Proteins

Question 1

What is the main protein found in hair ?

Answer 1

Keratin

Question 2

Which features found on some animals are made of keratin ?

Answer 2

Beaks and horns

Question 3

Proteins provide mechanical support in which things ?

Answer 3

Bone, cartilage and teeth

Question 4

What is one of the most important proteins found in teeth ?

Answer 4

Collagen

Question 5

Which proteins are found in muscles ?

Answer 5

Actin and myosin

Question 6

Which proteins are important in the storage and transport of oxygen ?

Answer 6

Myoglobin and haemoglobin

Question 7

Summarise the structure of myoglobin

Answer 7

It has 1 polypeptide chain and so contains 1 haem group and can bind 1 oxygen molecule

Question 8

What are the 2 groups into which proteins can be divided ?

Answer 8

Fibrous proteins - long, structural proteins
Globular proteins - functional roles

Question 9

Which protein is involved in sight ?

Answer 9

Rhodopsin is present in the membrane of the retina and it changes shapes shape in response to the stimulus

Question 10

What is a protein?

Answer 10

A linear sequence of amino acids folded to an elaborate functional structure

Question 11

What are the monomers of proteins ?

Answer 11

Amino acids

Question 12

What is the central carbon of an amino acid known as ?

Answer 12

Alpha carbon

Question 13

What are the 2 groups of amino acids ?

Answer 13

L - amino acids (all amino acids in our DNA)
D - amino acids

Question 14

What is the formula to calculate pH ?

Answer 14

pH = pKa + log[A-]/[HA]

[A-] = base
[HA] = acid

Question 15

What is the isoelectic point ?

Answer 15

When the overall charge is 0

Question 16

What are essential amino acids ?

Answer 16

Essential amino acids are required in the body but can’t be made

Question 17

What are non - essential amino acids ?

Answer 17

They can be made in the body as as long as there is sufficient nitrogen available

Question 18

Give a few examples of essential amino acids ?

Answer 18

Lysine, valine and methionine

Question 19

How can we increase the amount of amino acids in our diet ?

Answer 19

Consuming high quality proteins which :
- contain all essential amino acids
- correct proportions required
- easily digestible

Question 20

How do amino acids form amides ?

Answer 20

They react with ammonia or amines in a condensation reaction to form amides

Question 21

How do amino acids form proteins ?

Answer 21

The amino group of one amino acid will react with the carboxylic acid group of another amino acid in a condensation reaction to form a peptide bond

Question 22

What is an amino acid residue ?

Answer 22

A residue is each individual amino acid in the polypeptide chain

Question 23

How is the primary structure of a protein determined ?

Answer 23

By the order of amino acids from the N terminus to the C terminus

Question 24

Summarise the rotational property of the peptide bond

Answer 24

The lone pair of electrons on the nitrogen and the pi electrons of the C = O are delocalised across the peptide bond so it does not rotate

Question 25

Is the nitrogen of the amino group a hydrogen bond donor or acceptor ?

Answer 25

Good hydrogen bond donor

Question 26

Is the oxygen of the carboxylic acid group a hydrogen bond donor or acceptor ?

Answer 26

Good hydrogen bond acceptor

Question 27

How is the tertiary structure of a protein determined ?

Answer 27

By the sequence of amino acids

Question 28

How is protein structure organised ?

Answer 28

Protein structure has a hierarchical organisation :
- primary structure
- secondary structure
- tertiary structure
- quartenary structure

Question 29

What are the properties of hydrogen bonds ?

Answer 29

• relatively weak bonds
• strongest when linear
• the length between N and O is 2.8 Å

Question 30

What are some of the other bonds present in proteins ?

Answer 30

• Van der Waals or London forces - only significant when atoms are close
• ionic bonds (stronger than London forces)

Question 31

Summarise the secondary structure of proteins

Answer 31

• alpha helix
• beta pleated sheet : parallel and anti parallel

Question 32

How are the amino acids organised in an anti parallel beta pleated sheet ?

Answer 32

N terminus > C terminus
C terminus > N terminus

Question 33

How are the amino acids organised in a parallel beta pleated sheet ?

Answer 33

N terminus > C terminus
N terminus > C terminus

Question 34

Summarise the properties of an alpha helix

Answer 34

• hydrogen bonding
• right handed
• 3.6 residues per turn

Question 35

How are disulphide bridges oxidised and reduced ?

Answer 35

They are oxidised with hydrogen peroxide allowing them to form
They are reduced with thioglycolate which causes them to break

Question 36

Which amino acids are helix formers ?

Answer 36

• glutamate
• glutamine
• alanine
• histidine

Question 37

Which amino acid is a helix destabiliser ?

Answer 37

Tyrosine

Question 38

Which amino acid is a helix breaker ?

Answer 38

Proline

Question 39

What is a structural motif ?

Answer 39

It is the arrangements of secondary structures

Question 40

What is the secondary structure of immunoglobulin G ?

Answer 40

Anti parallel ß pleated sheet

Question 41

What is a domain ?

Answer 41

A domain is a recognisable globular unit formed by folding of part of a polypeptide chain

Question 42

What is the quarternary structure of a protein ?

Answer 42

Assembly of more than one polypeptide chain

Question 43

What is a cofactor ?

Answer 43

It is a small molecule which is essential for function

They can be subdivided into cofactors and coenzymes
Cofactors - metals
Coenzymes - small organic molecules e.g. vitamins