food tests

Question 1

how would you test for the presence of starch

Answer 1

1) add iodine solution to the test sample
2) if starch is present then the sample changes from brown to a dark, blue-black colour
3) if no starch is present then it remains brown

Question 2

how would you test for glucose

Answer 2

1) add Benedict’s reagent (blue) to a sample in a boiling tube
2) heat it in a water bath set to 75 degrees
3) if positive, coloured precipitate will form
4) the higher the concentration of glucose, the further the colour change goes

Question 3

when testing for glucose, what is the order of the colour precipitate it changes from

Answer 3

blue green yellow orange brick red

Question 4

how would you test for proteins

Answer 4

1) prepare a sample then transfer 2cm cubed of it to a test tube
2) add 2cm cubed of biuret solution to the sample and mix them by shaking gently
3) no = solution stay blue
4) yes = solution turn violet

Question 5

test name for
starch, glucose, protein

Answer 5

iodine test, benedicts test, biuret test

Question 6

when using visking tubing to model the gut, what molecules are and aren’t able to pass through the visking tubing into the surrounding water and why

Answer 6

starch and protein as they are too large but glucose can are small enough to diffuse through