Enzymes

Question 1

What do enzymes do?

Answer 1

They speed up chemical reactions by acting as biological catalysts.

Question 2

What is an important feature of a catalyst?

Answer 2

It speeds up a chemical reaction without being used in the reaction itself.

Question 3

Name a toxic by-product of several cellular activities and the enzyme that catalyses the breakdown of it.

Answer 3

Hydrogen peroxide (H2O2) / Catalase

Question 4

Name an extracellular enzyme and where it is found.

Answer 4

Amylase. Produced by the salivary glands and pancreas, Found in saliva and pancreatic juices in the small intestine.

Question 5

What extracellular enzyme is found outside the body and where?

Answer 5

Amylase in saliva, secreted by cells in the salivary glands.

Question 6

What type of protein in trypsin?

Where is it produced?

What does it do?

Answer 6

1) Protease
2) Cells in the pancreas and secreted into the small intestine.
3) Catalyses the hydrolysis of peptide bonds.

Question 7

A substrate bound to an enzyme becomes…

Answer 7

Enzyme-substrate complex

Question 8

A substrate bound to an enzyme becomes an …

Answer 8

Enzyme-substrate complex

Question 9

What is the term given to the amount of energy that is required by chemcials for a reaction to start?

Answer 9

Activation energy

Question 10

Give two examples of how forming an enzyme-substrate complex lowers activation energy.

Answer 10

1) If two substrate molecules need to be joined, attaching them to the enzyme holds them close together. Thus reducing the repulsion between the molecules.
2) If the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on the bonds in the substrate.

Question 11

Give two examples of how forming an enzyme-substrate complex lowers activation energy.

Answer 11

1) If two substrate molecules need to be joined, attaching them to the enzyme holds them close together. Thus reducing the repulsion between the molecules. 2) If the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on the bonds in the substrate.

Question 12

Name the two models of enzyme action.

Answer 12

Lock and Key / Induced Fit

Question 13

How is the induced fit hypothesis different from the lock and key hypothesis?

Answer 13

The lock and key hypothesis state that the substrate fits perfectly into the enzyme, like a lock and a key would. This is in contrast with the induced fit hypothesis, which states that both the substrate and the enzyme will deform a little to take on a shape that allows the enzyme to bind the substrate.

Question 14

What type of proteins are enzymes?

Answer 14

Globular

Question 15

Why do enzymes have a tertiary structure?

Answer 15

It allows them to create a specific 3D shape which is required for them to create an active site specific to the substrate.

Question 16

What 4 factors affect enzyme activity?

Answer 16

1) PH 2) Temperature 3) Enzyme Concentration 4) Substrate Concentration

Question 17

What effect does temperature have on enzyme activity?

Answer 17

More heat = more kinetic energy = more likely for substrate chemicals to collide with ezymes.

Question 18

The ideal temperature is called?

Answer 18

Optimum temperature.

Question 19

What happens if the temperature is too great?

Answer 19

The enzyme molecules vibrate too much and some of the bonds that hold the enzyme in shape are broken. The enzyme becomes denatured.

Question 20

When an enzyme breaks down it becomes…?

Answer 20

Denatured

Question 21

pH can affect the tertiary structure of an enzyme. Why?

Answer 21

The H+ and OH- ions can break the hydrogen and ionic bonds causing the enzymes active site to change shape.

Question 22

Name the two types of cofactors.

Answer 22

Inorganic / Organic (coenzymes)

Question 23

What do inorganic cofactors do and do not do?

Answer 23

They help bind the substrate and enzyme together. They do not participate in the reaction.

Question 24

What role to organic cofactors play?

Answer 24

They participate in the reaction and are continually recycled.

Question 25

If a cofactor is tightly bound to an enzyme it is called a?

Answer 25

Prosthetic group.

Question 26

Competitive and non-competitive inhibitors

Answer 26

Competitive inhibitors bind to the active site. Non-competitive inhibitors bind away from the active site (allosteric site) which causes the active area to change shape.

Question 27

How can you reverse the effects of a competitive inhibitor?

Answer 27

Increase the concentration of the substrate.

Question 28

What determins if a inhibitor is reversible or not?

Answer 28

The strength of the bonds between the enzyme and inhibitor.

Question 29

What type of bond attributes to a irriversible inhibitation.

Answer 29

Strong covalent bond.

Question 30

What type of bond attributes to a reversible inhibitation.

Answer 30

Weak hydrogen or ionic bonds.

Question 31

What type of drug is used to target HIV?

Answer 31

Enzyme inhibitor which inhibits the enzyme reverse transcriptase from catalysing the replication of viral DNA.

Question 32

How does penicillin work?

Answer 32

It inhibits the enzyme transpeptidase which catalyses the formation of proteins (peptidoglycan) in the cell wall. The cell wall becomes weak and prevents the bacterium from regulating its osmotic pressure causing it to burst.

Human cells do not make or need peptidoglycan.

Question 33

Describe the breakdown of starch.

Answer 33

1) Starch polymers partially are broken down into maltose by amylase.
2) Maltose is broken down into glucose by maltase.
3) Glucose absorbed by cells in the digestive system and then absorbed into the blood.

Question 34

All of the below can only happen as a result of enzymes.

Describe:

1) Metabolisim
2) Annabolism
3) Catabolism

Answer 34

1) The sum of all the different reactions in a cell or organism.
2) Building of molecules.
3) Breaking down of molecules.