Chemical Composition of Cells Lab

      Chemical Composition of Cells Lab

Purpose:

        Proteins: State the monomer for a protein and explain how the monomer joins to form a protein as well as identify proteins and peptides and explain the function of enzymes.

        Carbohydrates: State the monomer for starch and distinguish maltose starch and site the test used for identifying starch and sugar as well as describe the varied results of the Benedict’s test.

        Lipids: State the components of a fat and explain why fat is not soluble in water as well as describe how an emulsifier works.

Materials: “Refer to Chemical Composition of Cells Lab”

Procedure:

Proteins

Biuret Test;

1. Prepare 4 test tubes and mark them as test tube 1-4. Then mark them at 2cm and 4 cm levels.
2. For test tube 1, fill to the first mark with distilled water and to the second mark with biuret reagent.
3. Record the final colour in Table 3.2
4. For test tube 2, fill to eh first mark with albumin solution and t the second mark with biuret reagent.
5. Record final colour in Table 3.2
6. For test tube 3, fill to the first makr pepsin solution and to the second mark with biuret reagent.
7. Record final colour change in Table 3.2
8. For test tube 4, fill to the first mark with starch solution and to the second mark with biuret reagent.
9. Record final colour in Table 3.2

Enzyme Function of Proteins;

1. With a wax pencil, label as 1 and 2, and mark two clean test tubes at 2cm, 4cm, 6cm, and 8cm.
2. For test tube 1, fill to the 2cm mark with albumin solution, to the 4cm mark with water, and to the 6cm mark with hydrochloric acid (0.2% HCl).
3. Shake and incubate at 37͐ degree for 30 to 45 minutes.
4. After incubation, fill to the 8cm mark with biuret reagent. Note any colour change, and record the result in Table 3.3
5. For test tube 2, fill to the 2cm mark with albumin solution, to the 4cm mark with pepsin solution, and to the 6cm mark with hydrochloric acid (0.2% HCl).
6. Shake and incubate at 37 degrees for 30 to 45 minutes.
7. After incubation, fill to the 8cm mark with biuret reagent. Note any colour change, and record the result in Table 3.3

Carbohydrates

Test for starch;

1. With a wax pencil, label and mark two clean test tubes at the 1 cm level.
2. For test tube 1, fill to the 1cm mark with starch suspension (1%) and add five drops of iodine solution.
3. Note the final colour change, and record the results in Table 3.4
4. For test tube 2, fill to the 1cm mark with water, and add five drops of iodine solution.
5. Note the final colour change, and record the results in Table 3.4
6. Get a potato and slice a very thin piece, place it on a microscope slide, add a drop f water, coverslip, and observe under low power with the compound light microscope. Compare the slide to the photo micrograph of starch granules. Find the cell wall and the starch grains.
7. Without removing the coverslip, place two drops of iodine solution onto the microscope slide so that the iodine touches the coverslip. Draw the iodine under the coverslip by placing a small piece of paper towel in contact with the water on the opposite side of the coverslip.
8. Microscopically examine the potato again on the side closest to where the iodine solution was applied. Record the colour and chemical composition in Table 3.4
9. Get an onion, slice a small piece of onion and place it on a microscope slide with coverslip.
10. Add a large drop of iodine solution. Note the colour, and record it in Table 3.4        

Test for Sugar:

1. With a wax pencil, label and mark five clean test tubes at the 1cm and 3cm levels.
2. For test tube 1, fill the 1cm mark with water, and then add Benedict’s reagent to the 3cm mark.
3. Heat in a boiling water bath for 5-10 minutes, note any color change, and record in Table 3.6.
4. For test tube 2, fill to the 1cm mark with glucose solution, and then add benedict’s reagent to the 3cm mark.
5. Heat in a boiling water bath for 5-10 minutes, note any color change, and record in Table 3.6.
6. For test tube 3, place a few drops of onion juice in the test tube. (Obtain the juice by crushing a small piece of onion with a mortar and pestle.)
7. Fill to the 1cm mark with water, and then add Benedict’s reagent to the 3cm mark.
8. Heat in a boiling water bath 5-10 minutes, note any color change, and record in Table 3.6.
9. For test tube 4, place a few drops of potato juice in the test tube. (Obtain the juice by crushing a small piece of potato with a molar and pestle.)
10. Fill to the 1cm mark with water, and then add Benedict’s reagent to the 3cm mark.
11. Heat in a boiling water bath for 5-10 minutes, note any color change, and record in Table 3.6.
12. For test tube 5, fill to the 1 cm mark with starch suspension, and then add Benedict’s reagent to the 3cm mark.
13. Heat in a boiling water bath for 5-10 minutes, note any color change, and record in table 3.6.

Starch Composition

1. With a wax pencil, label and mark two clean test tubes at the 2cm, 4cm, and 6cm levels. Label a third tube similarity but also at the 8cm level.
2. For test tube 1, fill to the 2cm mark with water and to the 4cm mark with 1% alpha-amylase.
3. Shake and wait for 30 minutes.
4. Add benedict’s reagent to the 6cm level and heat in a boiling water bath.
5. Note any color change and record your results in Table 3.7.
6. For test tube 2, fill to the 2cm mark with starch and to the 4cm mark with amylase.
7. Shake and wait for 30 minutes.
8. Add benedict’s reagent and heat as before.
9. Note any color change and record your results in Table 3.7.
10. For test tube 3, fill to the 2cm mark with starch solution; to the 4cm mark with 1% pepsin; and to the 6cm mark with 0.2% HCl.
11. Shake and wait for 30 minutes.
12. Add Benedict’s reagent to the 8cm level and heat.
13. Note any color change and record your results in Table 3.7.

Lipids

Test for Lipids

1. Place a small drop of water on a square of brown paper. Describe the immediate effect.
2. Place a small drop of vegetable oil on a square piece of brown paper. Describe the immediate effect.
3. Wait at least 5 minutes. Evaluate which substance penetrates the paper and which is subject to evaporation. Record the data in Table 3.8

Emulsification of Lipids

1. With a wax pencil, label two clean test tubes 1 and 2. Mark tue 1 at 3 cm and 4cm levels. Mark tube 2 at 2cm, 3cm, and 4cm levels.
2. For test tube 1, fill to the 3cm mark with water and to the 4cm mark with vegetable oil. Shake.
3. Observe for the initial dispersal of oil, followed by rapid separation into two layers.]
4. For test tube 2, fill to the 2cm mark with water, to the 3cm mark with vegetable oil, and to the 4cm mark with available emulsifier. Shake.
5. Describe how the distribution of oil in ube 2 compares with test tube 1.
6. Let both tubes settle for 5 minutes. Label two microscope slides 1 and 2.
7. Using different droppers, remove a sample of the solution that is just below the layer of oil in each tube. Place each drop on the appropriate slide, add a coverslip, and examine with a low power of the compound light microscope.
8. Record observation in Table 3.9

Adipose Tissue

1. Obtain a slide of adipose tissue and view it under the microscope at high power.
2. Notice how the fat droplets push the cytoplasm to the edges of the cells.

Results:

Biuret Test (Table 3.2)

Action of Pepsin (Table 3.3)