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biology > 2.1.4: enzymes > Flashcards

2.1.4: enzymes Flashcards

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1
Q

what is an active site?

A

indents on the surface of an enzyme with a shape that is complementary to the shape of a substrate, meaning only the substrate will fit

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2
Q

what is a catalyst?

A

chemical that speeds up the rate of reaction by lowering the activation energy by providing an alternative pathway without being used up (reusable)

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3
Q

what is the difference between extracellular and intracellular?

A

extracellular = outside the cell
intracellular = inside the cell

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4
Q

what does metabolic/metabolism mean?

A

the chemical reactions that take place outside living cells or organisms

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5
Q

what is a substrate?

A

molecule that is altered by an enzyme-catalysed reaction

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6
Q

what is meant by the term “turnover number”?

A

number of substrate molecules converted into products per second

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7
Q

what are the advantages of enzymes compare to chemical catalysts?

A
  • work at lower temperatures
  • more specific
  • function well in conditions that sustain life
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8
Q

what proteins are enzymes made from?

A

tertiary and quaternary structure

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9
Q

how do enzymes and substrates collide?

A

randomly due to kinetic energy

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10
Q

how does and enzyme catalyse (equation)?

A

enzymes + substrate > enzyme-substrate complex > enzyme-product complex > enzyme + product

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11
Q

what energy can be provided to activate a chemical reaction?

A

heat which would increase the kinetic energy, making the more likely to collide

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12
Q

why can’t increasing temperature be used in cells to provide activation energy?

A

will cause proteins to denature and lipid structure in membranes to fall apart

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13
Q
A
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14
Q

what type of reaction allows 2 substrates to bond and what reaction occurs when the substrate needs to break down into 2 products?

A

anabolic reaction and catabolic reaction

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15
Q

what is an example of an intracellular enzyme and what are the products?

A

catalase that breaks down hydrogen monoxide producing 2 water molecules and an oxygen molecule

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16
Q

what is the turnover number for hydrogen peroxide?

A

6 million

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17
Q

what is an example of an extracellular enzyme?

A
  • digestive enzymes i.e. amylase
  • decomposing enzymes i.e. bacteria
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18
Q

what is the lock-and-key theory?

A

the enzyme active site has a fixed rigid shape. a substrate with a complementary shape into the active site

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19
Q

what is the induced fit model?

A

the active site and the substrate shapes don’t fit together at the start but when the substrate comes near the active site triggers a slight change in shape, allowing the substrate to fit

20
Q

what are 6 factors that affect the rate of enzyme activity?

A
  • temperature changes
  • water availability
  • ph changes
  • substrate concentration
  • enzyme concentration
  • inhibitors
21
Q

how does temperature affect enzyme activity?

A
  • temperature increases = rate of enzyme reaction increases
  • there is more kinetic energy for successful collisions
  • at the optimum temperature the enzyme works the best
  • after the optimum, the rate decreases because the enzymes slowly begin to denature
22
Q

how does temperature denature enzymes?

A

it causes the bonds in the tertiary structure to break, changing the shape of the active site

23
Q

how does ph affect enzyme activity?

A
  • ph increases = rate increases until the optimum ph is reached (when the enzyme works best)
  • when the ph increases further, the enzymes will slowly denature
  • rate will decrease
24
Q

how does ph denature enzymes?

A

the more hydrogen ions present (low ph), the less the r-groups in the enzyme are able to interact with each other and the bonds will break, causing the active site to change shape

25
Q

how does substrate concentration affect the rate of enzyme activity?

A
  • increase substrate concentration = rate will initially increase
  • more substrates to react
  • slowly plateau because the enzyme concentration will become the limiting factor
26
Q

how does enzyme concentration affect the rate of enzyme activity?

A
  • increase the amount of enzymes = rate will increase
  • more active sites for substrates to go into
  • rate will then plateau = substrate concentration will become the limiting factor
27
Q

what is it called when the rate of enzyme activity plateaus?

A

v max

28
Q

what is an inhibitor?

A

a factor that prevents or reduces the rate of of the enzyme- catalysed reaction

29
Q

what is a competitive inhibitor?

A

have a similar shape to the substrate molecule and they compete with the substrate to join the onto the enzyme active site, blocking the active site

30
Q

what are 2 examples of competitive inhibitors?

A

1) statins - bind to the enzyme that makes cholesterol = less is produced
2) aspirin - binds to the enzyme that makes prostaglandins (sensitive to pain in nervous system) = less sensitive to pain

31
Q

what is a competitive inhibitor which is reversible?

A

they are only temporarily attached to the enzyme

32
Q

what is a non-competitive inhibitor?

A

don’t have a similar shape to the substrate and therefore attach to the to the enzyme but not the active site (the allosteric site)

33
Q

how do inhibitors affect the rate of reaction and why?

A

decrease it because they change the shape of the active site

34
Q

what are 2 examples non-competitive inhibitors?

A

1) organophosphates - binds to the enzyme needed for nerve impulse transmission = paralysis
2) proton pump inhibitors - binds to the enzyme needed to make stomach acid = less acid made

35
Q

what is the end-product inhibition?

A

when the product of a reaction can inhibit one of the enzymes involved in its own production

36
Q

are end-product inhibitions reversible?

A

yes

37
Q

why is end-product inhibitions useful?

A

it cuts down on the products that would be a waste

38
Q

what is an example of an end-product inhibition?

A

atp can inhibit the enzyme phosphofructokinase, so once enough atp is made, it inhibits its own production

39
Q

many enzymes need an addition of a non-protein component for them to work. what are these called?

A

co-factors, co-enzymes and prosthetic groups

40
Q

what are co-factors?

A

inorganic molecules or ions that help the enzyme and substrate join. they don’t participate directly with the reaction

41
Q

what are co-enzymes?

A

organic molecules that alter reactions by acting as barriers, moving chemical groups between different enzymes in metabolic pathways

42
Q

what is an example of a co-factor?

A

chlorine ions needed to activate salivary amylase which digests starch

43
Q

what is an examples of a co-enzyme?

A

many vitamins, like vitamin b3 for respiratory enzymes

44
Q

what are prosthetic groups?

A

co-factors or co-enzymes that are very tightly attached to an enzyme and may even be permanently attached

45
Q

what is an example of a prosthetic group?

A

zinc ions are permanently attached to the enzyme carbonic anhydrase, which is involved in the carbon dioxide in the blood stream

46
Q

what is the method for investigating the effect of substrate concentration on enzyme activity?

A
  • grind a 2cm piece of potato and 5cm of distilled water to make a smooth paste
  • place 10cm of hydrogen peroxide in a test tube and use forceps to dip a filter paper disc into the enzyme suspension
  • drop the filter paper into the hydrogen peroxide and measure the time that is takes from striking to the surface to sink to float up again
  • remove the disk and repeat with different concentrations of hydrogen peroxide
47
Q

what are the variables in the experiment to investigate the effect of substrate concentration on enzyme activity?

A
  • independent variable = concentration of the hydrogen peroxide
  • dependent variable = time take for the disk to travel
  • control variables = same potato extract, total volume and same temperature

biology (10 decks)

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