practical needed

Question 1

a standard curve can sometimes not be accurate what is the remedies for this

Answer 1

use more concentrations of something to construct a standard curve.

Question 2

staining DNA for mitosis investigations

Answer 2

Add 20 drops of acetic-orcein stain into the watch glass centre using a second pipette.
This is used to stain the cell DNA.

Question 3

describe the food test for starch

Answer 3

add a few drops of iodine solution
-solution goes blue to black

Question 4

describe the food test for sugars

Answer 4

-benedict’s test-heat in a water bath
will turn green/yellow

Question 5

food test for lipds

Answer 5

1 Add a few drops of ethanol to the food solution.
2 Shake the test tube and leave for one minute.
3 Pour the ethanol into a test tube of water.
4 If the solution turns cloudy, the food contains lipids.

Question 6

food test for protein

Answer 6

1 Add a few drops of copper sulfate solution to your food solution. Add a few drops of sodium hydroxide solution.
2 If the solution turns purple, the food contains protein.

Question 7

food test for non reducing sugar

Answer 7

No colour change (i.e. the solution remains blue), indicates a lack of reducing sugars in the sample.

Question 8

how to test further non reducing sugars

Answer 8

Add dilute hydrochloric acid, then neutralise. The acid will break down the non-reducing sugars into monosaccharides. After adding acid, neutralise the solution with sodium hydrogencarbonate.
Heat and observe colour change. We can then do the Benedict’s test, as we did above for reducing sugars. If there are non-reducing sugars in the sample, we will observe a colour change similar to the one we see with reducing sugars (blue to green to yellow to orange to brick red).