Enzymes🧫

Question 1

What is metabolism?

Answer 1

Chemical reactions taking place in your body

Question 2

What are anabolic reactions?

Answer 2

Building up/synthesis

Question 3

What are catabolic reactions?

Answer 3

Breaking down

Question 4

What are enzymes?

Answer 4

Molecules controlling reactions in your body

Question 5

What level of protein structure is shown by enzymes?

Answer 5

Tertiary structure - globular, specific 3D shape, hydrogen bonds, ionic bonds, disulphide bonds

Question 6

Properties of enzymes

Answer 6

• Specific - will only catalyse with a particular reaction
• Not used up in the reactions - reusable
• Combine with their substrates to form enzyme/substrate complexes - release products when finished
• Only a small amount is used
• Fast acting - high turnover number
• Affected by changes in temp or pH
• Many can only work if a cofactor is present
• Can be slower or stopped by inhibitors

Question 7

What are intracellular enzymes?

Answer 7

Functions within the cell where it was produced

Question 8

What are extracellular enzymes?

Answer 8

Secreted by a cell and functions outside the cell

Question 9

What is the lock and key theory?

Answer 9

• Explains why enzymes are specific
• Enzymes have an active site made up of 3-12 amino acids - has the right structure to fit with the substrate
• The active site and substrate lock into place to form an enzyme/substrate complex
• Products are formed at active site - have different shape so are repelled - active site is freed up

Question 10

What is the induced fit theory?

Answer 10

• Suggests active site may not exactly correspond to shape of the substrate
• Active site is more flexible - module itself round the substrate
• When it’s binds closely to the substrate the active site catalyses the reaction
• Products are repelled
• Enzyme reverts to relaxed shape

Question 11

TIP

Answer 11

Always mention kinetic energy and more frequent successful collisions

Question 12

What is activation energy?

Answer 12

The energy needed to start a chemical reaction

Question 13

How does lowering the activation energy work?

Answer 13

Provides a different pathway for the reaction as the enzymes reduce the input of energy needed and allow reactions to take place at lower temperatures

Question 14

What does lysozyme do?

Answer 14

Breaks chemical bonds in the outer wall of the bacteria - targets peptidoglycan

Question 15

What is denaturing?

Answer 15

• When factors alter the tertiary structure of the enzymes/3D shape by breaking hydrogen bonds - includes active site
• Permanent change

Question 16

What is inactivation?

Answer 16

Cooling the enzyme below the optimum temperature

Question 17

How does temperature affect the rate of activity of enzymes?

Answer 17

• Increase give molecules more K.E which increases chance of successful collisions and impact - increases rate of reaction
• Only increases to an optimum temp - begins to denature - hydrogen bonds break

Question 18

How does pH affect the rate of activity of enzymes?

Answer 18

• Small changes in pH affect ROR - these are reversible - inactivation
• Extreme changes in pH can denature an enzyme
• Free H+ and OH- ions can affect the charges of amino acid side chains of the enzyme’s active site
• Affects hydrogen bonds - alters tertiary

Question 19

How can a pH buffer help the rate of activity of enzymes?

Answer 19

It is a chemical that maintains a constant pH by absorbing excess ions

Question 20

How does enzyme concentration affect the rate of activity of enzymes?

Answer 20

• ROR is directly proportional to the enzyme concentration

* Increasing enzyme concentration increases rate of reaction

Question 21

How does substrate concentration affect the rate of activity of enzymes?

Answer 21

• Increasing the substrate concentration increases ROR up to a certain point - increases frequency of successful collisions
• All the active sites become filled - working at maximum rate

Question 22

What is an inhibitor?

Answer 22

• A substance that can slow down or stop a reaction
• Combines with the enzyme and stops it from attaching to the substrate
• Either reversible or non-reversible

Question 23

What is a competitive inhibitor?

Answer 23

• Similar structure to substrate
• Competes with substrate for active site of enzyme
• Prevents formation of enzyme/substrate complexes - ROR decreases
• Increasing substrate concentration can reduce the effects of a competitive inhibitor

Question 24

What is a non competitive inhibitor?

Answer 24

• Doesn’t bind to active site - attaches to another part of the enzyme
• Alters overall shape of the enzyme - including active site
• Substrate can no longer bind to active site
• Increasing substrate concentration doesn’t affect inhibition - not competing with substrate

Question 25

What are immobilised enzymes?

Answer 25

Enzymes that are bound to inert (unreactive) or trapped in a matrix

Question 26

Advantages of immobilised enzymes

Answer 26

* More stable at higher temps and a wider range of pHs * Can be added or removed easily - helpful in controlling the reaction and avoids contamination, ensuring that a pure product is formed * Easily recovered and reused in industrial processes * A mixture of enzymes with different optimum pHs and temps can be used together

Question 27

Disadvantages of immobilising enzymes

Answer 27

Fixing process may damage enzymes

Question 28

Examples of immobilised enzymes

Answer 28

Biofuels, food production

Question 29

What are biosensors?

Answer 29

Device which uses enzymes to detect the presence of chemicals

Question 30

What is polymerisation?

Answer 30

Joining together of monomers

Question 31

When is the enzyme concentration the limiting factor?

Answer 31

At the start of the graph

Question 32

When is the substrate concentration the limiting factor?

Answer 32

Near the plateau when the reaction begins to slow down - most of the substrate has been converted into product - limits chance of a successful collision

Question 33

Why is the use of a control important in enzyme investigations?

Answer 33

It shows that it is the enzymes that are causing the effect that you are measuring (dependant variable)

Question 34

What is the usual control for an enzyme reaction?

Answer 34

* Boil and cool the enzyme solution * This denatures the enzymes and ensures they will not catalyse any reactions * The experiment should then be repeated using the boiled and cooled solution - if the same results are obtained, indicates another factor is influencing the results