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Photosynthesis/respiration Living things use energy to maintain homeostasis Photosynthesis = the process by which autotrophs capture energy from the sun.

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Presentation on theme: "Photosynthesis/respiration Living things use energy to maintain homeostasis Photosynthesis = the process by which autotrophs capture energy from the sun."— Presentation transcript:

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 CO H 2 O C 6 H 12 O O H 2 O 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. C 6 H 12 O O 2 6 CO H 2 O + ATP energy

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

3 Photosynthesis captures energy from the sun and stores the energy in the chemical bonds of glucose. Sun energy + 6 CO H 2 O C 6 H 12 O O H 2 O Occurs in chloroplasts in mesophyll cells in leaves. CO 2 and O 2 enter/exit leaves via stomata on leaf surfaces. Recall structure of chloroplast Phospholipid bilayer outer membrane Grana = stacks of thylakoids Stroma = space outside thylakoids Inner thylakoid space = pace inside thylakoid Chlorophyll = light sensitive pigment. Drives photosynthesis Combined process of light dependant and light independent Rx

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 ( ) Visible light spectrum ROYGBIV nm ( ) Light reflected is what we see Other are absorbed Plants use red and blue in photosynthesis Photon = mass of energy contained by all of ER

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 Photosynthetic pigments Chlorophyll a b carotenoids Generate: NADPH, ATP (by photophosphorylation) and O 2 Photosystem I and Photosystem II P700 P680

7 Noncyclic light dependant Rx 1.Light hits P680 in photosystem II. 2.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 H+ ions in inner thylakoid space (2) e- to replace those lost (2) in P680 O2O2

8 Noncyclic light dependant Rx 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. Now to continue our story…. 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? chemiosmosis H+ diffuse down [ ] gradient through ATP synthase To produce ATP (photophosphorylation)

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. 3.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 the carbon fixation pathway known as the light independent Rx or Calvin cycle

10 Light independent Rx Calvin Cycle ATP and NADPH are used to produce glyceraldehyde 3-phosphate from CO 2 (3) Carbon fixation 3 CO RuBP (ribulose biphosphate) 6 3-phosphoglycerate Reduction (6) 3-phosphoglycerate + ATP (6) 1,3-biphosphoglycerate (6) 1,3-biphosphoglycerate + NADPH (6) G3P (1)G3P become glucose or other compounds (5) G3P to regenerate RuBP Regeneration (5) G3P + ATP 3 RuBP Calvin cycle ready to begin again rubisco

11 Evolution in photosynthesis C3 plants Carbon fixation involves rubisco Hot dry weather CO 2 as stomata close to reduce water loss via transpiration O 2 can combine with rubisco and be sent to Calvin cycle instead of CO 2 Causing photorespiration = BAD Photorespiration = product broken down with no ADP formation Loss of G3P production No RuBP generated

12 C4 plants Bundle sheath cells arranged around veins of leaves Mesophyll cells between bundle sheaths and leaf surface In mesophyl : CO 2 + PEP (phosphoenolpyruvate) oxaloacetate (4C) PEP carboxylase Fixed carbon brought to bundle sheaths and released to Calvin cycle Minimizes photorespiration and increases photosynthetic productivity Efficient carbon fixation

13 CAM plants CAM plants = crassulacean acid plants succulents As in C4 plants, CO 2 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


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