Question

Enzymes _______ a. are proteins, except for a few RNAs b. lower the activation energy of a reaction c. are changed by participating in a reaction d. a and b

Short answer

d. a and b

Step-by-step solution

Understanding the Role of Enzymes

Enzymes are biological catalysts that speed up the rate of chemical reactions without being consumed in the process. They achieve this by lowering the activation energy, which is the energy barrier required for a reaction to proceed.

Analyzing the Options

Consider each given option: - Option a: This states that enzymes are proteins, which aligns with biochemical knowledge, as almost all known enzymes are proteins, except for some catalytic RNAs. - Option b: This accurately describes that enzymes lower the activation energy of reactions, allowing them to proceed faster. - Option c: This is incorrect because enzymes are not changed or consumed in a reaction; they remain intact and can be reused. - Option d: This is a combination of option a and option b, which are both correct.

Identifying the Correct Answer

Based on the analysis, options a and b are both accurate statements about enzymes. Therefore, the option that combines these two statements (option d) is correct.

Key concepts

Activation Energy

In every chemical reaction, molecules need to reach a certain energy level for the reaction to occur. This energy level is known as "activation energy." Think of it as a hill that reactants must climb over to transform into products. Activation energy represents the energy barrier that must be overcome. When this barrier is lowered, reactions can occur more easily and swiftly. Without sufficient activation energy, reactions are slow or might not happen at all. Enzymes play a crucial role in reducing this energy requirement, making them indispensable in biological processes.

Biological Catalysts

Biological catalysts, also known as enzymes, are special molecules that accelerate chemical reactions in living organisms. They do so without being consumed or altered during the reaction. This means they can be reused repeatedly to facilitate numerous reactions. Enzymes are highly specific, often targeting a single substrate or type of chemical bond. This specificity is crucial because it ensures reactions occur precisely where and when needed in cellular processes. Without biological catalysts like enzymes, these essential reactions would happen too slowly to sustain life.

Proteins

Most enzymes are proteins, large complex molecules made from chains of amino acids. Proteins fold into unique three-dimensional structures that create specific sites, known as active sites, where substrates bind during reactions. This folding is vital because the structure of the enzyme determines its function. The diversity in protein structures allows enzymes to catalyze a vast array of chemical reactions, each crucial for maintaining life's processes. While most enzymes are proteins, it's noteworthy that not all are; some RNA molecules can also exhibit catalytic properties.

Catalytic RNAs

Catalytic RNAs, or ribozymes, are RNA molecules that can catalyze specific biochemical reactions, similar to the way protein enzymes function. These ribozymes defy the common perception that enzymes must be proteins. They are involved in various crucial biological processes, such as RNA splicing and synthesis of proteins in ribosomes. The discovery of ribozymes proved that RNA isn't just a passive carrier of genetic information but also capable of participating actively in cellular metabolism and regulation. This unique attribute underlines the versatility and importance of RNA in biology.