2.4)Enzymes Flashcards

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1
Q

what are enzymes?

A

biological catalysts that speed up the rate of metabolic reactions without being used up

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2
Q

what type of proteins are enzymes?

A

globular

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3
Q

how do enzymes work?

A

interact with substrate mol. to form enzyme substrate complex (ES)

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4
Q

what is the turnover number?

A

number of reactions that an enzyme can catalyse in one second

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5
Q

what is a difference between chemical catalysts and enzymes?

A

-they can work at lower temp, neutral pH + lower press
-more specific than chemical catalysts

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6
Q

what effects do gene mutations have on enzymes?

A

-alter the AA sequence of a protein
-alter the enzymes tertiary structure
-prevent enzyme from functioning

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7
Q

what can a deficiency in enzymes cause?

A

metabolic disorder

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8
Q

what is an active sight?

A

indentation or cleft on the surface of the enzyme consisting of about 6~10 AA

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9
Q

what structure does the active sight have?

A

tertiary

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10
Q

why is the tertiary structure of the active sight crucial?

A

-shape is complementary to the shape of the substrate binding to it

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11
Q

why are enzymes specific?

A

the active sight is complementary to the substrate

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12
Q

how to enzymes affect the activation energy ?

A

lowers the activation energy to get the reaction started

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13
Q

what is the activation energy?

A

minimum energy to start a reaction

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14
Q

what are intracellular enzymes?

A

-act within cells
-structure and function of cells

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15
Q

what are the 3 pathways that intracellular enzymes take?

A

-metabolic
-anabolic
-catabolic

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16
Q

what is the metabolic pathway?

A

each step catalysed by a different enzyme

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17
Q

what is the anabolic pathway?

A

large mol. synthesised from small mol.

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18
Q

what is the catabolic pathway?

A

large mol. broken down into smaller mol.

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19
Q

what is one product of metabolic pathways?

A

hydrogen peroxide

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20
Q

which enzyme breaks down hydrogen peroxide?

A

catalase

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21
Q

how does catalase protect the cell from damage from reactive oxygen?

A

breaks it down into water + oxygen

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22
Q

what are extracellular enzymes?

A

work outside the cell

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23
Q

what is one type of the extracellular enzymes?

A

-digestive enzymes secreted from the cells lining the alimentary canal in the lumen of the gut
-digest large mol. (fat,protein + starch)
-absorbed into the bloodstream

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24
Q

what are 2 types of digestive enzymes?

A

-amylase
-trypsin

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25
Q

how do enzymes that work outside of the body work?

A

-release enzymes into their immediate surroundings
-breakdown large mol. into smaller mol.
-absorbed by cell

26
Q

what is a cofactor?

A

small non protein mol. that attaches to an enzyme

27
Q

what are cofactors for?

A

ensure that an enzyme catalysed reaction takes place at an appropriate rate

28
Q

what is a prosthetic group?

A

cofactor that is permanently bound with covalent bonds to an enzyme

29
Q

what is the prosthetic group in carbonic anhydrase?

A

zinc ion

30
Q

where is carbonic anhydrase found?

A

erythrocytes

31
Q

what reaction does carbonic anhydrase catalyse?

A

interconvention of CO2 + H2O to carbonic acid

32
Q

why is the catalytic reaction of carbonic anhydrase imporatant?

A

allows CO2 to be carried in the blood from respiring tissue to the lungs

33
Q

what hormone is zinc an important cofactor for?

A

polypeptide hormone into insulin

34
Q

can cofactors also be ions?

A

yes

35
Q

what type of bond is there between cofactors and substrate?

A

temporarily bound

36
Q

what effect do cofactors have on substrate on substrate mol.?

A

-ease the formation of the ES
-increase the rate of the enzyme catalysed reaction

37
Q

chloride ion is a cofactor for which enzyme?

A

amylase

38
Q

what are coenzymes?

A

small organic non proteins that bind temporarily to the AS

39
Q

what happens to coenzymes during chemical reaction?

A

chemically changed and need to be recycled to their original state

40
Q

what is the difference between a prosthetic group and a coenzyme?

A

prosthetic group bind permanently to enzyme, a coenzyme binds temporarily

41
Q

what effects can increased temperatures have on enzymes?

A

denature them

42
Q

what happens to the Ea when the substrate binds to the active sight?

A

-lowers the Ea

43
Q

what happens when there is a low Ea?

A

-⬆️ number of collisions
-speed up metabolic reactions

44
Q

what are the 2 hypothesis’ of the formation of an ES-complex?

A

1) lock & key
2) induced fit

45
Q

explain the lock & key hypothesis

A

-substrate fits into the AS like a key into a lock
-substrate held in way that the right atom groups are close enough to react
-R-groups react= form H bonds= ES-complex
-substrate mol. broken into smaller product mol. –> leave AS

46
Q

what type of energy do the enzyme + substrate have?

A

kinetic energy

47
Q

as the enzyme + substrate have KE, what does this cause?

A

-constantly moving
-2 mol. collide= ES-complex
-substrate mol. broken or built up to form= enzyme product complex
-product leaves AS = enzyme binds to another substrate mol.
-form another ES-complex

48
Q

who introduced the induced fit hypothesis?

A

Daniel Koshland

49
Q

what did the induced fit hypothesis suggest?

A

-substrate enters the AS
-induces a slight change in shape
-AS moulds itself around the substrate =good fit
-R-groups change shape slightly

50
Q

in an induced fit why is the conformation more precise?

A

R-groups change shape

51
Q

where is the ES-complex formed?

A

where the H bonds, ionic bonds, hydrophobic interactions + van der waals forces bind the substrate to the AS

52
Q

what happens when the product is released from the induced fit?

A

-has a slightly diff shape to the substrate
-detaches from the AS
-enzyme is free to bind to another substrate mol.

53
Q

what happens when a mixture of enzyme + substrate is heated?

A

-both mol. gain KE
-⬆️ number of collisions
-⬆️ rate of ES-complexes
-until the optimum temp

54
Q

what does increasing the temp cause to the bonds?

A

-mol. vibrate faster
-weaker bonds break
-H bonds + ionic bonds hold the tertiary structure together
-vibrations ⬆️= AS begins to change shape
-⬆️ temp even more= AS has irreversibly changed shape= no longer complementary
-denatured

55
Q

what does it mean when the enzyme has denatured?

A

-AS has completely changed shape
-no longer complementary

56
Q

which bonds break when the enzyme becomes denatured?

A

-tertiary bonds BREAK
-peptide bonds DO NOT break= primary structure is not altered

57
Q

what does the optimum temp mean?

A

temp at which the ROR is the highest

58
Q

why are some enzymes stable at really high temps?

A

-more disulphide bonds
-dont break with heat
-keep the shape of the tertiary structure

59
Q

how to calculate rate of reaction?

A

1/ time taken to reach end point

60
Q

what is the temperature coefficient Q10/

A

measure of how much the R.O.R increases with a 10C rise in temp

61
Q

what is the equation for Q10?

A

R.O.R at (T + 10C) / R.O.R at TC

62
Q
A