Sle212 Biochemistry

Front 1

what kind of catalyses does proteinase catalyse in this reaction?

Back 1

Proteinase, catalyses the hydrolysis of peptide bonds into a carboxyl and an amino group

Front 2

what kind of catalysis does proteinase hydrolyse in this reaction?

Back 2

proteinase hydrolyses an ester bond into an acid and an alcahole

Front 3

which reaction does the enzymes Trypsin and Thrombin cleave?

Back 3

Trypsin reactions with the carboxy peptide bond next to LYs and ARg

Thrombin reacts with the Peptide bond on the carboxy side of Arg in a unique peptide sequence

Front 4

what are the 6 classes of enzymes?

Key: OTHLIL (Old truths have lived innocent love)

Back 4

1) Oxidoreductase
2) Transferases
3) Hydrolases
4) Lyases
5) Isomerases
6) Ligases

Front 5

what kind of enzyme is responsible for this reaction?

Back 5

Oxidoreductases
Catalyse oxidation-reduction reactions
• Eg. Lactate dehydrogenase (EC 1.1.1.27)

Front 6

what kind of enzyme is responsible for this reaction?

Back 6

Transferases
Catalyse group transfer reactions
• May require co-enzymes
• Eg. Alanine transaminase (EC 2.6.1.2)

Front 7

what kind of enzyme is responsible?

Back 7

Hydrolases
• Catalyse hydrolysis
• Eg. Pyrophosphatase (EC 3.6.1.1)

Front 8

what kind of enzyme is responsible?

Back 8

Lysases

Lysis of a substrate, generates a double bond
• Not→ hydrolytic, oxidative
• Reverse direction→ + 1 substrate to double bond of 2nd
substrate
• Synthase- lyase that catalyses an addition reaction
• Eg. Pyruvate decarboxylase (EC 4.1.1.1)

Front 9

what kind of enzyme is responsible?

Back 9

Isomerase
• Catalyse structural change within a molecule
• Eg. Alanine racemase (EC 5.1.1.1)

Front 10

what kind of enzyme is responsible?

Back 10

Ligases

• Catalyse ligation
• Requires energy input (ATP)
• Also called synthethetases
• Eg. Glutamine synthetase (EC 6.3.1.2)

Front 11

what is an EC number?

Back 11

an enzyme class number made of 4 numbers that classify a class of enzyme and its type of reaction that it catalyses

Front 12

what are enzymes?

Back 12

catalysts that effect only the rate (speed) of a reaction

Front 13

how does an enzyme speed up a reaction?

Back 13

by stabilising the transition state by lowering the amount of free energy of activation

Front 14

the free energy of activation is higher during a catalysed or an uncatalysed reaction? why?

Back 14

free energy of activation is higher during a catalysed reaction rather than an uncatalysed reaction,
hence a catalysed reaction uses more free energy to stabilise the transition state

Front 15

how does free energy of activation activate the reaction to go forward on its own?

Back 15

the free energy of activation once added to the system is able to do this because it becomes activated and this free fall of energy forces reaction to move on its own, this it is called free energy

Front 16

in the activation of free energy, the rate of reaction is proportional to what parameter?

Back 16

reaction rate is proportional to concentration of the transitional state

Front 17

what is activation energy?

Back 17

the minimal energy needed to start a reaction

Front 18

what is free enregy

Back 18

the amount of work that a system can perform, it is free energy once it has free fallen past the transition state, after free energy of activation has been added to the system

Front 19

how does the concentration of the transition state effect the rate of reaction

Back 19

the higher the C of transitional state, the faster the reaction goes, hence C is proportional to Pressure

Front 20

9s the free energy of the transitional state regarded as free energy that is released when the transitional state is converted into products?

Back 20

no, it is a separate entity

Front 21

describe classical competitive inhibition, what does it bind and what is the effect on Km and Vmax?

Keyword: race

Back 21

Competitive inhibitor competes with the substrate, it binds to the Enzyme, increasing Km and leaving Vmax unchanged

can be overcome by increasing [S]

Front 22

describe Uncompetitive inhibition, what does it bind and what is the effect on Km and Vmax?

Keyword: different

Back 22

Binds to the ES complex, lowering both Vmax and Km proportionally, the ratio of Vmax/Km (slop) stays the same

it Cannot be overcome by increasing [S]

Front 23

describe Noncompetitive inhibition, what does it bind and what is the effect on Km and Vmax?

Keyword: friends

Back 23

binds to the E or the ES complex, lowering Vmax only and leaving Km unchanged

It cannot be overcome by increasing [S]

Front 24

to which inhibitor type does this belong? how can you tell?

Back 24

Competitive inhibition

since Km is increased, but Vmax is unchanged and only the Enzyme has been bound

Front 25

to which inhibitor type does this belong? how can you tell?

Back 25

Uncompetitive inhibition,

since it lowers both Vmax and Km it binds to the ES complex only, forming ESI complex which results in an unproductive reaction since it is a dud substrate

Front 26

to which inhibitor type does this belong? how can you tell?

Back 26

Noncompetitive inhibition

since it decreases Vmax and leaves Km untouched, the inhibitor binds to the E and ES complex

Front 27

what does allosteric activation do to Km? what does allosteric inhibition do to Km?

Back 27

activator shifts the sigmoidal curve towards hyperbola, lowering the Km and raising the activity of [S]

the inhibitor raises the Km and lower the activity of [S]

Front 28

what forces are involve in a substrate binding to an active site?

Back 28

weak forces:

H bonds, Van der waals, and hydrophobic effect

Front 29

describe the arrangement of amino acids in a primary structure (sequence of aa's) Vs a tertiary arrangement

Back 29

amino acids are far apart in a primary structure but close together in a tertiary structure, where a small portion of amino acids form the substrate binding site, the other aa's form the structural building material of the active site

Front 30

why is the activation energy lower in a catalysed reaction compared to an uncatalysed reaction

Back 30

because the catalyst enzyme stabilizes the Transitional state

Front 31

if given a Lineweaver burk plot, with the value, y=0.174 x + 0.435, what is the Km and the Vmax?

how would you plot this?

Back 31

Vmax = 1/0.435 = 2.30

Km = 0.174 x 2.30 = 0.4

Front 32

what is the site on an enzyme where a reaction occurs?

Back 32

active site

Front 33

what is the substance that the enzyme binds and converts to products?

Back 33

the substrates

Front 34

what are enzymes that dont have the required cofactor bound?

Back 34

apoenzymes

Front 35

the Kcat is referred to as the

Back 35

turnover number

Front 36

what is a frequent action which catalysis occurs?

Back 36

stabilisation of the transition state

Front 37

the steady state assumption as applied to enzyme kinetics, implies

Back 37

the ES complex is formed and broken down at equivalent rates

Front 38

true of false

at saturating levels of substrate, the rate of an enzyme catalyzed reaction is proportional to the enzyme concentration

Back 38

true

Front 39

true or false

if enough substrate is added, the normal Vmax of a reaction can be attained even in the presence of a competitive inhibitor

Back 39

true

Front 40

true or false

the rate of a reaction decreases steadily with time as substrate is depleted

Back 40

true

Front 41

true or false, the activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, bu the equilibrium constant is more favourable in the enzyme catalyzed reaction

Back 41

false

Front 42

true or false
the michaelis menten constant Km equals the [S] at which V= half of Vmax

Back 42

true

Front 43

enzyme accelerates the rate of a chemical reaction by doing what to the free energy of activation of the reaction

Back 43

decreasing it

Front 44

what kind of inhibitor has a structure similar to the substrate and reversibly binds to the active site of the enzyme

Back 44

competitive inhibitor

Front 45

the straigtht line kinetic plot of 1/Vo versus 1/S is called a

Back 45

Lineweaver Burk Plot

Front 46

give definition for initial rate

Back 46

Vo

Front 47

give definition for Vmax

Back 47

maximal rate when all active sites are full

Front 48

give definition for [S]

Back 48

Substrate concentration

Front 49

give definition for Km

Back 49

michealis constant

Front 50

Which of the following statements is FALSE?

Enzymes speed up the attainment of a reaction equilibrium.

Enzymes lower the amount of energy needed for a reaction.

Enzymes make reactions 103 to 1020 times faster.

Enzymes are proteins.
Enzymes are chemically unchanged during the actual catalytic process.

Back 50

Enzymes are chemically unchanged during the actual catalytic process.

Front 51

Unlike typical catalyzed reactions in organic chemistry enzyme catalyzed reactions are

modulated to change activity levels.

reaction specific.

essentially 100% efficient.

usually stereospecific.

All of the above

Back 51

All of the above

Front 52

The hydrophobic cleft in globular proteins which binds substrate molecules is called the ________.

substrate pocket

active site

modulator site

oligomeric site

activity site

Back 52

active site

Front 53

An enzyme that catalyzes conversions of L-sugars to D-sugars is called a/an ________.

hydrolase

lyase

isomerase

synthetase

synthase

Back 53

isomerase

Front 54

In a first order chemical reaction, the velocity of the reaction is proportional to the ________, while in a zero order reaction, the velocity of the reaction is proportional to the ________.

concentration of substrate; amount of enzyme

concentration of substrate; speed of the reaction

amount of enzyme; concentration of substrate

speed of the reaction; concentration of substrate

Back 54

concentration of substrate; amount of enzyme

Front 55

The main difference between chemical and enzyme kinetics is that

enzyme reactions depend on the concentration of the substrate.

the rate constant for the formation of products is k2.

enzyme reactions are altered by pH.

enzyme reactions depend on the concentration of the enzyme and its recycling.

Back 55

enzyme reactions depend on the concentration of the enzyme and its recycling.

Front 56

At the beginning of an enzyme-catalyzed reaction the ________ is negligible.

formation of E + P

disappearance of ES

formation of ES

conversion of ES to E + S

Back 56

formation of E + P

Front 57

The initial velocity of an enzyme reaction (v0) describes

the concentration of both at the start of the reaction.

the concentration of the enzyme at maximal velocity.

the concentration of substrate at maximal velocity.

the rate of the reaction at when the substrate and enzyme are first mixed.

Back 57

the rate of the reaction at when the substrate and enzyme are first mixed.

Front 58

Which enzyme below is fastest?

papain, kcat = 10

kinase, kcat = 10^3

carboxypeptidase, kcat = 10^2

catalase, kcat = 10^7

Back 58

catalase, kcat = 10^7

Front 59

The Michaelis constant, Km, is equal to the ________.

substrate concentration which gives the best enzyme assay for an enzyme reaction

substrate concentration when the rate is equal to half its maximal value

maximum velocity divided by two

maximum velocity that any given enzyme reaction can achieve

Back 59

substrate concentration when the rate is equal to half its maximal value

Front 60

The assumptions made in calculating the Michaelis-Menten Equation include

that the concentration of the substrate is much greater than the concentration of E.

that the value of k-2 can be ignored.

that the formation and decomposition of ES is the same for a period of time.

A, B and C

A and B only

Back 60

A, B and C

Front 61

The (lower, higher) the value of Km, the (less, more) tightly the enzyme is bound to the substrate.

lower, less

lower, more

higher, less

higher, more

B and C

Back 61

B and C

Front 62

It is difficult to determine either Km or Vmax from a graph of velocity vs. substrate concentration because

an asymptotic value must be determined from the graph.

the graph is sigmoidal.

too much substrate is required to determine them.

the points on the graph are often not spread out on the hyperbola.

Back 62

an asymptotic value must be determined from the graph.

Front 63

What distinguishes reversible inhibitors from irreversible inhibitors?

There is an equilibrium between bound and unbound reversible inhibitor. There usually is little back reaction for the binding of an irreversible inhibitor.

Reversible inhibitors are not covalently bound to enzymes but irreversible inhibitors are.


All of the above


None of the above

Back 63

All of the above

Front 64

An inhibitor binds to a site other than the active site of the enzyme. Which statement below correlates with this observation?

The inhibition must be irreversible.

It must be a competitive inhibitor.

It could be noncompetitive or uncompetitive inhibition.

It could be irreversible, competitive, noncompetitive or uncompetitive. The data do not relate to the type of inhibition.

Back 64

It could be noncompetitive or uncompetitive inhibition.

Front 65

Which statement is false about allosteric regulation?

Allosteric modulators bind non-covalently at sites other than the active site and induce conformational changes in the enzyme.

The regulation usually is important to the conservation of energy and materials in cells.

It is usually the mode of regulation for the last step in reaction pathways since this step produces the final product.

Cellular response is faster with allosteric control than by controlling enzyme concentration in the cell.

Back 65

It is usually the mode of regulation for the last step in reaction pathways since this step produces the final product.

Front 66

Allosteric modulators seldom resemble the substrate or product of the enzyme. What does this observation show?

Modulators always act as activators.

The enzyme catalyzes more than one reaction.

Modulators bind non-covalently to the enzyme.

Modulators likely bind at a site other than the active site.

Back 66

Modulators likely bind at a site other than the active site.

Front 67

At sufficiently high substrate concentration all types of reversible inhibition can be overwhelmed. At high substrate concentration the enzyme will be saturated and the reaction will proceed at the same maximum velocity as in the absence of inhibitor.

True

False

Back 67

False

Front 68

out of L-glyceradlahyde and D-Glyceraldehyde, which one occurs in vivo, which isomer is present in nature?

Back 68

the D isomer occurs in nature and D isomer occurs in vivo