Human Body: Digestive System

It converts the milk protein casein into curd

Step 1: The stomach secretes gastric juice which contains several components including HCl, pepsin, and rennin. Step 2: Rennin is a special enzyme that acts specifically on the milk protein called casein. Step 3: Rennin converts liquid casein (dissolved in milk) into a semi-solid curd, which stays in the stomach longer and can be digested more effectively. Step 4: This enzyme is particularly important in babies and young children who drink a lot of milk. Step 5: Option A is wrong — starch is converted to maltose by salivary amylase. Option C is wrong — pepsin converts proteins into peptones. O

Amino acids

Step 1: Protein digestion is a multi-step process. Let us trace it carefully. Step 2: In the stomach, pepsin breaks down proteins into simpler compounds called peptones. This is partial digestion. Step 3: In the duodenum, the pancreatic enzyme trypsin converts proteins and peptones into even simpler compounds called peptides. Step 4: Finally, in the ileum, the intestinal enzyme erepsin converts peptides into amino acids — the final, simplest form of proteins. Step 5: Amino acids are then absorbed by the villi into the blood. Option A (peptones and peptides) are intermediate products, not final

Amylase → digests starch; Trypsin → digests proteins/peptones; Lipase → digests emulsified fats

Step 1: The pancreas is a large gland below the stomach that secretes pancreatic juice into the duodenum. Step 2: Pancreatic amylase acts on starch (a carbohydrate) and converts it into maltose — just like salivary amylase but in the small intestine. Step 3: Trypsin acts on proteins and peptones (which were partially digested in the stomach) and converts them into peptides. Step 4: Lipase acts on emulsified fats (fats that have already been broken into tiny droplets by bile) and converts them into fatty acids and glycerol. Step 5: All other options incorrectly assign the enzymes to wrong subst

Caecum → Colon → Rectum → Anus

Step 1: After the small intestine completes digestion and absorption, the remaining undigested material passes into the large intestine. Step 2: The large intestine has three regions. The first region is the caecum, which receives the undigested food from the small intestine. Step 3: From the caecum, the material moves into the colon. The colon's main job is to absorb water from the undigested material, making it semi-solid. Step 4: The now semi-solid waste (called faeces) moves into the rectum, the last part of the large intestine (about 15 cm long), where it is stored temporarily. Step 5: Fi