uses the H+ gradient and proton motive force to turn ADP into ATP

  • This ATP is used in the Calvin Cycle to create glucose

Dark Reaction (Calvin Cycle)

Where: Stroma of Chloroplast
What: Fixes CO2 into 2 G3P(glucose)

1) Carboxylation

• reaction catalyzed by enzyme RiBisCo

• 6CO2 + 6RuBP → 12 PGA

2) Reduction

• 12 ATP + 12NADPH converts 12PGA to 12G3P

3) Regeneration

• 6ATP convert 10G3P to 6RuBP

4) Carbohydrate Synthesis

• 2 G30 used to form glucose

  • 1 glucose produces after

C4 Photosynthesis

Alters location of photosynthesis

• CO2 moved to bundle sheath cells to minimize photorespiration & H2O loss

• Produces intermediary 4-carbon compound and uses 1 extra ATP

CAM Photosynthesis

WHERE: mesophyll cells

• Fixes Co2 at night instead of day to minimize photorespiration and H2O loss

• C02 converts to malic acid