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lab report for biology

Lab Report:
Food Tests


Introduction: This is the first experiment of the first unit in the year 10 MYP biology course, digestion. The experiment

Aim: The aim of this experiment is to research which substances are found in different foods. To do this we will test different types of foods, starch, sugar, protein and fat with different chemicals to find out which substances are in those foods.

Hypothesis: I think that in our test for starch, when iodine is added, the food will turn blue/black. I predict that the lipids (fats) in the filter paper test will turn translucent and I also predict that the colours of all the chemicals poured into the negative control test should stay unchanged.

Apparatus:

For all of the food tests (except for fat) we used:

• Test tubes (3 for each experiment)
• Test tube rack
• Pipette
• Iodine solution (for starch)
• Fehlings A+B solution (for reducing sugars)
• Sodium Hydroxide + Copper Sulphate solution (for proteins)
• Starch, sugar, protein dissolved in water
• Water bath

For the filter paper test for fat, we used:
· Filter paper
· Fat dissolved in water
· Pipette

Method:
Test for Starch: Three test tubes, one test tube rack, starch dissolved in water, cereal, water and iodine solution were taken. In the first test tube, crushed cornflakes (starch) were added; around five drops of iodine were poured and mixed with the cornflakes. In the second tube the negative control test was done. Water was poured into the test tube and iodine was added, this test is necessary because it determines if the solution is right. The positive control test was done in the third test tube. In the positive control test iodine was added to starch solution. The positive control test is important because it determines whether the results are correct or not. The results for all the three tests were recorded in a table.
Test for reducing sugars: and Fehlings A+B solution (this test could also be done with Benedicts solution instead of Fehlings A and B solutions) were taken. A few drops of ketchup were put in the first test tube. Five drops of Fehlings A and Fehlings B solution were added. The test tube was put in a water bath for 10 minutes. The negative control test was done in the second test tube (water + Fehlings A+B solution). Positive control test was done. Fehlings A and Fehlings B solution were added to Sugar, which was dissolved in water. The results for all three tests were recorded in a table.

Test for Protein: Three test tubes, one test tube rack; protein reduced in water, sodium hydroxide (NaOH), copper sulphate solution ( CuSO4) and a piece of cheese (protein) were added. The first test was the test with real food. The piece of cheese was taken and put into a test tube. Five drops of (NaOH) were added and the test tube was shaken. After a few minutes of shaking the tube, five drops of (CuSO4) were added. The test tube was put in a water bath for ten minutes. The negative control test was done in the second test tube (water + CuSO4+ NaOH). Positive test was done in the third test tube, protein which was dissolved in water was poured into the test tube, and Sodium Hydroxide and Copper Sulphate solution were added. The results for the three tests were recorded in a table.

Test for fat: for these test three filter papers, fat dissolved in water, water and a piece of bacon was taken. For the test with real foods the piece of bacon was rubbed on the paper. The negative test was done; a few drops of water were poured on the filter paper. The positive control test was done, fast dissolved in water was poured onto the filter paper. The three results were recorded in a table.

Results:

Number
Food Test
Method
Test with real food
Colour-VE (negative)
Colour+VE
(positive)

1

Starch
Iodine Solution
Blue/Black
Yellow
Blue/Black

2

Reducing
Sugars
Fehlings
A+B
Orange/Green
Stayed blue
Orange

3

Proteins
Sodium Hydroxide+
Copper Sulphate solution.
Brown/Green

Neutral
Brown/Green

4

Lipids
(fats)
Filter paper test
Translucent
Stayed the same
Translucent



Conclusion: By doing this experiment I found that all of these foods should be included in a balanced diet, I think that you should eat less fat in your diet and more proteins because they are good for you and fat is bad. In my hypothesis I said that the starch will turn blue black and it did. The fat turned translucent and the negative tests stayed the same, so I was right with my predictions. To sum up I think that in your balanced diet you should follow the food pyramid and eat the same amounts of different foods.