Lab Notes and Procedures-06 Biology 1004

North Arkansas College

Topic: Photosynthesis

(Experiment 5)

  1. Process by which solar energy from sunlight is used to produce carbohydrates & chemical energy (in the form of ATP).
  2. The chemical bond energy of carbohydrates is eventually converted into useable energy in the form of ATP.
  3. Plants, algae and a few bacteria are photosynthetic. Of these, plants and green algae contain the pigment chlorophyll.
  4. There are 2 types of chlorophyll (A & B). Chlorophyll A absorbs most of the light. Chlorophyll A absorbs mainly violet and visible light (violets and some reds). Chlorophyll reflects the green light.
  5. Chlorophyll B also absorbs light in the blue to green region and transfers the electrons to Chlorophyll A (the active center for photosynthesis).
  6. The overall process of photosynthesis employs the use of CO2 & H20 & Sunlight » CH20 (C6H1206) and 02.
  7. Chlorophyll absorbs a packet of solar energy - photon.
  8. This energy splits water (hydrolysis, photolysis) releasing electron(s), to produce a proton (H+) and release a molecule of 02.
  9. The 02 is given off, the electrons become "excited", and form ATP (and NADPH+). Two pathways are involved in photosynthesis.
  1. The Light Dependent Pathway (reaction) requires solar energy in the form of sunlight. This process is described in Steps 7-9. This process also uses 2 other pigments besides chlorophyll A & B: carotenes - yellows and oranges, xanthophylls - yellow.
  2. The Light Independent Pathway (or Calvin-Benson Cycle) occurs in the dark and in light, but it does not require the light. In Step 1, CO2 (carbon dioxide) is fixed to a five-carbon compound (RuBP = ribulose biphosphate). This is unstable and breaks down to two three-carbon compounds. In Step 2, the three-carbon compound is reduced by NADPH and forms PGA (phosphoglyceric acid). In Step 3, PGA is converted to glucose (C6H1206), other carbohydrates, and regenerate RuBP to continue the cycle. Glucose and other carbohydrates form the chemical bond energy that is used as a nutrient by plants and all other species.

Chromatography

Chromatography separates compounds on the basis of their solubility in a solvent. The more soluble the substance is in the solvent, the further it moves during chromatography. The less soluble it is, the slower it moves. Solvent: 90% petroleum ether and 10% acetone.

Lab Project

For experiment, cut up piece of elodea, and put cut end up to give off 02. Measure the 02 given off. Calculate the Rf for each pigment. Measure the distance in mm from sample line to top where solvent migrated. Measure from the center of sample line to center of each pigment line.

Distance pigment moved

Distance solvent moved

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