4.4 proteins

Question 1

what atoms do protein molecules contain?

Answer 1

carbon; hydrogen; oxygen; nitrogen; sulfur (small amounts)

Question 2

what are protein molecules made of?

Answer 2

long chains of smaller molecules joined end to end

Question 3

what are those long chains of smaller molecules called?

Answer 3

amino acids

Question 4

how many different amino acids are there?

Answer 4

20 different kinds

Question 5

does the order of molecules with amino acids affect the function and type of protein it makes?

Answer 5

yes

Question 6

what is an example of water-soluble protein?

Answer 6

haemoglobin

Question 7

what is an example of water-insoluble protein?

Answer 7

keratin; makes up hair and fingernails

Question 8

what are the functions of proteins?

Answer 8

• to make cells
• to form structure e.g. keratin (hair, fingernails)
• to repair damaged parts of the body
• to provide immunity by antibodies and enzymes
• to transport oxygen by haemoglobin
• to digest food by enzymes
• energy store for developing embryo

Question 9

what parts of the cell contains a lot of protein?

Answer 9

cell membrane and cytoplasm

Question 10

_____ are also proteins

Answer 10

enzymes

Question 11

what factor of protein molecules directly affects its function?

Answer 11

its shape

Question 12

what results different shapes of protein molecules?

Answer 12

different sequences of amino acids

Question 13

what do different sequences of amino acids affect?

Answer 13

• the kind of antibody it forms

- the shape of protein molecules

Question 14

what is the test executed to testing for protein?

Answer 14

biuret test

Question 15

what are the steps of the biuret test?

Answer 15

1. mix the food in water
2. add dilute copper sulfate solution
3. add potassium hydroxide solution gently
   - purple colour = protein is present
   - blue colour = protein is absent

Question 16

amino acids join together by
_______ and form
_________

Answer 16

peptide bonds; polypeptide chains