6.4.2: Proteins

Question 1

Proteins

Answer 1

Condensation polymers of amino acids which are joined by peptide links.

Question 2

Two amino acids form a

with a … link

Answer 2

dipeptide

with a peptide link

Question 3

Peptide link

Answer 3

C(=O)-N(-H)

Question 4

If the two amino acids forming a dipeptide are different…

Answer 4

then two different dipeptides can be formed,

because the amino acids can join either way round

Question 5

Method for hydrolysing proteins

Answer 5

aqueous 6 moldm-3 hydrochloric acid

and then heat the mixture under reflux for 24hrs

Question 6

Four stages of protein structure

Answer 6

primary
secondary
tertiary
quaternary

Question 7

Primary structure

Answer 7

The sequence of amino acids in the polypeptide chain

Question 8

Secondary structure

Answer 8

Peptide links between amino acids form hydrogen bonds with each other, causing the chain to spiral into an alpha helix or fold into a beta pleated sheet.

Question 9

Tertiary structure

Answer 9

The chain of amino acids becomes coiled and folded in a way that identifies the protein and forms a 3D structure. Extra bonds such as disulfide and hydrogen bonds form in different parts of the polypeptide chain.

Question 10

Two types of bonds that hold proteins in shape

Answer 10

hydrogen bonds

disulfide bonds

Question 11

Residue

Answer 11

An amino acid that is part of a protein

Question 12

Disulfide bonds

Answer 12

Occurs between residues of the amino acid cysteine

to form -S-S-

Question 13

Disulfide bonds in proteins

Answer 13

help to stabilise the tertiary structure

Question 14

Factors that affect hydrogen and disulfide bonds so can change the shape of proteins
2

Answer 14

temperature and pH