Basis of Photosynthesis Law of conservation of energy: Energy cannot be created or destroyed. Energy can be changed from one form to another. Light energy is used to create sugar, in which energy can be stored in the chemical bonds. Green plants; some bacteria and protists Evolved ca. 3.5 billion YA

Leaf cross section O2 and CO2 Waxy cuticle Xylem and phloem (vascular bundle) Epidermis Pallisade layer (Photosynthesis) Spongy mesophyll (storage; starch) Mesophyll layer Guard cell Guard cell Stoma (pl. stomata) O2 and CO2

Chloroplast ultrastructure: 1. outer membrane 2. intermembrane space 3 Chloroplast ultrastructure: 1. outer membrane 2. intermembrane space 3. inner membrane (1+2+3: envelope) 4. stroma (aqueous fluid) 5. thylakoid lumen (inside of thylakoid) 6. thylakoid membrane 7. granum (stack of thylakoids) 8. thylakoid (lamella) 9. starch 10. ribosome 11. plastidial DNA 12. plastoglobule (drop of lipids) Granum (stacks, 10-100) Thykaloid (lamella; plates) Stroma DNA Ribosomes

Light Reactions Light (photons) absorbed: - in Photosystem II and I -By chlorophylls a 680 and a 700 -in the thykaloid membranes Lumen: phosphorylation; addition phosphates (PO43−) PS II and I: Z Scheme

AKA: photosystem II and photosystem I Z – Scheme Proteins involved: The Electron Transport Pathway from Water (H2O) to NADP+ (the Nicotinamide Adenine Dinucleotide Phosphate, oxidized form). AKA: photosystem II and photosystem I Z – Scheme Proteins involved: PQ = plastoquinol Cytochrome b6 F complex PC = plastocyanin Fd = ferrodixin For an informative video watch https://www.youtube.com/watch?v=_hUxKPSNTl0

Photosystem II and I: Z scheme P680 and P700 = Chlorophyll a that absorbs light at 680 nm and 700 nm (red) High P700 **** P680 **** Fd Electron Transport Chain 4e- PQ Cyt b Complex PC photons 2NADP+ + 2H+ 2NADPH Electron Transport Chain photons 4e- Energy level of electrons NADP reductase ADP + P043- ATP ATP synthase 4e- P700 P680 4 e- low Calvin Cycle (Dark Reaction) 2H20 4H+ + O2

The Calvin Cycle (Dark Reaction): Occurs in stroma of chloroplast; usually in day time (C3). Light is not required 3 CO2 + 6 NADPH + 5 H2O + 9 ATP → glyceraldehyde-3-phosphate (G3P or PGAL) + 2 H+ + 6 NADP+ + 9 ADP + 8 Pi     (Pi = inorganic phosphate, or P034- INPUTS: ATP and NADPH from PSII and PSI CO2 from air a C5 sugar (ribulose-1,5-bisphosphate), part of the Calvin Cycle RuBisCo = Ribulose-1,5-bisphosphate carboxylase/oxygenase, The Calvin Cycle must happen 6 times to produce enough PGAL (AKA 3-phosphoglyceraldehyde) to make one molecule of Glucose (C6H12O6)

Calvin Cycle (C3 plants) Carboxylation, carbon fixation PGAL 6 glucose