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
Which one of the following statements about Km value is true? 
Select and explain. 
A. Km is substrate concentration at maximal velocity, B. Numerical value of km is propoional to affinity of enzyme for substrate, C. Km is independent of enzyme concentration, D. Km denotes that 100% of enzyme molecules are bound with substrat molecules at that concentration
C: Km is independent of enzyme concentration
Answer: C: Km is independent of enzyme concentration 
Explanation: Substrate Concentration, A small Km indicates that the enzyme requires only a small amount of substrate to become saturated. Hence, the maximum velocity is reached at relatively low substrate concentrations. A large Km indicates the need for high substrate concentrations to achieve maximum reaction velocity.