Practice Quiz: Which Molecules Include Enzymes

Enzymes are predominantly proteins that catalyze biochemical reactions. Although other biological molecules perform various functions, enzymes are almost exclusively proteins responsible for speeding up reactions.

Enzymes function as catalysts that lower activation energy, thereby accelerating reaction rates. They are not involved in storing genetic material or slowing down reactions.

Enzymes lower the activation energy by stabilizing the transition state, which makes it easier for the reaction to occur. This temporary stabilization is key to increasing the rate of biochemical reactions.

Enzymes are distributed all over the cell, functioning in the cytoplasm, within organelles, and even in the nucleus. This widespread distribution allows them to participate in a variety of metabolic processes.

High specificity means that each enzyme is designed to catalyze a particular reaction with a specific substrate. This characteristic ensures proper regulation of metabolic pathways in the cell.

Catalysts work by lowering the activation energy without undergoing permanent changes themselves. This allows them to be reused in subsequent reactions.

Oxidoreductases are responsible for catalyzing redox reactions involving electron or hydrogen transfer. These reactions are pivotal in cellular energy production and metabolism.

Transferases catalyze the movement of functional groups (such as methyl or phosphate groups) between substrates. This transfer is essential for many biochemical reactions, especially in metabolism.

Extreme temperatures can disrupt the delicate three-dimensional structure of enzymes, leading to denaturation. Once denatured, enzymes lose their ability to bind substrates and catalyze reactions.

Competitive inhibitors resemble the substrate and bind to the active site, thereby blocking the substrate from binding. This competition decreases the reaction rate until the inhibitor is displaced.

The active site is the specific region of the enzyme where substrate molecules bind and undergo a chemical reaction. Its exact shape and chemical environment are crucial for the enzyme's specificity and efficiency.

Substrate concentration is a key factor that affects reaction rates; as the concentration increases, more substrate molecules are available to bind the enzyme, thereby accelerating the reaction until saturation is reached. This relationship is fundamental in enzyme kinetics.

The specificity of enzymes ensures that only targeted substrates participate in particular reactions, minimizing the risk of unwanted side reactions. This precision is essential for maintaining the integrity and balance of metabolic pathways.

Allosteric inhibitors bind to sites other than the active site, causing a conformational change that reduces enzyme activity. This is in contrast to competitive inhibitors, which compete directly with the substrate at the active site.

A significant drop in pH can alter the ionization of amino acids within the enzyme, potentially causing the enzyme to denature. Denaturation disrupts the active site and can substantially reduce the enzyme's catalytic effectiveness.

Km represents the substrate concentration at which the reaction rate is half of Vmax, and a lower Km reflects a higher affinity for the substrate. This parameter is fundamental in determining enzyme efficiency.

Non-competitive inhibitors bind to an allosteric site, which alters the enzyme's overall activity by decreasing the total number of functional enzyme sites. This results in a lower Vmax while Km remains unchanged because substrate affinity at the remaining active sites is not affected.

Feedback inhibition is a regulatory mechanism whereby the final product of a metabolic pathway inhibits an enzyme involved earlier in the pathway. This process prevents excessive accumulation of end products, thereby maintaining metabolic balance.

Many enzymes require non-protein molecules called cofactors to be fully active. Vitamin-derived cofactors such as NAD+ or FAD assist in electron transfer and other critical aspects of catalysis.

ACE inhibitors are a class of drugs that lower blood pressure by blocking the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. This therapeutic inhibition leads to vasodilation and decreased blood pressure.