CBSE Class 10 Answered
10. Nitrogen is essential for growth and reproduction in both plants and animals. It is found in amino acids that make up proteins, in nucleic acids, that comprise the hereditary material and life’s blueprint for all cells, and in many other organic and inorganic compounds. Nitrogen is a component of amino acids and urea. Amino acids are the building blocks of all proteins. Proteins comprise not only structural components such as muscle, tissue and organs, but also enzymes and hormones essential for the functioning of all living things. The nitrogen in protein and urea is organic nitrogen.
11. Nutrition in Amoeba:
- Amoeba engulfs food by temporary finger-like projections of its body surface called pseudopodia.
- When a pseudopodium fuses with the food particle, it forms a food vacuole.
- Complex substances are broken down into simple substances inside the food vacuole. These simple substances are then diffused into the cytoplasm.
- The remaining unwanted material is taken to the cell surface and is thrown out.
12. Saliva is a watery secretion in the mouth produced by the salivary glands that aids in the digestion of food.
Functions of saliva in the digestion of food:
- Salivary amylase present in saliva converts starch into maltose and dextrose sugars.
- Mucus present in saliva lubricates food and thus helps in the swallowing of food.
- Saliva moistens and lubricates the inner lining of the mouth cavity and the surface of the tongue and helps us in speaking.
- Saliva acts as a solvent for some food particles and stimulates the taste buds of the tongue.
- It helps to convert food into a softball called bolus, which can easily pass through the pharynx.
- Saliva cleans the mouth and prevents the growth of germs in the mouth, thus curbing tooth decay.
- When water content of saliva is less, it leads to dryness in the mouth and induces the feeling of thirst. On drinking water, the water balance of the body is maintained.
13. Peristalsis is a wave of contraction caused by the circular muscles of the gut pushing the food along.