9th Class Computer Online Tests

Both break bonds, but Hydrolases strictly require water to perform the cleavage, whereas Lyases do not.

Thermophilic (heat-loving) bacteria have evolved structurally stable enzymes that function optimally at extremely high temperatures, often well above 50 C.

Competitive inhibitors compete directly with the actual substrate for access to the active site.

Since the non-competitive inhibitor changes the actual shape of the active site from the outside, adding more substrate doesn't help because the substrate can no longer physically fit.

Changes in pH alter the concentration of H+ and OH- ions, which changes the ionization state of the R-groups in the active site, disrupting substrate binding.

Because penicillin forms a permanent covalent bond with the bacterial enzyme, destroying its function entirely, it is an irreversible inhibitor.

The optimum temperature is the exact thermal point where molecular collisions are maximized before denaturation begins.

The reaction rate plateaus (levels off) when all available enzyme active sites become saturated with substrate.

Because enzyme function depends entirely on the precise shape of the active site, any alteration prevents the substrate from binding.

Because they are unaltered by the reaction, a single enzyme can catalyze the same reaction thousands or millions of times.

Since glucose and fructose share the same molecular formula (C6H12O6) but have different structures, an enzyme that converts them is an Isomerase.

Enzyme inhibitors are specific molecules that interfere with catalysis by blocking the active site or altering the enzyme's shape.

Since enzymes are proteins, they are synthesized by ribosomes during the process of translation.

Many essential vitamins (especially B-complex vitamins) act as precursors for, or directly function as, coenzymes.

The extreme shift from an acidic to an alkaline environment would alter the ionic charges of pepsin's amino acids, destroying its active site structure.

Digestive enzymes almost universally utilize water to break peptide, glycosidic, and ester bonds, defining them as Hydrolases.

Unlike the stomach, the small intestine is slightly alkaline, so trypsin functions optimally at a pH around 8.0.

Isomerases rearrange the atoms within a single molecule to convert it into a different isomeric form.

Reversible inhibitors bind weakly and can be displaced, while irreversible inhibitors form permanent covalent bonds that destroy the enzyme.

Excessive heat increases kinetic energy so much that the weak bonds holding the protein's 3D structure together break, causing denaturation.

High temperatures break the weak hydrogen and ionic bonds holding the enzyme's 3D structure together, denaturing the active site.

A prosthetic group is a non-protein organic molecule that is tightly and permanently bound (often covalently) to its enzyme.

Cofactors are non-protein by definition. Polypeptides are chains of amino acids (proteins), so they cannot be cofactors.

Cofactors often induce a conformational shape change in the enzyme that is required for the substrate to bind correctly.

Irreversible inhibitors, like nerve gases or heavy metals, form unbreakable covalent bonds with the enzyme, destroying its function forever.

NAD+ is reduced to NADH when it accepts a hydrogen atom (and electrons) during metabolic oxidation reactions.

When the final product of a chain reaction circles back to shut down an earlier enzyme, it is classic feedback inhibition.

Coenzymes frequently act as carriers, shuttling electrons, hydrogen atoms, or specific functional groups between enzymes.

During cellular respiration, NAD+ accepts electrons and hydrogen atoms from the breakdown of glucose, serving as a carrier to the electron transport chain.

Metal ions interact with the enzyme to induce a conformational change, turning an inactive active site into a functional one capable of binding substrate.

Pepsin functions in the highly acidic environment of the stomach, and has adapted an optimum pH of roughly 2.0.

The 3D shape creates strict specificity, ensuring only a complementary substrate molecule can fit and bind correctly.

The active site has a binding site (which holds the substrate) and a catalytic site (which performs the chemical reaction).

Transferases are responsible for moving functional chemical groups between molecules.

The active site is a small cleft or depression consisting of only a few specific amino acids that directly interact with the substrate.

The main distinction is binding affinity: prosthetic groups are permanently and tightly bound, while coenzymes bind loosely and temporarily.

Because the enzyme was in 'large excess,' the reaction stopped because it ran out of the 'fixed amount' of substrate.

Enzymes are not consumed or permanently changed by the reactions they catalyze, allowing a single enzyme molecule to be used repeatedly.

Dialysis removes loosely attached small molecules. Because the activity was lost, the enzyme relies on a loosely bound cofactor, which could be a coenzyme or a metal ion.

The spatial arrangement of these enzymes is crucial for their sequential action. Membrane damage would directly disrupt the Krebs cycle.

Oxidoreductases facilitate oxidation-reduction (redox) reactions by transferring electrons or hydrogen atoms.

Ligases form new chemical bonds to join two molecules together, a process that requires energy input, typically derived from ATP.

Because hematin is an organic molecule that binds tightly via covalent bonds to its enzyme, it fits the definition of a prosthetic group.

High heat disrupts the fragile hydrogen bonds and ionic interactions that hold the secondary and tertiary structures of the protein together.

Hematin is an organic prosthetic group tightly bound to certain enzymes, like cytochromes and hemoglobin.

Digestive enzymes like lipase and amylase break down large macromolecules by adding water, making them Hydrolases.

Because hexokinase transfers a phosphate functional group, it is categorized as a Transferase.

Many pharmaceutical drugs (like statins or penicillin) are designed to target and inhibit the specific active sites of enzymes related to diseases or pathogens.

Non-competitive inhibitors do not bind to the active site; they bind to a secondary location called the allosteric site.

Enzymes are globular proteins, meaning their polypeptide chains are folded into specific, compact 3D structures.

Coenzymes are non-protein organic molecules that bind loosely and temporarily to an enzyme to assist in reaction transfers.

Heavy metals like mercury and silver covalently bond to sulfhydryl groups on the enzyme, irreversibly altering its structure.

Cold temperatures do not permanently destroy enzymes; they simply reduce kinetic energy so much that enzyme-substrate collisions rarely happen.

At maximum velocity (Vmax), the enzymes are working as fast as possible; every active site is occupied, so adding more substrate has no effect.

Since vitamins are key components of coenzymes, a deficiency directly reduces the availability of cofactors, impairing enzyme function.

Enzymes are commonly called biocatalysts because they are biological molecules that catalyze (speed up) reactions.

Non-competitive inhibitors lower the maximum possible reaction rate (Vmax) because they effectively remove functional enzymes from the pool, but they do not change the remaining enzymes' affinity for the substrate.

Because the inhibitor and substrate compete for the same site, flooding the solution with a massive amount of substrate increases its chances of binding over the inhibitor.

Different cell types express different genes, leading to different sets of enzymes that dictate their specific metabolic functions.

Enzymes are globular proteins that act as biological catalysts, specifically speeding up chemical reactions without being consumed.

Synthesizing proteases as inactive zymogens is a cellular regulatory mechanism to prevent auto-digestion.

The suffix '-ase' is added to the root of the substrate. Therefore, proteases break down proteins.

The active site is the specific 3D cleft or pocket on the enzyme where the substrate binds and the reaction takes place.

Hydrolases catalyze hydrolysis reactions, breaking chemical bonds through the consumption of water molecules.

Classification is based on the reaction type. Hexokinase physically transfers a phosphate group from ATP to a glucose molecule.

Lyases cleave bonds (or add groups to double bonds) through mechanisms that do not involve hydrolysis (water) or oxidation.

It prevents the cell from over-producing a substance; once enough final product is made, it acts as an inhibitor to shut down its own synthesis pathway.

Substrates are held in the active site primarily by weak forces such as hydrogen bonds, ionic bonds, and hydrophobic interactions.

Since the metal ion is required to maintain the functional shape of the active site, its removal causes a complete loss of catalytic activity.

Nicotinamide adenine dinucleotide (NAD+) is the most crucial coenzyme involved in cellular redox reactions.

Pepsin digests proteins. If produced in its active form, it would digest and destroy the cellular structures of the cells that synthesized it.

Enzymes drastically lower activation energy, accelerating reactions by a factor of 10^3 to 10^8 (or even higher) compared to uncatalyzed reactions.

A molecule that perfectly mimics the shape and charge of the active site will act as a competitive inhibitor, blocking the actual substrate.

Metal ions help stabilize the enzyme structure or directly participate in catalysis, altering the active site into a functional shape.

Because the toxin binds directly to the active site, it acts as a competitive inhibitor. Adding excessive substrate can outcompete the toxin.

The massive acceleration of a specific chemical reaction by a protein strongly indicates that the protein is an enzyme.

Because there is plenty of substrate available, the reaction rate is directly proportional to the amount of enzyme present.

Ligases (like DNA ligase) are specifically responsible for catalyzing the joining together of two molecules into one larger molecule.

Adding heat increases the kinetic energy of the molecules, causing them to move faster and collide with the active sites more frequently and with more energy.

Just like temperature, every enzyme has an optimum pH where the ionization states of its amino acids are perfectly suited for catalysis.

Most human enzymes have evolved to function best at normal human core body temperature, which is approximately 37 C.

Binding at the allosteric site induces a conformational shift that distorts the active site, preventing the substrate from binding.

Isomerases simply shuffle the existing atoms inside a molecule, changing its 3D structure without adding or removing any atoms.

The standard nomenclature and classification of enzymes rely entirely on the type of chemical reaction they catalyze and the specific substrate involved.

NAD+ acts as a universal electron carrier, harvesting energy-rich electrons from food oxidation for use in ATP synthesis.

To survive in extreme heat, these bacteria have evolved enzymes with stronger internal bonds that prevent denaturation at high optimum temperatures.

Competitive, non-competitive, and irreversible are the primary classifications of inhibition. 'Catalytic' is not a type of inhibition.

Because it mimics the shape and charge of the natural substrate, a competitive inhibitor can physically fit into the active site.

Cofactors provide necessary chemical groups or structural stability that the amino acid residues of the enzyme cannot provide alone.

Cofactors are non-protein helper molecules that are required for the proper functioning of many enzymes.

Because it removes a functional group (CO2) without using water, it is classified as a Lyase.