Tag: introduction to excretory system

In the stomach, the enzyme pepsin breaks protein into smaller pieces called polypeptides. For proper functioning of pepsin, acidic pH is necessary; a pH of 2 is optimum for pepsin function. Antacids neutralize the normal stomach acid pH and brings it upto 6 to 7. As pH rises above 4, pepsin activity decreases or stops. That is why when a person takes too much antacid the pH of the stomach may rise upto 11, which affect pepsin production severely. Maltase, Lactase, Lipase and Sucrase are produced in small intestine and they are active in pH range from 2 to 6.

1. Amylase is an enzyme that catalyses the hydrolysis of starch into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. 
2. The pancreas and salivary gland make amylase to hydrolyse dietary starch into disaccharides and trisaccharides which are converted by other enzymes to glucose to supply the body with energy. 
3. Foods that contain large amounts of starch but little sugar, such as rice and potatoes, may acquire a slightly sweet taste as they are chewed because amylase degrades some of their starch into sugar. Hence, the enzyme that converts starch to disaccharide is known as amylase.
   

Digestive enzymes are the enzymes that involve in the digestion process which secretes through glands like salivary glands, pancreas, stomach and small intestine but liver does not produce any enzyme. It produces bile juice which provides alkaline condition for enzymatic reaction in small intestine.

The digestive system includes alimentary canal and associated glands to carry out the digestion of food and release the energy stored in these food substances. The nutrients from digested food are then absorbed in the small intestine of the alimentary canal and carried to different organs via the circulatory system. The primary function of the respiratory system is to allow atmospheric oxygen from the air to enter the blood and carbon dioxide from the blood to exit into the air. The endocrine system includes endocrine glands and maintains the homeostasis of the body through hormonal actions. Nervous system serves in the reception of sensory input followed by their integration in the brain and spinal cord and generation of motor output to produce the response. Thus, the correct answer is A.

During the process of respiration organisms breakdown (burn) assimilated food to release energy in the form of ATP which is utilized for performing various activities and CO$ _2$ and water vapour are released as byproducts.

The digestive system plays an important role in the absorption of nutrients into the body. It takes the food we ingest, breaks it down mechanically and chemically in the mouth and stomach. It then absorbs nutrients, fats, proteins, and water in the intestines before eliminating the waste through the rectum. The movement of food in the alimentary canal occurs through peristalsis.

No significant digestive activity occurs in the large intestine. The functions of large intestine are :