Photosynthesis/respiration

1. Photosynthesis/respiration Living things use energy to maintain homeostasis Photosynthesis = the process by which autotrophs capture energy from the sun and store it in the chemical bonds of glucose. Occurs in chloroplast. Sun energy + 6 CO2 + 12 H2O  C6H12O6 + 6 O2 + 6 H2O Respiration = process by which living things break down glucose. The energy from the chemical bonds in glucose are captured in ATP molecules for use by an organism to do work.. Occurs in mitochondria. C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP energy

2. Redox RX Oxidation/reduction processes = transfer of energy by the loss/gain of electrons OILRIG Oxidation Is Losing Reduction Is Gaining Electrons moved from carrier molecule to carrier molecule Photosynthesis and respiration use redox Rx to convert the suns energy into energy that is usable by living things

3. Photosynthesis Photosynthesis captures energy from the sun and stores the energy in the chemical bonds of glucose. Sun energy + 6 CO2 + 12 H2O  C6H12O6 + 6 O2 + 6 H2O Occurs in chloroplasts in mesophyll cells in leaves. CO2 and O2 enter/exit leaves via stomata on leaf surfaces. Combined process of light dependant and light independent Rx Recall structure of chloroplast Inner thylakoid space = pace inside thylakoid Phospholipid bilayer outer membrane Grana = stacks of thylakoids Chlorophyll = light sensitive pigment. Drives photosynthesis Stroma = space outside thylakoids

4. light Electromagnetic radiation (ER) = all the wavelengths () of electromagnetic energy Wavelength () = distance between peak  peak of trough  trough Higher frequency () = shorter () lower frequency () = longer () Photon = ‘mass’ of energy contained by all  of ER ROYGBIV Visible light spectrum  400-700 nm () Light reflected is what  we ‘see’ Other  are absorbed Plants use red and blue  in photosynthesis

5. Conversion of light energy into the chemical bonds of glucose occurs In the light dependant (photosystem II and photosystem I) and light independent (Calvin cycle) reactions

6. Light dependant RX Generate: NADPH, ATP (by photophosphorylation) and O2 Photosynthetic pigments Chlorophyll a Chlorophyll b carotenoids Photosystem I and Photosystem II P680 P700

7. Noncyclic light dependant Rx • Light hits P680 in photosystem II. • Two excited electroms (e-) leave P680 (to a higher energy level) • and are captured by a primary e- acceptor. 3. The e- are passed ‘down’ to photosystem I via carrier molecules Plastoquinone (Pq), a cytochrome complex, and plastocyanin. 4. Energy from e- is used to pump H+ from stroma into inner thylakoid space contributing to the production of ATP. 5. When e- reach photosystem I, they join P700 (fill in for missing e-) IN THE MEANTIME An enzyme was used to split water to form O2 H+ ions in inner thylakoid space (2) e- to replace those lost (2) in P680

8. Noncyclic light dependant Rx Now to continue our story…. 6.. Light hits P700 in photosystem I 7. Two excited electroms (e-) leave P700 (to a higher energy level) and are captured by a primary e- acceptor. 8. Electrons are passed from the primary acceptor to a carrier molecule Ferredoxin (Fd) 9. NADP+ reductase transfers the e- from Fd to NADP to form NADPH What happens to all the H+ building up in the inner thylakoid space? H+ diffuse down [ ] gradient through ATP synthase To produce ATP (photophosphorylation) chemiosmosis

9. Cyclic light dependant Rx Produces ATP but no NADPH 1. Light hits P700 in photosystem I 2. Two excited electroms (e-) leave P700 (to a higher energy level) and are captured by a primary e- acceptor. • Electrons are passed ‘down’ and returned to P700 via carrier molecules • Fd from photosystem I and • cytochrome complex and Pc from photosystem II Energy is used to produce ATP via chemiosmosis ATP and NADPH are used in thecarbon fixation pathway known as thelight independent RxorCalvin cycle

10. Light independent Rx ATP and NADPH are used to produce glyceraldehyde 3-phosphate from CO2 (3) Calvin Cycle Carbon fixation rubisco 3 CO2 + 3 RuBP (ribulose biphosphate)  6 3-phosphoglycerate Reduction (6) 3-phosphoglycerate + ATP  (6) 1,3-biphosphoglycerate (6) 1,3-biphosphoglycerate + NADPH  (6) G3P • G3P  become glucose or other compounds • (5) G3P to regenerate RuBP Regeneration Calvin cycle ready to begin again (5) G3P + ATP  3 RuBP

11. Evolution in photosynthesis Carbon fixation involves rubisco C3 plants Hot dry weather  CO2 as stomata close to reduce water loss via transpiration O2 can combine with rubisco and be sent to Calvin cycle instead of CO2 Causing photorespiration = BAD Photorespiration = product broken down with no ADP formation Loss of G3P production No RuBP generated

12. C4 plants C4 plants Bundle sheath cells arranged around veins of leaves Mesophyll cells between bundle sheaths and leaf surface PEP carboxylase In mesophyl : CO2 + PEP (phosphoenolpyruvate)  oxaloacetate (4C) Efficient carbon fixation Fixed carbon brought to bundle sheaths and released to Calvin cycle Minimizes photorespiration and increases photosynthetic productivity

13. CAM plants CAM plants = crassulacean acid plants succulents As in C4 plants, CO2 is fixed into intermediate organic molecules Carbon fixation takes place at night when stomata are open Carbon released into Calvin cycle during the day (stomata closed) when light is available for ATP, NADPH production