Proteins

Question 1

What are the monomers of proteins?

Answer 1

Amino acids.

Question 2

What is a dipeptide?

Answer 2

A molecule that is formed when two amino acids join together.

Question 3

What is a polypeptide?

Answer 3

A molecule that is formed when more than two amino acids join together.

Question 4

What are proteins made up of?

Answer 4

One or more polypeptides.

Question 5

What is the general structure of an amino acid?

Answer 5

A carboxyl group (-COOH).
An amine group (-NH2)
An R group (variable side group).

Question 6

How many amino acids are there in total?

Answer 6

20.

Question 7

What reaction links amino acids?

Answer 7

Condensation reaction to form dipeptides or polypeptides.

Question 8

What is released when amino acids join together?

Answer 8

A molecule of water.

Question 9

What type of bonds form between amino acids?

Answer 9

Peptide bonds.

Question 10

What reaction occurs when dipeptides and peptides are broken down?

Answer 10

Hydrolysis reaction.

Question 11

What are the 4 levels of a protein’s structure?

Answer 11

Primary.
Secondary.
Tertiary.
Quaternary.

Question 12

What is the primary structure of a protein?

Answer 12

The sequence of amino acids in the polypeptide chain.

Question 13

What bonds form between the amino acids in the chain to form the secondary structure of a protein?

Answer 13

Hydrogen bonds.

Question 14

What do the hydrogen bonds in the secondary structure cause to happen?

Answer 14

The chain coils into an alpha helix, or folds into a beta pleated sheet.

Question 15

What happens in the tertiary structure of a protein?

Answer 15

The coiled or folded chain or amino acids is coiled and folded further.

Question 16

What forms between different parts of the chain in the tertiary structure?

Answer 16

More bonds form, including hydrogen bonds and ionic bonds.

Question 17

What happens when two molecules of cysteine come close together in the tertiary structure of a protein?

Answer 17

Disulphide bridges form - the sulphur atom in one cysteine bonds to the sulphur atom in the other.

Question 18

For what type of proteins is the tertiary structure the final 3D structure?

Answer 18

Proteins made from a single polypeptide chain.

Question 19

What is the quaternary structure of a protein.

Answer 19

The way multiple polypeptide chains are assembled together.

Question 20

For what type of proteins is the quaternary structure the final 3D structure?

Answer 20

For proteins made from more than one polypeptide chain.

Question 21

What is the test for proteins?

Answer 21

The Biuret Test.

Question 22

How do you carry out the biuret test for proteins?

Answer 22

The test solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution.
Then you add some copper sulphate solution.

Question 23

What is a positive result of the biuret test?

Answer 23

If protein is present, the solution turns purple. If there is no protein present, it will stay blue.