M2 (Biological Molecules) Ch4: Enzymes

Question 1

Enzymes

Answer 1

Enzymes are biological catalysts - they are gllobular proteins that interact with substrate molecules causing them to react faster

Question 2

Metabolism

Answer 2

Metabolism is the sum of all the different reactions and reaction pathways happening in a cell or organism

Question 3

Anabolic

Answer 3

Anabolic - reactions used for building up (growth)

Question 4

Catabolic

Answer 4

Catabolic - reactions used for breaking down substrates

Question 5

Vmax

Answer 5

Vmax - enzymes only increasing a reaction to a point - maximum initial velocity of the enzyme-catalysed reaction

Question 6

Activation energy

Answer 6

Activation energy is the energy needed for most reactions to start because molecules need to collide in the right orientation, of which high temperatures and pressure (energy) increases frequency of sucessful collisions

Question 7

Lock and key hypothesis

Answer 7

Lock and key hypothesis:
substrate binds to active site, enzyme substrate complex forms, substrates then react and products are formed in an enzyme product complex

Question 8

Induced fit hypothesis for enzymes

Answer 8

-As substrate forms bonds with amino acids in the active site of the enzyme, tertiary structure of enzyme changes so that the active site moulds itself tightly around the substrate
-Bonds formed between substrate and enzyme help catalyse the reaction

Question 9

Intracellular enezymes

Answer 9

Intracellular enzymes are found within cells

Question 10

Extracellular enzymes

Answer 10

Extracellular enzymes works outside of the cell

Question 11

Examples of extracellular enzymes

Answer 11

Extracellular enzymes:
-Catalase (hydrogen peroxide > water + oxygen)
-Amylase (starch > maltose)
-Trypsin (proteins > peptides)

Question 12

How does the structure of amino acids determine enzyme activity?

Answer 12

How structure of amino acids determine enzyme activity:
-Specific 3D shape/Tertiary structure > formation of active site > binds to substrate > catalyses the reaction

Question 13

Trypsin

Answer 13

Trypsin is a protease enzyme, and is produced in pancreas and then released into the small intestine

Question 14

Amylase

Answer 14

Amylase is produced by salivary gland and pancreas, and breaks down starch polymers into maltose (a disaccharide)

Question 15

Maltase

Answer 15

Maltase is an enzyme present in the small intestine, and break downs maltose into glucose (a monosoaccharide) which is small enough to be absorbed by cells lining the digestive enzyme to be absorbed into the bloodstream

Question 16

Digestion of starch

Answer 16

Digestion of starch
1). Amylase beaks down starch polymers into maltose (disaccharide)
2) Maltase breaks down maltose into glucose (monosaccharide) so that it’s small enough to be absorbed into bloodstream

Question 17

Factors that affect enzyme activity

Answer 17

The factors that affect enzyme activity are pH, temperature, enzyme concentration and
substrate concentration

Question 18

How does temperature affect enzyme activity?

Answer 18

Temperature increases the kinetic energy of particles meaning they collide more often, which increases the rate of the reaction

Question 19

What must happen in order for enzymes to catalyse reactions?

Answer 19

Enzymes must come into contact with the substrate, and the enzyme has to be complementary to the substrate

Question 20

What is meant by ‘temperature coefficient Q10’?

Answer 20

Temperature coefficient Q10 is a measure of how much the rate of a reaction increases with a 10 degree rise in temperature

Question 21

How do high temperatures affect the rate of enzyme activity? (below or at the optimum)

Answer 21

High temperatures -> increased kinetic energy of molecules -> increased chance of collisions between enzyme and substrate -> rate of reaction faster -> increasing by 10 (Q10) doubles rate of reaction

Question 22

How does pH affect the rate of enzyme activity? (below or at the optimum)

Answer 22

Changing the pH changes number of hydroxide and hydrogen ions present
-These interact with the charges on the enzyme’s amino acids, affecting hydrogen and ionic bonding, so resulting in changes to the tertiary structure

Question 23

Optimum pH

Answer 23

Optimum pH is the point at which enzymes work the best. This is because if the pH is too acidic or alkaline, the active site can be altered.

Question 24

What is renaturation?

Answer 24

Renaturation is when the optimum pH of enzymes are restored meaning the enzyme returns to it’s original shape

Question 25

How does substrate and enzyme concentration affect enzyme activity?

Answer 25

As concentration of substrate/enzyme increases, there is a higher collision rate with active sites of the enzymes, meaning there are more enzyme-substrate complexes, rate of reaction increases

Question 26

What are Enzyme Inhibitors ?

Answer 26

Enzyme inhibitors are molecules that prevent enzymes from carrying out their function. They can be competitive or non-competitive.

Question 27

Competitive Inhibitors

Answer 27

Competitive inhibitors blocks substrates from entering active site to stop the enzyme from catalysing the reaction, as it binds to the active site due to having a similar shape to the substrate. The inhibitor and substrate are in competition with eachother to reach the active site. Effects are usually reversible but can be non-reversible eg penicillin and aspirin

Question 28

How can the effect of competitive inhibitors be reduced?

Answer 28

Reduce the effect of competitive inhibitors by increasing the concentration of the substrate - meaning vmax can still be reached

Question 29

Non-competitive inhibitors

Answer 29

Non-competitive inhibitors binds to the allosteric site (away from the active site) which causes tertiary structure of enzyme to change, meaning the shape changes, therefore reducing the rate of reaction as substrate can no longer bind to active site. Effects can be reversible or non-reversible

Question 30

Effect of increasing substrate conc on non-competitive inhibitors

Answer 30

Increasing substrate concentration does not overcome the effect the non-competitive inhibitor

Question 31

End product inhibition

Answer 31

In end product inhibition, the final product in the metabolic pathway inhibits an early-stage enzyme to reduce the rate of the metabolic pathway. It stops excess product being made and resources being wasted.

Question 32

Cofactors

Answer 32

Cofactors are non-protein helper components that help enzymes carry out their function. They may transfer atoms or groups from one reaction to another in a multi-stop pathway or form part of the active site

Question 33

Coenzymes

Answer 33

Cofactors that are organic molecules are called coenzymes. They are derives from vitamins found in diet

Question 34

Inorganic cofactors

Answer 34

Inorganic cofactors are obtains from diet as minerals ie iron, calcium, chloride, zinc ions

Question 35

Prosthetic groups

Answer 35

Prosthetic groups are cofactors that are permanetly attached to enzymes in order for them to carry out their function eg haem for haemoglobin, and zinc for carbonic anhydrase

Question 36

Precursor activation

Answer 36

Precursor activation is when enzymes are produced in an inactive form called inactive precursor enzymes. A cofactor is added to them to change their shape/tertiary structure so active site changes and they can be activated.

Question 37

Precursor protein before adding cofactor

Answer 37

Precursor proteins before adding a cofactor is called an apoenzyme

Question 38

Precursor protein after adding cofactor

Answer 38

Precursor proteins after adding a cofactor is called a holoenzyme

Question 39

What are precursor enzymes called?

Answer 39

Precursor enzymes are called zymogens or proenzymes

Question 40

Why is the rate of amylase action found by measuring substrate dissapearance?

Answer 40

-Starch is the substrate
-Starch concentration can be measured via iodine test

Question 41

Why is the rate of catalase action found by measuring product build-up?

Answer 41

-Oxygen gas is a product of catalase action
-Oxygen can be collected eg via gas syringe

Question 42

Enzymes used in secretion that acts in the small intestine

Answer 42

Amylase and trypsin are secretion enzymes used in the small intestine

Question 43

Example of a multi-step metabolic process controlled by a series of enzymes inside animal cells

Answer 43

Respiration is a multi-step metabolic process controlled by a series of enzymes inside animal cells

Question 44

Role of the digestive enzymes in the small intestine

Answer 44

The digestive enzymes in the small intestine catalyse hydrolysis reactions, characterised by the breaking of bonds by addition of a molecule of water

Question 45

How do competitive inhibitors treat people suffering with bacterial infections

Answer 45

Competitive inhibitors eg penicillin, inhibits the bacteria by binding to the active site to prevent the entrance of the substrate

Question 46

Intracellular enzymes

Answer 46

Intracellular enzymes control metabolism inside cells

Question 47

Which reactions do digestive enzymes in the small intestine catalyse?

Answer 47

Digestive enzymes in the small intestine catalyses hydrolysis reactions

Question 48

Breakdown of hydrogen peroxide

Answer 48

Catalase breakdowns hydrogen peroxide into water and oxygen

Question 49

Effect of increasing/ pH and/or temperature above the optimum on enzymes

Answer 49

Changes the enzyme’s structure as it can affect chemical bonds within the active site -> denatured

Question 50

Zymogens

Answer 50

Zymogens:
-Inactive precursor enzymes
-Needs to be cleaved to be activated (activation of the enzyme is irreversible)
-Inactive precursors are a way of regulating enzyme activity
-Eg chymotrypsin which is a precursor to trypsin

Question 51

Inactive precursors function

Answer 51

Inactive precursors are a way to regulate enzyme activity

Question 52

End of a protein

Answer 52

Ends of a protein does not have a peptide bond
-Has an amino group on one end a carboxyl group on the other

Question 53

Protein structure

Answer 53

Proteins - polymers made up of amino acid monomers - connected by peptide bonds - end of proteins are amine group on one end and a carboxyl group on the other

Question 54

Why is insulin given via injection into the blood rather than by pill for people with type 1 diabetes?

Answer 54

-Insulin in pill form -> will break down by protease enzymes in the stomach or the small intestine
-If some insulin managed to escape digestion it would likely be denatured by the low pH of the stomach
-If survived both things -> would not be small enough to be abosbred in the small intestine in the bloodstream and therefore would not reach the body tissues

Question 55

Intracellular enzymes

Answer 55

Intracellular enzymes:
-Enzymes that are present inside the cell membrane
-Intracellular enzymes may reside in the cytoplasmic fluid or they may be bound to cellular organelles.

Question 56

Extracellular enzymes

Answer 56

Extracellular enzymes:
-Extracellular enzymes are those which are present outside the cell - reactions do not occur inside the cell eg on leaves

Question 57

Catalase

Answer 57

Catalase:
Catalase is an enzyme found in the cells of most organisms that breaks hydrogen peroxide down into water and oxygen. Hydrogen peroxide and catalase are combined and the volume of oxygen generated is measured in a set time.