F.       Enzyme X and Enzyme Y are both involved in monosaccharide metabolism. Enzyme X uses  
          glucose as a substrate while Enzyme Y uses fructose as a substrate.  At pH=7.0, Enzyme X    
          has a Vmax of 10 

μ

M/s while Enzyme Y has a Vmax of 20 

μ

M/s. Both enzymes have a K

M

          of  3.0 mM for their respective substrates.(Questions 31-37) 
 

31._____ 

Which aspects of its reaction will be changed by Enzyme Y? 

 a) 

the activation energy of the reaction and the energy of the product 

 b) 

the rate of the reaction and the energy of the transition state 

 c) 

the equilibrium position of the reaction and the energy of the substrate 

 d) 

the reversibility of the reaction and the energy of the active site 

32._____           When its reaction is carried out at pH = 2.0, the Vmax of Enzyme X is 1.0 

μ

M/s 

because 

a) 

the enzyme is inhibited by its product at low pH. 

b) 

the enzyme is saturated with substrate at low pH. 

c) 

the enzyme is able to stabilize the transition state at low pH. 

d) 

the enzyme is partially denatured as R-groups protonate at low pH. 

 
33._____ 

When the reaction is carried out at pH = 7.0 and the substrate concentration is 
equal to the K

M

 value 

a) 

X will produce more product than Y. 

b) 

Y will produce more product than X. 

c) 

X and Y will produce the same amount of product. 

d) 

X and Y will both work at their Vmax value. 

 
34._____ 

Enzyme Y can also use the monosaccharide galactose as a substrate with a K

M

 of 

8.0 mM. Which will be a characteristic of Y as it binds galactose compared to its 
binding to fructose? 

a) 

Y will form more non-covalent bonds with galactose. 

b) 

Y will form more covalent bonds with galactose. 

c) 

Y will have an active site that is less complementary to galactose. 

d) 

Y will undergo a greater conformational change as it binds galactose. 

 
35._____            Which interaction is likely to occur as Enzyme X carries out its reaction? 
                         

a)       A hydrogen bond could form between a serine R-group in the active site  

                                    and a carbonyl group in the transition state.  

b)

An ionic bond could form between a glutamate R-group in the active site and 
a carboxyl group in the substrate. 

c)

A hydrophobic interaction could form between an asparagine R-group in the 
active site and a methyl group in the substrate. 

d)

A hydrogen bond could form between a valine R-group in the active site and 
a hydroxyl group in the transition state.