Microbiology Practice Exam

Which of the following best describes enzymes?

1. They are substances that change after a reaction

2. They speed up chemical reactions without being consumed

3. They work on a one-to-one basis with substrates

4. They can function under any environmental condition

The correct answer is: They speed up chemical reactions without being consumed

Enzymes are biological catalysts that play a crucial role in facilitating and speeding up chemical reactions within living organisms. The defining characteristic of enzymes is their ability to increase the rate of reactions without undergoing any permanent change themselves; they remain unaltered at the end of the reaction. This property allows them to be reused multiple times, making them highly efficient in metabolic processes. Other options present characteristics that do not accurately represent enzymes. While enzymes interact with substrates, they do not change after the reaction, which eliminates the first choice. The statement about a one-to-one interaction with substrates is misleading, as enzymes can interact with multiple substrate molecules over time and are not limited to a single substrate molecule for each catalytic cycle. Lastly, enzymes are sensitive to environmental conditions such as pH, temperature, and ionic strength; thus, they do not function optimally under all potential conditions, which contradicts the last option.