Cell: The Unit Of Life – Maharashtra Board Class 9 Solutions for Science and Technology (English Medium)
All cells contain jellylike matrix called cytoplasm surrounded by plasma membrane. In plant cells, the outermost covering is cell wall. Within the cell there are various cell organelles to carry out specific functions. Nucleus is the most important amongst them as it controls all the activities of the cell. Inside it chromatin network is present containing DNA molecules which hold the genetic information. Mitochondria produce ATP molecules. Osmotic pressure and turgidity is maintained by vacuoles, while mitochondria can be compared with a turbine of the cell.
- Plasma membrane or cell membrane
- Endoplasmic reticulum
- Genes/ DNA molecules
- Cell wall
- False (Only chromoplasts have pigments.)
- False (Cellulose is a carbohydrate.)
- Lysosomes have digestive enzymes. These enzymes remove worn out organelles and organic debris by the process called autolysis.
- When a cell becomes old or is damaged, lysosomes burst and the enzymes digest their own cells.
- Therefore, lysosomes are called suicide bags.
- All organisms are composed of cells. All vital functions of an organism occur within the cells.
- All cells arise only from pre-existing cells.
- Every living organism starts its life as a single cell.
- Therefore, a cell is called the structural and functional unit of life.
- Mitochondria are cell organelles which produce energy in the form of ATP molecules with the help of enzymes present in them.
- Mitochondria oxidise carbohydrates and fats present in the cell.
- During this process, energy is released. By using this energy, mitochondria produce energy-rich ATP molecules.
- The body uses energy stored in ATP molecules for different functions of the body.
- Therefore, the mitochondrion is called the power house of the cell.
Internal structure of the mitochondrion
Internal structure of the chloroplast
Robert Hooke discovered the cell in 1665. He was observing thin slices of cork under the microscope which he had designed. He saw empty blocks resembling the structure of a honey comb. He named them cells which mean small rooms in Latin. This is how the cell was discovered.