enzymes Flashcards

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1
Q

what are enzymes

A

-tertiary structure proteins which catalyse reactions

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2
Q

what is special about the active site of an enzyme

A

-its specific and unique in shape due to the specific folding and bonding in tertiary structure of protein
- complementary to substrate to form enzyme substrate complex

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3
Q

give the chemical reaction equation

A

reactants→ products

(arrow indicates its an enzyme controlled reaction)

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4
Q

when can a product form in a chemical reaction

A

-when bonds are broken and reformed
-bond breaking requires activation energy

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5
Q

what is activation energy

A

the minimum energy required for a successful chemical reaction

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6
Q

how do enzymes increase the rate of reaction

A

-by lowering the activation energy
-the active site stresses/weakens the bonds in substrate (reactant) when enzyme-substrate complex is formed
-this allows reactions which would usually require higher temperatures, to work at lower temps

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7
Q

give an example of an enzyme-catalysed reaction

A

-in digestion enzymes allow large complex molecules POLYMERS to be broke down by hydrolysis into smaller simple molecules MONOMERS before absorption and assimilation-at body temp 37 degrees

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8
Q

describe the structure of an enzyme

A

-single polypeptide of about 50 amino acids which form enzyme
-hydrogen bonds maintain its shape
-active site typically made up of less than 10 amino acid R groups

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9
Q

what does the lock and key theory state

A

-the active site is specifically/fully complementary to its substrate
-active site is rigid doesn’t change shape
-the substrate bind to active sit and is an exact fit to it (they are complimentary)
-products are formed and no longer fit to active site

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10
Q

what does the induced fit model state

A

-active site is not fixed/rigid, it can change shape and is slightly flexible
-when substrate binds to enzyme it ‘induces’ a change in shape of active site making it more complimentary
-enzyme can alter its tertiary structure

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11
Q

describe the induced fit model of enzyme action

A

-active site and enzyme are not complimentary
-so when substrate enters the active site the active site changes shape as ESC forms -this is done by stressing or distorting the bons within substrate molecule making it more complimentary
-when substrate leaves the active site goes back to og shape

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12
Q

what is the optimum temp

A

-maximum energy that can be supplied to the molecules before the hydrogen and ionic bonds start to break

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13
Q

describe the effect of temp on rate of reaction

A

at start there’s low levels of KE so there’s less successful collisions and low chance of forming ESC so rate is low

temp increase- enzyme and substrate molecules increased in KE and more likely to successfully collide and react. ROR increases because more ESC form per second

temp increase-optimum temperature is when there’s max KE and highest rate

temp increase- denaturation

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14
Q

what happens to enzyme when temp is too high

A

enzyme vibrate faster because they have lots of KE bonds to break which may change shape of active site, no more ESC formed as substrate is no longer complimentary

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15
Q

what is rate

A

How much and how quickly

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16
Q

when temps exceeds optimum why does the reaction still occur

A

there’s lots of same enzymes in given volume soreaction will occurs at a slower rate until all enzymes have been denatured

17
Q

what is pH

A

measure of H+ ions

18
Q

what happens to an enzyme if the pH is changed

A

the charge on R groups of amino acids is altered and the ionic and weak hydrogen bonds are broken so the active site changes shape and enzyme becomes denatured

19
Q

what happens to an enzyme if it has a small pH change

A

it inactivates the enzyme and may flip the charges on R groups of amino acids but its reversible as this is only a temporary change, if you put enzyme back in optimum pH it will be active again

20
Q

how does substrate concentration affect the rate of reaction

A

-as substrate concentration increases the ROR increases as more ESC are formed per second ( substrate is a limiting factor)
-however eventually the ROR plateaus since all active sites are saturated /in use (enzyme concentration is now the limiting factor)

21
Q

how do you work out reaction rate at a given point

A

draw a tangent and work out gradient

22
Q

give an example of enzyme catalysed reactions

A

-digestion (hydrolysis)
-photosynthesis
-end-product inhibition
-DNA replication

23
Q

how do you work out initial reaction rate

A

draw a tangent on curve starting at 0 and then find gradient

24
Q

how do you work out rate of reaction between 2 points

A

work out gradient

25
Q

what are inhibitors

A

substances which decrease the rate of reaction

26
Q

describe competitive inhibitors

A

-they have similar structures to substrates
-they bind to the active site and prevent substrate from binding temporarily
-so fewer products are formed per second (however some product will still be formed because some active sites can bind to substrates)
-this can be overcome by increasing substrate concentration as they’ll knock off these inhibitors

27
Q

describe non-competitive inhibitors

A

-they bind to a site which is away from active site (allosteric site)
-when they bind to an enzyme it causes a conformational change to the shape of the active site so that substrates cannot bind
-binding can be temporary or permanent
-if the inhibitor molecule detaches from enzyme it can bind to another
-fewer ESC can be formed decreasing rate of reaction
-increasing substrate con wont have an affect on this

28
Q

describe the graph for the inhibitors

A

-when there is no inhibitors maximum ROR is reached and then graph plateaus
-when there is a competitive inhibitor present the line will not be as steep but it will always level off with the no inhibitors curve
-when there is a non competitive inhibitor the ROR wont be at its maximum (usually half of it) and it’ll plateau early