Enzymes

Question 1

What is a simple protein?

Answer 1

A simple protein is a protein without a prosthetic group

Question 2

What are conjugated proteins?

Answer 2

Conjugated proteins are proteins with a prosthetic group of a metal ion, molecule or biological molecule

Question 3

What are enzymes?

Answer 3

Biological catalysts, globular proteins

Question 4

How do enzymes react?

Answer 4

Interaction of a substrate with an active site

Question 5

What is anabolism?

Answer 5

Building up of molecules, e.g. metabolism in steroid hormones

Question 6

What is catabolism?

Answer 6

Breaking down of molecules, e.g. breaking down of ATP to use energy

Question 7

What are the roles of enzymes?

Answer 7

Anabolism, catabolism, digestion

Question 8

What are the mechanisms of enzyme reaction?

Answer 8

Lock and key, induced-fit

Question 9

How does the lock and key theory work?

Answer 9

• enzyme has an active site with a specific shape
• substrate is complementary to the active site
• substrate binds to form a enzyme-substrate complex
• this reacts to form a enzyme-product complex
• the interaction of the R-groups form weak bonds while reacting

Question 10

How does the induced-fit theory work?

Answer 10

• active site changes shape to strengthen R-group interactions
• this is called the induced-fit hypothesis
• therefore the tertiary structure of the enzyme changes
• this weakens bond/s in the substrate which lowers the activation energy

Question 11

What is the aim of enzymes?

Answer 11

Lower activation energy of reaction, reaching Vmax

Question 12

What effects the rate of reaction for enzymes?

Answer 12

Temperature, substrate concentration and pH

Question 13

What are intracellular enzymes with examples?

Answer 13

Enzymes that catalyse reactions inside of the cell, e.g. Catalase for hydrogen peroxide, synthesis of polymers and polysaccharides

Question 14

What are extracellular enzymes with examples?

Answer 14

Enzymes that catalyse reactions outside of the cell, e.g. Trypsin and amylase for digestion, breaking down of larger molecules into monomers and monosaccharides

Question 15

How is starch digested?

Answer 15

• Starch is broken down into maltose by amylase in the saliva
• Maltose is broken down into glucose by maltase in the small intestine
• glucose is small enough to be absorbed into the lining of the digestive tract and then the blood stream

Question 16

How are proteins digested?

Answer 16

Trypsin catalyses the digestion of proteins into smaller peptides, which can then be broken down into amino acids by other proteases

Question 17

Where is trypsin made?

Answer 17

The pancreas

Question 18

How does increasing the temperature effect enzyme activity?

Answer 18

• as thermal energy increases, kinetic energy also increases
• this increases the number of successful substrate-active site collisions
• however the bonds in the enzyme also vibrate
• the more the bonds vibrate, the more they strain and eventually will break
• this is denaturation

Question 19

What happens when an enzyme denatures?

Answer 19

The active site changes shape permanently and is no longer complementary to the substrate

Question 20

What is the optimum temperature?

Answer 20

The temperature where an enzyme is at its highest rate of activity, 40 oC for animals

Question 21

What is optimum pH?

Answer 21

The pH where an enzyme is at its highest rate of activity

Question 22

What happens if the pH changes too significantly?

Answer 22

The tertiary shape of the protein is irreversibly altered and the active site will no longer be complementary to the shape of the substrate

Question 23

What are the enzymes present in salvia and what are their function?

Answer 23

Amylase, breaking down starch into maltose

Question 24

What are the enzymes present in gastric juice and what are their function?

Answer 24

Pepsin, breaking down proteins into polypeptides

Question 25

What are the enzymes present in pancreatic juice and what are their function?

Answer 25

Trypsin, breaking down proteins into polypeptides

Question 26

What happens when the concentration of substrate is increased?

Answer 26

The rate of successful collision between the active site and substrate of a protein increases, therefore the rate of reaction increases

Question 27

What is the difference between an increase of the concentration of substrate and the increase of the concentration of an enzyme?

Answer 27

None, rate of reaction will increase with both

Question 28

What is the Vmax?

Answer 28

The maximum point of the rate of reaction, after Vmax it'll either decrease or plateau. The only way to increase is to add another limiting factor

Question 29

Why can't enzyme related reactions happen too fast?

Answer 29

There will be an excess of products

Question 30

What are enzyme inhibitors?

Answer 30

Molecules that prevent/slow down enzymes from carrying out their regular function, there are 2 types- competitive and non-competitive

Question 31

What is competitive inhibition?

Answer 31

Molecules with a similar shape to the active site and can block the substrate from catalysing the reaction, therefore slowing down the rate of reaction

Question 32

What is non-competitive inhibition?

Answer 32

A molecule that binds to an enzyme at an area different to the active site called the 'allosteric site'. This causes the tertiary structure of the enzyme to change, which means the active site changes and the substrate cannot bind to the enzyme, therefore the rate of reaction decreases

Question 33

Can Vmax be achieved by changing the concentration of enzyme/substrate for inhibition?

Answer 33

Competitive - eventually, yes | Non-competitive - no

Question 34

What are the positive effects of inhibition?

Answer 34

Controls enzyme activity, may kill foreign bodies, may be reversible

Question 35

What are the negative effects of inhibition?

Answer 35

Enzyme shape may be permanently changed, may be a foreign body itself, could kill organism

Question 36

What is an example of competitive inhibition?

Answer 36

Statins competitively inhibit the enzyme that produces cholesterol, and are prescribed to prevent heart disease

Question 37

What is an example of non-competitive inhibition?

Answer 37

HIV Protease inhibitor, binds to allosteric site on HIV protease to prevent longer strands of HIV RNA being replicated

Question 38

What is end-product inhibition?

Answer 38

When a product produced by an enzyme reaction inhibits the enzyme that produced it. This acts as a control mechanism

Question 39

What are cofactors?

Answer 39

An inorganic non-protein component that helps an enzyme carry out its function

Question 40

Name an example of a cofactor

Answer 40

Chloride ions in amylase that are essential in active site formation

Question 41

What are coenzymes?

Answer 41

Organic cofactors

Question 42

What are coenzymes made of?

Answer 42

Vitamins

Question 43

Name an example of a coenzyme

Answer 43

Vitamin B5 which is used to make coenzyme A, which breaks down fatty acids and carbohydrates in respiration

Question 44

What is another term used for cofactors?

Answer 44

Prosthetic groups

Question 45

What is the difference between cofactors and prosthetic groups?

Answer 45

Cofactors are loosely bound and prosthetic groups are tightly bound

Question 46

Name an example of a prosthetic group

Answer 46

Zinc ions that form carbonic anhydrase, which is used in the metabolism of carbon dioxide

Question 47

What are inactive precursor enzymes?

Answer 47

Enzymes in their inactive form that only need to be activated under certain conditions because they may be damaging to cells/tissues in their surroundings

Question 48

How are precursor enzymes activated?

Answer 48

Addition of a cofactor that changes the tertiary structure, and therefore the active site so the substrate can bind

Question 49

What is a precursor enzyme called before and after a cofactor is added?

Answer 49

Before - apoenzyme | After - holoenzyme

Question 50

What are other factors that could activate precursor enzymes?

Answer 50

pH changes, other enzymes, temperature: before - zymogens after - proenzymes

Question 52

Name an example of a precursor enzyme

Answer 52

Pepsinogen that gets activated by the acidic pH of the stomach acid

Question 53

What are biological catalysts?

Answer 53

Enzymes used in metabolism that alter rate of reaction and lower activation energy

Question 54

How are hydrogen bonds formed in tertiary structure?

Answer 54

Between nitrogen, oxygen and phosphorous; between electronegative and electropositive

Question 55

Why does rate of reaction increase with the increase of substrate concentration?

Answer 55

Because more active sites are being occupied to achieve Vmax

Question 56

Why does rate of reaction increase with the increase of substrate concentration?

Answer 56

Because more active sites are being occupied to achieve Vmax