In 'competitive inhibition' of enzyme reaction:
|A||Km remains unchanged|
|B||Vmax is decreased|
|D||Vmax remains same and Km is increased|
In inhibition of an enzyme by a competitive inhibitor the Vmax of the reaction remains unchanged because the same reaction velocity that was there in the absence of the competitive inhibitor can be achieved even in the presence of the latter by infinitely increasing the substrate concentration. However, the competitive inhibitor increases the apparent Km for the substrate.