Proteins

Question 1

What elements are proteins made up of?

Answer 1

Carbon, hydrogen, oxygen, nitrogen (and sometimes sulfur and phosphorus)

Question 2

What happens during the formation of a dipeptide?

Answer 2

The amino group reacts with a carboxyl group (H and OH) eliminating water and forming a peptide bond between the C of the carboxyl group and the N of the amino group

Question 3

What is the primary structure of a protein?

Answer 3

The order of the amino acids in the polypeptide chain.

Question 4

What bonds are found in the primary structure of proteins?

Answer 4

They are linked by peptide bonds only.

Question 5

What is the secondary structure of a protein?

Answer 5

The shape of that the polypeptide chain makes as a result of hydrogen bonding. This causes the chain to be twisted into a 3-D shape.

Question 6

What are the 2 common shapes of a protein with a secondary structure?

Answer 6

A spiral shape call an alpha-helix or less commonly a beta-pleated sheet.

Question 7

What is the tertiary structure of proteins?

Answer 7

The alpha helix and the beta pleated sheet can be further folded to give a more complex 3D structure. This folding can also make it more compact.

Question 8

What bonds can occur in the tertiary structure of a protein?

Answer 8

Hydrogen and ionic bonding, disulfide bridges and hydrophobic interactions.

R-groups may interact to form bonds which help to maintain the structure’s 3D shape.

Question 9

What is the quarternary structure of a protein?

Answer 9

More than one polypeptide chain bonded together

Question 10

Why do some polypeptide chains combine with others?

Answer 10

Because some are not functional unless they are in combination.

Question 11

What is the structure of haemoglobin?

Answer 11

It contains two alpha helix polypeptides and two beta-pleated sheets (4 polypeptide chains) each with a haem group in the centre (this is a non-protein iron containing group)

Question 12

Are fibrous proteins soluble or insoluble in water?

Answer 12

Insoluble

Question 13

What is the structure of a fibrous protein?

Answer 13

Polypeptide in parallel sheets with cross-linkages forming long fibres.

Question 14

What are the uses of fibrous proteins?

Answer 14

Strength, structure and support

Collagen in tendons

Question 15

What are the uses of globular proteins ?

Answer 15

Enzymes, antibodies, plasma proteins, hormones

Question 16

Are globular proteins insoluble or soluble in water?

Answer 16

Soluble

Question 17

What is the structure of a globular protein?

Answer 17

They are compact and folded into spherical molecules.

Question 18

What is the test for proteins?

Answer 18

It is called the Biuret test. You add biuret reagent. The sodium hydroxide and the copper (ii) sulphate in this reacts to make copper hydroxide which interacts with the peptide bonds to make biuret which is purple.

Question 19

What is the structure of a collagen molecule?

Answer 19

Three polypeptide chains bounded together in a swirl joined by hydrogen bonds.

Question 20

How many amino acids are there and how are they different?

Answer 20

20 and they differ by their R groups