Photosynthesis

I. Introduction A.Goal of photosynthesis To construct food using light energy Food = Glucose Converting radient energy (sun) to Chemical energy.

I. Introduction B. Photosynthetic organisms Called Autotrophs Examples – Plants, Algae

II. The Physics of Light A.Light travels in wave Wavelength – distance peak to peak Frequency – height of wave

II. The Physics of Light B. Visible Light spectrum

II. The Physics of Light C. Energy in light Highest energy = Short wavelength High frequency

III. Photosynthesis and Pigments A.Pigments absorb some colors and reflect others 1. Reflected colors is what we see

III. Photosynthesis and Pigments A.Pigments absorb some colors and reflect others 2. Absorbed colors raises electrons to higher energy levels – generates heat

III. Photosynthesis and Pigments B. Pigments in plants 1. Chlorophyll A – absorbs from ends of visible spectrum 2. Chlorophyll B – absorbs toward the middle of the spectrum

III. Photosynthesis and Pigments B. Pigments in plants 3. Carotenoids – Aid Chlorophyll. Orange and yellow in color

III. Photosynthesis and Pigments C. Chloroplast structure Double membrane Filled with dense solution – Stroma Thylakoid membranes Thylakoids stack up = Grana (granum)

III. Photosynthesis and Pigments C. Chloroplast structure

III. Photosynthesis and Pigments D. Chloroplasts – locations Green areas – mainly leaves

IV. Photosynthesis Process A.Two parts 1. Light Reactions (Sun necessary) Goal – convert sun energy to chemical energy 2. Dark Reactions (No light needed) Goal – Build Glucose

IV. Photosynthesis Process B. The Light Reaction 1. Photosystem 2 Pigments receive sun energy Electrons are raised to high energy level Electrons passed down an Electron transport chain, loosing energy as they go Electron Energy used to convert ADP to ATP Electrons are passed to next step Lost electrons are replaced by splitting water

IV. Photosynthesis Process B. The Light Reaction 2. Photosystem 1 Receives electrons from P2 Electrons energized by sun Two directions for electrons a. Non-cyclic flow Electrons become part of NADPH (Chem. Energy)

IV. Photosynthesis Process B. The Light Reaction 2. Photosystem 1 Two directions for electons b. Cyclic flow Energized Electrons Make H move through enzyme ATP Synthase Makes lots of ATP! Used electrons cycle back

IV. Photosynthesis Process B. The Light Reaction Summary of light reactions Photosystem 2 Sends ATP energy to Dark Reactions Photosystem 1 Non-cyclic – Sends NADPH to Dark R. (High energy electron carrier) Cyclic – Sends ATP to Dark Reactions Key – Light reactions convert sun energy to chemical energy to power the dark reactions

IV. Photosynthesis Process B. The Dark Reactions Called the Calvin Cycle This is the “Glucose Machine” Powered by ATP and NADPH from the light reactions CO2 provides carbon to make Glucose Oxygen is the waste product (Given off from light reaction)