Some questions about coenzymes, the organic cofactors of enzymes


(E-12) FMN and FAD have in common that in both structures we can find:


a)     riboflavin

b)     adenosine

c)      AMP

d)     Ribose

e)     Adenine


(E-13) FMN, FAD, NAD+ and NADP+ are organic cofactors in reactions catalyzed by enzymes:


a)     oxidoreductases

b)     lyases

c)      ligases

d)     isomerases

e)     hydrolases

f)       transferases


(E-14) A compound present in NAD+ and NADP+ but not in FMN and FAD is:


a)     Niacin

b)     Riboflavin

c)      Adenin

d)     Ribose

e)     Phosphate


Q: About the regulation of the enzyme activity


(E-11) Which kind of process is represented in the diagram that appears below, considering that:


          increasing the concentration of the Substrate S the activity of the enzyme increases.


          The compound I is not related to the metabolic pathway in which this enzyme participates


          Vmax is not affected by the compound I


          Km increases as result of the presence of I






a)      allosteric activation


b)      allosteric inhibition


c)      competitive inhibition


d)     homotropic interaction


e)      heterotropic interaction


f)       irreversible inhibition


g)      feed back inhibition


h)      feed back activation


i)        non competitive inhibition


Q: About Michaellis Constant (Km)

Enzyme Question No.10 (E-10)



The measuring of the Km in an isomerase that catalyzes the transformation of different D-carbohydrates in the corresponding L- isomers,  show different values, depending on the carbohydrate that is transformed. Given the following carbohydrates  with the corresponding values of Km, mark the one for which the enzyme show less affinity:


a) D-glucose                    Km =  2000 uM


b) D-galactose                Km =   4500 uM


c) D-mannose                Km =  8000 uM


d) D-Ribose                    Km = 10000 uM


e) D-fructose                   Km =  9000 uM


Q: About Enzyme Regulation

Enzyme Question (E-09)


A Protein Kinase

A Protein Kinase







Protein kinases are enzymes that act on other enzymes by adding phosphates groups. When the enzyme is phosphorylated, it changes its activity (it becomes more or less active, depending on the enzyme). This regulatory mechanism of enzymatic activity is called:


a)     Allosteric Control


b)     Competitive inhibition


c)      Covalent Modification


d)     Isozymes Modification


e)     Zymogen activation


Extended Match Question about Enzymes

Read the following options:


a)     absolute specificity over substrate

b)     cooperativity

c)      enzyme activity Unit

d)     heterotropic interaction

e)     homotropic interaction

f)       relative specificity over substrate

g)     specificity of action



Which of them correspond to the definitions described below?


(E-06 ) The fact that an enzyme only catalyzes one of the possible transformations of a substrate:




(E-07 ) The activity that catalyzes the transformation of 1 micromol/minute of substrate:




(E-08 ) The effect of one ligand on an allosteric enzyme, that produces a modification on the binding of a different ligand:




Basic Questions about Enzymes.



Choose the best answer:



Enzyme Question E-02



Inactive precursors of some enzymes that are activated through hydrolysis reactions are called:


a)     allosteric enzymes

b)     apoenzymes

c)      holloenzymes

d)     prosthetic groups

e)     zymogens




Enzyme Question E-03


L-amino acid dehydrogenase is an enzyme that can catalyze the oxidation of different L-amino acids. It can not catalyze the oxidation of D-amino acids or other L-compounds. Based on these characteristics we can say that this enzyme shows:


a)     absolute specificity over substrate

b)     allosteric regulation

c)      relative specificity over substrate

d)     specificity of action

e)     specific inhibition




Enzyme Question E-04


These enzymes have different structure but the same catalytic function. Frequently they are oligomers made from different polypeptide chains. These enzymes are called:


a)     allosteric enzymes

b)     isozymes

c)      lyases

d)     proenzymes

e)     zymogens





Enzyme Question E-05



The model that explain that the active site is flexible and the catalytic group(s) of the enzyme is (are) brought into proper alignment by the substrate is called


a)     Concerted model

b)     Induced fit model

c)      Lock and key model

d)     Michaellis Menten model

e)     Sequential model