4 Which statement best describes the graph shown? Original reaction
Reaction B
Energy -
products
reactants
Reaction progress -
FIG. 2.5.1
a. More energy is released by the original reaction.
b. Less energy is needed to start reaction B.
c. The original reaction is catalyzed.
d. Reaction B occurs at a slower rate.

Graph attached

b. Less energy is needed to start reaction B.

Explanation:

The graph shows two different reactions and the energy required over time

a. More energy is released by the original reaction.  - this is false, more energy is required for the original reaction to proceed

b. Less energy is needed to start reaction B.  - this is true, the peak of the curve is lower showing less energy is required

c. The original reaction is catalyzed.  - this is false, likely reaction B is catalyzed

d. Reaction B occurs at a slower rate.- false, they occur at the same rate.

Answer and Explanation: In enzyme kinetics, one constant describing enzyme activity is Maximal Velocity (Vmax). It indicates how fast an enzyme can catalyze the reaction. It is dependent on substrate concentration.

As the muscle is an organ which needs a great amount of energy, the enzyme glycogen phosphorilase is very active on the organ, compared to the liver, where glicose is stored. So, the Vmax of glycogen phosphorylase expressed in muscle is faster than when expressed in the liver, means the enzyme in muscle has a bigger concentration of substrate and therefore will reach Vmax faster, i.e. will be significantly larger.