[Maximum number: 1]
Fig. 1.1 is a diagram of an antibody molecule.
Fig. 1.1
(a)
(i)
Name the bond labelled Y.
[ 1 ]
[Maximum number: 2]
Fig. 1.1 shows the structures of four biological molecules A, B, C and D.
Fig. 1.1
(a)
Some of the molecules in Fig. 1.1 can form polymers.
[ 2 ]
(i)
Molecule D can form macromolecules with other similar monomers.
These macromolecules have three dimensional shapes held in place by interactions or bonds other than those between adjacent monomers.
Name two of these interactions or bonds.
1.
2.
[ 2 ]
[Maximum number: 3]
The cell surface membrane has a fluid mosaic structure.
(a)
High temperature can damage cell membranes. One factor contributing to this damage is the denaturation of membrane proteins.
Describe how proteins become denatured at high temperature and explain how this could lead to damaging cell membranes.
[ 3 ]
(a)
Fig. 1.2 is a ribbon diagram showing the three-dimensional structure of a protein from the bacterium Streptococcus.
Fig. 1.2
[ 3 ]
(i)
An analysis of the amino acid composition of the protein in Fig. 1.2 showed that it does not contain any cysteine residues.
Explain how the three-dimensional structure of the protein shown in Fig. 1.2 is held in place.
[ 3 ]
[Maximum number: 3]
Fig. 2.1 is a diagram of the structure of a protein channel for ions in a cell surface membrane.
Fig. 2.1a
Fig. 2.1 b
(a)
Channel proteins are examples of transmembrane proteins. The polypeptides are held together and also interact with phospholipids in the membrane.
Suggest how the polypeptides are held together and suggest how they interact with phospholipids.
[ 3 ]
(a)
Goblet cells in the human gas exchange system produce proteins called mucins.
[ 1 ]
(i)
The ends of mucin molecules contain many cysteine residues. Mucin strands are formed by joining the ends of mucin molecules together through covalent bonds between R-groups.
State the name of these covalent bonds.
[ 1 ]
[Maximum number: 1]
Which bonds are the last to break when an enzyme is heated?
A
disulfide
B
hydrogen
C
hydrophobic interactions
D
ionic
[Maximum number: 1]
Which have properties that are dependent on hydrogen bonds?
1 cellulose
2 a molecule of haemoglobin
3 water
A
1, 2 and 3
B
1 and 2 only
C
1 and 3 only
D
2 and 3 only
[Maximum number: 1]
Which type of bond holds together an -helix or -pleated sheet of a protein?
A
disulfide
B
hydrogen
C
ionic
D
peptide