Question

Can someone help me rewrite procedure #3 in paragraph notation. It should be written so that anyone reading it could replicate what you did.

1. Place cell growth media in 37degree incubator for at least 30 minutes. 2. Remove tubes containing frozen cells from liquid nitrogen tanks and quickly place the tubes on dry ice. Cells should thaw in about a minute. 3. Once thawed, transfer the cells into a 50ml conical tube and add 50ml of warm growth media from step 1. 4. Gently rock the tube allowing the media and cells to mix. Transfer cell/media mixture into a tissue culture flask and place in 37degree incubator. 5. Check on cells the next day. Visualize them using a light microscope. Procedure #2: 1. Put 100 μL of transformation solution into an Eppendorf tube. Using a toothpick, select an E. coli colony and transfer to the tube. 2. Add 1 μしof transforming DNA to the tube 3. Incubate on ice for 10 minutes. 4. Transfer tube to a 42°C heat block for 45 seconds. 5. Place tube back on ice for 2 minutes. 6. Add 20OuL LB broth and spread on an LB+Amp plate. Procedure #3: Performing a Benedict's test 1. Prepare a boiling water bath as follows: add 200ml water to a 400ml beaker and place the beaker on a hotplate set to high. 2. Add 2 ml of each of the following solutions to separate test tubes: 1% starch solution, 0.1M glucose, 0.1M galactose, and your unknown solution 3. To each of the tubes, add 2ml Benedict's reagent and mix well. 4. Place the tubes in the boiling water bath and let stand for 3 minutes. 5. Using tongs, remove the tubes from the bath and observe and record your results.

Answer 1

Procedure 3 :- Take a water bath but if not available the take a 400 ml beaker and add 200 ml water into it and place the beaker on a hotplate which is in contact with heat.This will work as a water bath. Take 4 test tubes and number them 1,2,3,4.Now add 2 ml of 1% starch solution into test tube 1,2 ml of 0.1M glucose solution into test tube 2, 2 ml of 0.1M galactose solution into test tube 3, 2 ml of unknown solution into test tube 4.Then add 2 ml of Benedict's reagent into each test tube and mix well.After mixing place those test tubes in boiling water bath for 3 minutes.At last remove these test tubes from water bath, observe the change then record the result.

S.No.	sample solution (2ml)	Benedict's reagents	Result
Test tube 1	1% starch	2 ml	-ve
Test tube 2	0.1M glucose	2 ml	+ve
Test tube 3	0.1M galactose	2 ml	+ve
Test tube 4	unknown	2 ml	Depends on type of sugar

Benedict's test is used for the detection of reducing sugar within the solution.Reducing sugar act as a reducing agent because they have free aldehyding and ketonic group.

Benedict's reagent = Copper (II) sulphate (CuSO₄ 5H₂O) + sodium citrate + sodium carbonate (Na₂CO₃).It is blue in colour,if there is any reducing sugar within the solution then on addition of this reagent there will be change in the solution colour on heating or appearence of red precipitate with in the solution. This indicate the presence of reducing sugar and the result for this test is positive.

Starch does not give this test because glucose units are connected by 1-4 glycosidic bond.Starch will give +ve result on on hydrolysis.Both glucose and galactose are reducing sugar so both give + ve Benedict's test.Unknown solution reducing solution result will depends upon the type os sugar.