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Increasing the substrate concentration may increase the viscosity of the media, lowers the rate of oxygen diffusivity, and affect the osmolarity of the system. [1] These effects can be detrimental to cell growth, and by extension, the yield of product.
Increasing the substrate concentration would diminish the "competition" for the substrate to properly bind to the active site and allow a reaction to occur. [3] When the substrate is of higher concentration than the concentration of the competitive inhibitor, it is more probable that the substrate will come into contact with the enzyme's active ...
The substrate concentration midway between these two limiting cases is denoted by K M. Thus, K M is the substrate concentration at which the reaction velocity is half of the maximum velocity. [2] The two important properties of enzyme kinetics are how easily the enzyme can be saturated with a substrate, and the maximum rate it can achieve.
Increasing the substrate concentration increases the rate of reaction (enzyme activity). However, enzyme saturation limits reaction rates. An enzyme is saturated when the active sites of all the molecules are occupied most of the time. At the saturation point, the reaction will not speed up, no matter how much additional substrate is added.
[17]: 134–135 However, the apparent K m will increase as it takes a higher concentration of the substrate to reach the K m point, or half the V max. Competitive inhibitors are often similar in structure to the real substrate (see for example the "methotrexate versus folate" figure in the "Drugs" section). [17]: 134
The reaction changes from approximately first-order in substrate concentration at low concentrations to approximately zeroth order at high concentrations. At small values of the substrate concentration this approximates to a first-order dependence of the rate on the substrate concentration:
It can be recognized by two observations: first, it cannot be reversed by increasing the substrate concentration , and second, linear plots show effects on and , seen, for example, in the Lineweaver–Burk plot as parallel rather than intersecting lines. It is sometimes explained by supposing that the inhibitor can bind to the enzyme-substrate ...
However this is a general effect and is seen in non-addition or transfer reactions where it occurs due to an increase in the "effective concentration" of the reagents. This is understood when considering how increases in concentration leads to increases in reaction rate: essentially when the reactants are more concentrated, they collide more ...