Enzymes

Question 1

What type of proteins are enzymes

Answer 1

Globular proteins

Question 2

Enzyme definition

Answer 2

Protein molecule that acts as a biological catalyst and increases the rate of reactions inside an organism with a complex tertiary structure.

Question 3

What is the active site of an enzyme

Answer 3

Part of the enzyme which binds to the substrate and catalyses the reaction.

Question 4

Lock and key theory

Answer 4

Active site shape is complementary to shape of substrate. Substrate molecules form temporary bonds with AAs of active site (charged groups attract) to produce enzyme-substrate complex. Reaction complete-products released and enzyme unchanged. Enzyme only catalyse one specific reaction as active site only complementary with one specific substrate.

Question 5

Induced fit theory

Answer 5

Substrate enters active site enzyme changes shape slightly to fit shape of substrate. Only specifically shaped substrate induces correct change in enzyme active site.

Question 6

Activation energy

Answer 6

Minimum amount of energy required to break bonds and start the reaction and for products to be formed. The energy makes molecules unstable enough to react.

Question 7

How do enzymes reduce activation energy

Answer 7

Reduce the stability of bonds in the reactants making it more reactive. Provide an alternative reaction pathway with lower AE.

Question 8

Why are enzymes needed inside organisms

Answer 8

Without them reactions would be too slow, would need extremely high temperatures and pressures to reach activation energy which would kill body cells.

Question 9

What is the metabolism of an organism

Answer 9

The sum of all the chemical reactions occurring within it.

Question 10

Intracellular enzymes

Answer 10

Produced and function inside the cell

Question 11

Extracellular enzymes

Answer 11

Secreted by cells and catalyse reactions outside cells

Question 12

Example of intracellular enzyme

Answer 12

Catalase, converts hydrogen peroxide which is a harmful by product into water and oxygen

Question 13

Example of extracellular enzyme

Answer 13

Amylase- extracellular as macromolecules being digested too big to enter cell, hydrolyses starch into simple sugars.

Question 14

What is a catabolic reaction

Answer 14

When large substrate molecules are broken down into smaller molecules

Question 15

What is an anabolic reaction

Answer 15

When smaller molecules are built up into bigger molecules

Question 16

How does enzyme concentration affect rate

Answer 16

Increase concen=increases number of active sites available for substrate to collide with= more ES complexes. Rate stops increasing when amount of substrate becomes limiting factor.

Question 17

How does substrate concentration affect enzyme action

Answer 17

Increases rate as there are more substrate molecules= more collisions so more ES complexes. Rate slows as enzyme concen becomes limiting factor , when all active sites occupied(saturation point) rate no longer increases

Question 18

How does temperature affect enzyme action

Answer 18

As temp increases so does rate as more KE so molecules move faster so more freq collisions between enzymes and substrates= increases number of ES complexes. Once temp goes over optimum temp for enzyme the rate decreases, eventually denatured

Question 19

How does an enzyme become denatured

Answer 19

At high temps enzyme molecules vibrate too much and bonds are broken which maintain tertiary structure, active site changes shape=no more ES complexes can be made as substrate no longer fits

Question 20

How does pH affect enzyme action

Answer 20

Each enzyme has optimum pH, above and below this the H+ and OH- ions disrupt ionic and hydrogen bonds holding tertiary structure in place= active site changes shape and no more ES complexes can form as denatured

Question 21

What are enzyme inhibitors

Answer 21

Molecules other than the substrate specific to the enzyme which bind to the enzyme and slow or prevent enzyme activity

Question 22

What are competitive inhibitors and where do they bind

Answer 22

Have a similar shape to substrate so bind to active site of enzyme, block active site so substrate cannot bind=no ES complex formed

Question 23

What are non-competitive inhibitors and where do they bind

Answer 23

Have a different shape to that of the substrate so do not bind to active site but to site away from this called allosteric site.

Question 24

How do non-competitive inhibitors stop enzymes binding to substrates

Answer 24

Bind to allosteric site which causes the active site of the enzyme to change=no longer complimentary to substrate=no ES complexes can be formed.