All upstream products, prior to the action of enzyme C, will start to increase in concentration because each enzyme is reversible. Directly, product 3 will build up and product 4 will decrease. This will lead product 5 to decrease because there is no 4 to make it. As 3 builds up, enzyme B will start working in reverse, converting it back into product 2, according to Le Chatelier's principle. Then, when 2 starts to build up, it will also be converted backwards into product 1.

Reversible binding in the active site is typical of a competitive inhibitor. Other kinds of inhibitors bind to the active site after the normal substrate has already bound, such as in uncompetitive inhibition. Alternatively, allosteric inhibitors can bind to sites other than the active site and induce a shape change that diminishes affinity for the typical substrate.

Only competitive inhibition can be overcome by the addition of more substrate. Competitive inhibitors work by binding to and blocking the enzyme's active site. If more substrate is added, it increases the chance that an enzyme molecule will bind to the substrate instead of the inhibitor. Noncompetitive inhibition is not affected by the amount of substrate, uncompetitive inhibition is not tested on the MCAT, and "substrate-sensitive" is not a type of inhibition.

Noncompetitive inhibitors do not bind at the active site of an enzyme. Instead, they bind at another position on the enzyme and alter its conformation. This passive approach to inhibition makes an enzyme unable to attach to the substrate at the active site. Only irreversible inhibitors bond covalently; both competitive and noncompetitive inhibitors bind noncovalently.

Whenever you read that an enzyme inhibitor has covalently bonded to an enzyme, you can conclude that it is an irreversible inhibitor. Both competitive and noncompetitive inhibitors bind noncovalently to the target enzyme.

Negative feedback provides the body with a method for shutting down a reaction once sufficient product has been created. Parathyroid hormone (PTH) is responsible for increasing blood calcium levels, but once the level is sufficient, the parathyroid glands detect the sufficient calcium level and no longer produce PTH. PTH works in coordination with calcitonin to maintain this balance via its negative feedback loop.

Positive feedback, in contrast, involves the exponential increase of a reaction upon detection. Very few examples of positive feedback exist in the body, though oxytocin follows this model during childbirth.

Competitive inhibitors block substrates by binding noncovalently to the active site on enzymes. This prevents the substrate from entering the active site.

Noncompetitive inhibitors, in contrast, will act on regions outside of the active site to prevent binding. Uncompetitive inhibition is a specialized form of noncomptitive inhibition in which the inhibitor binds to the enzyme complex after the substrate has entered the active site. Irreversible inhibitors form covalent bonds, and fall outside the common inhibitor classifications.

Noncompetitive inhibitors of enzymes function by binding to a site other than the active site on the enzyme, known as an allosteric site. This causes the enzyme to go through a conformational shift and inhibits binding of the substrate.

Competitive inhibitors bind to the enzyme active site to prevent substrate action. Uncompetitive inhibitors are a sub-category of noncompetitive inhibitors, and bind to an allosteric site only after the substrate has entered the active site, thus preventing the substrate from leaving.

Competitive inhibitors bind to the active site of the enzyme, blocking substrate entry. Increasing the concentration of the substrate helps overcome this type of inhibition by increasing the proportion of substrate to inhibitor in solution. By increasing substrate, the active site is more likely to bind substrate than inhibitor.

Noncompetitive inhibitors and uncompetitive inhibitors are types of allosteric inhibitors, meaning that they bind the enzyme in a site other than the active site. Increasing substrate concentration cannot overcome these types of inhibition because the inhibitor and enzyme are not in direct competition for binding sites.

Enzymes are catalysts that speed up the rate at which a reaction occurs. Competitive inhibitors bind to the active site, affecting the Michaelis constant, but not the maximum reaction rate. Competitive inhibitors can be overcome by adding more substrate to displace the inhibitor. Non-competitive inhibitors bind to an allosteric site, affecting the maximum reaction rate, but not the Michaelis constant. No amount of additional substrate can overcome the inhibitor's effect.

In uncompetitive inhibition, the inhibitor binds to the enzyme-substrate complex. The substrate is required to bind the active site, affecting the Michaelis constant, and is then held in place by the inhibitor, affecting the maximum reaction rate. Uncompetitive inhibitors are, thus, as special class of inhibitor that will affect both values.