Enzymes

Question 1

What is metabolism

Answer 1

the combination of all the chemical reaction in the body, that occur in sequences called metabolic pathways

Question 2

What are anabolic reactions

Answer 2

They build up large molecules from smaller ones, eg, glucose into starch

Question 3

What are catabolic reactions

Answer 3

They break down large molecules into smaller ones, eg, proteins into amino acids

Question 4

What are intracellular enzymes

Answer 4

They work inside the cell

Question 5

What are extracellular enzymes

Answer 5

They work outside the cell

Question 6

Enzymes are proteins with what type of structure and therefore are held in shape by what type of bonds

Answer 6

They have a tertiary structure and can therefore be held together by hydrogen, ionic and disulphide bridge bonds

Question 7

What are thermostable enzymes

Answer 7

Enzymes that are more resistant to high temperatures

Question 8

How do enzymes work

Answer 8

They lower the activation energy needed for a reaction to occur making it easier to start a reaction

Question 9

What effect does temperature have on enzyme-controlled reactions

Answer 9

It speeds them up initially as the kinetic energy is increased. Then as it gets hotter the active site is weakened and the reaction slows rapidly

Question 10

What are thermophilic bacteria

Answer 10

Bacteria with enzymes that are highly thermostable

Question 11

What are acidophile bacteria

Answer 11

Bacteria that can survive pH 1

Question 12

What effect does the concentration of substrate have on enzyme-controlled reactions

Answer 12

A greater concentration increases the rate of reaction before plateauing as all the active sites are occupied

Question 13

What is competitive inhibition and give an example

Answer 13

Where a molecule that is a similar shape to the substrate fits the active site of an enzyme and prevents the substrate being broken down. For example, methanol inhibits ethanol being broken down by alcohol dehydrogenase

Question 14

What is non-competitive inhibition and give an example

Answer 14

When a molecule binds to an enzyme somewhere other than the active site and changes the shape of the active site so the substrate not longer fits. For example, potassium cyanide binds to cytochrome oxidase and prevents respiration reactions

Question 15

What is end-product inhibition and give an example

Answer 15

Where the end product in a metabolic pathway is an inhibitor for another stage of the pathway, stopping more product being created. For example, ATP is capable of inhibiting stage 1 of the respiratory metabolic pathway

Question 16

What is an allosteric enzyme

Answer 16

They only work if an activator molecule attaches to it and causes the active site to change shape to accommodate a substrate

Question 17

What is a buffer

Answer 17

Used to maintain a constant pH in enzyme-controlled reactions

Question 18

How are enzymes immobilised

Answer 18

By trapping them in a large, insoluble matrix or in a mesh.

Question 19

What are the benefits of using immobilised enzymes

Answer 19

Less likely to denature
Are more thermostable
Easy to recover and reuse after a reaction
Allows you to easily add or remove enzymes giving you greater control over a reaction

Question 20

How do biosensors work

Answer 20

Enzymes can detect the presence of specific molecules in a mixture. They produce a chemical signal which, when connected to an electrical device is able to produce an electrical impulse which is proportional to the concentration of the molecules in the mixture.

Question 21

What are biosensors used for

Answer 21

Blood glucose monitors used by diabetics

Question 22

What are the two possible structures for the enzyme-substrate complex

Answer 22

Induced fit and lock & key