AP Biology Lab Four: Plant Pigments and Photosynthesis
Abstract: The purpose of this lab is to separate and identify pigments and other molecules within plant cells by a process called chromatography. We will also be measuring the rate of photosynthesis in isolated chloroplasts. Beta carotene, the most abundant carotene in plants, is carried along near the solvent front because it is very soluble in the solvent being used and because it forms no hydrogen bonds with cellulose. Xanthophyll is found further from the solvent font because it is less soluble in the solvent and has been slowed down by hydrogen bonding to the cellulose. Chlorophylls contain oxygen and nitrogen and are bound more tightly to the paper than the other pigments. Chlorophyll a is the primary photosynthetic pigment in plants. A molecule of chlorophyll a is located at the reaction center of the photo systems. The pigments collect light energy and send it to the reaction center. Carotenoids also protect the photosynthetic systems from damaging effects of ultraviolet light.
Problem: What is the effect of light and temperature on plants?
Hypothesis: If there is a change in the light received or temperature, then the rate of photosynthesis will be affected.
1) Obtain a 50 ml graduated cylinder which has about 1 cm of solvent at the bottom. 2) Cut a piece of filter paper which will be long enough to reach the solvent. Draw a line about 1.5 cm from the bottom of the paper.
3) Use a quarter to extract the pigments from spinach leaf cells. Place a small section of leaf on the top of the pencil line. Use the ribbed edge of the coin to crush the leaf cells. Be sure the pigment line is on top of the pencil line. 4) Place the chromatography paper in the cylinder.
5) Cover the cylinder. When the solvent is about 1 cm from the top of the paper, remove the paper and immediately mark the location of the solvent front before it evaporates. 6) Mark the...
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