Cells and Tissues

1) Why Cell Wall Is Present in Plant Cell Whereas Absent in Animal Cell?

• Plants cannot move like animals; instead, they grow and develop in a fixed place.
• For this reason plants cannot protect themselves from harsh weather conditions and other types of physical stress.
• So, plants have an additional layer over their cells called the cell wall. It is a rigid, waxy and hard structure that protects the cells and the other components of the cell.

2) Why Are Some Plastids Termed Chloroplasts?

• Some plastids are termed chloroplasts because of the presence of chlorophyll.
• Chlorophyll is a green pigment that helps in trapping sunlight during photosynthesis.

3) Which Cellular Component Is Called the ‘Powerhouse of the Cell’?

• Mitochondria are called the ‘powerhouse of the cell’ because they are the organs of cellular respiration.
• They produce energy from the food after digestion.

4) Why Nucleus Is Called the Brain of the Cell?

• The nucleus is called the ‘brain’ of the cell because it is the centre of vital cellular activities like cell division.
• It also controls the functioning of cell organelles.
• The nucleus contains genetic materials that determine certain physical characteristics like eye colour, height, skin colour etc.