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AP BIOLOGY LAB 4B Photosynthesis

AP BIOLOGY LAB 4B Photosynthesis. DPIP. When chloroplasts are exposed to light, electrons reduce NADP + to NADPH. ELECTRON ACCEPTOR. DPIP= substitute for NADP + DPIP ox = BLUE DPIP re = colorless. SPECTROPHOTOMETER. Measures % light transmitted

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AP BIOLOGY LAB 4B Photosynthesis

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  1. AP BIOLOGYLAB 4BPhotosynthesis

  2. DPIP When chloroplasts are exposed to light, electrons reduce NADP+ to NADPH

  3. ELECTRON ACCEPTOR • DPIP= substitute for NADP+ • DPIPox = BLUE • DPIPre = colorless

  4. SPECTROPHOTOMETER • Measures % light transmitted • If DPIP is oxidized (blue) % transmittance will be low • If electrons are excited and move to reduce DPIP(colorless) % transmittance will increase

  5. SET UP LIGHT SINK Image modified from Holtzclaw & Holtzclaw Study Guide

  6. Cover tube # 2 completely with foilMake a removable foil top

  7. SET UP TUBES Add Phosphate buffer, distilled water, & DPIP totubes as shown WAIT TO ADD CHLOROPLASTS!

  8. SPECTROPHOTOMETER • BLANK has all ingredients except DPIP • Use Blank to calibrate machine • Spectrophotometer is not digital • Slow to respond • Adjust dial and WAIT!BE PATIENT!

  9. ZERO MACHINE • Place BLANK in chamber and close lid • Slowly turn dial on front until window reads 100% (Wait for lag time!) • 100% with blank • 0% with no tube/door closed

  10. Add 3 drops of UNBOILED CHLOROPLASTS to tube #2 • Put Parafilm on top and gently mix • Remove from foil sleeve and immediately put sample in chamber, read % transmittance, and record in lab book • Remove sample from chamber and return to foil sleeve, cover and place in test tube rack under light • Start timer • Take and record readings at 5, 10, & 15 min

  11. REPEAT WITH EACH TUBE • You can run multiple timers • Just make sure you stagger time points so you are not taking readings of multiple tubes at same time • Use cuvette #1 (blank) occasionally to check and adjust the spectrophotometer to 100% transmittance

  12. Image modified from Holtzclaw & Holtzclaw Study Guide

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