Question

Which of the following is not true about enzymes? a. They are consumed by the reactions they catalyze. b. They are usually made of amino acids. c. They lower the activation energy of chemical reactions. d. Each one is specific to the particular substrate(s) to which it binds.

Short answer

A. Enzymes are consumed by the reactions they catalyze. B. Enzymes are usually made of amino acids. C. Enzymes lower the activation energy of chemical reactions. D. Enzymes are specific to the particular substrate(s) to which they bind. Answer: A. Enzymes are consumed by the reactions they catalyze.

Step-by-step solution

Understanding enzyme properties

Enzymes are biological molecules, typically proteins, that speed up the rate of chemical reactions in living organisms. They act as biological catalysts, which means they lower the activation energy of a reaction without being consumed or changed by the reactions they catalyze. Enzymes are made up of amino acids and are very specific to their substrates.

Option A

This option says that enzymes are consumed by the reactions they catalyze. This statement is false, as enzymes only act as catalysts and are not consumed during the reactions. An enzyme can be used repeatedly and maintain its original structure.

Option B

This option says that enzymes are usually made of amino acids. This is true, as enzymes are proteins and proteins are made up of amino acids. Enzymes have a specific sequence of amino acids that determines their structure and function.

Option C

This option says that enzymes lower the activation energy of chemical reactions. This statement is true, as one of the principal functions of enzymes is to lower the activation energy of reactions, making it easier for the reactions to occur. By lowering the activation energy, enzymes speed up the rate of chemical reactions.

Option D

This option says that enzymes are specific to the particular substrate(s) to which they bind. This statement is also true. Enzymes have a unique active site that binds to a specific substrate(s) to catalyze a particular reaction. This specificity is responsible for the high selectivity and precision of biological pathways in living organisms.

Conclusion

Based on our understanding of enzyme properties, option A is the statement that is not true about enzymes. Enzymes are not consumed by the reactions they catalyze but instead act as catalysts that lower the activation energy and specifically bind to their substrate(s).

Key concepts

Enzyme Properties

Enzymes are remarkable biological molecules that play a crucial role in speeding up chemical reactions within living organisms. They are typically made of proteins, which are composed of long chains of amino acids. This composition allows enzymes to have unique shapes, structure, and functions. Noteworthy properties of enzymes include:

• They are not consumed in the reactions they catalyze. This means they can be reused multiple times without changing their structure.
• Enzymes are highly efficient and can greatly accelerate the rate of biochemical reactions.
• They are specific to the substrates they bind with, playing a vital role in maintaining precise biological functions.

This specificity and efficiency are what make enzymes indispensable in physiological processes.

Catalysis

Catalysis refers to the process where the rate of a chemical reaction is increased by a catalyst. In biological systems, enzymes act as natural catalysts. One of the most fascinating aspects of enzyme catalysis is that it allows reactions to occur at a much faster rate than they would under normal conditions. This is essential for sustaining life and supporting rapid metabolic processes.

• Enzymes facilitate reactions by providing an alternative reaction pathway with lower energy requirements.
• They stabilize the transition state, which is a high-energy state that occurs during a reaction, making it easier for the reaction to proceed.
• This catalytic action ensures that reactions can take place swiftly and efficiently, even at the relatively low temperatures found within living organisms.

The ability of enzymes to act as catalysts underlies much of the biochemical machinery in cells, enabling them to function optimally.

Activation Energy

Activation energy is the minimum amount of energy required to start a chemical reaction. In many biochemical reactions, this energy barrier can be quite high, making reactions slow or impractical under normal conditions. Enzymes play a pivotal role in overcoming these limitations.

• They lower the activation energy required for reactions, effectively making the reaction easier to occur.
• By reducing this energy barrier, enzymes make reactions faster without requiring additional external energy input.
• This process is crucial because it allows necessary biochemical reactions to progress at speeds necessary for life processes, allowing cells to function efficiently.

Thus, by lowering activation energy, enzymes ensure that vital biological reactions can occur effortlessly within the body.

Enzyme-Substrate Specificity

Enzyme-substrate specificity is a concept that highlights the precision with which enzymes interact with substrates. Each enzyme has a unique active site, a distinct region that binds to a specific substrate, facilitating the transformation of the substrate into the product.

• This specificity stems from the unique three-dimensional shape of the enzyme's active site, which perfectly complements the shape of the substrate, much like a lock and key.
• Such specificity ensures that enzymes catalyze only particular reactions, preventing unnecessary chemical transformations.
• It is crucial for maintaining the efficiency and order of metabolic pathways, ensuring that cellular processes run smoothly and accurately.

Enzyme-substrate specificity is instrumental in ensuring the meticulous regulation and execution of biochemical reactions in cells.