Enzymes

Question 1

The function of oxidoreductases is to […] and the three types of oxidoreductases are […]

Answer 1

Oxidoreductases catalyze redox reactions/transfer electrons (hydride ions or H atoms)

1) Dehydrogenases
2) Oxygenases
3) Peroxidases

Question 2

Dehydrogenases are responsible for […] and they are a subsclass of […]

Answer 2

Transferring hydrogens between substrate and coenzyme (e.g., NAD , NADP, FAD, FMN)

They are a subclass of oxireductases.

Question 3

Oxygenases are responsible for […] and they are a subsclass of […]

Answer 3

Using O2 as substrate

They are a subclass of Oxidoreductases.

Question 4

Peroxidases are responsible for […] and they are a subsclass of […]

Answer 4

Using H2O2 or organic peroxide as substrate

They are a subclass of Oxidoreductases.

Question 5

The function of transferases is to […] and the five types of transferases are […]

Answer 5

Transfer a group from one molecule to another

1) kinases
2) phosphorylases
3) peptidyl transferase
4) Glycosyl transferase
5) Transaminase

Question 6

Kinases’ function is to […] and they are a subclass of […]

Answer 6

Tansfer phosphate from ATP to another substrate

Also work in the reverse direction! Can add P to ADP => ATP

They are a subclass of transferases

Question 7

Phosphorylases’ function is to […] and they are a subclass of […]

Answer 7

Transfer inorganic phosphate to another substrate without using ATP

They are a subclass of transferases

Question 8

Peptidyl Transferase’ function is to […] and they are a subclass of […]

Answer 8

Transfer peptide group

They are a subclass of transferases

Question 9

Glycosyl transferase function is to […] and they are a subclass of […]

Answer 9

Transfer MONOsaccharide

They are a subclass of transferases

Question 10

Transaminase function is to […] and they are a subclass of […]

Answer 10

Transfer amino group. (Amine functional group)

They are a subclass of transferases

Question 11

Hydrolases’ function is to […]

Answer 11

Cleave by the addition of water. Most digestive and lysosomal enzymes are hydrolases (lipases, peptidases, nucleases)

Question 12

Lyases’ function is to […] and the three types of lyases are […]

Answer 12

Remove a group nonhydrolytically, forming a double bond.
Lyases don’t break molecule into smaller pieces; traditionally don’t break sigma bonds. forming/breaking double bonds

1) dehydratases
2) decarboxylases
3) synthetases

Question 13

Dehydratases’ function is to […] and they are a subclass of […]

Answer 13

Eliminate water to yield double bond

They are a subclass of lyases

Question 14

Decarboxylases’ function is to […] and they are a subclass of […]

Answer 14

Eliminate CO2

They are a subclass of lyases

Question 15

Synthetases’ function is to […] and they are a subclass of […]

Answer 15

Act in reverse: loss of double bond to create a new bond

They are a subclass of lyases

Question 16

Isomerases’s function is to […]

Answer 16

Interconvert positional, geometric or optical isomers

Question 17

Ligases’ function is to […]

Answer 17

Form a new bond (C-C, C-O, or C-N) via condensation reactions coupled to cleavage of ATP or similar cofactor.

Example: glutamine synthetase

glutamate+ NH3 + ATP –> glutamine + ADP + Pi

Question 18

Co-factors refer to […] and one example is […]

Answer 18

An INORGANIC ion required by enzyme. One example is magnesium

Question 19

Coenzymes refer to […] and one example is […]

Answer 19

Coenzymes are organic or metaloorganic molecules derived from vitamins. They function as transient carriers of specific functional groups.

One example is biotin.

Question 20

Biotin’s function is to [….] and it is [….] soluble

Answer 20

Carry Co2 for carboxylase enzymes. Biotin is water soluble.

Question 21

A prosthetic group is a […] that is […] bound to the enzyme protein

Answer 21

A prosthetic group is a cofactor/coenzyme that is tightly/covalently bound to enzyme protein.

Question 22

Holoenzyme refers to the […]

Answer 22

Complete, catalytically active enzyme together with its prosthetic group

Holo = Whole

Question 23

Apoenzyme refers to the […]

Answer 23

Protein part of the enzyme which does not have the prosthetic group

Question 24

The binding energy (GB) is […] and it is calculated by the […]

Answer 24

The energy derived from the E-S interaction. It is calculated by the difference in energy between the catalyzed and uncatalyzed reaction

Question 25

The E-S interaction releases so much energy because 1) ... and 2)...

Answer 25

1) formation of weak bonds between enzyme and substrate 2) weak interactions are optimized in the reaction transition state=the enzyme's active sites are complementary to the transition states (rather than to the substrate/product)

Question 26

The enzyme's active site in catalyzed reaction is complementary to [...]

Answer 26

Active site is complementary to the transition states through which the substrates pass as they are concerted to products during an enzymatic reaction.

Question 27

Kcat refers to [...]

Answer 27

the number of substrate molecules converted to product in a given unit of time on a single enzyme molecule when the enzyme is saturated with substrate. Kcat is the rate constant of the rate-limiting step of any enzyme-catalyzed reaction. (in michaelis mentel it's the same as K2)

Question 28

High affinity between enzyme and substrate makes the | Km [...]

Answer 28

Lower

Question 29

In lineweaver-burke plot, the larger x-intercept, the [...] Km

Answer 29

The larger x-intercept the larger Km

Question 30

In lineweaver-burke plot, the larger y-intercept, the [...] Vmax

Answer 30

The larger y-intercept, the smaller Vmax

Question 31

In lineweaver-burke plot, the x-intercept is [...]

Answer 31

-1/km

Question 32

In lineweaver-burke plot, the y-intercept is [...]

Answer 32

1/vmax

Question 33

In lineweaver-burke plot, the y-axis is [...] and the units are [...]

Answer 33

Y-axis: 1/v0 and the units are (1/uM/min)

Question 34

In lineweaver-burke plot, x-axis is [...] and the units are [...]

Answer 34

X-axis: 1/[s] and the units are 1/mM

Question 35

In lineweaver-burke plot, the slope is [...] and its two components are [...]

Answer 35

Slope = Km/Vmax and they are both constants for each enzyme

Question 36

Isoenzymes refer to [...] and a famous example is [...]

Answer 36

enzymes that catalyze the same reaction but with different kinetic properties (i.e., different Km, Vmax) The example is glucokinase and hexokinase. Both catalyze the first step in glycolysis.

Question 37

Between glucokinase and hexokinase, which one has higher Km and higher Vmax?

Answer 37

Glucokinase

Question 38

Which tissues does glucokinase work in? and Hexokinase?

Answer 38

Glucokinase: liver and pancreas. Hexokinase: all other cells