Biology (practicals)

Question 1

whats the test for starch

Answer 1

place 2cm3 of food solution in a test tube
add a few drops of IODINE solution (orange)
if starch is present the iodine solution will turn blue/black

if not it’ll stay orange

Question 2

whats the test for sugars

Answer 2

only works for some sugars like glucose

place 2cm3 of food solution in a test tube
add 10 drops of BENNEDICTs solution (blue)
place test tube in a beaker thats half full of hot water
wait 5 minutes

green - small amount of sugar
yellow - more
brick red - a lot more

Question 3

the test for protein

Answer 3

place 2cm3 of food solution in a test tube
add 2cm3 of biuret solution (BLUE)
if protein is present it turns purple

Question 4

the test for lipids/fats

Answer 4

place 2cm3 of food solution in a test tube
add a few drops of distilled water
add a few drops of ethanol and shake
if lipids are present a cloudy white emulsion forms

Question 5

osmosis practical (potato)

Answer 5

peel the potato
use a cork borer to get 3 cylinder shaped potatoes
get all the potatoes the same length (3cm)
measure the length and mass

put one in a test tube, add 10cm3 of 0.5 molar sugar solution

put the second in another tt with 0.25 molar sugar solution

and distilled water in the third test tube

leave them overnight for osmosis to occur
take them out and roll them over paper towels to remove surface moisture

measure the length and mass again to see the difference