Proteins

Question 1

Describe the primary structure of a protein.

Answer 1

The exact sequence of amino acid residues within the polypeptide chain.

Question 2

Describe the secondary structure of a protein.

Answer 2

The spatial arrangement of amino acid residues which are close together in a linear sequence.
Results in alpha helix or Beta pleated sheet

Question 3

Describe the tertiary structure of a protein.

Answer 3

The spatial arrangement of amino acid residues which are far apart in a linear sequence.
Held together by Hydrogen bonds, Disulphide Bridges, Van Der Waal forces, Ionic Interactions and Hydrophobic Interactions.

Question 4

Describe the quaternary structure of a protein.

Answer 4

The spatial arrangement of individual polypeptide chains within a multi subunit protein.

Question 5

What isomer of amino acids do proteins consist of?

Answer 5

L isomer

Question 6

What type of bond links two amino acid residues in a polypeptide chain?

Answer 6

Peptide bond

Question 7

What is the R group of Glycine?

Answer 7

H

Question 8

What is the R group of Alanine?

Answer 8

CH3

Question 9

What is the R group of Valine?

Answer 9

C(CH3)2H

Question 10

What is the R group of Tyrosine?

Answer 10

CH2PHENOL

Question 11

What is the R group of Lysine?

Answer 11

(CH2)4NH2

Question 12

What degrees of the structure of a protein does denaturation effect?

Answer 12

Secondary and Tertiary.

Question 13

What are the four main effects of denaturation of a protein?

Answer 13

• Reduced solubility
• Increased digestibility
• Altered water binding ability
• Loss of biological function

Question 14

What is the mechanism of action of peptidases?

Answer 14

Cleavage of peptide bonds

Question 15

What is the mechanism of action of exopeptidases?

Answer 15

Cleavage of one amino acid at a time

Question 16

What is the mechanism of action of endopeptidases?

Answer 16

Cleavage of internal bonds

Question 17

What is the mechanism of action of carboxypeptidases?

Answer 17

Cleavage at the -COOH terminal

Question 18

What is the mechanism of action of aminopeptidases?

Answer 18

Cleavage at the -NH2 terminal

Question 19

What are glycoproteins?

Answer 19

Structures composed of proteins and carbohydrates

Question 20

Where does glycosylation occur?

Answer 20

At the ER and Golgi Apparatus

Question 21

What are the functions of glycosylation?

Answer 21

• Proteins stabilisation
• Protein Orientation
• Affects solubility
• Creates compounds which can be used for signalling and cell to cell recognition.

Question 22

What are lipoproteins?

Answer 22

Structures containing proteins and lipids covalently or non-covalently bonded together,

Question 23

What is the function of lipoproteins?

Answer 23

The transport of water insoluble fats and cholesterol in the blood.

Question 24

What are metalloproteins

Answer 24

Protein molecules with a bound metal ion

Question 25

What is the role of haemoglobin?

Answer 25

Transport oxygen in the blood

Question 26

What type of protein is haemoglobin?

Answer 26

Quaternary metalloprotein

Question 27

What is meant by 'cooperative binding' of oxygen to haemoglobin?

Answer 27

Once one oxygen has bound to one haem group in the haemoglobin molecule, a conformational change occurs, making it easier for a second oxygen molecule to bind to a second haem group. This process repeats for the third and fourth haem group/ oxygen binding process.

Question 28

What is a peptide bond?

Answer 28

Covalent bond formed between the amino group on one amino acid and the carboxyl group on another. Involves the elimination of a H20 molecule.

Question 29

At what part of the cell should a peptide bond form?

Answer 29

At the ribosome

Question 30

What structure of a protein will not be affected by denaturation?

Answer 30

Primary structure

Question 31

What is the difference between fibrous and globular proteins?

Answer 31

Fibrous proteins are non- water soluble and have their function in support and structure. Globular proteins are water soluble and have their function in metabolic reactions (enzymes)