Post on 18-Jan-2018
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Intro to Photosynthesis & the Light ReactionsAP BiologyChapter 10.1-10.2
Learning Target 1 (10.1)I can describe how photosynthesis converts light energy into the chemical energy of food.
Quick Review: Obtaining Energy Life on Earth is solar
powered Directly: autotrophs Indirectly:
heterotrophs
Chloroplasts
Photosynthetic prokaryotes lack chloroplasts photosynthetic membranes = enfolded regions
of the plasma membrane
Key structures:o Stromao Thylakoido Grana
Photosynthesis Equation:
Part I: Light Dependent Reactions (thylakoid membrane)
Part II: Light Independent Reactions (stroma)
oxidation
reduction
Plant Structure Roots Stems Leaves
Epidermis Waxy covering to prevent excess water loss
Mesophyll Contains photosynthetic cells
Stoma Openings for gas exchange Guard cells control
Learning Target 2 (10.2)I can explain how the light reactions work to convert solar energy to the chemical energy of ATP and NADPH.
Light Form of electromagnetic radiation Energy is inversely related to its
wavelength Shorter wavelengths pack more energy
Visible light is 380-750 nm
Plants are green because… Chlorophyll absorbs two wavelengths of
light: Blue (420 nm) Red (660 nm)
Green light is reflected
Light ReactionsPart of photosynthesis that prepares to make glucose
Photosystems Photosynthetic units within chloroplast
grana
Electron Carrier NADP+
Same function as carriers in CR Remember “P” for photosynthesis
Light Dependent Reactions – Non-cyclic (Linear) Electron Flow Produces ATP and NADPH using
Photosystems I & II
1. Sunlight strikes the Photosystem II complex and excites electrons, eventually passing it to the primary electron acceptor
2. Excited electron splits H2O into H+ ions and O2 gas
3. Electrons flow through a series of membrane proteins, pumping H+ ions into the thylakoid space
4. Collection of H+ ions pass back to stroma through ATP synthase in thylakoid membrane
5. ADP is converted into ATP
6. Sluggish electrons receive another photon of light in PSI
7. Excited electrons are passed to NADP reducing it into NADPH
Light Reaction Summary Reactants:
H2O Light NADP+
ADP + Pi Products:
O2 NADPH ATP
Light Dependent Reactions – Cyclic Electron Flow Produces ATP only using photosystem I Evolutionary “leftover” of
photosynthetic bacteria?
Light Dependent Reaction Animation http://
highered.mcgraw-hill.com/olc/dl/120072/bio13.swf