In competitive inhibition the substrate and inhibitor cannot bind to the enzyme at the same time. This usually results from the inhibitor having an affinity for the active site of an enzyme where the substrate also binds; the substrate and inhibitor compete for access to the enzymes active site. This type of inhibition can be overcome by sufficiently high concentrations of substrate (V remains constant), i.e., by out-competing the inhibitor. However, the apparent K will increase as it takes a higher concentration of the substrate to reach the K point, or half the V'. Competitive inhibitors are often similar in structure to the real substrate (see for example the "methotrexate versus folate" figure in the "Drugs" section).