Question

1. Digestion & Absorption

   1. Identify the enzymes that work to chemically digest each of the three macronutrients present in a well- balanced diet.

      1. Name the enzymes.

      2. What cells or organs produce them?

      3. Where they are first present in the alimentary canal?

   2. For each macronutrient in (a), what type of vessel does the digested product get absorbed into?

Answer 1

Generally, a well-balanced diet consists of carbohydrates, proteins and lipids and each of these are digested through a series of steps within the alimentary canal in presence of different enzymes. Hence depending on the macronutrients, here are the enzymes responsible for its breakdown.,

Carbohydrates – The first enzyme which is responsible for breaking down the carbohydrate is salivary amylase which is present in saliva. This enzyme is responsible for breaking starch into disaccharides. The next enzyme is pancreatic amylase which is release from small intestine and produced in pancreas. The pancreatic amylase helps in breakdown of disaccharide and oligosaccharide in monosaccharide. The remainder of carbohydrate is broken into maltose by pancreatic amylase in small intestine. Maltase enzyme is present along the small intestine lining and helps in breaking down maltose into glucose. The sucrase and lactase enzymes in small intestine and it helps in digestion of sucrose and lactose respectively. The sucrase digests the sucrose into glucose and fructose. The lactase breaks lactose into glucose and galactose. The carbohydrate is absorbed by the upper part of the small intestine in structures which are called as microvilli and villi.

Proteins – The enzyme which is responsible for protein degradation is protease. As the protein reaches the stomach, the HCl and protease breaks down the proteins into amino acids. Protease is responsible for breaking the peptide bond. The pancreatic enzymes like trypsin, chymotrypsin and carboxypeptidase helps in breakdown of the protein in small intestine. These proteins are broken down into free amino acid and they pass through the small intestine lining and hence enters the bloodstream. The protease enzyme pepsin is activated within the stomach with help of HCl. The inactive form of trypsin and chymotrypsin is produced in the acinar cells of pancreas and they are further activated in the duodenum.

Lipids – The lipid is broken down in the small intestine and it produces lipase which helps in breakdown of dietary fat. The lipase is enzyme which helps in breakdown of fat and into fatty acid and monoglycerides and they are easily able to cross the small intestine lining and hence enters the bloodstream. The lipase enzyme is produced by the tongue and the pancreas.