Why are cuvettes kept in the dark

Chromatography is a process used to separate mixtures that can separate plant pigments. This lab uses paper chromatography where a piece of paper is used to wick solvent up to the pigments and separate them according to solubilities. The rate of migration on a chromatogram is the Rf value. Plants contain several different pigments, and the rate of photosynthesis in plant cells is directly related to light and temperature. This exercise required 1 mL graduated cylinder, a small amount of a solvent, a stopper, filter paper, scissors, a pencil, spinach leaves, and a quarter.

The materials needed for this part of the lab were a spectrophotometer, a light, a water flask, a test tube rack, ice, 5 labeled cuvettes, lens tissue, foil, and parafilm.

The substances put in the cuvettes were 5 mL of phosphate buffer, approximately 16 mL of distilled water, 9 drops of unboiled chloroplasts, and 3 drops of boiled chloroplasts. A mL graduated cylinder was filled with about 1 cm of solvent and then tightly stoppered. The filter paper was then cut to a point on one end, and a line was drawn 1. Using the ribbed edge of a quarter, spinach cells were extracted onto the pencil line.

This procedure was repeated times using a new portion of the leaf each time. The filter paper was then placed in the cylinder with the tip barely touching the solvent and none of the edges touching the sides. When the solvent reached 1 cm below the top of the paper, it was removed from the cylinder. The solvent location was immediately marked, and then the bottom of each pigment band was also marked.

The spectrophotometer was set to nm and allowed to warm up. The chloroplast suspensions were prepared the previous day, part of which were boiled, and stored on ice until they were ready for use. An incubation area was prepared with a flood light, water flask, and test tube rack, by using the flask as a heat sink between the light and the rack. Five cuvettes were numbered respectively and then wiped with lens tissue. The walls and bottom of cuvette 2 were covered with foil and a foil cap was made for the top.

To each cuvette 1 mL of phosphate buffer was added. Then, to cuvette 1 4 mL of distilled water was added, but to cuvettes 2, 3, and 4 3 mL of distilled water was added. To cuvette 1, 3 drops of unboiled chloroplasts were added.

The spectrophotometer was brought back to zero and the contents of cuvette 1 were mixed by inverting and placed in the sample holder.

Cuvette 1 was used periodically through this experiment to recalibrate the spectrophotometer. Three drops of unboiled chloroplasts were added to cuvette 2.

After removing the foil sleeve, it was placed in the sample holder and the transmittance was recorded. Additional readings were also taken at 5, 10, and 15 minutes. Next, three drops of unboiled chloroplasts were transferred to cuvette 3. Using an artificial electron acceptor will allow for the production of oxygen during the course of the light reaction.

However, without the formation of NADPH2, the dark reaction will not occur and organic product will not form. The phenomena described in question 6 was the basis for separating the light reaction from the dark reaction. Hill used ferricyanide, however, as an artificial electron acceptor. He is credited with isolating the light reaction. Analyze the slopes and discuss your results. In such an experiment several cuvettes are set up similarly to the one kept in the light in the experiment the students just did.

However, the use lights of different wavelengths. The data for each cuvette is plotted and compared. Mystery Spot. Activities Collections.

Graph l - Plot time vs. You will need three Y columns. Use lines to connect the points so that the three lines can be compared. Graph 2 - Plot time vs. Submit these graphs for questions 11 and Label all Y-column headings to receive full credit the plotter will make a legend for you.

Carefully examine your graphs, then answer question Course Schedule. Study Guides. WebAssign: homework quizzes, grades. Pigments and Photosynthetic Activity.