[Maximum number: 1]

Which statement is only true for the induced fit theory of enzyme action?

A few amino acids give the active site a specific shape.

An enzyme has a substrate with a specific shape.

The enzyme changes shape in the presence of the substrate.

The substrate molecules are complementary to the active site.

[Maximum number: 1]

The following statements are about enzymes.
1 Folding of an enzyme molecule causes the formation of the active site.
2 The shape of the active site changes to enable the substrate to bind.
3 Temporary bonds hold the substrate in the active site.
4 More enzyme-substrate complexes are formed at the optimum temperature.
Which statements are correct for the induced fit hypothesis?

1 and 2

1 and 3

2, 3 and 4

2 and 4 only

[Maximum number: 4]

Fig. 3.1 shows the structure of the enzyme lysozyme.

Fig. 3.1

(a)

Lysozyme hydrolyses the $\beta-1,4$ glycosidic bonds present in compounds found in bacterial cell walls.

[ 4 ]

(i)

Lysozyme uses the induced fit mechanism.

Explain the mode of action of an enzyme that uses the induced fit mechanism.

[ 4 ]

[Maximum number: 1]

Influenza virus has an enzyme called neuraminidase which breaks down glycoproteins in the membrane of the cell that the virus will infect. The glycoprotein binds to the active site of neuraminidase by induced fit.

Which statements about the induced fit hypothesis of enzyme action are correct?
1 The active site must have a complementary shape to the substrate for them to bind together.

2 This enzyme is less likely to be affected by non-competitive inhibitors than an enzyme working by the lock and key mechanism.

3 The substrate is converted to product by specific R-groups in the active site just like the lock and key mechanism.

1 and 2

2 and 3

2 only

3 only

[Maximum number: 3]

Tobacco smoking is known to be associated with atherosclerosis and emphysema.

(a)

The synthesis and release of elastase enzymes by macrophages and neutrophils is an important feature in the development and progression of emphysema. Elastase causes the breakdown of the protein elastin, the main component of elastic fibres.

[ 3 ]

(i)

Elastase has an active site with a specific shape. The mode of action of this enzyme supports the lock and key hypothesis.

Explain the mode of action of elastase.
You may use the space below to draw a diagram or diagrams to help your answer.

[ 3 ]

[Maximum number: 1]

What describes the induced fit mode of action of an enzyme?

The binding of the active site to the substrate causes the enzyme to change shape.

The substrate and active site have complementary shapes that form temporary bonds.

The substrate causes a change in enzyme shape so the active site can bind.

The substrate changes shape so it can bind to the active site.

[Maximum number: 1]

Which levels of protein structure would always be changed if an enzyme works by the induced fit hypothesis?

primary

secondary

tertiary

quaternary

key

✓

$\boldsymbol{\chi}$

$\boldsymbol{\times}$

✓ = always changed

$\boldsymbol{\chi}$

✓

$\boldsymbol{\times}$

x= not changed

$\boldsymbol{\chi}$

✓

$\boldsymbol{\times}$

[Maximum number: 1]

Influenza virus has an enzyme called neuraminidase which breaks down glycoproteins in the surface membrane of the cell that the virus will infect. The glycoprotein binds to the active site of neuraminidase by induced fit.

Which statements about the induced fit hypothesis of enzyme action are correct?
1 The active site must have the same shape as the substrate for them to bind together.

2 This enzyme is less likely to be affected by non-competitive inhibitors than an enzyme working by the lock-and-key mechanism.

3 The substrate is converted to product by specific R-groups in the active site just like the lock-and-key mechanism.

1 and 2

2 and 3

2 only

3 only