Enzymes

Quiz Content

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. Most enzymes function within a narrow range of pH. Many have a closely defined optimum pH. Enzymes which function in the stomach usually have lower pH optima than those which are found in the intestine. Enzymes could be expected to be sensitive to minor pH changes because:

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. Some very powerful digestive enzymes are produced as inactive zymogens in the pancreas and transported to the intestines, where they are activated by removal of a protein "keeper." These enzymes then act during digestion, and also act on other zymogens, activating them. Occasionally, an infection or injury to the pancreas causes these enzymes to become chemically activated within the pancreas. Under these conditions:

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. Most growing cells require folic acid. Bacteria synthesize their folic acid from a number of materials, including para-aminobenzoic acid. We slow bacterial growth by treating infections in humans with sulfa drugs. (The sulfa drugs are very similar to para-aminobenzoic acid and act as competitive inhibitors, keeping the bacteria from synthesizing folic acid.) If the sulfa drugs kill bacteria, why don't they harm the human, too?

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. Enzymes have a distinct advantage over non-biological catalysts because they:

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. In a Lineweaver-Burk plot of enzyme activity, the highest values of [S] and Km are found:

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. Most synthetic reactions in which carbon dioxide is used require the vitamin biotin. The biotin becomes covalently bound to a lysine molecule which is part of an enzyme, and the biotin can then attach to and carry the carbon dioxide molecule. Biotin is best referred to as a/an:

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. The fact that allosteric enzymes are remarkably sensitive to control makes them ideal candidates for:

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. If you wanted to explain the concept of Km to someone who didn't know as much about biochemistry as you, you might say that:

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. Methanol is a very poisonous substance, accounting for a number of deaths and many cases of blindness yearly. While the methanol itself is sometimes not toxic, it may be metabolized by the liver to more toxic molecules such as formic acid or formaldehyde. Before more efficacious treatments were developed, a person who had ingested methanol was often given a large amount of ethanol orally. The purpose of this treatment was:

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. Most coenzymes may be included in classes of foodstuffs known as:

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. The major effect of a catalyst on a reaction is to:

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. It is more useful for biochemists to know the specific activity of an enzyme than the activity of the enzyme because:

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. An enzyme in liver which removes glucose from blood has a high Km; another which does the same thing in brain tissue has a small Km. The usefulness of these two different values is that:

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. A molecule of an enzyme which has a high turnover number:

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. Most amino acids found in living things are L-form amino acids. A few amino acids found in antibiotics are D-form. The enzyme which converts D-alanine to L-alanine is best classified as an:

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. In addition to activation and inhibition, enzymes may be controlled by

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. Consider the reaction: ethyl acetate + H2OC> ethanol + acetic acid The enzyme which catalyzes this reaction is classified as a/an:

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. One way to tell whether an enzymatic reaction is carried out by an oxidoreductase is to:

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. Parkinson's disease is caused by a deficiency of dopamine in the substantia nigra of the brain. Dopamine is produced in the brain from L-DOPA (L-dihydroxyphenylalanine) by removal of a molecule of carbon dioxide. The L-DOPA is produced by oxidation of tyrosine, which is in turn produced from phenylalanine by another oxidoreductase. The enzyme which converts L-DOPA to dopamine is best classified as a/an:

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. As a solution containing an enzymatic reaction is heated, the temperature rises and the reaction velocity rises gradually for some period, but typically falls off very rapidly after reaching the optimum temperature because:

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. During replication, a number of DNA fragments are produced. Energy is required for an enzyme to join these fragments together to form an intact strand of DNA. The enzyme is classified as a/an:

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. Melanin, the dark pigment in our hair and skin, is produced by a series of enzymatic reactions which start with phenylalanine. The phenylalanine is converted to tyrosine, then to L-DOPA, and finally though a series of steps to melanin and other substances. If the conversion of phenylalanine to tyrosine were blocked, the individual affected would probably:

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