Objective: To discuss light waves, how plants absorb light and describe how light dependent reactions occur. 8.2 notes

What are light waves? Sun’s energy= light, looks white but is different wavelengths. Different wavelengths are different colors. Plants gather sunlight with pigments Chlorophyll= main plant pigment Can have chlorophyll a and chlorophyll b

What are light waves? Plants absorb colors blue-violet and red very well. Plants don’t absorb green  they reflect this color, which is why they look green.

How do plants absorb light? When chlorophyll absorbs light, energy is transferred to electrons (in chlorophyll) This makes photosynthesis work

Chloroplasts have thylakoids Thylakoids are in stacks called grana or granum Stroma- space outside of the thylakoid in chloroplast

How do light dependent reactions occur? Photosystems- clusters of pigment and protein that absorb light (within thylakoid) Photosynthesis has 2 parts Light dependent and light independent L. D. = Happens in thylakoid L. I. = happens during calvin cycle in stroma

How do light dependent reactions occur? Light dependent (in thylakoid): photosystem II happens before photosystem I Pigments absorb light, e- are passed on the electron transport chain (transferring energy) New e- are supplied by splitting water into 2 H+ and 1 O (the O is released into the air)

How do light dependent reactions occur? Photosystem I uses light energy to reenergize the e- NADP and the H+ (from photosytem II) => NADPH which carries energy There is a build up of + ions (From the H from photosystem II) on the inside of the thylakoid

Diffusion allows the H+ to leave the thylakoid, but it has to go through ATP synthase. When the H+ goes through ATP synthase ADP+P= ATP!