Chloroplast and Mitochondrion in Plant Cells
Mitochondrion and chloroplast are two organelles that are very important to organisms. Both provide energy and nourishment to the cell. While chloroplast is found in plant cells only, mitochondrion is found in both animal and plant cells. It is believed that these two organelles were once bacterial cells on their own, but then they were engulfed by other bacteria. This theory is called the Endosymbiotic Theory. This theory is proven by the fact that chloroplast and mitochondrion are the only organelles, within a cell, that have their own DNA. They also use this DNA to produce their own enzymes and proteins. Further ...view middle of the document...
3. Chop the tissue as fine as possible. Add the tissue to an ice-cold mortar containing 15 ml of grinding solution and grind to a fine paste.
4. Filter the solution through double layered cheesecloth into a beaker and squeeze the tissue pulp to recover all of the suspension.
5. Transfer the green suspension to a cold 50 ml. centrifuge tube and centrifuge at 200 X g for I minute at 4° C to pellet the unbroken cells and fragments.
6. Decant the supernatant into a clean centrifuge tube and recentrifuge at 1000 X g for 7 minutes. The pellet formed during this centrifugation contains chloroplasts. Decant and discard the supernatant.
7. Resuspend the pellet in 5.0 ml. of cold suspension solution or 0.035 M NaCl. Use a glass stirring rod to gently disrupt the packed pellet. This is the chloroplast suspension for use in subsequent procedures.
8. Enclose the tube in aluminum foil and place it in an ice bucket.
9. Determine the number of chloroplasts/mi of suspension media using a hemocytometer.
10. Record the # of chloroplasts/ml
Part 2: Elodea Cells and Chloroplast
1. Remove a young leaf from the tip of a sprig of Elodea (a common pond weed used frequently to study photosynthesis, cellular structure, and cytoplasmic streaming.
2. Place the leaf in a drop of H2O on a microscope slide with the top surface of the leaf facing up (the cells on the upper surface are larger and easier to examine).
3. Add a cover slip. Do not let the leaf dry. If necessary, add another drop of H2O.
4. Examine the leaf under the microscope. Start with low magnification, and then switch to high dry. Each of the small, regularly shaped units you see are cells surrounded by cell walls made primarily of cellulose. The plasma membrane lies just inside the cell wall.
Part 3: Mitochondrion in Onion Cells
1. On a clean slide, mix two or three drops of the Janus Green B stain with one drop of 7% sucrose.
2. Prepare a thin piece of onion as you did in a previous exercise and mount it in the staining solution. Add a coverslip.
3. Search the periphery of cells to locate stained mitochondria. They are small blue spheres about 1mm in diameter. The color will...