Question

If \(\mathrm{pH}\) of stomach is \(1.6\), then which enzyme will digest protein? (a) Amylase (b) Trypsin (c) Erypsin (d) Pepsin

Short answer

Pepsin will digest protein at a pH of 1.6.

Step-by-step solution

Understanding pH and enzyme activity

The pH of a solution is a measure of its acidity or alkalinity. Enzymes are biologically active proteins that have optimal activity at specific pH ranges. The stomach's acidic environment (pH around 1.6) favours enzymes that are active in acidic conditions.

Identifying the enzyme based on pH

Based on the specific pH, we can deduce which enzyme is most likely to be active in the acidic environment of the stomach. The correct enzyme for protein digestion in the stomach needs to operate effectively at a low pH.

Matching the enzyme to the stomach's pH

Pepsin is the enzyme that digests proteins in the highly acidic environment of the stomach. While amylase, trypsin, and erepsin are active in different pH ranges, pepsin is known to work optimally around a pH of 2. Therefore, in an environment with a pH of 1.6, pepsin is the enzyme responsible for protein digestion.

Key concepts

pH and Enzyme Activity

Enzymes are remarkable biological catalysts that speed up chemical reactions in the body. They are highly selective and have optimal conditions under which they perform best, including temperature and pH levels. pH, which stands for the 'potential of hydrogen,' is a scale used to determine the acidity or alkalinity of an aqueous solution. The pH scale ranges from 0 to 14, with 7 being neutral. A pH less than 7 indicates acidity, while a pH greater than 7 indicates alkalinity.

The pH level affects the shape and function of an enzyme. Each enzyme has an optimal pH range that helps maintain its shape and allows it to bind to substrates effectively. Outside of this range, the enzyme's structure can become denatured, which can result in a decrease or complete halt in its catalytic activity. For example, enzymes involved in digestion, such as pepsin, require an acidic pH to maintain their activity. This explains why certain enzymes are found in specific locations within the body, such as the acidic environment of the stomach, to ensure they are functioning in their prime conditions.

Protein Digestion

Proteins are essential macromolecules composed of long chains of amino acids. The process of breaking down these complex molecules into their constituent amino acids is crucial for the body to use them in various metabolic processes. Protein digestion begins in the stomach, where the acidic environment denatures the protein structures, exposing the peptide bonds.

Enzymes such as pepsin are central to the digestion of proteins. The stomach's acidic pH is ideal for pepsin to cleave the peptide bonds between amino acids, breaking the proteins into smaller peptides. As the digestive process continues, these peptides are further broken down in the small intestine by other proteases, such as trypsin and erepsin, until the amino acids are small enough to be absorbed through the intestinal lining into the bloodstream. This step-by-step breakdown is necessary because proteins are too large to be absorbed directly by the body's cells.

Pepsin Function

Pepsin is a vital digestive enzyme that functions in the stomach to break down protein molecules into smaller pieces called peptides. It is unique among proteases because it thrives in a highly acidic environment, with an optimal pH of around 2, which is why it is not active in neutral or alkaline conditions.

The enzyme works by attacking the peptide bonds in the denatured protein, which have become more accessible due to the unfolding of the protein in the stomach's acid. This unfolding is critical as it allows pepsin to efficiently cleave the bonds and ensure that proteins are reduced to small peptides. Pepsin's activity in the stomach is a perfect illustration of the body's ability to optimize enzyme function, leveraging the extreme pH conditions to regulate digestion and prepare proteins for subsequent absorption and utilization in the body.