2.4- Enzymes

Question 1

What is an enzyme?

Answer 1

A biological catalyst that speeds up metabolic reactions within living organisms. They’re globular proteins and are complementary to the shape of the substrate molecule. They have a tertiary structure.

Question 2

What is meant by tertiary structure?

Answer 2

An enzyme is a 3D shape made up of a polypeptide chain held together with hydrogen bonds.

Question 3

What is a catabolic reaction?

Answer 3

Breaking down of larger molecules

Question 4

What is an anabolic reaction?

Answer 4

Synthesis of larger molecules

Question 5

Where do enzymes work?

Answer 5

Intracellular and extracellular

Question 6

Where is catalase found and what does it do?

Answer 6

Catalase is found in nearly all organisms that are exposed to oxygen and breaks down hydrogen peroxide (a potentially harmful bi-product from many metabolic reactions) into water and oxygen

Question 7

What is a cofactor?

Answer 7

A small non-protein molecule that attaches to an enzyme that allow an enzyme to work or speed up the reaction. Ions, coenzymes and prosthetic groups are all coenzymes.

Question 8

What is a prosthetic group?

Answer 8

A cofactor that is permanently bound, by covalent bonds, to an enzyme molecule. e.g. the enzyme carbonic anhydrase contains a zinc ion permanently bound to its active site.

Question 9

What are ions that act as cofactors?

Answer 9

Ions that do not permanently bind to the enzyme however bind temporarily bind to either the enzyme or the substrate to ease the formation of the ES complex. They do the by either changing the shape of the active site or, changing the charge on the surface of the enzyme or substrate to allow them to be more attracted to each other more.
e.g. the enzyme amylase digests starch into maltose but will only work if a chloride ion is present.

Question 10

What are coenzymes?

Answer 10

Coenzymes are small organic non-protein, organic molecules the bind temporarily to the active site of enzyme molecules,either just before or at the same time the substrate binds. The coenzymes are chemically changed during the reaction, and the need to be recycled to their orginal state, sometimes by a different enzymes. Many coeenzymes are deriveed from water-soluble vitamins.

Question 11

What is the induced -fit hypothysis?

Answer 11

The active site changed shape slightly to mould itself around the substrate molecule.

Question 12

What do enzymes do?

Answer 12

Enzymes lower the activation energy of a reaction because they have an active site specific to only the substrate molecules, they bring the substrate molecule close enough together without excessive heat.

Question 13

What is the temperature coefficient?

Answer 13

The temperature coefficient here refers to the increase in the rate of a process when the temperature is increased by 10 degrees

Question 14

How changes in pH affects bonds within molecules?

Answer 14

Excess hydrogen ions will interfere with these hydrogen bonds and ionic forces, and so the active site of the enzyme molecule will change shape. Changes from the optimum pH would slow the reaction. Hydrogen bonds can re-form and the active site’s shape is restored. At extremes of pH, the enzyme’s active site may be permanently changed.

Question 15

What is an inhibitor?

Answer 15

Inhibitors are substances that reduce the activity of an enzyme. They do this by combing with the enzyme molecule in a way that influences how the substrate binds to the enzyme or affects the enzyme turnover number. Some may block the active site and some that change the shape of the shape of the active site. Both of these actions will inhibit the formation of ES complexes.

Question 16

What are competitive inhibitors?

Answer 16

A competitive inhibitor fits into the active site and so a substrate molecule cannot enter. The amount of inhibition depends on the relative concentration of substrate molecule and inhibitor molecules.

Question 17

What are non-competitive inhibitors?

Answer 17

Non-competitive inhibitors do not compete with substrate molecules for a place on an enzyme’s active site. They attach to the enzyme molecule in a region known as the allosteric site. They disrupt the enzyme’s tertiary structure and change it’s shape.

Question 18

What is end-product inhibition?

Answer 18

After the catalysed reaction has reached completion, product molecules may tightly stay bound to the enzyme. In this way, the enzyme cannot form more of the product than the cell needs. Such regulation id an example of negative feedback.

Question 19

What is two examples harmful inhibitors?

Answer 19

.Cyanide

.Snake venom

Question 20

What does snake venom do to the body? (inhibitor)

Answer 20

The venom of the green mamba snake contains a chemical that inhibits the enzyme acetylcholinsterase (AChE). This enzyme is important at neuromuscular synapses to break down the neurotransmitter acetylocholine (ACh). If this enzyme is inhibited, the ACh stays attaches to receptors on the membrane and keeps molecules contracted. This causes paralysis, as movement depends on muscles being able to contract and relax alternately. If the muscles involved in breathing are paralyzed, then the victims die of suffocation.

Question 21

What does cyanide do to the body? (inhibitor)

Answer 21

Potassium cyanide (KCN) is highly toxic because it inhibits aerobic respiration. it also inhibits catalase.
when ingested, KCN is hydrolysed to produce hydrogen cyanide, it is a very toxic gas that can readily dissociate into H+ and CN- ions.
The CN- ions bind irreversibly to an enzyme found in mitochondria and inhibit the final stage of aerobic respiration. Because the final stage is inhibited, earlier stages cannot run and aerobic respiration stops.

Question 22

What enzyme does the chemical in snake venom inhibit?

Answer 22

Acetylcholinesterase (AChE)

Question 23

What are some examples of medical drugs acting by enzyme inhibitors?

Answer 23

.Aspirin

.ACE inhibitors

Question 24

What does aspirin to do the body? (Inhibitor)

Answer 24

Aspirin prevents the formation of prostaglandins because salicylic acid binds to enzymes that catalyse the formation of prostaglandins. Prostaglandins make nerve cells for sensitive to pain so taking acts as a painkiller.
Aspirin also acts as a blood thinner and is used to reduce the risk of blood clotting and reduce the risk of strokes.

Question 25

What does aspirin inhibit the production of?

Answer 25

Prostaglandins

Question 26

What do ACE inhibitors do to the body?

Answer 26

These are medical drugs that inhibit the antiotensin converting enzymes (ACE), which normally operates in a metabolic pathway that unitmately increases your blood pressure. They are used to:
.Lower blood pressure
.Treat heart failure
.Minimise risk of a second heart attack or strokes