Question

Researchers analyzed a cell extract-a mixture of molecules isolated from a certain type of cell-and studied a chemical reaction in which a carbohydrate was broken down into smaller molecules. When they added a protease to the cell extract, they discovered that the protease greatly inhibited the rate of the reaction. Based on this observation, you could conclude that the reaction is a. exergonic. b. endergonic. c. catalyzed by an enzyme. d. catalyzed by a ribozyme. e. Both b and c are true of this reaction.

Short answer

The correct answer is option c: The reaction is catalyzed by an enzyme.

Step-by-step solution

Understanding Proteases

Proteases are enzymes that catalyze proteolysis, the breakdown of proteins into smaller polypeptides or single amino acids. They do not influence the energy of reactions, but they do influence the speed of certain reactions--specifically protein-related reactions.

Evaluating the Impact of Protease

Here, when protease is added to a mixture, it greatly inhibits the rate of the reaction. This suggests that the reaction may have been initially facilitated or catalyzed by a protein. Why is this? It's simple: Proteases break down proteins, so if a protein was facilitating the reaction, its breakdown by the protease would slow or stop the reaction.

Considering the Options

Now, consider the options given. An exergonic reaction releases energy, and an endergonic reaction absorbs energy. As for a ribozyme, it is a type of RNA molecule that can catalyze reactions. None of these three options are inferred by the information given in the problem statement. Thus, the only valid clear conclusion is that the reaction is catalyzed by an enzyme (which could be a protein). This leads to the selection of option c. 'Both b and c are true of this reaction' is not correct because there's no information that suggests the reaction is endergonic.

Key concepts

Protease

Proteases are fascinating enzymes, central to biological processes where the breakdown of proteins is required. These specialized enzymes catalyze the cleavage of peptide bonds found within proteins, effectively chopping them into smaller peptides or even down to individual amino acids.
This process is vital for many biological functions, affecting digestion, cell regulation, and even signaling pathways.

• Catalytic Action: Proteases do not influence the energy output of reactions but are crucial in determining the speed of protein-related transformations.
• Types: They can be further categorized based on their site of action, such as serine proteases, cysteine proteases, and more.
• Inhibition: When a reaction involves or is facilitated by proteins, the addition of proteases can inhibit it by breaking down those proteins.

Understanding how proteases work helps comprehend their intricate role in maintaining life through regulation and balance of protein levels.

Enzymes

Enzymes are biological catalysts that increase the rate of chemical reactions in the body without undergoing any permanent chemical change themselves. They specifically speed up reactions by lowering the activation energy required.

• Specificity: Each enzyme is specific to a substrate (the reactant an enzyme acts upon). This specificity is akin to a lock-and-key mechanism, where only a particular substrate (key) fits into the enzyme (lock).
• Function: Enzymes play roles in digestion, metabolism, DNA replication, and much more.

The presence of enzymes is crucial for controlling the rates of countless biochemical reactions, ensuring they happen efficiently and effectively enough to sustain life.

Catalysis

Catalysis is a fundamental concept in chemistry and biology, referring to the process of increasing the rate of a chemical reaction by the addition of a catalyst. In biological systems, enzymes serve as these catalysts.

• Reaction Rate: Catalysts are essential as they accelerate reactions that would otherwise occur too slowly, hindering vital processes like metabolism.
• Mechanism: Enzymes achieve catalysis by lowering the activation energy barrier of a reaction.

This ability to speed up reactions without being consumed enables enzymes to participate in multiple reaction cycles, continuously facilitating cellular processes.

Protein Breakdown

Protein breakdown is a crucial biological reaction involving the deconstruction of large protein molecules into smaller units—polypeptides or amino acids. This process is mostly mediated by proteases and is integral to physiological processes such as nutrient absorption and cellular recycling.

• Role: Breaking down proteins is essential for nutrient processing, allowing the body to absorb and utilize amino acids for synthesizing new proteins, among other functions.
• Biological Significance: It is crucial in cell maintenance by removing damaged or unnecessary proteins, recycling components and keeping cellular functions optimal.

By understanding protein breakdown, one gains insight into how cells maintain balance, manage resources, and support overall health and function.