May I please also get an explanation for why the answers are true or false. Your
ID: 200508 • Letter: M
Question
May I please also get an explanation for why the answers are true or false. Your help would be greatly appreciated!
Two enzymes Xam1 and Xam2 have Kms of 34mM and 76mM respectively. Which enzyme will have the higher Vmax? T F ? Xaml since it has the lower Km (hence higher affinity and higher Vmax). T F ? Xam2 since it has the higher Km(hence lower affinity and higher Vmax). T F . T F ? we cannot tell. Vmax does not depend on the Km. TaLX ? We cannot tell Vmax depends on activation energy, not KmExplanation / Answer
Ans. Option A, B- Incorrect. # MM equation- Vo = Vmax [S] / (Km + [S])
# Km is defined as the [S] at which half-Vmax is attained. Km is an indirect measure of affinity of the enzyme for the substrate- a lower Km value means higher affinity of the enzyme for the substrate.
Note that, Vmax is the intrinsic property of an enzyme towards specified substrate. If substrate is changed, Vmax is most likely to be changed.
Consider a hypothetical example- If two substrates A and B are catalyzed by the same enzyme t same Vmax, and Km of A < B, then instantaneous reaction velocity Vo for A is greater than that of B. It is the Vo than depends on Km; Vmax remains independent of Km –and vice-versa.
Therefore, simply looking at the Km, Vmax can’t be predicted. However, Vo can be predicted if Km are known and Vmax is kept constant.
Since Xam1 and Xam2 are different enzymes, they would have their own intrinsic Vmax, which can’t be correlated by looking at their respective Km values.
# Option C. Incorrect. Enzymes are biocatalyst. No doubt, Vmax depends on the activation energy, but NOT only on activation energy. Vmax is also characterized by the nature of enzyme, substrate, and physiological conditions like pH, salt concertation, etc.
For example, two different enzyme, say xam1 and xam2 need not have the same Vmax even if they have the same activation energy for catalysis.
# Option D. Correct. As explained above, both Km and Vmax are intrinsic properties of the enzyme. So, looking at the Km of two enzymes, their respective Vmax values can’t be correlated.
Also, as explained above, it is Vo that depends on Km; Vamx remains independent of Km.
So, option D is the most appropriate one.