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biochem sem 1 > week 6 > Flashcards

week 6 Flashcards

1
Q

what are enzymes

A

enzymes are catalysts which means that they increase reaction rates without being used up

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2
Q

most enzymes are globular proteins - true or false

A

true

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3
Q

is it only enzymes that can catalyze reactions?

A

no, some RNA can also catalyze reactions

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4
Q

why do we prefer biocatalysis over inorganic catalysts?

A

because biocatalysis has greater reaction specificity and it avoids side products.

it has milder reaction conditions, in cells the conditions can be around 37 degree, pH 7.

Biocatalysis is a process where enzymes (proteins that speed up chemical reactions) are used as catalysts to make chemical reactions happen faster. Compared to inorganic catalysts (non-living materials), biocatalysts are more specific in the reactions they catalyze, meaning they only react with certain molecules and not others. Biocatalysis also avoids creating unwanted side products. Additionally, the conditions in which biocatalysts work are often mild, similar to the conditions found in cells (around 37 degrees Celsius and pH 7), making them more suitable for biological applications.

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5
Q

what can decide the enzymes structure and the active site?

A

specific amino acid sequences ensure structure of whole enzyme as well as the active site

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6
Q

what kind of a binding is the “weak interactions” that bind the substrate to the enzyme?

A

it is hydrogen binding

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7
Q

what is the names of the two substrates that can fit the active site?

A
  1. key in lock principle: where the substrate will fit the active site of the enzyme exactly.
  2. induced fit -when the substrate binds to the enzyme’s active site, the enzyme can adjust its shape slightly to better accommodate the substrate. This can enhance the enzyme’s ability to catalyze the reaction and increase its efficiency.
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8
Q

enzymes do affect the equlibrium, true or false?

A

the enzyme do not affect the equilibrium because the enzyme cannot affect the free energy of the reaction

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9
Q

the enzyme that is added to a reaction will change the substrates energy and the products energy, true or false

A

FALSE

the enzyme will not change the substrates energy or the products energy. it will only decrease the amount of energy needed to achieve the transition state.

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10
Q

for enzymes additional molecules are required to function, true or false?

A

TRUE

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11
Q

what are the molecule called for when they are needed for an enzyme to function?

A

cofactors

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12
Q

cofactors can be inorganic ions such as

A

Fe2+, Zn2+, Mg2+, Mn2+

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13
Q

cofactors are complex organic molecules, true or false

A

FALSE

Cofactors are inorganic ions

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14
Q

coenzymes are inorganic ions, true or false

A

FALSE

coenzymes are complex organic molecules

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15
Q

If cofactor is tightly bound to the enzyme is called _____

A

prosthetic group

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16
Q

prosthetic groups are cofactors that is loosely bound to the enzyme, true or false

A

FALSE

the cofactors are bound tightly to the enzyme and not loosely.

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17
Q

prosthetic groups are cofactors that are loosely bound to the enzyme, true or false?

A

FALSE

the cofactors are bound tightly to the enzyme and not loosely.

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18
Q

complete functional enzyme with its cofactor is called

A

Holoenzyme

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19
Q

Apoenzyme + cofactor = ?

A

holoenzyme

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20
Q

? + cofactor = holoenzyme

A

apoenzyme

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21
Q

apoenzyme + ? = holoenzyme

A

cofactor

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22
Q

what determines the enzyme specificity?

A

the enzyme specificity depends on the buildup of active site. the enzyme can catalyze reactions with one or several substrate.

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23
Q

when the enzyme can only bind one substrate it is called

A

absolute substrate specificity

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24
Q

when an enzyme can catalyze several substrates it is called as

A

relative substrate specificity

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25
Q

what does EC stands for?

A

Enzyme commission

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26
Q

what is the suffix of enzyme?

A

ase

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27
Q

how many enzyme classes are there?

A

7 classes

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28
Q

name all the enzyme classes

A

oxidoreductases
transferases
hydrolases
lyases
isomerases
ligases
translocases

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29
Q

describe oxidoreductases

A

to catalyse oxidation/reduction reactions, transfer of O and H atoms or electrons from one substance to another.

recognition: NAD –> NADH
FAD –> FADH

Oxidoreductases uses riboflavin - vitamin B2 and Niacin - vitamin B3 as cofactors.

examples: dehydrogenase, oxidase, reductase, oxygenase

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30
Q

describe transferases

A

transfer of a functional group from one substance to another.

recognition –> exchange of functional group

transferase use pyridoxine - vitamin B6 as cofactors.

the group may be methyl-, acyl, amino or phosphate group.

example: kinase, phosphorylase, aminotransferase

31
Q

describe hydrolases

A

formation of 2 product from one substrate by hydrolysis + addition of H20

recognition water is used. break bonds + add water.

example:
endo/exo nuclease
endo/exo peptidase
glycosylase
lipase
phosphatase
esterase
phosphodiesterase
phosphodipase
protease

32
Q

describe lyases

A

non-hydrolytic (without water)
addition or removal of groups from substrates
c-c
c-n
c-s
c-0 bonds may be cleaved

example: synthase, decarboxylase, aldolase

33
Q

describe isomerase

A

intramolecular rearrangement = changes within a single molecule
recognition –> same sumformula but different structure
ex: mutase, epimerase, racemases

34
Q

describe ligases

A

ligases will join together two molecules by synthesis of new C-O, C-S, C-N or C-C bonds with simultaneous breakdown of ATP.

35
Q

describe translocases

A
36
Q

proteins are broken down into small peptides by…

A

proteases

37
Q

a example of protease is…. that cuts peptides

A

chymotrypsin

38
Q

name the factors that can influence the enzyme activity

A

non-specific enzyme activity regulation

specific enzyme activity regulation

reversible enzyme acitivity regulation

irreversible enzyme activity regulation

39
Q

amount of enzymes in the cell annotate change, true or false

A

FALSE

the amount of enzymes can change

40
Q

all the enzymes in our body is active and expressed at the same time, true or false?

A

FALSE

not all enzymes are active and expressed at the same time

41
Q

what is the reason why not all enzymes are active at the same time?

A

it is because the activity of an enzyme is determined by the protein nature. we have the so called non-specific and specific regulation of enzymes.

42
Q

non-specific regulation of enzymes affect specific enzymes, true or false?

A

FALSE

non-specific regulation of enzymes affect all enzymes.

43
Q

specific regulation of enzymes affect all enzymes, true or false

A

FALSE

specific regulation of enzymes affect specific enzymes

44
Q

name some non-specific activity regulations

A

-the amount of substrate can affect the enzymes activity. more substrate will lead to decrease of enzymatic activit.

temperature

strong acids or base

radiation

pH

45
Q

more substrate will lead to more enzymatic activity because the enzyme will have enough substrate, true or false?

A

FALSE

increasing the amount of substrates will not lead to increase of enzymatic activity or the speed of the reaction.

46
Q

by increasing the temperature it will lead to…

A

denaturation

47
Q

the pH is around 7 in the cells but in some organelles the pH is lower. What is the name of this organelle.

A

Lysosome. The pH will be acidic.

48
Q

which system will have the highest variety of pH

A

digestive system will have the highest variety of pH.

49
Q

name some specific activity regulation of enzymes

A

proteolytic cleavage
covalent modification
competitive inhibition

50
Q

specific activity regulation of enzymes can only result in activation, true or false?

A

FALSE - specific activity regulation leads to enzymes either being activated or inhibited.

51
Q

enzymes secreted in an inactive form is called

A

zymogen or proenzyme

52
Q

zymogen is the active form of enzymes, true or false

A

FALSE

it is enzymes in inactive form

53
Q

zymogen is activated by adding an additional part of the enzyme, true or false?

A

FALSE

zymogen is activated by removing a part on the enzyme.

54
Q

the removal of a part of the zymogen is done by

A

proteolytic cleavage

55
Q

proteolytic cleavage of zymogen will lead to an active form, true or false?

A

TRUE

56
Q

the activation of zymogen by proteolytic cleavage is irreversible, true or false?

A

TRUE

57
Q

what is meant by the following “the activation of zymogen by proteolytic cleavage is irreversible”?

A

The statement “the activation of zymogen by proteolytic cleavage is irreversible” means that once the zymogen has been activated through proteolytic cleavage, it cannot go back to its inactive form. The enzyme is permanently activated and will continue to function until it is broken down or degraded by other processes.

58
Q

covalent modification is done by other enzyme, true or false?

A

TRUE

59
Q

competitive inhibtion competes with the substrate for active site, true or false?

A

TRUE

60
Q

what will determine if competitive inhibition is irreversible?

A

if the bond that are formed is covalent bond then it is irreversible competitive inhibitor. It is a strong bond.

61
Q

what will determine if competitive inhibition is reversible?

A

if the bond that are formed is not strong bonds and the inhibitor is capable of diffusing out of the active site then it is reversible competitive inhibitor.

62
Q

the rate of enzymatic reactions is affected by?

A
  • enzyme
  • substrate
  • effectors
  • temperature
  • no-specific regulator
63
Q

what is Vmax?

A

Vmax is the maximal velocity of enzyme. Usually it is expressed in moles/minute/mg of protein

64
Q

How is 1U defined?

A

1U (molecules/min) is defined as the amount of the enzymes that catalyze the conversion of one micromole of substrate per minute.

65
Q

What does Kcat mean?

A

Kcat is turnover number, expressed as number of substrate molecules turned into product per enzyme site per minute.

66
Q

what does Km mean?

A

Km is substrate concentration at which enzyme achieves half of maximal speed.

Km is used to describe enzymes affinity to substrate.

67
Q

what does Km mean?

A

What is Km?

Km is a measure of how well an enzyme can bind to its substrate. It represents the concentration of substrate at which the enzyme works at half of its maximum speed.

68
Q

what does a high Km mean?

A

High Km means that a lot of substrate must be present to saturate the enzyme, meaning the enzyme has low affinity (love) for the substrate.

69
Q

what does low Km mean?

A

a low Km mean only a small amount of substrate is needed to saturate the enzyme, indicating a high affinity (love) for substrate.

70
Q

do uncompetitive inhibitor affect the catalytic function of an enzyme?

A

yes uncompetitive inhibitor will inhibit catalytic function

71
Q

do uncompetitive inhibition affect substrate binding?

A

no uncompetitive inhibition do not affect substrate bidning. because the substrate and the inhibitor has different sites to bind to in the enzyme.

72
Q

do competitive inhibition change the Vmax?

A

no competitive inhibition do not change the Vmax

73
Q

do competitive inhibition affect catalysis of the enzyme?

A

no competitive inhibtion does not affect the catalysis of the enzyme

biochem sem 1 (8 decks)

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