Question

Name the enzymes involved in the digestion of starch, protein, and fat, and tell where these enzymes are active and what they do. (page 165 )

Short answer

The enzymes involved in the digestion of starch, protein, and fat are: 1. Starch: Amylase (in the mouth and small intestine) breaks starch into maltose, and maltase (in the small intestine) breaks maltose into glucose. 2. Protein: Pepsin (in the stomach) breaks proteins into smaller polypeptides, trypsin (in the small intestine) breaks polypeptides into smaller peptides, and peptidase (in the small intestine) breaks peptides into amino acids. 3. Fat: Lipase (in the small intestine) breaks fats into fatty acids and glycerol, with bile aiding in emulsification.

Step-by-step solution

Enzymes involved in the digestion of starch

Starch is a complex carbohydrate that needs to be broken down into simpler sugars to be absorbed by our bodies. The enzymes involved in the digestion of starch are amylase and maltase. - Amylase: This enzyme is produced in the salivary glands and the pancreas. In the mouth, salivary amylase initiates the breakdown of starch into maltose (a disaccharide), and in the small intestine, pancreatic amylase continues this process. - Maltase: This enzyme is produced by the cells lining the small intestine. Maltase acts on maltose and breaks it down into two glucose molecules, which can then be absorbed by the body.

Enzymes involved in the digestion of proteins

Proteins are made up of chains of amino acids and need to be broken down into individual amino acids to be absorbed by the body. The enzymes involved in the digestion of proteins are pepsin, trypsin, and peptidase. - Pepsin: Pepsin is produced in the stomach by chief cells as the inactive enzyme pepsinogen. The acidic environment of the stomach activates pepsinogen into pepsin, which begins the process of breaking down protein into smaller polypeptides. - Trypsin: Trypsin is produced in the pancreas as the inactive enzyme trypsinogen and is secreted into the small intestine. Enterokinase, an enzyme produced by the cells lining the small intestine, activates trypsinogen into trypsin. Trypsin then breaks down the smaller polypeptides into even smaller peptides. - Peptidase: Peptidases are produced by the cells lining the small intestine. They complete the digestion of proteins by breaking down the small peptides into individual amino acids, which can then be absorbed by the body.

Enzymes involved in the digestion of fats

Fats are large molecules that need to be broken down into fatty acids and glycerol to be absorbed by the body. The primary enzyme involved in the digestion of fats is lipase. - Lipase: Lipase is produced in the pancreas and secreted into the small intestine. It breaks down the fats into their constituent fatty acids and glycerol. Bile, produced in the liver and stored in the gallbladder, is also secreted into the small intestine to help emulsify the fats, creating a larger surface area for lipase to work on. In conclusion, the enzymes involved in the digestion of starch, protein, and fat are amylase and maltase for starch, pepsin, trypsin, and peptidase for protein, and lipase for fat. These enzymes are active in different parts of the digestive system and are responsible for breaking down their respective macromolecules into simpler forms that can be absorbed by our bodies.

Key concepts

Amylase

Amylase is a crucial enzyme in the digestive system, actively involved in breaking down carbohydrates. It is primarily found in two key areas of the body: the salivary glands and the pancreas. When you start eating, the salivary glands release saliva that contains amylase. This enzyme kicks off the digestion of starch, turning it into maltose, a simpler sugar, right in the mouth.
As the food progresses into the small intestine, the pancreas secretes pancreatic amylase to continue starch digestion. Here, the amylase further processes starch into maltose, facilitating the breakdown process begun in the mouth. Without amylase, our bodies would struggle to efficiently digest starches into absorbable sugars.

Pepsin

Pepsin is a powerful digestive enzyme specifically tailored for protein breakdown. It plays a vital role in the stomach, which provides the ideal acidic conditions needed for its activation. Produced by the stomach's chief cells, pepsin originates as pepsinogen, an inactive form. Exposed to the stomach's acidic environment, pepsinogen transforms into pepsin.
This active enzyme targets protein, fragmenting it into smaller polypeptides. These smaller units are necessary for further digestion and eventual absorption as individual amino acids. Pepsin's ability to initiate protein breakdown underscores its importance in proper digestive function.

Lipase

Lipase is the hero enyzme when it comes to digesting fats. This enzyme is secreted by the pancreas and becomes active in the small intestine, where it breaks down fats into fatty acids and glycerol. These simpler molecules are essential for body absorption and utilization.
To improve lipase's efficiency, bile produced by the liver and stored in the gallbladder is released into the small intestine. Bile emulsifies fats, which means it breaks them into tinier droplets, increasing the surface area available for lipase action. This process ensures that fats are digested as effectively as possible, aiding in our overall nutrition.

Maltase

Maltase is an enzyme that takes the starch digestion process to its final stage. Produced by the cells lining the small intestine, maltase focuses on breaking down maltose into two glucose molecules. This final step is crucial as glucose represents a form that the body can readily absorb and use for energy.
After amylase reduces starches to maltose, maltase acts directly on these simpler sugars. By ensuring maltose conversion into glucose, maltase supports the body’s ability to efficiently absorb carbohydrates, providing the energy essential for various bodily functions.

Trypsin

Trypsin is another enzyme that excels in protein digestion beyond the stomach. Produced by the pancreas, it initially exists as trypsinogen, an inactive precursor. Once secreted into the small intestine, it is activated into trypsin by enterokinase, an enzyme found in the intestine lining.
Trypsin aids in the digestion by taking polypeptides, which pepsin has already worked on, and breaking them down into even smaller peptide chains. It collaborates closely with other enzymes to further split these chains into individual amino acids. Thus, trypsin is an essential component of the protein digestion pathway, ensuring nutrients are accessible for absorption.