This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
In competitive inhibition the relation Km and Vmax is one of the following 
Select and explain. 
A. Km and Vmax are the same, B. km increases and Vmax are the same, C. Km decreases and Vmax increases, D. Km and Vmax decreases
B: km increases and Vmax are the same
Answer: B: km increases and Vmax are the same 
Explanation: Most reversible inhibitors follow the classic Michaelis-Menten scheme, where an enzyme (E) binds to its substrate(S) to form an enzyme-substrate complex (ES). km is the Michaelis constant that corresponds to the concentration of the substrate when the velocity is half the maximum. Vmax is the maximum velocity of the enzyme. Competitive inhibitors can only bind to E and not to ES. They increase Km by interfering with the binding of the substrate, but they do not affect Vmax because the inhibitor does not change the catalysis in ES because it cannot bind to ES.