Photosynthesis

Light Absorption Sun gives off visible light (ROYGBIV) Unabsorbed light reflects to our eyes –Most green light not absorbed by leaves Chlorophyll absorbs sunlight –Absorb mostly reds and blues

The Chloroplast Site of photosynthesis Thylakoid membranes: light dependent reactions Stroma (fluid interior): light independent reactions

Stomata: pore underneath leaves through which gases enter/exit

Photosynthesis Overview Two Stages 1) Light Dependent Reactions –Photosystems: groups of molecules that capture/transfer energy –Creates: O 2, ATP, NADPH 2) Light Independent Reactions –Creates: Glucose

Light Dependent Reactions: Photosystem II Step 1: Chlorophyll absorbs sunlight –Chlorophyll e - become excited & transfer to thylakoid membrane ›Thylakoid membrane becomes negatively charged –Starts an electron transport chain

Step 2 & 3: H 2 O broken into H +, e -, and O 2 ›e - replace those lost by chlorophyll ›O 2 waste ›H + pumped inside the thylakoids and accumulate

e e e e e e ee e e e Thylakoid membrane Thylakoid membrane becomes negatively charged chlorophyll e e ee H H O H H O H H O Oxygen waste is released Electrons replace those which left chlorophyll

Light Dependent Reactions: Photosystem I Chlorophyll absorbs sunlight –Chlorophyll e-e- become excited & transfer to thylakoid membrane ›Accumulate with those from photosystem II e-

NADPH produced (H taxi) ›e - causes H + to bond with NADP ATP produced ›H + ions diffuse and bond ADP with P i H+ ATP

Light Dependent Summary O 2, ATP, NADPH created NO GLUCOSE CREATED!

Light Independent Reactions (Calvin Cycle) Step 1: CO 2 bonds with RuBP (5C) molecule to make a 6C molecule

RuBP CO2 6C molecule

Step 2: 6C molecule splits into two PGAL molecules (3C) »ATP & NADPH provide the energy

6C molecule ATP ADP ATP ADP NADPH

Some PGAL (3C) bonds to make glucose (6C) Some PGAL recycled to start the cycle over

glucose!

CO 2, ATP, & NADPH create glucose Light Independent Summary

Your essay question on the next test! Trace the flow of energy, including ATP, from the sun to your muscles, after eating a green leaf salad.