Hi Abhinav,

Mixed inhibitors are known to bind at any site on the enzyme, besides the active site. They are known to preferentially bind on an enzyme without a substrate or bind on an enzyme-substrate complex. Whichever the inhibitor decides to bind to, the Vmax of the reaction would always decrease. Mixed inhibitors also cause a conformational change on the active site, which is guaranteed to either affect substrate binding.

Noncompetitive inhibitors are mixed inhibitors because they (1) bind to a site other than the active site, (2) bind to an enzyme alone or an E-S complex, and (3) decrease Vmax. However, unlike other mixed inhibitors, noncompetitive inhibitors don't have preferential binding and don't affect the substrate's affinity for enzyme's active site (i.e. still allows substrates to bind with same affinity, hence the unaffected Km). Pretty much, mixed inhibitors and noncompetitive inhibitors greatly subdue the conversion of E-S complex to product.

I feel like knowing that mix inhibition exists is good enough for the MCAT. However, don't stress too much about it. I suggest focusing your attention on competitive, uncompetitive, and noncompetitive inhibition, especially on how their Michaelis-Menten graph vs Lineweaver-Burke Plot would look like.

Hope these help!