Enzymes

Question 1

what are enzymes

Answer 1

Biological catalysts that lowers the activation energy of a reaction

Question 2

Explain the lock and key model

Answer 2

• Active site is a fixed shape , it is complementary to one substrate.
• after a successful collision, an enzyme substrate complex forms leading to a reaction.

Question 3

Explain the induced fit model

Answer 3

Before the reaction the enzyme active site is not complementary to substrate so doesn’t fit in

• Active site shape changes as substrate binds and an enzyme substrate complex is formed
• This distorts bonds in substrate leading to a reaction

Question 4

What determines the property of an enzyme

Answer 4

The properties of an enzyme relates to the tertiary structure of its active site and its ability to combine with complementary substrate to form an enzyme substrate complex

Question 5

How r enzymes specific

Answer 5

• they have a specific shaped tertiary structure and active site. The sequence of amino acids determine the tertiary structure.
• Active site is complementary to a specific substrate
• Enabling only this enzyme to bind to the active site which allows ES complex to form

Question 6

How does enzyme concentration effect the rate of reations.

Answer 6

Increasing the enzyme conc=rate of reaction increases
More enzymes are added so more available active sites so more successful ES collisions and ES complexes. But at a certain point rate of reaction plateaus because the substrate is limiting factor as all substrate are in use

Question 7

How does substrate concentration effect the rate of reaction

Answer 7

Increasing substrate conc.=rate of reaction increases
There is more successful ES collisions and ES complexes. But at a certain point the rate of reaction plateaus because the enzyme conc. is limiting as all active site saturated

Question 8

How does temperature effect the rate of reactions

Answer 8

Increasing temp to optimum = rate of reaction increases as there is increase in kinetic energy so more successful ES collisions and ES complexes.

However increasing temp above optimum = rate of reaction fall.
Enzymes are denatured as tertiary structure and active site change shapes (hydrogen, ionic bonds break) so fewer ES collisions and ES complexes formed as substrate no longer binds to active site

Question 9

How does pH effect rate of reaction

Answer 9

pH above/below optimum= the rate of reaction decreases cause teh enzymes are denatured; tertiary structure and active site change shape.
Complementary substrate no longer binds so fewer ES collisions and ES complexes.

Question 10

Role of competitive inhibitors

Answer 10

They decrease the rate of reaction.

They have similar shape to substrate and compete for active sites so substrate cannot bind. So fewer ES complexes.

Increasing the substrate conc. reduces the effect of the inhibitor.

Question 11

Role of non competitive inhibitors

Answer 11

Decrease rate of reaction

Bind to Allosteric site.
Enzyme tertiary structure change shape so substrate can’t bind to active site
Fewer complexes
Increasing the substrate conc. has no effect on rate of reaction as causes permanent change to active site.