Enzymes

Question 1

What are anabolic reactions?

Answer 1

Reactions that build larger, more complex molecules from smaller, simpler ones, requiring an input of energy, typically from ATP

Question 2

What are catabolic reactions?

Answer 2

Reactions that break down large, complex molecules into smaller, simpler ones and in the process release energy. Eg hydrolysis

Question 3

How do enzymes catalyse reactions?

Answer 3

By lowering the activation energy

Question 4

What level of protein structure do enzymes have?

Answer 4

They are tertiary globular proteins

Question 5

Lock and key hypothesis means�

Answer 5

The substrate fits perfects into the enzyme active site

Question 6

Theory of induced fit means�

Answer 6

The shape of the active site changes to fit more perfectly around the substrate, putting pressure on the bonds in the substrate to lower the activation energy

Question 7

What is formed when the substrate binds to the enzyme’s active site?

Answer 7

An enzyme substrate complex

Question 8

Which enzymes work inside the cell?

Answer 8

Intracellular

Question 9

Which enzymes work outside the cell?

Answer 9

Extracellular

Question 10

The active site and substrate shapes are�

Answer 10

Complementary

Question 11

Enzymes only catalyse one substrate, so they are described as�

Answer 11

Specific

Question 12

The rate of an enzyme catalysed reaction increases with increasing temperature due to…

Answer 12

Increased kinetic energy causing increased frequency of successful collisions

Question 13

When the temperature is too high enzymes will…

Answer 13

Denature, meaning the hydrogen bonds break and the shape of the active site is lost

Question 14

Enzyme controlled reactions will be fastest at a temperature and pH described as the

Answer 14

Optimum

Question 15

The four factors that can limit the rate of an enzyme controlled reaction are

Answer 15

Temperature, pH, enzyme concentration, substrate concentration

Question 16

What does a buffer do?

Answer 16

Maintain a constant pH

Question 17

What happens when pH is only slightly above or below the optimum?

Answer 17

Small changes in pH cause small reversible changes in enzyme structure, causing inactivation of the enzyme. This will reduce the rate of reaction

Question 18

What happens when pH is far above or below the optimum?

Answer 18

Ionic bonds and hydrogen bonds are broken, so the enzyme will permanently denature and lose its shape

Question 19

What happens when you increase the substrate concentration in an enzyme controlled reaction?

Answer 19

More successful collisions will occur forming more enzyme substrate complexes and more products. However eventually a plateau will be reached as all the enzyme active sites are occupied at one time. Enzyme concentration becomes the limiting factor.

Question 20

What happens when you increase the enzyme concentration in an enzyme controlled reaction with excess substrate present?

Answer 20

More successful collisions will occur forming more enzyme substrate complexes and more products. However eventually a plateau will be reached as the substrate concentration becomes the limiting factor.

Question 21

What is inhibition?

Answer 21

Inhibition is when enzyme action is slowed down or stopped by another substance

Question 22

What is a competitive inhibitor?

Answer 22

A competitive inhibitor is structurally similar to the substrate and binds to the enzyme active site, blocking it.

Question 23

What is turnover number?

Answer 23

An enzyme’s turnover number is the maximum number of substrate molecules it can convert to product molecules per unit time.

Question 24

What is a non competitive inhibitor?

Answer 24

Non-competitive inhibition involves an inhibitor binding away from the active site at an allosteric site, altering the active site’s shape so the substrate can no longer bind

Question 25

What effect will increasing substrate concentration have when a competitive inhibitor is present?

Answer 25

If the substrate concentration is increased so will the rate of reaction.

Question 26

What effect will increasing substrate concentration have when a non competitive inhibitor is present?

Answer 26

There will be no change to the rate of reaction

Question 27

What do you call a site that is not the active site?

Answer 27

Allosteric site

Question 28

Give an example of a non competitive inhibitor and which reaction it affects

Answer 28

Cyanide is a respiratory inhibitor

Question 29

Why are enzymes useful in industry?

Answer 29

They lower the activation energy of a reaction so it occurs at a lower temperature, saving energy and increasing efficiency

Question 30

What are immobilised enzymes?

Answer 30

Enzymes which are held in an inert support or matrix, for example immobilised in beads

Question 31

Give the advantages of immobilising enzymes

Answer 31

They can be re-used, they are more stable at extremes of temperature and pH, they do not contaminate the product, enzymes can be combined or used in continuous processes

Question 32

Give the disadvantages of immobilised enzymes in alginate beads

Answer 32

The substrate must diffuse into the gel, which takes time. The gel can alter the shape of the active site. Both of these lower the reaction rate. It can be expensive to initially set up and to sterilise the system if contaminated

Question 33

What is a biosensor?

Answer 33

An instrument that uses enzymes to detect a specific molecule in a mixture of molecules. Eg glucose in blood. They are used for medical and environmental monitoring