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Biology A-Level OCR > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

What is a simple protein?

A

A simple protein is a protein without a prosthetic group

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2
Q

What are conjugated proteins?

A

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

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3
Q

What are enzymes?

A

Biological catalysts, globular proteins

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4
Q

How do enzymes react?

A

Interaction of a substrate with an active site

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5
Q

What is anabolism?

A

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

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6
Q

What is catabolism?

A

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

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7
Q

What are the roles of enzymes?

A

Anabolism, catabolism, digestion

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8
Q

What are the mechanisms of enzyme reaction?

A

Lock and key, induced-fit

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9
Q

How does the lock and key theory work?

A
  • 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
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10
Q

How does the induced-fit theory work?

A
  • 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
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11
Q

What is the aim of enzymes?

A

Lower activation energy of reaction, reaching Vmax

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12
Q

What effects the rate of reaction for enzymes?

A

Temperature, substrate concentration and pH

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13
Q

What are intracellular enzymes with examples?

A

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

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14
Q

What are extracellular enzymes with examples?

A

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

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15
Q

How is starch digested?

A
  • 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
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16
Q

How are proteins digested?

A

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

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17
Q

Where is trypsin made?

A

The pancreas

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18
Q

How does increasing the temperature effect enzyme activity?

A
  • 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
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19
Q

What happens when an enzyme denatures?

A

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

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20
Q

What is the optimum temperature?

A

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

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21
Q

What is optimum pH?

A

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

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22
Q

What happens if the pH changes too significantly?

A

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

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23
Q

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

A

Amylase, breaking down starch into maltose

24
Q

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

A

Pepsin, breaking down proteins into polypeptides

25
Q

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

A

Trypsin, breaking down proteins into polypeptides

26
Q

What happens when the concentration of substrate is increased?

A

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

27
Q

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

A

None, rate of reaction will increase with both

28
Q

What is the Vmax?

A

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

29
Q

Why can’t enzyme related reactions happen too fast?

A

There will be an excess of products

30
Q

What are enzyme inhibitors?

A

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

31
Q

What is competitive inhibition?

A

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

32
Q

What is non-competitive inhibition?

A

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

33
Q

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

A

Competitive - eventually, yes

Non-competitive - no

34
Q

What are the positive effects of inhibition?

A

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

35
Q

What are the negative effects of inhibition?

A

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

36
Q

What is an example of competitive inhibition?

A

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

37
Q

What is an example of non-competitive inhibition?

A

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

38
Q

What is end-product inhibition?

A

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

39
Q

What are cofactors?

A

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

40
Q

Name an example of a cofactor

A

Chloride ions in amylase that are essential in active site formation

41
Q

What are coenzymes?

A

Organic cofactors

42
Q

What are coenzymes made of?

A

Vitamins

43
Q

Name an example of a coenzyme

A

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

44
Q

What is another term used for cofactors?

A

Prosthetic groups

45
Q

What is the difference between cofactors and prosthetic groups?

A

Cofactors are loosely bound and prosthetic groups are tightly bound

46
Q

Name an example of a prosthetic group

A

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

47
Q

What are inactive precursor enzymes?

A

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

48
Q

How are precursor enzymes activated?

A

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

49
Q

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

A

Before - apoenzyme

After - holoenzyme

50
Q

What are other factors that could activate precursor enzymes?

A

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

52
Q

Name an example of a precursor enzyme

A

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

53
Q

What are biological catalysts?

A

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

54
Q

How are hydrogen bonds formed in tertiary structure?

A

Between nitrogen, oxygen and phosphorous; between electronegative and electropositive

55
Q

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

A

Because more active sites are being occupied to achieve Vmax

56
Q

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

A

Because more active sites are being occupied to achieve Vmax

Biology A-Level OCR (26 decks)

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