Enzyme Quiz

Noncompetitive Inhibition

A noncompetitive inhibitor reacts with an enzyme but not at the active site. This binding to the enzyme not at the active site causes changes in shapes of the enzyme with changes shape of its active site so that substrates can no longer bind to it and react. Reversible. An example of a non-competitive inhibitor is ATP. When ATP accumulates it binds to a site other than the active site on the enzyme phosphofructokinase. In doing so it changes the enzyme conformation and lowers the rate of reaction so that less ATP is produced.

Competitive Inhibition

Compound that resembles a substrate and competes for the same active site. This is an inhibitor, It binds to the active site and sticks and prevents any substrate molecule from reacting with an enzyme. This is reversible. for example, Malonate is structurally similar to the substrate succinate. Succinate is found in the Krebs cycle of aerobic respiration and binds to the active site of the dehydrogenase enzyme. Malonate can compete with succinate for the active site and in doing so it can prevent succinate from binding.

Enzyme Denaturation

Enzyme denaturation is when something causes the enzyme to change shape, thus changing shape of the active site and not allowing any substrate molecules to fit in the site and bind. Denaturation makes it so reactions don't occur between the substrate and the enzyme. Denaturation can occur through extreme temperatures, extreme pH levels and salinity.

Effects of Substrate Concentration

Increasing substrate concentration increases the rate of reaction. This is because more substrate molecules will collide with enzymes molecules and thus, more product will be formed. Decreasing substrate concentration will have opposite affect. But at some point of increasing substrate concentration, the rate of reaction will stop increasing and stay the same because there aren't enough enzymes to bind to a produce product.

Induced Fit

Induced Fit is when an enzyme's active site changes slightly just before or just after a substrate binds with it in order for the substrate to fit better. This slight change in shape is due to the charges between the enzyme and the substrate and also any reactions that may bring them together.

Enzyme

Proteins that serve as catalysts, which are chemical agents that change the rate of reaction without being consumed by the reaction.

Effects of pH

The usual optimal pH at which an enzyme is most active is between 6 and 8. Changes in this can alter shape of the enzyme and its active site, or change the charge properties so that substrates won't be able to bind to the active site.

Effects of Temperature

The velocity of an enzymatic reaction increases with increasing temperature. But the thermal agitation of the enzyme molecule disrupts hydrogen bonds, ionic bonds, and other interactions that stabilize the active conformation, and the enzyme denatures.

Metabolic Pathways

These pathways are made up of chemical reactions that are catalyzed by enzymes. The product of the last reaction in the pathway inhibits the enzyme that catalyses the first reaction of the pathway. The product of the last reaction of the pathway binds to a site that's not the active site of the first enzyme. This site is the allosteric site. When the inhibitor leaves, substrate will be ables to bind. Using end product inhibition is beneficial because when there's an excess of end product, the whole pathway gets shut down. But inhibiting the 1st enzyme, less end product will be formed. When the levels of end product decrease, the enzymes work again and the pathway is switched on.

Active Site

Typically, a pocket or groove on the surface of an enzyme. It is formed by a few of the enzyme's amino acids, and the rest of the enzyme providing a famework that reinforces the configuration of the active site. This groove is where the substrate will attach to in order to produce a reaction.