1.4 enzymes

Question 1

what is a catalyst

Answer 1

a substance that speeds up a reaction without changing the substances produced or being changed itself.

Question 2

what is an enzyme

Answer 2

proteins that have a very specific shape as a result of their primary, secondary, tertiary and quaternary structures. They act as biological catalysts and each enzyme will only catalyse a specific reaction or group of reactions.

Question 3

what is specificity

Answer 3

the characteristic of enzymes that means that, as a result of the very specific shapes resulting from their tertiary and quaternary structures, each enzyme will only catalyse a specific reaction or group of reactions.

Question 4

what is an anabolic reaction

Answer 4

is the reaction that builds up (synthesises) new molecules in a cell.

Question 5

what is a catabolic reaction

Answer 5

is a reaction which breaks down substances within a cell.

Question 6

what is metabolism

Answer 6

Metabolism is the sum of the anabolic and catabolic processes in a cell.

Question 7

what is a metabolic chain

Answer 7

A metabolic chain (metabolic pathway) is a series of linked reactions in the metabolism of a cell.

Question 8

what are intercellular enzymes

Answer 8

Intracellular enzymes are enzymes that catalyse reactions within the cell

Question 9

what are extracellular enzymes

Answer 9

enzymes that catalyse reactions outside of the cell in which they were made.

Question 10

what is activation energy

Answer 10

the energy needed for a reaction to get started.

Question 11

what is a substrate

Answer 11

the molecule or molecules on which an enzyme acts.

Question 12

what is the lock ad key hypothesis

Answer 12

the model that explains enzyme action by an active site in the protein structure that has a very specific shape. The enzyme and substrate slot together to form a complex as a key fits in a lock.

Question 13

what Is an active site

Answer 13

is the area of an enzyme that has a specific shape into which the substrate(s) of a reaction fit.

Question 14

what is the induced fit theory

Answer 14

is a modified version of the L+K hypothesis for enzyme action where the active site is considered to have a more flexible shape. Once the substrate enters the active site, the shape of that site is modified around it to form the active complex. Once the products have left the complex, the enzyme reverts to its inactive, relaxed form.

Question 15

why is the initial rate of reaction taken

Answer 15

is the measure taken to compare the rates of enzyme controlled reactions under different conditions.

Question 16

what is molecular activity

Answer 16

(turnover number) is the number of substrate molecules transformed per minute by a single enzyme molecule.

Question 17

what is the temperature coefficient

Answer 17

(Q0) is the measure of the effect of temperature on the rate of a reaction.

Question 18

what are enzyme exhibitors

Answer 18

are substances that slow down enzymes or stop them from working.

Question 19

what are reversible inhibition

Answer 19

is inhibition of the action of an enzyme by an inhibitor that does not permanently affect the functioning of the enzyme and can be removed from the enzyme. It is often used to control reaction rates within a cell.

Question 20

what are competitive inhibition

Answer 20

is inhibition in which the inhibitor molecule is similar in shape to the substrate molecule and competes with it for the active site of the enzyme (affected by both inhibitor and substrate concentrations).

Question 21

what are irreversible inhibition

Answer 21

is inhibition of the action of an enzyme that is permanent and cannot be undone. It is never used within cells to control the rate of reactions.

Question 22

what are noncompetitive inhibition

Answer 22

is inhibition in which the inhibitor does not compete for the active site but forms a complex with the enzyme or enzyme/substrate complex and changes the shape of the active site so it can no longer catalyse the reaction (affected only by concentration of inhibitor).

Question 23

what are regulatory enzymes

Answer 23

are enzymes that have a site separate to the active site where another molecule ca bind to have either an activating or inhibitory effect.

Question 24

what are end-product inhibition

Answer 24

is a control system in many metabolic pathways in which an enzyme at the beginning of the pathway is inhibited by one of the end products of the reaction.