3.1.4.1 proteins

Question 1

what is the monomer of a protein?

Answer 1

amino acid

Question 2

what are the three groups that make up an amino acid?

Answer 2

• amine group (NH₂).
• r group.
• carboxyl group (COOH).

Question 3

how many different R groups/ amino acids are there?

Answer 3

20

Question 4

what is a chain of amino acids called?

Answer 4

polypeptide chain.

Question 5

how is a dipeptide formed?

Answer 5

• the formation of two amino acids by a condensation reaction.
• formed between a carboxyl and amine group.
• releases water.
• forms a peptide bond.

Question 6

what kind of bond forms between two amino acids?

Answer 6

peptide bond.

Question 7

how can a dipeptide be broken apart?

Answer 7

by a hydrolysis reaction which requires water.

Question 8

what is the primary structure of a protein?

Answer 8

a long chain of amino acids held together by peptide bonds, in which the order and sequence of amino acids are key in determining the positions of the R groups and therefore the 2D and 3D shapes formed.

Question 9

what is the secondary structure of a protein?

Answer 9

• when the amino acid chain folds into either an alpha helix or beta-pleated sheet.
• what causes the chain to fold up is the hydrogen bonds between the R groups.

Question 10

what is the tertiary structure of a protein?

Answer 10

• when the polypeptiode chain folds up into a complex, specific 3D shape.
• this is due to various forces of attraction between the R groups.

Question 11

what does the tertiary structure determine?

Answer 11

whether a protein is globular or fibrous.

Question 12

what is the quaternary structure of a protein?

Answer 12

• it is made up of two or more polypeptide chains.
• the polypeptide chains are held together by the intermolecular forces between the R groups.
• quaternary structures may involve prosthetic groups.

Question 13

what type of forces are in the primary structure of proteins?

Answer 13

peptide bonds

Question 14

what type of forces are in the secondary structure of proteins?

Answer 14

peptide and hydrogen

Question 15

what type of forces are in the tertiary structure of proteins?

Answer 15

peptide, hydrogen, ionic, disulphide, london.

Question 16

what type of forces are in the quaternary structure of proteins?

Answer 16

peptide, hydrogen, ionic, disulphide, london.

Question 17

what are hydrogen bonds?

Answer 17

the weak attraction between slightly positive H+ ions and the slightly negative O/N/F ions.

Question 18

what can break hydrogen bonds?

Answer 18

high temperatures or altered pHs.

Question 19

what are ionic bonds?

Answer 19

the electrostatic attraction between negative and positive ions.

Question 20

what can break ionic bonds?

Answer 20

changing pH.

Question 21

what are disulphide bridges?

Answer 21

STRONGEST BOND
covalent bonds between sulfur molecules and cystine R group.

Question 22

how can disulphide bridges be broken?

Answer 22

by reducing agents.

Question 23

what are london forces?

Answer 23

the weak forces of attraction between non-polar R groups.

Question 24

what can break london forces?

Answer 24

an increase in temperature.

Question 25

what are some examples of globular proteins?

Answer 25

enzymes and haemoglobin.

Question 26

what are some examples of fibrous proteins?

Answer 26

collagen and keratin.

Question 27

how many chains is haemoglobin made up of?

Answer 27

4 polypeptide chains.
= 2 beta chains and 2 alpha chains.

Question 28

what are some characteristics of haemoglobin?

Answer 28

• 4 prosthetic haem groups.
• globular protein.
• soluble.
• has hydrophilic parts on the outside.

Question 29

what are some characteristics of fibrous proteins?

Answer 29

insoluble in water = good for structure and support

Question 30

what is the test for proteins?

Answer 30

biuret test:
positive colour from blue to purple.