M1:09 Enzymes at work and interference

Question 1

What is an inhibitor?

Answer 1

a substance that reduces the reaction rate in an enzyme-controlled reaction by affecting the enzyme molecule in some way

Question 2

Name 2 ways inhibitors affect enzymes

Answer 2

They have their effect on the active site of one enzyme or affect another part of the molecules, indirectly causing a change in shape of the active site

Question 3

Does 1 inhibitor affect 1 enzyme?

Answer 3

Often they can affect many different enzymes

Question 4

What is a competitive inhibitor?

Answer 4

molecules that have a similar shape to the substrate, meaning they can occupy the active site, forming enzyme-inhibitor complexes. (But does not form a product as the inhibitor is a slightly different shape to the active site)

Question 5

Why does enzyme inhibition occur?

Answer 5

Because whenever an inhibitor molecule is occupying an active site, a substrate molecule cannot be catalysed, so the rate of reaction decreases.

Question 6

What does the level of inhibition depend on in terms of competitive inhibitors?

Answer 6

the concentration levels of substrate and the inhibitor (as it is random collision)

Question 7

What is effectively happening when you increase the amount of substrates when inihibitors are present?

Answer 7

diluting the effects of the inhibitors

Question 8

What is a non-competitive inhibitor? and how does it work?

Answer 8

an inhibitor that does not compete for the active site, instead they attach to the enzyme molecule in a region away from the active site. which distorts the tertiary structure, and therefore the active site so the substrate no longer fits the active site

Question 9

What does the level of inhibition depend on in terms of non-competitive inhibitors?

Answer 9

the number of inhibitor molecules present, if there are enough present- they can even stop a reaction

Question 10

What does not affect the effect of non-competitive inhibition?

Answer 10

the concentration of substrates

Question 11

Why is the effect of competitive inhibitors often referred to as reversible?

Answer 11

As most of them do not bind permanently to the active site, and so once they leave- the enzyme is unaffected

Question 12

Why is the effect of non-competitive inhibitors often referred to as irreversible?

Answer 12

As although they also dont bind permanently, once the shape of the tertiary structure has been changed, it is denatured

Question 13

Is inhibition always a bad thing? why?

Answer 13

No, as the regulation of a number of metabollic pathways often involved the inhibition of enzymes to control the rate of reactions.

Question 14

What is a cofactor?

Answer 14

any (non-protein) substance that must be present to ensure enzyme controlled reactions take place at the appropriate rate. (some are part of the enzyme eg prosthetic groups, others affect the enzymes on a temp basis, eg coenzymes and inorganic ion cofactors.

Question 15

what is a coenzyme?

Answer 15

small, organic, non-protein molecules that bind for a short period to the active site.

Question 16

When do coenzymes bind with the enzyme?

Answer 16

either just before, or at the same time as the substrate.

Question 17

What happens to a coenzyme during a reaction?

Answer 17

they are often changed, like the substrate in some way, but unlike substrates they are recycled back to take part in the reaction again

Question 18

What is often the role of a coenzyme?

Answer 18

to carry chemical groups between enzymes so they link together enzyme-controlled reactions that dont need to take place in the sequence.

Question 19

What does vitamin B3 do

Answer 19

(nicotinamide) which helps the body break down carbohydrates and fat to release energy. and to make a coenzyme that is required for the enzyme pyruvate dehydrogenease to function properly.

Question 20

What is pyruvate dehydrogenease?

Answer 20

it is an enzyme that catalyses one of the reactions in the sequence of respiration

Question 21

What happens if you have a diet without vitamin B3?

Answer 21

normal growth and development cant occur , and can even get a disease called pellagra

Question 22

What is the prosthetic group of an enzyme?

Answer 22

the coenzyme that is a permanent part of an enzyme. They are also found in other protein molecules

Question 23

Why are prosthetic groups vital in enzymes and proteins?

Answer 23

As they contribute to the final tertiary structure and to other properties of the molecule such as charges.

Question 24

Give an example of a prosthetic group in an enzyme

Answer 24

The enzyme carbonic anhydrase contains a zync based prosthetic group which is a vital component in RBC as it is involved in catalysing the combining of co2 and water to produce carbonic acid.

Question 25

What do inorganic ion cofactors do?

Answer 25

they increase the reaction rate, as the ions combine with either the enzyme or the substrate, allowing the enzyme-substrate complex to form more easily by affecting the charge distribution, and sometimes even the shape of the enzyme-substrate complex.

Question 26

What is need for amylase to catalyse the break down of starch to maltose molecules?

Answer 26

chloride ions.

Question 27

How do poisonous substances work?Give an example

Answer 27

They inhibit or even overactivate enzymeseg potassium cyanide, a noncompetitive inhibitor for a vital respiratory enzyme called cytochrome oxidase found in the mitochondria, inhibits cell respiration and inhibition of this enzyme decreases the use of oxygen so ATP cant be made, so the organism can only respire anaerobically, which leads to a build up of lactic acid in the blood

Question 28

How much cynide must be absorbed for an adult to lose consciousness, how long does this take? and what is the effect if left untreated?

Answer 28

100-200mg, can take as little as 10 secondsafter 45 minutes, coma2 hours= death.

Question 29

What does a bisensor do?

Answer 29

uses enzyme controlled reactions to detect the presence of substances in a highly sensitive and specific way.

Question 30

Is an inhibitor always a bad thing? give an example

Answer 30

No it can act as both a poison and a drugeg alcohol- excess alcohol over a period of time can lead to liver damage, but alcohol is a treatment for ethylene glycol poisoning

Question 31

How are viruses, such as HIV treated?

Answer 31

using chemicals that act as protease (competitive) inhibitors, which prevent viruses from replicating by inhibiting the activity of protease,

Question 32

What do viruses need protease for?

Answer 32

to build new virus coats

Question 33

What is the main problem caused by cystic fibrosis? and how is it treated?

Answer 33

the passage of digestive enzymes is blocked so patients struggle to digest food. treated with enzymes in tablet form that are packaged in an acid resistant coat so they arent destroyed in the acid and protein digesting enzymes in the stomach.

Question 34

Where is ethylene glycol found? and why is it so dangerous?

Answer 34

in the anti freeze used in car engines, as although its not poisonous, when its broken down in the liver by the enzyme alcohol dehydrogenease- the breakdown product oxalic acid is extremely toxic.

Question 35

How is ethylene glycol poisoning treated?

Answer 35

a massive dose of ethanol (alcohol) which leads to severe alcohol intoxication , but reduces the production of oxalic acid, allowing the ethylene glycol to be excreted harmlessly.

Question 36

What do antibiotics do, and what are they used to treat?

Answer 36

kill or inhibit the growth of an organismbacterial infections

Question 37

How does penicillin work?

Answer 37

it forms cross links in the cell wall of some bacteria, meaning the walls of growing bacteria are not made- so bacterial reproduction is halted

Question 38

Why do many forms of bacterial resistance occur?

Answer 38

As among populations of bacteria, there may be an individual with a mutation/ altered enzymes which are capable of inactivating antibiotics

Question 39

What is snake venom made up of?

Answer 39

a mixture of toxins and different enzymes(phosphodiesterases, enzyme hyaluronidase, ATPases and the inhibitor of the enzyme acetyl cholinesterase are usually present)

Question 40

What do phosphodiesterases’ do?

Answer 40

interfere with the working of a snakes’ preys heart and causes a fall in blood pressure

Question 41

What does the inhibitor of the enzyme acetyl cholinesterase do?

Answer 41

results is paralysis (as the enzyme is involved in nerve transmission)

Question 42

What is the enzyme hyaluronidases’ function?

Answer 42

its a digestive tissue that breaks down connective tissue and so helps toxins to penetrate tissues quickly

Question 43

What are ATP-ases used for?

Answer 43

to break down ATP to disrupt preys use of energy

Question 44

How much do enzymes increase reaction rates, why is it limited?

Answer 44

By up to 10 million times, with it being limited to how quickly the substrate and the active site colliding

Question 45

Why must enzyme activity be controlled?

Answer 45

As uncontrolled enzyme activity is just as dangerous to an organism as a lack of enzymes.

Question 46

Give an example of why enzyme activity must be controlled

Answer 46

Multiple sclerosis, the immune system of sufferers wrongly sets destructive enzymes against part of nerve cells, which results in the nervous system breaking down, which can lead to paralysis.

Question 47

What is the turn over number of an enzyme?

Answer 47

the number of reactions an enzyme molecule can catatlyse in one second. In catalase, the turn over number is up to 200,000.

Question 48

Give 2 examples of complex metabolic sequences. why are they complex?

Answer 48

respirationphotosynthesisas the product of the first enzyme-substrate complex is the substrate for the next, and so on..

Question 49

What is a metabolic pathway?

Answer 49

the product of the first enzyme-substrate complex is the substrate for the next, and so on..

Question 50

How is metabolic pathways controlled?

Answer 50

As often the end product of the sequence can attach to one of the enzymes in an earlier sequence so there isnt a build up. (Which is exactly the same as non-competitive inhibition)

Question 51

What happens with the end product of a metabolic pathway?

Answer 51

It binds to the enzyme in a part of the enzyme away from the active site, which changes the shape of the active site- slowing down the rate of reaction.

Question 52

Name an enzyme that is found in all organisms and what its role is

Answer 52

ATP synthase, which catalyses the addition of an inorganic phosphate to an ADP molecule.

Question 53

What is disease often caused by?

Answer 53

the lack of functioning of a specific enzyme in a metabolic sequence due to a mutation. These are called inborn errors of metabolism.

Question 54

What is phenylketonuria?

Answer 54

an inborn error of metabolism, people with this condition lack the functioning version of the enzyme phenylalaine hydroxylase, which breaks down excess phenylalanine (an amino acid in the diet) to tyrosine.