1.6- proteins

Question 1

what combines to form proteins?

Answer 1

polypeptides

Question 2

amino acids

Answer 2

monomers from which proteins are made

Question 3

structure of amino acids

Answer 3

amino group (-NH2)
carboxylic acid group (-COOH)
hydrogen group (-H)
R group (carbon containing chain)

Question 4

How many different amino acids are there?

Answer 4

20- each determined by R groups

Question 5

How are amino acids combined?

Answer 5

peptide bonds formed in condensation reaction

Question 6

How can the peptide bond of a dipeptide be broken down to give 2 constituent amino acids?

Answer 6

hydrolisis

Question 7

dipeptide

Answer 7

contains 2 amino acids

Question 8

polypeptide

Answer 8

contains three or more amino acids

Question 9

Through a series of condensation reactions, many amino acid monomers can be joined together in a process called…

Answer 9

polymerisation

Question 10

Describe the primary structure of a protein

Answer 10

Primary structure of a protein is the order and number of amino acids in a protein. This
primary structure contains the initial sequence of amino acids and will therefore
determine the proteins function in the end.

Question 11

Describe the secondary structure of proteins

Answer 11

shape which the polypeptide chain forms as a result of hydrogen bonding. This is most often a spiral known as alpha helix or beta pleated sheet-

hydrogen has slight positive charge whilst oxygen slight negative charge, as a result weak hydrogen bonds form= different structure eg a helix/ beta sheets

Question 12

Describe the tertiary structure of proteins

Answer 12

3D shape of the protein and is formed from further
twisting and folding. A number of different bonds maintain the structure, these are:
- Disulfide bridges - these are strong and not easily broken.
- Ionic bonds - form between the carboxyl and amino groups that are not involved in
the peptide bond. They are easily broken by pH and are weaker than disulfide
bridges.
- Hydrogen bonds - numerous and easily broken

Question 13

Describe the quaternary structure

Answer 13

arises from the combination of a number of polypeptide chains and associated non- protein groups into a large, complex protein molecule e.g haemoglobin

Question 14

globular proteins

Answer 14

enzymes are compact

Question 15

fibrous proteins

Answer 15

eg keratin, long and thus can be used to form fibres

Question 16

what is the name for the test in proteins

Answer 16

Biuret test- detects peptide bonds

Question 17

describe the Biuret test

Answer 17

1. Place the sample to be tested in a test tube and add an equal volume of sodium
   hydroxide at room temperature.
2. Add a few drops of very dilute (0.05%) copper (II) sulfate soliton and mix gently.
3. A purple colouration indicates the presence of a peptide bond and hence a protein. A
   negative result would mean the solution remains blue.