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Biology AS Rafa > 2.4 - Enzymes > Flashcards

2.4 - Enzymes Flashcards

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1
Q

Why are enzymes so remarkable?

A
  • Low temperatures
  • Normal pH and pressure
  • More specific
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2
Q

How many amino acids is the active site made from?

A

About 6 to 10.

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3
Q

What happens in catabolic reactions?

A

Metabolites are broken down.

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4
Q

What happens in anabolic reactions?

A

Synthesis of larger molecules.

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5
Q

Where is catalase found in eukaryotic cells?

A

Small vesicles called peroxisomes.

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6
Q

In our digestive system, where are enzymes secreted from?

A

Cells lining the alimentary canal, into the gut lumen.

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7
Q

Which enzyme contains a zinc ion as a prosthetic group?

A

Carbonic anhydrase

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8
Q

What does carbonic anhydrase do?

A

Catalysed the inter conversion of carbon dioxide and carbonic acid which then breaks down to protons and hydrogencarbonate ions.

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9
Q

Which ion must be present from amylase to make maltose?

A

Chloride.

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10
Q

What are coenzymes?

A

Small, organic non-protein molecules that bind temporarily to the active site of the enzyme.

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11
Q

Where are many coenzymes derived from?

A

Water soluble vitamins.

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12
Q

Define enzyme substrate complex

A

enzyme model with substrate molecule in active site, joined temporarily by non-covalent forces

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13
Q

what is Q10?

A

temperature coefficient, calculated by dividing rate of reaction at (T+10) by the rate of reaction at T

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14
Q

How does pH affect enzymes?

A

Excess H+ ions interfere with hydrogen bonds and ionic forces, changing shape

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15
Q

Benefits of enzyme degradation

A

elimination of abnormal proteins

eliminating superfluous enzymes

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16
Q

What regulates an enzyme controlled reaction

A

End product inhibition

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17
Q

How do many toxins work?

A

By inhibiting or inactivating enzymes

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18
Q

What are two poisons/toxins that inhibit enzyme action?

A
  • cyanide
  • snake venom
  • malonate (respiration)
  • arsenic (respiration)
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19
Q

What does cyanide inhibit?

A

catalase

stop final stage of aerobic respiration

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20
Q

Which medicinal drugs act as enzymes inhibitors and how?

A
  • some antiviral drugs (eg reverse transcriptase inhibit reverse transcriptase which catalyses the replication of viral DNA)
  • some antibiotics (penicillin inhibits transpeptidase which catalyses the formation of proteins in bacterial cell walls. this weakens the cell wall and the bacterium cant regulate osmotic pressure and bursts)
21
Q

What type of reactions do enzymes catalyse?

A

Cellular (eg respiration) and whole body (digestion)

Structural ( eg production of collagen) and function (eg respiration)

22
Q

What enzyme catalyses intracellular reactions?

A

catalase

23
Q

What enzyme catalyses extracellular reactions?

A

trypsin

24
Q

Describe the role of catalase

A

Hydrogen peroxide to oxygen and water

25
Q

Describe the role of trypsin

A

Catalyses the hydrolysis of peptide bonds

made in pancreas and secreted into small intestine

26
Q

Describe the role of amylase

A

found in saliva

hydrolysis of starch to maltose

27
Q

What about enzymes is responsible for lowering activation energy?

A

The formation of the enzyme-substrate complex

28
Q

Why does the enzyme substrate complex lower the activation energy?

A
  • if they need to be joined, they are held close together

- if they need to be separated, the active site puts strain on the bonds in the substrate

29
Q

What does Q10 show?

A

How much the rat of a reaction changes when the temperature is raised by 10 degrees

30
Q

What does a Q10 value of 2 demonstrate?

A

Rate doubles when temp is raised by 10 degrees

31
Q

What are the factors affecting the rate on enzyme controlled reaction?

A
  • temperature
  • pH
  • enzyme concentration
  • substrate concentration
32
Q

Describe two ways of measuring the rate of an enzyme controlled reaction

A

1) How fast the product appears, eg for catalase you could collect volume of oxygen
2) you could measure the disappearance of a substrate and compare with different conditions

33
Q

Describe an experiment that investigates the effect of temperature of catalase activity

A
  • boiling tubes with hydrogen peroxide
  • add equal volumes of buffer solution for constant pH
  • put each boiling tube in different water bath temp
  • add catalase
  • calculate volume of oxygen produced and repeat
34
Q

Whats the difference between cofactors and coenzymes?

A

Coenzymes are cofactors that are organic molecules

  • cofactors don’t get used up
  • coenzymes are changed by reactions and recycled
35
Q

Whats a source of coenzyme?

A

Vitamins

36
Q

What an enzymes prosthetic group?

A

When a cofactor is tightly bound to the enzyme,

permanent part of active site

37
Q

Cofactor of amylase

A

Cl-

38
Q

Prosthetic group of carbonic anhydrase

A

Zn2+

39
Q

Describe competitive inhibition

A
  • similar shape to substrate

- compete for active site

40
Q

Describe non-competitive inhibition

A

-binds at allosteric site which causes the active site to change shape

41
Q

What happens when you increase the substrate concentration in competitive and non-competitive inhibition?

A

competitive - increase rate of reaction

non-competitive - wont make any difference an enzyme activity will still be inhibited

42
Q

When is inhibition irreversible?

A

when there are strong, covalent bonds and the inhibitor cannot be removed

43
Q

When is enzyme inhibition non-reversible?

A

when there are weaker hydrogen bonds or weak ionic bonds and the inhibitor can be removed

44
Q

Why are enzymes sometimes synthesised as inactive precursors in metabolic pathways?

A

to prevent them causing damage to cells

45
Q

Example of an enzyme acting as a inactive precursor

A

some proteases (which break down proteins) are inactive precursors so they don’t damage proteins in the cell that they are made

46
Q

How do inactive precursor molecules work?

A

part of the precursor molecule inhibits its action as an enzyme and this part can be removed when the enzyme needs to be active

47
Q

Why do we need small amounts of cofactors in our bodies?

A
  • they can be reused
  • enzyme mass is small
  • some enzymes don’t need cofactors
48
Q

What are models used for?

A

simple representations of processes

49
Q

Define enzyme/biological catalyst.

A

proteins used in metabolism
that alter the rate of chemical reaction
lower activation energy
not used up in the process

Biology AS Rafa (13 decks)

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