Question

Ire intibitor which closely resembles the substrate in its molecular stucture and inhibits the enzyme activity by binding to the active site of the enzyme is called (a) feed back inhibitor (b) non-competitive inhibitor (c) competitive inhibitor (d) allosteric modulator.

Short answer

The inhibitor is a (c) competitive inhibitor.

Step-by-step solution

Understanding Inhibition Mechanisms

Firstly, recognize that there are various types of enzyme inhibitors, and each has a different mode of action. One type mimics the substrate's structure and competes with the substrate for binding at the enzyme's active site.

Differentiating Between Types of Inhibitors

A competitive inhibitor resembles the substrate and binds to the active site of the enzyme. A non-competitive inhibitor binds to a different site, not the active site, and a feedback inhibitor is part of a regulatory mechanism where the end product inhibits an earlier step. An allosteric modulator binds to a site other than the active site, causing a change in enzyme activity.

Identifying the Correct Type of Inhibitor

Based on the description provided in the exercise, an inhibitor that closely resembles the substrate and blocks the enzyme activity by binding to its active site is known as a competitive inhibitor.

Key concepts

Enzyme Inhibition

Enzyme inhibition is a regulatory mechanism where a molecule, known as an inhibitor, binds to an enzyme and decreases its activity. There are different types of inhibitors, including competitive, non-competitive, and irreversible inhibitors.

Competitive inhibitors are molecules that closely resemble the enzyme's normal substrate and compete for the same active site on the enzyme. Because of this competition, the presence of a competitive inhibitor reduces the rate of reaction since the actual substrate has fewer chances of binding to the enzyme's active site. On the other hand, non-competitive inhibitors bind to other parts of the enzyme, causing a change in the shape of the enzyme so that the substrate can no longer bind effectively, regardless of the concentration of the substrate. Unlike competitive inhibition, which can be overcome by increasing substrate concentration, non-competitive inhibition is not affected by substrate levels.

Understanding enzyme inhibition is crucial for drug design and can help in creating medicines that can control enzyme activity in cases of diseases or metabolic imbalances.

Enzyme Active Site

The enzyme active site is a specific region on an enzyme where substrates bind and undergo a chemical reaction. It is typically a small pocket or groove on the enzyme’s surface, which is well-suited to the shape of the substrate, allowing for a high degree of specificity.

Enzymes are biological catalysts, and the active site is critical for their function. When the substrate enters the active site, it forms a temporary intermediate called an enzyme-substrate complex. This complex lowers the activation energy required for the reaction to take place, leading to the formation of the products.

Induced Fit Model

The 'induced fit' model describes how enzymes change shape on substrate binding. Unlike the 'lock and key' model where the enzyme's shape does not change, in the induced fit model, the enzyme's active site adjusts to fit snugly around the substrate.

Enzyme activity can be regulated by factors such as pH, temperature, and the presence of inhibitors, which can bind to the active site or another part of the enzyme to alter its function.

Biological Molecules

Biological molecules are an essential component of every living organism and include macromolecules like proteins, nucleic acids, carbohydrates, and lipids, as well as smaller molecules like metabolites and cofactors.

Proteins carry out a variety of functions within cells, including acting as enzymes that catalyze biochemical reactions. Carbohydrates serve as energy sources or structural components, while lipids make up cell membranes and also provide energy storage. Nucleic acids, such as DNA and RNA, are responsible for storing and transmitting genetic information.

Each of these types of biological molecules plays a distinct role in cellular structure and function. For instance, enzymes, which are proteins, are crucial for metabolic pathways. Understanding the structure and function of these biological molecules is key to grasping how various biochemical reactions occur within the body, including enzyme-mediated reactions affected by competitive and other forms of inhibition.