Biological molecules

Question 1

What are the chemical elements that make up carbohydrates?

Answer 1

Carbon, hydrogen and oxygen

Question 2

What are the chemical elements that make up proteins?

Answer 2

carbon
nitrogen
hydrogen
oxygen

Question 3

What are the chemical elements that make up lipids?

Answer 3

hydrogen
carbon
oxygen

Question 4

What are the smaller molecules of glucose?

Answer 4

starch, glycogen, cellulose

Question 5

What are the smaller molecules that make up proteins?

Answer 5

amino acids

Question 6

What are the smaller molecules that make up lipids?

Answer 6

fatty acids and glycerol

Question 7

Describe the structure of DNA

Answer 7

• two strands coiled together to form a double
  helix
• each strand contains chemicals called bases
• bonds between pairs of bases hold the
  strands together
• the bases always pair up in the same way:
  A with T, and C with G (full names are not
  required)

Question 8

What food test tests for starch?

Answer 8

Iodine solution

Question 9

Describe the test for starch and how it’s done.

Answer 9

take the food sample, add a few iodine drops
= in case it’s positive it’ll turn blue/black

Question 10

What food test tests for reducing sugars?

Answer 10

benedict’s solution test

Question 11

Describe the test for reducing sugars and how it’s done.

Answer 11

add a few drops of benedict’s sol to the samples and put them inside a water bath
the one that turns green<yellow<orange<brick red
(by concentration) means it’s posituve

Question 12

What food test tests for proteins?

Answer 12

Biuret test

Question 13

Describe the test for proteins and how it’s done

Answer 13

add a few drops of biruet sol to samples, if it’s positive it’ll turn purple or violet

Question 14

What food test tests for fats and oils?

Answer 14

Ethanol emulsion test

Question 15

Describe the test for fats and oils and how it’s done

Answer 15

Ethanol test
add 2cm3 of Ethanol to the food test in the test tube and shake it gently, followed by 2cm3 of distilled water
positive result: white emulsion

Question 16

What food test tests for vitamin C

Answer 16

DCPIP

Question 17

Describe the test for vitamin C and how it’s done

Answer 17

add sample of DCPIP by drops to the food sample in the test tube and shake it gently until a colour change is reached(colourless)
if positive-will turn sol colourless

Question 18

What do you need to do before a food test?

Answer 18

to make a food sample

Question 19

How do you make a food sample?

Answer 19

take a food sample and grind it up with a pestle and mortar and distilled water to get a paste
then transfer the paste to a beaker where we add more distilled water, where we’ll stir the solution with a glass rod so that chemicals in food dissolve in water
lastly, you then filter the solution by filtration and with filtrate paper to remove any suspended food particles as residue behind