2.4- Enzymes

Question 1

What are enzymes?

Answer 1

Biological catalyst which speed up chemical reaction.

They work both at a cellular level and for the organism as a whole

Question 2

What are the two main types of enzyme action called?

Answer 2

Intracellular and extracellular

Question 3

What are three examples of processes which involve enzymes?

Answer 3

Respiration
Digestion
Production of collagen

Question 4

What is an example of an intracellular enzyme?

Answer 4

Catalase

Question 5

What is the function of catalase?

Answer 5

It works inside cells to catalyses the breakdown of hydrogen peroxide to harmless oxygen and water

Question 6

What are two examples of extracellular enzymes?

Answer 6

Amylase

Trypsin

Question 7

What is the function of amylase?

Answer 7

It is found in saliva and catalyses the breakdown of starch into maltose in the mouth

Question 8

What is the function of trypsin?

Answer 8

Trypsin catalyses the hydrolysis of peptide bonds turning big polypeptides into smaller ones
It is produced in the pancreas and secreted into the small intestine

Question 9

What type of proteins are enzymes?

Answer 9

Globular

Question 10

Ronald is labelling an image of an enzyme in action. What are three things he should label?

Answer 10

Active site
Substrate
Products

Question 11

What is the specific shape of an active site determined by?

Answer 11

The enzymes tertiary structure

Question 12

How do enzymes affect activation energy?

Answer 12

They reduce the amount of activation energy that is needed which speeds up the rate of reaction

Question 13

When a substrate binds to an active site, an enzyme-substrate complex is formed. How does this lower the activation energy?

Answer 13

Attaching molecules close together reduces repulsion between the molecules so they can bond more easily
An active site puts a strain on bonds in the substrate so it can break up more easily

Question 14

What are the two models which explain the action of enzymes?

Answer 14

The lock and key model

The induced fit model

Question 15

What is explained in the induced fit model which is not in the lock and key model?

Answer 15

Why enzymes are so specific and only Bond to one particular substrate
How the active site changes shape slightly

Question 16

Explain how temperature affects enzyme activity.

Answer 16

An increase in temperature means that molecules have more energy and the more likely to collide and create enzyme-substrate complexes
If the temperature goes above a certain level some of the bonds that hold enzyme in shape of broken and the active site changes shape. At this point the enzyme is denatured

Question 17

How can we show how the rate of reaction changes with temperature?

Answer 17

With the temperature coefficient Q10

Q10=2 means the rate doubles when temperature is increased by 10 degrees celcius

Question 18

How does pH affect enzyme activity?

Answer 18

All enzymes have an optimum PH value
Above and below optimum pH, hydrogen and hydroxide ions can interfere with ionic and hydrogen bonds which hold enzymes tertiary structure in place. This makes the active site change shape

Question 19

How does enzyme concentration affect the rate of reaction?

Answer 19

The more enzyme molecules that are , the more likely a substrate is to collide with one and form an enzyme substrate complex. So increasing the concentration of the enzyme increases the rate of reaction.
However, if the amount of substrate is limited, there is a point where enzyme concentration has no further effect

Question 20

How does substrate concentration affect the rate of reaction?

Answer 20

The high the substrate concentration the faster the reaction, as more substrate molecules means achalasia green substrate and enzyme is more likely
However, this is only true up to a certain point as once all the active sites are full, adding more substrate makes no difference to the rate of reaction

Question 21

How can you measure the rate of an enzyme controlled reaction? (two-ways)

Answer 21

Using a gas syringe

Regular sampling of a mixture at timed intervals

Question 22

What is the definition of a cofactor?

Answer 22

A substance which an enzyme needs to work. They help the enzyme and substrate bind together. They don’t get used up.

Question 23

What is the definition of a coenzyme?

Answer 23

An organic cofactor is a molecule that acts as a carrier between enzymes. they are continually recycled during this process.

Question 24

If a cofactor is tightly bound to an enzyme, what is it known as?

Answer 24

The prosthetic group

Question 25

What are the two types of enzyme inhibition?

Answer 25

Competitive and non-competitive

Question 26

What is the definition of a competitive inhibitor?

Answer 26

A molecule that has a similar shape to that of the substrate.
They block the active site so no substrate molecules can fit in.

Question 27

What is the definition of a non-competitive inhibitor?

Answer 27

A molecule that binds to the enzyme or way from its active site.
This course is the active site to change shape so the substrate can no longer bind to it

Question 28

What is the site that non competitive inhibitors bind to called?

Answer 28

Allosteric site

Question 29

Shawna adds an inhibitor which has strong covalent bonds to a reaction. Why is this inhibitor irreversible?

Answer 29

The inhibitor can’t be removed easily

Question 30

Shawna adds a reversible inhibitor to a reaction. What type of bonds must the inhibitor have?

Answer 30

Weaker hydrogen bonds are weak ionic bonds which can be easily

Question 31

How are reverse transcriptase inhibitors a medicinal drug?

Answer 31

They inhibit the enzyme reverse transcriptase which catalyses the replication of viral DNA.
This prevents the virus from replicating

Question 32

How do antibiotics act as a medicinal drug?

Answer 32

Penicillin inhibits the enzyme transpeptidase which catalyses the formation of proteins in bacterial cell walls.
This weakens the cell wall and prevents the bacterium for regulating its osmotic pressure which causes the cell to burst.

Question 33

What does cyanide inhibit?

Answer 33

cytochrome c oxidase -An enzyme that catalyses respiration reactions

Question 34

What does malonate inhibit?

Answer 34

succinate dehydrogenase- An enzyme which catalyses respiration reactions

Question 35

What does arsenic inhibit?

Answer 35

pyruvate dehydrogenase- An enzyme which catalyses respiration reactions

Question 36

How can protease enzyme inhibition help protect cells?

Answer 36

Proteases are synthesized as inactive precursors to stop them damaging proteins in the cell in which they are made

Question 37

give an example of a cofactor and its enzyme

Answer 37

Chloride ions (Cl-) are cofactors for the enzyme amylase

Question 38

give an example of a prosthetic group and its enzyme

Answer 38

Zn ions (Zn2+) are a prosthetic group for carbonic anhydrase (an enzyme in red blood cells which catalyses the carbonic acid from water and carbon dioxide)