Core Concepts: Enzymes

Question 1

What is an Enzyme

Answer 1

A biological catalyst

Question 2

What is an Anabolic reaction

Answer 2

A reaction that builds up molecules

Question 3

What is a Catabolic reaction

Answer 3

A reaction that breaks down molecules

Question 4

What is Metabolism

Answer 4

All the organism’s chemical processes

Question 5

What is Metabolic Pathway

Answer 5

A series of enzyme controlled reactions in which a product of one reaction is a reactant in the next

Question 6

What is the structure of enzymes

Answer 6

• Globular proteins that have a tertiary structure
• The 3D shape of an enzyme molecule creates an active site.
• The active site has a specific shape, which is determined by the sequence of amino acids in the polypeptide.
• If the sequence of amino acids changes then the active site will change shape and the substrate will not bind to the active site because they are no longer complementary

Question 7

What are the theories on how enzymes work

Answer 7

• Lock & Key
• Induced Fit

Question 8

What is the wording on how enzymes work

Answer 8

• Enzyme has a specifically shaped active site
• Substrate is complementary in shape
• Enzyme + Substrate for an Enzyme Substrate Complex
• Products are released

Question 9

What is the Lock & Key Model

Answer 9

• Substrate is complementary to the enzym
• Substrate fits into the active site forming an ESC
• The reaction occurs and the products are released
• Enzyme remains unchanged

Question 10

What is the Induced Fit Model

Answer 10

• The active site and substrate are not
  fully complementary in shape
• Reactive groups in these areas align and the substrate forces its way into the active site
• Both areas change structure slightly and the bonds in the substrate weaken
• Reaction occurs at a lower activation energy
• Lysosome

Question 11

Why do changes in PH of a solution affect the structure of a Protein

Answer 11

Large changes in pH can disrupt ionic and hydrogen bonds in the enzyme causing permanent changes to the shape of the active site. This prevents the formation of enzyme/substrate complexes, denaturing the enzyme

Question 12

What factors affect Enzyme Rate of Reaction

Answer 12

• Temperature - E_K
• PH
• Enzyme Concentration
• Substrate Concentration
• Inhibitors

Question 13

How can you measure enzyme rates of reactions

Answer 13

• Time taken for reaction to occur
• Mass / Volume of product formed
• Mass / Volume of substrate

Question 14

What happens to enzyme rate of reaction at low temperatures

Answer 14

At low temperatures there will be low kinetic energy
Per unit of time there will be:
* Fewer enzyme substrate collisions
* Therefore fewer enzyme substrate complexes will form
* Fewer products will be produced

Question 15

What happens to an enzyme rate of reaction at the optimum temperature (50°C)

Answer 15

At the optimum temperature -50C
Per unit of time there will be:
* The maximum number of enzyme substrate collisions
* The maximum number of enzyme substrate complexes will
form
* The maximum number of products will be produced

Question 16

What happens to enzyme rate of reaction as the temperature goes over the optimum

Answer 16

At temperatures over the optimum- too much kinetic energy.
60-900C
Structural impact:
* The hydrogen, ionic, disulphide and hydrophobic bonds will
begin to break.
* The specific tertiary structure will be change and
* The specific shaped active site will no longer be
complementary to the substrate.
* Enzymes have denatured
Per unit of time there will be:
* Less/ no successful enzyme substrate collisions
* Therefore less/ no enzyme substrate complexes will form
* Less/ no products will be produced

Question 17

How does a competetive inhibitor work

Answer 17

• Competitive inhibitors are complementary in shape to the active site of the enzyme
• They prevent the formation of enzyme substrate complexes by blocking
  the active site.
• They do not bind permanently

Question 18

How does a non competetive inhibitor work

Answer 18

• Non-competitive inhibitors bind to the enzyme away from the active site at an
  ‘allosteric’ site
• This alters the shape of the active site so no enzyme-substrate complexes can be formed
• Some inhibitors bind reversibly, while others bind irreversibly

Question 19

Can an enzyme with a competetive inhibitor reach it’s maximum rate

Answer 19

Yes

Question 20

Can an enzyme with a non competetive inhibitor reach it’s maximum rate

Answer 20

No

Question 21

How can enzymes be immobilised and what is the effect on the enzymes

Answer 21

• Immobilised on an alginate membrane
• Reduces ability of the polypeptide chain to move
• Stabilises enzyme and changes to temperature have less of an effect on 3d shape

Question 22

Why are immobilised enzymes used in industry

Answer 22

• The enzyme can be recovered and reused redusing costs
• Only small amounts of an enzyme are needed
• Product is also not contaminated by the enzyme
• Several enzymes can be used at once
• Lower/higher temperatures can be used

*

*

Question 22

What is an example of an immobilised enzyme being used in industry and how does it work

Answer 22

An industrial example is the use of immobilised lactase, which is used to produce lactose-free milk:
* the enzyme is immobilised in alginate gel beads
milk is passed over the beads and the enzymes digest the lactose into glucose and galactose
* the milk is not contaminated by the enzyme and the beads can be used many times

Question 22

How are immobilised enzymes used in medicine

Answer 22

• Because enzymes are specific to a particular substrate, they can be used as biosensors or analytical reagents.
• The glucose oxidase electrode is one example of a biosensor that is important for diabetics, as it can detect glucose levels in the blood. The biosensor works as follows:
  - the enzyme glucose oxidase is immobilised in a gel
  - a small sample of blood is passed over the enzyme
  - when glucose in the blood comes into contact with the enzyme, a reaction occurs,
  - which releases energy (chemical)
  - the energy released is converted into electrical impulses
  - the more energy released, the higher the concentration of glucose in the blood
  - a digital display of accurate concentration is available by referring to reference data stored in the processing unit