Proteins

Question 1

Amino acids

Answer 1

A protein monomer

Question 2

Amino acid structure

Answer 2

NH2 group joined to CH joined to CHR joined to COOH

Question 3

Dipeptide

Answer 3

2 amino acids joining together by a peptide bond in a condensation reaction (removal of water)

Question 4

Polypeptide

Answer 4

More than 2 amino acids joined together

Question 5

Structure of proteins - Primary

Answer 5

The sequence and number of amino acids in a protein
- This happens through many condensation reactions of amino acids (Polymerisation)
- This chain is called a polypeptide

Question 6

Structure of proteins - Secondary

Answer 6

The shape between the amino acids in the polypeptide chain by the formation of hydrogen bonds
- The shape is either an alpha-helix or a beta-pleated sheet

Question 7

Structure of proteins - Tertiary

Answer 7

The shape is twisted and folded to create a complex 3D shape
- The structure is maintained by 3 bonds:
- Disulfide bridges = strong and not easily broken
- Ionic bonds = easily broken by changes in pH
- Hydrogen bonds = easily broken

Question 8

Structure of proteins - Quaternary

Answer 8

The way polypeptide chains are assembled together
- Happens when large proteins form complex molecules containing a number of individual polypeptide chains

Question 9

Test for proteins

Answer 9

Biuret test
1) Place sample into test tube and add equal volume of sodium hydroxide
2) Add a few drops of dilute copper (II) sulfate solution and mix
3) Purple = positive test (Protein present) Blue = negative test