STPM Biology - chapter 3: Revision essay question 10

Explain the effects of competitive and non-competitive inhibition on Competitive inhibition and Non-competitive inhibition.

Answer:

Competitive inhibition

The competitive inhibition increases the K_m without affecting V_max.

Competitive inhibitor and substrate compete for the same active site of the enzyme. A higher substrate concentration is needed to overcome the competitive competition to achieve the same velocity reached in the absence of the competitor. Can be reached if there is sufficient substrate. One half would require a higher substrate concentration, thus K_m is larger.

Non-competitive inhibition

The non-competitive inhibition decreases V_max without affecting K_m.

Non-competitive inhibition cannot be overcome by increasing the substrate concentration. Thus the V_max decreases. The non-competitive inhibitor and substrate bind to different different sites on the enzyme. The enzyme therefore shows the same K_m in the presence or absence of the non-competitive inhibitor. 

Assignment submitted by S.M., Kang, E.S., Ong, T.W., Tan, K.Y., Ho. X.H., Wong 2011/2012 (IBM)