Chapter 7Photosynthesis

Overview of Photosynthesis

chem rx produces sugar in presence of light6CO2 + 12H2O C6H12O6 + 6O2 + H2O

Requires:lightchlorophyll to capture lightraw materials (CO2 and H2O)

Rate depends on:availability of raw materialslight intensitytemperature

Light Energy

All life on Earth depends on a star 93 million miles awayOnly 42% of sun’s energy directed towards Earth reaches surfaceOf this, only 2% is captured by photosynthesizersOf this, only a tiny portion results in biomass

Structure of Plant Cell

Structure of Chloroplast

Process of Photosynthesis

Light Reaction: can only occur in the presence of light; forms materials for next phase1) Chlorophyll in grana absorbs light photon2) Energy from photon excites e-

3) Excited e- moves along e- transport chain4) e- releases energy to form ATP (P+ADP)5) e- lost from chlorophyll replaced by photolysis: H2O He- + H+ + O2

6) O2 is released to the environment

products = ATP + H+ + O2

Light Reaction in Photosynthesis

Dark Reactions of Photosynthesis

also called Calvin Cycle; uses light reaction products to form glucose; occurs in in stroma

1) CO2 + RuBP (5-C) + ATP 2PGA (3-C)

2) PGA + H+ PGAL (3-C)3) PGAL used to manufacture RuBP to continue

cycle4) Some PGAL used to manufacture glucose

2 PGAL (3-C) C6H12O6

2 cycles must occur before glucose is made

Dark Reaction (Calvin Cycle)

Simplified Photosynthesis Reaction

Complete Photosynthesis Reactions

The End