Structure of Proteins 3.6

Question 1

Polypeptides

Answer 1

These consist of more than one peptide which is an amino acid chain

Question 2

Peptide Bonds

Answer 2

Amino acids join together and this makes a peptide bond which is a type of condensation reaction as it also makes a product of water and a dipeptide

Question 3

Protein Synthesis

Answer 3

Different R-groups can interact to form different types of bonds. This will then determine how the polypeptide folds and the shape of the protein that will be produced.

Question 4

Primary Structure

Answer 4

The specific sequence of amino acids that is determined from DNA and will later on influence how the polypeptide will fold. The only bonds used are peptide bonds

Question 5

Secondary Structure

Answer 5

This is how the polypeptide starts to fold as the hydrogen, oxygen and nitrogen start to interact with each other to form hydrogen bonds and some ionic bonds

Question 6

Alpha Helix

Answer 6

One secondary structure is the alpha helix which happens when hydrogen bonds form in the amino acid chain, making it bend into a helix shape

Question 7

Beta Pleated Sheet

Answer 7

Another secondary structure is the beta pleated sheet which happens when there are hydrogen bonds formed between two parallel amino acid chains. The individual patterns in the amino acids make the pleats

Question 8

Tertiary Structure

Answer 8

This is the further folding of the polypeptide. This is after the secondary structure, the R-groups move closer together so can form bonds.

Question 9

Hydrophilic/Hydrophobic Interactions

Answer 9

This is when a polar and non polar R-group bond with each other, it’s a weak bond

Question 10

Disulfide bonds

Answer 10

This is a strong covalent bond between two R-groups that have sulfur atoms in them

Question 11

Quaternary structure

Answer 11

This is when 2 or more proteins called subunits interact with each other, it’s the same interactions as the tertiary structure. Enzymes are 2, haemoglobin is 4

Question 12

Hydrophilic R-groups

Answer 12

This means the R-groups will be on the outside of the protein

Question 13

Hydrophobic R-groups

Answer 13

This means the R-groups will be in the centre of the proteins, shielded from the water

Question 14

Biuret Test

Answer 14

Add sodium hydroxide and copper II sulphate solution or just Biuret reagent which contains both.
Leave for 5 mins
It should turn violet if there is protein because the peptide bonds interact with the reagent to form violet colour