In this article, we will discuss three main types of enzymes that break down three essential biological molecules: carbohydrates, proteins, and fats. Carbohydrates, proteins, and lipids are three biological molecules that are present in our diet. These molecules give us energy. The enzymes present in our digestive system break down these molecules into simpler units. Before discussing the enzymes that break down these molecules, first, let us recall what are enzymes and what role do they play in our body.
What are Enzymes?
We know that enzymes act as biological catalysts, i.e. they speed up the reaction. After the reaction, the nature of the enzymes remains unchanged which means that they do not get used up during the reaction. They are referred to as "biological catalysts" because they are made up of living cells.
Enzymes are essential to carry out certain processes in living organisms that are critical for their survival. For instance, digestive enzymes present in the human body enable us to digest food within hours. If these enzymes would not be there, then it would take us weeks to digest even a single meal.
Many factors affect the activity of enzymes, but the three main factors are:
- Temperature: High and low temperatures affect the ability of enzymes to react with the substrates in different ways. At low temperature, the molecular movement reduces which decrease the number of collisions between the substrate and enzymes. High temperatures distort the shape of the enzyme's active site, thus decreasing the number of collisions.
- pH: pH also alters the shape of the enzyme's active site. Extreme pH can also cause denaturation of the enzymes.
- Substrate and enzyme concentration: If the concentration levels of substrate and enzymes increase beyond a certain level, then the enzyme action becomes slow or even stops.
Three Main Types of Digestive Enzymes
Digestion is the process in which our body breaks down large, insoluble food molecules into smaller, water-soluble molecules. Large insoluble molecules like proteins and starch are made up of chains of smaller molecules. These chains are held together through chemical bonds which need to be broken. This breakdown occurs with the help of mechanical and chemical processes. Mechanical digestion occurs through:
- chewing of food in the mouth with the help of teeth
- churning in the stomach
For chemical digestion, we need enzymes. The three main types of digestive enzymes are:
Carbohydrase are digestive enzymes that break down carbohydrates into simple sugar. These enzymes are secreted by our mouth, pancreas, and small intestine.
Enzymes that break down different types of carbohydrates
Different types of carbohydrates are broken down by different types of carbohydrase enzymes. Some of these are listed and explained below:
- Amylase: Starch is a kind of carbohydrate that is broken down by a carbohydrase enzyme known as amylase. Amylase is secreted by our mouth and is present in saliva. It begins working as soon as we start chewing our food. Long, complex starch molecules known as polysaccharides are broken down by the amylase enzyme into smaller and simpler disaccharide molecules known as maltose. The word equation of this reaction is given below:
- Maltase: Maltose is a disaccharide molecule that needs to be digested further before absorption. The enzyme known as maltase breaks down maltose into glucose. The word equation of this reaction is given below:
- Sucrase: The sucrase enzyme is responsible for breaking down the dietary sugar "sucrose" into glucose and fructose. Sucrose is also a disaccharide molecule. The word equation for this reaction is given below:
Sucrose glucose + fructose
- Lactase: Lactose is another dietary sugar that is a disaccharide molecule. The enzyme lactase breaks down "lactose" into glucose and galactose. The word equation of this reaction is given below:
Lactose glucose + galactose
The enzymes that digest proteins in our food are known as proteases. These enzymes are secreted by our stomach, pancreas, and small intestine. Our stomach secretes a protease enzyme known as pepsin. Proteins are made of long chains of amino acids. The protease enzymes break down these long chains into peptides and individual amino acids. Peptides are smaller chains of amino acids and individual amino acids are even smaller molecules that can be absorbed easily in the small intestine. The word equation of this reaction is given below:
Proteins amino acids
The enzymes that break down complex lipid or fat molecules present in our diet into simpler, soluble fatty acid and glycerol molecules are referred to as lipase. These enzymes are secreted by our pancreas and the walls of the small intestine. The word equation of fat break down is given below:
Lipids fatty acids + glycerol
Other Substances that Aid in Digestion
Different enzymes require different pH values to show their best performance. The substances present in different parts of our body also work together with enzymes to digest food.
Saliva is present in our mouth that is slightly alkaline. The enzymes in our saliva convert starch into glucose.
Hydrochloric acid is produced in our stomach that kills several harmful microorganisms which we might swallow along with our food. The enzymes present in our stomach work best at low pH, i.e. acidic conditions.
Food goes into the small intestine after passing through the stomach. The enzymes present in our small intestine work best in alkaline conditions. However, the food is acidic because of the hydrochloric acid in the stomach. Our liver produces bile and stores it in the gall bladder. From the lever the bile is secreted into the small intestine which has the following two effects:
- It provides the alkaline conditions required in the small intestine to neutralize the acid.
- It emulsifies fats which means that it provides a larger surface area for the lipase enzymes to work on
Products of Digestion
- New carbohydrates, proteins, and lipids are built up using the products of digestion which are needed by our cells for their proper functioning and growth
- The breakdown of carbohydrate molecules releases glucose that is used in respiration to release energy. This released energy fuels activities of the cell
- Proteins such as enzymes and antibodies are built up using amino acids
- The products of lipid digestion are employed to build hormones and new cell membranes
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