Enzymes 2.4 Flashcards

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1
Q

What is an enzyme?

A

A biological catalyst

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2
Q

What do enzymes do?

A

They reduce the activation energy for biochemical reactions

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3
Q

What is activation energy?

A

The energy needed to break the bonds to start the reactions

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4
Q

What is an intracellular enzyme?

A

An enzyme that works inside cells

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5
Q

What are the 2 examples of intracellular enzymes?

A
  • catalase which breaks down hydrogen peroxide into water and oxygen
  • lysozyme which is found in lysosomes and digests old organelles and foreign bodies
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6
Q

What is an extracellular enzyme?

A

An enzyme that works outside cells

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7
Q

What are the 2 examples of extracellular enzymes?

A
  • amylase which is found in saliva to catalyse the hydrolysis of starch into maltose
  • trypsine which is produced by the pancrease and released into the small intestine to catalyse the hydrolysis opeptide bonds of large polypeptides into smaller ones which are then turned into amino acids by other enzymes
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8
Q

What are the two enzymes which catalyse protein hydrolysis?

A
  • trypsin turns proteins into amino acids from the pancrease
  • pepsine turns proteins into amino acids from the stomach
  • difference in PH causes a need for different enzymes
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9
Q

What are the two mechanisms of enzyme action?

A
  • lock and key model
  • induced fit model
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10
Q

What is the lock and key model?

A

Where the substrate is complimentary to the specific active site of the enzyme and it slots int the active site to form an enzyme substrate complex where it is then broken down into the products

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11
Q

What is the induced fit model?

A

When a substrate fits into the active site of an enzyme as they have an aproximate complimentary shape and once an enzyme substrate complex has formed the enzyme slightly changes shape to fit the substrate better and to apply pressure on the bonds of the substrate, breaking or making the substrate to then form an enzyme product complex where the the products are released

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12
Q

What is a catalyst?

A

A substance that speeds up chemical reactions by lowering the activation energy without being used up

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13
Q

Why is the induced fit model considered better?

A
  • it shows how other molecules can affect enzyme activity
  • it shows how the activation energy is lowered
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14
Q

What are the factors affecting enzyme activity?

A
  • PH
  • temperature
  • conc. of enzymes
  • conc. of substrate
  • inhibitors ( competitive and non)
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15
Q

What happenes to enzymes if the temperatures too hot?

A

The enzymes vibrate too much due to an increase in kinetic energy causing the bonds between the R groups to break, changing the tertiary structure therefore causing the enzymes to denature

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16
Q

What happenes to enzymes if the temperatures too cold?

A

The kinetic energy of the enzymes decreases so much that they no longer have enogh energy to have any successful collisions meaning that no reaction can happen as they can not reach the activation energy

17
Q

What does Q10 stand for?

A
  • temperature coefficient
  • it shows how much the rate of reaction changes when the temperature is increased by 10 degrees celcius
18
Q

What does a Q10 of 2 mean?

A

If you increase the temperature by 10 degrees celcius, the rate of reaction doubles

19
Q

How does PH affect enzymes?

A

H+ ions and OH- ions found in acids and alkalis break the ionic and hydrogen bonds that hold the enzymes tertiary structure in place

20
Q

How does enzyme and substrate conc. affect rate of reaction?

A

It causes the rate of reaction to increase until it plateaus at the point of saturation where all the enzyme active sites have been filled as much as they can and there is another limiting factor stopping the rate of reaction from increasing any more

21
Q

What do these represent in an enzyme/ substrate, rate of reaction graph?
- steeper line
- flat line
- 2 lines levelling out at the same point
- 2 lines levelling out at different points
- 1st line to level off first

A
  • faster rate of reaction
  • reaction has stopped
  • all of the reactants have been used up
  • they made a different mass of product so there was a different limiting factor
  • enzymes have denatured
22
Q

What does a competitive inhibitor do?

A

It has a similar shape to the substrate so it binds to the active site but no reaction takes place so the active site is blocked temporarily

23
Q

What does a non competitive inhibitor do?

A

It binds to an allosteric site which causes the enzymes active site to change shape so that the substrate molecule no longer fits

24
Q

What is reversible inhibition?

A

When the inhibitor binds with weaker bonds like hydrogen or ionic, so the inhibitor can be removed and the substrate can bind as normal

25
Q

What is a non reversible inhibitor?

A

When the inhibitor binds with stronger covalent bonds so the inhibitor can not be removed easily

26
Q

What are the differences in the inhibitor graphs?

A
  • the line of the competitive inhibitor is not as steep as the one with no inhibitor meaning that it causes a slower rate of reaction but it eventually plateaus at the same point as the line with no inhibitors
  • the line of the non competitive inhibitir is significantly less steep than the one with no inhibitor and plateaus much quicker and lower than the line with no inhibitors
27
Q

What is a cofactor?

A

A molecule that is not made of protein that will bind to and enzyme to help it work better; some enzymes will only work if there is another non protein substance bound to them

28
Q

What is a prosthetic group?

A

A cofactor that is tightly bound to an enzyme to the point where it is basically permanent

29
Q

What do inorganic cofactors do?

A

They help the enzyme and substrate bind together but do not directly participate in the reaction and they are not used up or changed in any way

30
Q

What do organic cofactors (coenzymes) do?

A

They often act as carriers moving chemical groups between enzymes and participate in the reaction and are changed so the are continually recycled during the process

31
Q

What is a source for coenzymes?

A

Vitamines
Eg/ NDA = from vitamine B3

32
Q

What is an example of a prosthetic group that aids enzymes?

A

Zinc ions (Zn+2) is a prosthetic group for carbonic anhydrase where the ions are permanently bound to the enzymes active site (carbonic anhydrase is in RBCs and catalyses the reaction of carbonic acid into carbon dioxide and water)

33
Q

What are examples of inhibitor poisons?

A
  • cyanide inhibits respiration enzyme (non competitive)
  • snake venom enzymes involved with neuro transmitters
34
Q

What are exapmles of medicinal inhibitors?

A
  • HIV protease inhibitors
  • ethanol as an antifreeze poisoning treatment