Question

Three of the following statements about enzymes are correct and one is wrong. Which one is wrong?
A. Most enzymes are proteins but some are lipids.
B. Enzymes require optimum pH for maximal activity.
C. Enzymes are denatured at high temperatures but in certain exceptional organisms, they are effective even at temperatures $80 - 90^\circ C$.
D. Enzymes are highly specific.

Answer 1

Enzymes are chemical substances with high molecular weights. They are macromolecules. They are usually secreted from the exocrine glands. Based on the reactants, enzymes are classified as proteases and lipases.

Complete answer: Enzymes are high molecular weight chemicals. Enzymes are biological catalysts. They are generally made up of globular proteins that are complex macromolecules. Some enzymes are RNA also known as the Ribozymes or the catalytic RNAs. Enzymes have a three-dimensional tertiary structure. They are made up of proteins as well as non-proteins. The non-proteins help the enzymes in their functioning. They are further organic or inorganic. Enzymes have two kinds of reactants, proteins, and lipids. However, they are made up of proteins or in some cases nucleic acids only. Enzymes are thermolabile substances. They catalyze the biological reactions that are within a very narrow range of pH and temperature. This means that they function their best at optimum temperatures. Enzyme activity is directly proportional to the temperature. It ceases at or below 0 degrees and above 80 degrees. In some bacteria like thermophiles that inhabit the hot water springs, there are enzymes that help them in functioning even at extremely high temperatures of 70 degrees or more. The activity of enzymes is best in their pH range and it increases or decreases if the pH increases or decreases respectively. Also, the enzymes have specific actions. Every enzyme catalyzes a particular kind of reaction and reacts with specific substrates only. Thus, based on the above information we can conclude that the statement that most enzymes are proteins but some are lipids is wrong.
Hence, the correct answer is option (A).

Note: Enzymes are made up of protein and non-protein parts. The protein part of the enzyme is known as the apoenzyme. On the other hand, the non-protein part of the enzyme is known as the co-enzyme or the cofactor. This non-protein cofactor part can be organic or inorganic compounds. The organic compounds are either tightly bonded with proteins or loosely bonded with proteins. If the organic co-enzyme is tightly bonded with proteins then it is known as a prosthetic group. However, if the organic co-enzyme is loosely bonded with proteins it is known as co-enzyme only. The inorganic compound or metal cofactor is known as the activator.