Chapter 7 Photosynthesis

Overview of Photosynthesis chem rx produces sugar in presence of light 6CO H 2 O  C 6 H 12 O 6 + 6O 2 + H 2 O Requires: light chlorophyll to capture light raw materials (CO 2 and H 2 O) Rate depends on: availability of raw materials light intensity temperature

Light Energy All life on Earth depends on a star 93 million miles away Only 42% of sun’s energy directed towards Earth reaches surface Of this, only 2% is captured by photosynthesizers Of 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 phase 1) Chlorophyll in grana absorbs light photon 2) Energy from photon excites e - 3) Excited e - moves along e - transport chain 4) e - releases energy to form ATP (P+ADP) 5) e - lost from chlorophyll replaced by photolysis: H 2 O  He - + H + + O 2 6) O 2 is released to the environment products = ATP + H + + O 2

Light Reaction in Photosynthesis

Dark Reactions of Photosynthesis also called Calvin Cycle; uses light reaction products to form glucose; occurs in in stroma 1) CO 2 + RuBP (5-C) + ATP  2PGA (3-C) 2) PGA + H +  PGAL (3-C) 3) PGAL used to manufacture RuBP to continue cycle 4) Some PGAL used to manufacture glucose 2 PGAL (3-C)  C 6 H 12 O 6 2 cycles must occur before glucose is made

Dark Reaction (Calvin Cycle)

Simplified Photosynthesis Reaction

Complete Photosynthesis Reactions

The End