Enzymes

Question 1

a prosthetic group can never be composed of

Answer 1

amino acids

Question 2

what are co-enzymes often derived from

Answer 2

vitamins

Question 3

what is the difference between coenzymes and prosthetic groups

Answer 3

coenzymes are helper/partner molecules that bind loosely to the enzyme while prosthetic groups bind tightly to an enzyme

Question 4

what enzyme was first isolated and what is it now known as

Answer 4

diastase now known as amylase

Question 5

what name was first given to enzymes

Answer 5

ferments

Question 6

how are proteolytic enzymes named and give an example

Answer 6

end with “in” for example trypsin

Question 7

give an example of an enzyme that indicate the nature of the reaction without specifying the substrates

Answer 7

trans-carboxylase

Question 8

what are the six primary classes of enzymes

Answer 8

oxidoreductases (EC1), transferases (EC2), hydrolases (EC3), lyases (EC4), isomerases (EC5), and ligases (EC6)

Question 9

what new class of enzymes was added in 2018

Answer 9

translocases (EC7)

Question 10

what is are the second digits of oxidoreductases

Answer 10

Second digit Hydrogen or electron donor
1 Alcohol ( >CHOH )
2 Aldehyde or ketone ( >C=O )
3 -CH = CH-
4 Primary amine ( -CHNH2 or -CHNH3 )
5 Secondary amine ( >CHNH- )
6 NADH or NADPH

Question 11

what are the third digits of oxidoreductases

Answer 11

Third digit Hydrogen or electron acceptor
1 NAD+ or NADP+
2 Fe+³ ( e.g. cytochromes )
3 O2
99 An otherwise unclassified
acceptor

Question 12

what are the second digits of transferases

Answer 12

Second digit Group transferred

 1                          1-carbon group
 2                          aldehyde or ketone group ( >C=O )
 3                          acyl group    (  –C–R )
                                                        ||
                                                       O
 4                          glycosyl ( carbohydrate ) group
 7                          phosphate  group

Question 13

what are the third didgits of transferases

Answer 13

E.C. 2.1.1 : Enyzmes are methyltransferases (transfer –CH 3 )
E.C. 2.1.2 : Enyzmes are hydroxymethyltransferases
(transfer –CH 2OH )
E.C. 2.1.3 : Enyzmes are carboxyl- or carbamoyl-transferases

E.C. 2.4.1 : Enyzmes are hexosyltransferases (transfer hexose units)
E.C. 2.4.2 : Enyzmes are pentosyltransferases (transfer pentose units)

Question 14

what is the exception of the third digit of tranferases

Answer 14

where there is transfer of phosphate groups: these cannot be described further, so there is opportunity to indicate the acceptor

Question 15

give the digits of phosphate group transferases

Answer 15

E.C. 2.7.1 : Enzymes are phosphotransferases with an
alcohol group as acceptor
E.C. 2.7.2 : Enzymes are phosphotransferases with a
carboxyl group as acceptor
E.C. 2.7.3 : Enzymes are phosphotransferases with a
nitrogenous group as acceptor

Question 16

what is the second digits of hydrolases

Answer 16

Second digit Bond hydrolysed

 1                  ester
 2                  glycosidic ( linking carbohydrate
                     units )
 4                  peptide  
 5                  C – N bonds other than peptides

Question 17

describe the third digits of hydrolases

Answer 17

E.C. 3.1.1 enzymes are carboxylic ester hydrolases
E.C. 3.1.2 enzymes are thiol ester hydrolases
E.C. 3.1.3 enzymes are phosphoric monoester
hydrolases
E.C. 3.1.4 enzymes are phosphoric diester hydrolases

Question 18

what are the second digits of lyases

Answer 18

Second digit Bond broken

 1                          C – C
 2                          C – O
 3                          C – N
 4                          C – S

Question 19

what are the third digits of lyases

Answer 19

Third digit Group removed

  1                       Carboxyl group ( CO2 )

  2                       Aldehyde group  ( –CH=O )

  3                       Ketoacid group ( –C.CO2 )
                                                         | |
                                                         O

Question 20

what is the second digit of isomerases

Answer 20

Second digit Type of reaction

1                                Racemization or epimerization

2                                Cis-trans izomerization

3                                Intramolecular oxidoreductases

4                                Intramolecular transfer reactions

Question 21

what are the third digits of isomerases

Answer 21

Third digit Substrate

1                     Amino acids

2                     Hydroxy acids

3                     Carbohydrates

Question 22

what are the second digits of ligases

Answer 22

Second digit Bond synthesized

1                              C — O
2                              C — S
3                              C — N
4                              C — C

Question 23

what are the third digits of ligases

Answer 23

The third digit further describes the bond being formed. Thus,
O
||
E.C. 6.3.1 enzymes are acid-ammonia ligases ( amide, —C —NH2 synthetases)
O
||
E.C. 6.3.2 enzymes are acid-amino ligases ( peptide, —C —N —, synthetases )

Question 24

what are the main classes of specificity of an enzyme

Answer 24

1. absolute specificity
2. group specificity (common functional group)
3. Linkage specificity (particular type of chemical bond)
4. stereospecificity (between D and L stereoisomers)

Question 25

true or false, catalysts effect equilibria

Answer 25

false

Question 26

what is the rate-limiting step

Answer 26

step in the overall reaction with the highest activation energy (highest-energy point in the diagram for interconversion of S and P)

Question 27

what equation is used to relate Keq and G

Answer 27

ΔG’° = -RT ln K’eq

Question 28

What is one I.U. defined as

Answer 28

as the amount of enzyme that can convert 1 micromole (μmol) of substrate into product per min at 25 ̊C

Question 29

what is specific activity

Answer 29

number of International Units of enzyme per milligram (mg) of protein. This term indicates the purity of the enzyme preparation

Question 30

what is the turnover number

Answer 30

amount of enzyme activity (in International Units) per mole of enzyme. tells how many substrate molecules are converted into products by each enzyme molecule

Question 31

at what temperature does enzymatic rates rise significantly

Answer 31

10 ̊C

Question 32

what is the pH rate for

a) pepsin
c) trypsin

Answer 32

a) 1-2

b) 7-8

Question 33

how does pH affect enzyme activity

Answer 33

Substrates can possess acidic or basic functional groups that also are affected by the pH solution. significantly influences the tertiary structure of the enzyme molecule and, thus, the activity of the enzyme

Question 34

where is glucose-6-phosphate found, and what is its optimum pH

Answer 34

in hepatocytes with optimum of 7.8

Question 35

what is Km

Answer 35

The substrate concentration that produces a velocity of 1/2 Vmax i.e. the Michaelis-Menten constant

Question 36

what happens to the Michaelis-Menten equation when the substrate concentration is very high

Answer 36

Michaelis-Menten equation reduces v ~ Vmax

Question 37

what cant increase the velocity of the reaction

Answer 37

increasing the substrate concentration

Question 38

what dies Km indicate

Answer 38

indicates the affinity of the substrate for the enzyme active site
small Km= strong affinity

Question 39

what happens when a phosphoryl group is added to Ser, Thr or Tyr residue

Answer 39

introduces a bulky, charged group into a region that was only moderately polar