Enzymes part 2 Flashcards

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1
Q

What does latic acid dissociate into

A

H+ and lactate

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2
Q

What does pyruvic acid dissociate into

A

H+ and pyruvate

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3
Q

What is a buffer

A

A buffer is something that resists change in pH so the pH of the blood remains at about 7.4

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4
Q

How does a buffer work

A
  • a buffer donates or accepts hydrogen ions

- some proteins such as haemoglobin can also donate or accept protons and act as buffers

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5
Q

How does pH affect the bonds in molecules

A
  • a hydrogen ion is attracted to the negative charged ions or molecules or parts of molecules,
  • excess hydrogen ions interfere with the hydrogen bonds and ionic forces holding the tertiary structure of the enzyme together therefore the enzymes tertiary structure changes and the active site changes shape meaning that the substrate can no longer fit into the active site lowering the rate of reaction
  • increasing the concentration of hydrogen ions will also alter the charges on the active site of enzyme molecules because more proteins cluster around the negatively charged group which interferes with the binding of the substrate molecules onto the active site
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6
Q

why is pH so important to enzymes

A

enzymes work with a narrow change in pH

  • small changes either side of the optimum pH slows the rate of reaction as the active site is disrupted
  • if normal pH is restored then the enzyme can form hydrogen bonds again and the tertiary structure is formed again so the active site is restored
  • at extremes of pH the active site is permanently changed and the enzyme is denatured and can no longer catalyse the reaction
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7
Q

Draw the pH graph for enzymes

A

DRAW IT

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8
Q

Draw the temperature graph for enzymes

A

DRAW IT

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9
Q

What is the pH of intracellular enzymes

A

they have an optimum pH that is close to 7

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10
Q

What is the pH of extracellular enzymes

A

they have optimum pH values which are different from pH 7,

For example amylase in the mouth works best at pH 6.8

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11
Q

What is the pH of the stomach

A

between 1 and 2 as this is what pepsin works best in

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12
Q

what is the pH in the small intestine

A

7.8 as this is the optimal for protein digesting enzymes such as trypsin and enterokinase so digest peptides into amino acids

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13
Q

What is the effect of increasing substrate concentration on the rate of reaction

A

if you increase the concentration of substrate the rate of reaction increases
- more enzyme substrate complexes can form
- more product molecules are formed
- substrate concentration is limiting in the reaction because as it increases the rate of reaction increases therefore it is a limiting factor
The reaction will reach its maximum amount when the substrate is increased even further then this happens…..
- adding more substrate molecules to increase substrate concentration will not increase the reaction
- all the enzymes active sites are occupied by substrate molecules
- if more substrate molecules are added then they cannot successfully collide and fit into the enzymes active site

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14
Q

Draw the effect of changing enzyme concentration graph

A

DRAW IT

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15
Q

What is the effect of enzyme concentration on the rate of reaction

A

As the enzyme concentration increases the rate of reaction increases this is because

  • more active sites of the enzyme become available
  • more successful collisions between the enzyme and substrate occur
  • more enzyme-substrate complexes can form per unit time so the rate of reaction increases
  • enzyme concentration is the limiting factor as it increases and so does the rate of reaction
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16
Q

What happens when the substrate concentration is fixed and you try to increase the rate of reaction by increasing the enzyme concentration

A
  • the reaction would have reached the maximum rate
  • so if the enzyme concentration has increased further then there will be no increase in the rate of reaction because the active site of the extra enzyme molecules will not be occupied by substrate molecules
  • the enzyme concentration is no longer the limiting factor as enzyme concentration increases the rate of reaction increases
  • substrate concentration is now the limiting factor as lack of substrate molecules is preventing the rate of reaction from increasing
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17
Q

What is enzyme synthesis

A

this is when depending on the cells needs, genes for synthesising particular enzymes can be switched on o r off

18
Q

What is enzyme degradation

A

cells are continuously degrading old enzyme molecules to their component amino acids and synthesising new enzyme molecules from amino acids

19
Q

What are the advantages for enzyme degradation

A
  • elimination of abnormally shaped proteins that might otherwise accumulate and harm the cell
  • the regulation of metabolism in the cell by eliminating any superfluous enzymes
    it is important in order for a cell to regulate its metabolism properly
20
Q

DRAW graph for enzyme concentration on the rate of reaction

A

DRAW IT

21
Q

Describe how the rate of reaction catalysed by an enzyme progresses over time

A
  • At the beginning of the reaction, enzyme and substrate molecules are in high concentration and are moving randomly this means that there is a greater chance of a substrate molecule colliding with an enzymes active site
  • as the reaction goes on the substrate molecules are used up as they are converted to products therefore the concentration of the substrate drops
  • therefore the frequency of the collisions between enzymes and substrate molecules decreases because enzymes may collide with product molecules therefore the rate of the reaction decreases
  • the initial rate is the maximum rate
22
Q

what are inhibitors

A

they are substance that reduces or stops a reaction by reducing the activity of an enzyme

23
Q

How do inhibitors work

A

they collide with an enzyme molecule in a way which effects how the substrate binds to the enzymes r effects the enzymes turnover number
- some block the active site while others change the shape of the active site

24
Q

what are competitive inhibitors

A

this is where the enzyme has a similar shape to that of the substrate molecule and competes with the substrate molecules for the enzymes active site, it blocks the active site and prevents the formation from enzyme-substrate complex

25
Q

How do competitive inhibitors work

A
  • the competitive inhibitors fit into the active site so a substrate cannot enter
  • the amount of inhibition depends on the relative concentration of substrate and inhibitor molecules, more inhibitor molecules collide with active sites so the effect of inhibition is greater
  • increasing the substrate concentration would reduce the effect of the inhibitor, if enough substrate is added the inhibitor will not collide with the enzyme
26
Q

How do substrate and competitive inhibitors compete with each other

A
  • inhibitors compete directly with the substrate molecule for the enzymes active site they form an enzyme-inhibitor complex which inactivates the enzyme
  • the inhibitor is not changed by the active site of the molecule
  • the presence of the inhibitor effects the substrate molecule from joining to the active site which reduces the rate of formation of the ES complex and the product molecule formation
  • inhibitor reduces the number of free enzyme active sites available for the substrate molecule
  • mostly reversible as collisions between enzyme and substrate and enzyme and inhibitor are random therefore by increasing the concentration of the substrate you increase the chance that the substrate will collide with the enzyme and form an ES complex rather than the inhibitor
  • when binding irreversibly to the active site it is called an inactivator
27
Q

What is a non-competitive inhibition

A

this is where the competitor molecule that attaches to a part of the enzyme molecule that is not the active site - it binds to the allosteric site, this changes shape of the active site which prevents the ES complex from forming this is because the enzymes active site is no longer complementary in shape to the substrate molecule

28
Q

Draw graph with the competitive inhibitor

A

DRAW IT

29
Q

Draw graph with non-competitive inhibitor

A

DRAW IT

30
Q

How do non-competitive inhibitors work

A
  • they bind to the allosteric site this changes the tertiary\ry structure of the enzyme which changes its active site this means that the substrate molecule can no longer bind to the enzyme and a ES complex cannot form as the active site is no longer complementary
  • this reduces the maximum rate of reaction, by adding more substrate” the reaction will be able to carry on at this lower rate but adding the concentration of substrate will not allow it to return to its maximum rate
  • the more inhibitor molecules present the greater the inhibition as more enzyme molecules are distorted and cannot either form ES complexes or cannot complete catalytic reaction involving ES complexes
  • can be reversible but mostly irreversible
31
Q

What is end-product inhibition

A

after the enzyme catalyses reaction has reached completion product molecules may be tightly bound to the enzyme therefore the enzyme cannot form more of the product that the cell needs this is negative feedback

32
Q

How does the presence of organelles within a cell increase the efficiency of metabolic reactions

A
  • many metabolic reactions are carried out in particular regions of the cell organelles this increases the efficiency of metabolism, some enzymes within organelles are bound into the organelle membrane
33
Q

What do multi-enzyme complexes do

A

they increase the efficiency of metabolic reactions without increasing substrate concentration as they keep the enzyme and substrate molecules in the same vicinity and reduce diffusion time

34
Q

How do metabolic sequences work

A
  • the product of one enzyme catalysed reaction becomes the substrate of the next enzyme catalysed reaction in the metabolic pathway
  • cells do not need to accumulate to much end product therefore the last enxyme catalyses reaction may also attach to part of the first enzyme in its pathway but not the active site
  • this changes the active site of the first enzyme preventing the pathway from running it is non-competitive inhibition but it is reversible
  • the concentration of this product within the cell falls and the molecules with detach from enzyme 1 and allow its active site to resume to its normal shape therefore the metabolic pathway can run again
35
Q

How does cyanide work

A

when ingested potassium cyanide is hydrolysed to produce hydrogen cyanide, this is a toxic gas that can dissociate into H+ and CN- ions
- the CN- ions bind irreversibly to an enzyme found in the mitochondria and inhibit the final stage of aerobic respiration, this is because the final stage in inhibited, earlier stages cannot run and aerobic respiration stops

36
Q

How does snake venom work

A

Venom of the green mamba snake contains a chemical that inhibits the enzyme AChE, this enzyme is important at neuromuscular synapse to break down the neurotransmitter ACh, if this enzyme is inhibited the ACh stays attached to the receptors on the muscle membrane and keeps the muscle contracted
- causes paralysis as movement depends on muscles being able to relax alternately, if muscles are involved in breathing are paralysed then victims die from suffocation

37
Q

How does aspirin work

A

Professeur John Vane discovered that salicylic acid binds to enzymes to catalyse the formation of prostaglandins, this prevents the formation of prostaglandins that are cell signalling molecules produced by cells when tissues are infected or damaged this makes nerve cells more sensitive to pain and increase swelling during inflammation

  • reduces the risk of blood clots forming and reduces the risk of strokes
  • can damage stomach lining
38
Q

How does ATPase inhibitors work

A

estracts from foxglove leaves are used to treat heart failure and atrial arrhythmia

  • these chemicals are now known as cardiac glycosides
  • these inhibit the sodium potassium pump in the cell membranes of heart muscle cells and allow more calcium ions to enter the cell, calcium ions increase muscle concentration and strengthen the heartbeat
39
Q

How does ACE inhibitors work

A

they are medical drugs which inhibit the angiotensin converting enzyme ACE which normally operates in a metabolic pathway which increases the blood pressure

  • they reduce blood pressure in patients with hypertension who cannot take beta-blockers
  • to treat heart failure - low dose at first and patients blood pressure is checked in case it falls to low
  • to minimise risk of a second heart attack or stroke in patients who suffered myocardial infarction
40
Q

What do protease inhibitors do

A

protease inhibitors such as amprenavir and ritonavir and are used to treat viral infections in order to prevent the replication of virus particles within the host cells by inhibiting protease enzymes so viral coats cannot be made - this happens by competitive inhibition

41
Q

How does Nucleoside reverse and transcriptase inhibitors work

A
  • many antiviral drugs such as zidovudine and abacavir are used to treat patients who are HIV positive are nucleoside reverse transcriptase inhibitors, these inhibit enzymes involved in making DNA using the viral RNA as a template