M2, C4 Enzymes Flashcards

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1
Q

define enzyme

A

Enzymes are proteins used in metabolic pathways, they increase the rate of metabolic reaction by finding an alternative pathway with a lower activation energy.

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2
Q

what are enzymes made of

A

globular proteins

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3
Q

define anabolic

A

reactions of metabolism that construct molecules from smaller units
they require energy from the hydrolysis of ATP

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4
Q

define active site

A

area of an enzyme with a shape complementary to a specific substrate, allowing the enzyme to bind a substrate with specificity

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5
Q

define activation energy

A

the energy required to initiate a reaction

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6
Q

define catabolic

A

reactions of metabolism that break molecules down into smaller units
these release energy

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7
Q

define substrate

A

a substance used, or acted on, by another process or substrate
eg. a reactant in an enzyme catalysed reaction

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8
Q

how does an enzyme speed up a reaction

A

it lowers the activation energy

this means it takes less energy to initiate a reaction hence speeding the reaction up

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9
Q

what is the lock and key hypothesis

A
  • an enzyme has a specific active site which is complementary to the shape of the substrate
  • when the substrate is bound to the active site and enzyme-substrate complex is formed
  • the substrates then react forming an enzyme-product complex
  • the products are released leaving the enzyme unchanged
  • temporary bonds are also formed when the R groups of the enzymes interact with the substrate which helps the reaction along
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10
Q

what is the induced fit hypothesis

A

Substrate is complementary to active site of enzyme
Substrate bind to active site of the enzyme
The shape of the active site of the enzyme changes slightly to form a tighter fit between the substrate and enzyme (the induced fit)
This forms an enzyme substrate complex
Straining of bonds in the substrate forms an enzyme product complex
Products leave active site

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11
Q

how would you work out metabolism

A

catabolic reactions + anabolic reactions

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12
Q

how is starch digested

A

starch polymers are broken down into maltose by amylase
amylase is produced by the salivary glands and pancreas and released in the saliva and pancreatic juice in the small intestine

maltose is then broken down into glucose by maltase
maltase is present in the small intestine

glucose is then absorbed into the bloodstream

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13
Q

how is protein digested

give an example of protease

A

trypsin is a protease
it catalases proteins into smaller peptides
peptides are broken into amino acids
trypsin are produced in the pancreas and released in the pancreatic juice in the small intestine
amino acids are absorbed by cells lining the digestive system and go into the bloodstream

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14
Q

As temperature increases how does enzyme activity change?

What’s the optimum temp in humans?

A

Increasing temp, increases kinetic energy in particles. The particles collide more frequently. This would mean more successful collisions between the substrate and the enzyme which increases the rate of reaction.

Optimum temperature in humans is 37

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15
Q

Why do enzymes denature at a too high temp?

A

As temperature gets high the bonds between proteins vibrate more. Bonds will then strain and break. This changes the shape of the tertiary structure of the protein.
The active site changes shape so won’t fit with the substrate so the enzyme can no longer act as a catalyst.

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16
Q

What does the graph look like of temperature against rate of reaction

A

Slow increase up to the optimum temp and then a rapid decrease

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17
Q

What adaptions do enzymes have which are in the cold and in the hot?

A

More flexible structures making them less stable

Enzymes at high temp have more bonds so are more stable and are more resistant to change

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18
Q

What is pH and what is its relation to hydrogen ions

A

It’s the measure of hydrogen ion concentration

The lower the pH, the more hydrogen ions are (more acidic)

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19
Q

How does pH affect enzyme reactions

A

Hydrogen ions are attracted to negatively charged areas. Different amino acids have different charges and hydrogen ionic bonds holds amino acids in a very precise shape.
Hydrogen ions interfere with these bonds and thus change the structure of the enzyme and its active site.

20
Q

What is the optimum pH for amylase? For pepsin?

A

Amylase - pH 7.8

Pepsin - pH 1.8

21
Q

How does substrate concentration affect the rate of reaction

A

More concentration increases the rate of reaction because there is a higher collision rate.
However eventually all the active sites are used up and the rate of reaction can no longer increase. This is the V max.

22
Q

what are intracellular enzymes

A

enzymes that act within the cells

eg. hydrogen peroxide which is broken down by catalase

23
Q

what are extracellular enzymes

A

enzymes that break down substances outside of cells
for example nutrients and proteins which need to be transported from cell to cell may be too big to get into the cell so enzymes can break them down so they can fit.
they can make smaller molecules for digestion.

24
Q

what are enzyme inhibitors

A

molecules that prevent enzymes from carrying out their normal function of catalysis
two types - competitive and non-competitive

25
Q

what is competitive inhibition

A

A molecule that has a similar shape to the substrate of an enzyme fits into the active site of that enzyme.
It blocks the substrate from entering the active site, preventing the enzyme catalysing the reaction.
The enzyme is said to be inhibited.
The number of substrates binding with active sites reduces, hence slowing down the rate of reaction.
The inhibitor only binds temporarily for most cases.

26
Q

what are some examples of competitive inhibition

A

Statins - inhibits the enzyme that synthesises cholesterol to stop high cholesterol levels

Aspirin - irreversibly inhibits enzymes that synthesise prostaglandins and thromboxane which produce pain and fever

27
Q

what is non-competitive inhibition

A

The inhibitor binds to the enzyme at a location other than the active site - this is called the allosteric site.
This causes the tertiary structure of the enzyme to change which changes the shape of the active site.
The substrate therefore can no longer bind with the enzyme and is said to be inhibited.
Active sites therefore become unavailable hence decreasing the rate of reaction.
Can be reversible or irreversible

28
Q

what are some examples of irreversible non-competitive inhibitors

A

NCI in medicines
Penicillin- Is an antibiotic which binds to active site of enzyme transpeptidase which catalysed the formation of proteins in bacterial cell walls

NCI in metabolic poisons:
Cyanide- Is a poison which binds to allosteric site in eznyme cytochrome c oxidase which is an enzyme involved respiration

29
Q

what is end-product inhibition

A

When a product of a reaction then acts as an inhibitor to the enzyme that produces it.
Serves as a negative feedback control mechanism.
Stops excess products being made and stops resources being wasted.
It is non-competitive reversible inhibition.

30
Q

How does respiration involve end-product inhibition

A
  • Breaking down a glucose molecule involves the enzyme PFK (phosphofructokinase).
  • This enzyme is competitively inhibited by ATP. It therefore regulates its own production.
  • When ATP levels are high, more ATP binds to PFK which stops glucose being broken down.
  • As ATP is used up less binds to PFK so the enzyme can catalyse more so respiration resumes leading to the production of more ATP.
31
Q

define cofactor

A

non-protein components necessary for the effective functioning of an enzyme

32
Q

define prosthetic group

A

non-protein component that binds tightly to a protein or enzyme and aids with its function

33
Q

what is a coenzyme

A

an organic cofactor

34
Q

where are inorganic cofactors obtained from

A

the diet as minerals

eg. iron, calcium, chloride and zinc

35
Q

what cofactor is in amylase

A

chloride ion

36
Q

where are coenzymes derived from

A

vitamins in the diet

37
Q

whats the difference between cofactors and prosthetic groups

A

cofactors are temporary and prosthetic groups are tightly bound to the enzyme and can be permanent

38
Q

what are precursor enzymes

A

inactive enzymes which are produced like that

39
Q

why is it important that some enzymes are precursor

A

so they don’t cause damage

so they can be controlled and activated only under certain conditions

40
Q

how are precursor enzymes activated

A

they need to undergo a change in shape to the tertiary structure
this is done by adding a cofactor

41
Q

what is an apoenzyme

A

a precursor enzyme before a cofactor is added

42
Q

what is a holoenzyme

A

when a cofactor is added to a precursor enzyme so it is activated

43
Q

In blood clotting describe the enzyme activation process / the coagulation cascade

A

when platelets touch the collagen of the skin, they become aggregated and release factor X
It is activated by the cofactor vitamin K
When it is activated it converts prothrombin to thrombin by changing the structure
Thrombin is a protease which converts soluble fibrinogen to insoluble fibrin fibres
Fibrin forms the blood clot

44
Q

What is the temperature coefficient Q10

A

The temperature coefficient shows how the rate of an enzyme controlled reaction changes with a 10 degree increase in temperature

If Q10=2, it means that the rate of reaction is doubled for every 10 degree increase in temperature.

45
Q

What is the formula for the temperature coefficient Q10

A

Q10 = Rate of Temperature 2/ Rate at Temperature 1

46
Q

What enzyme is Zn2+ the cofactor for

A

Carbonic Anhydrase

47
Q

What enzyme of Cl- the cofactor for

A

Amylase