NCERT Solutions for Class 9th Science
Chapter 5. The Fundamental Unit of Life
- The fundamental organisational unit of life is called cell.
- Cells were first discovered by Robert Hooke in 1665.
- The movement of water molecules through such a selectively permeable membrane is called osmosis.
- The plasma membrane is flexible and is made up of organic molecules called lipids
- Nucleus is a largest cell organelle which consists inside the cell. Nuclei are found in all eukaryotic cells. It contains chromatin. Nucleus is a largest cell organelle which consists inside the cell. Nuclei are found in all eukaryotic cells. It contains chromatin.
- Cellulose is a complex substance and provides structural strength to plants.
- The nucleus has a double layered covering called nuclear membrane.
- Functional segments of DNA are called genes.
- Mitochondria are known as the powerhouses of the cell.
- ATP is known as the energy currency of the cell.
- The internal organisation of the plastids consists of numerous membrane layers embedded in a material called the stroma.
- Most plant cells have large membranous organelles called plastids, which are of two types – chromoplasts and leucoplasts.
- Chromoplasts that contain chlorophyll are called chloroplasts and they perform photosynthesis.
- Most mature plant cells have a large central vacuole that helps to maintain the turgidity of the cell and stores important substances including wastes.
- If the medium surrounding the cell has a higher water concentration than the cell is known as hypotonic solution.
- If the medium has exactly same water concentration than the cell is known as isotonic solution.
- If the medium surrounding the cell has a lower concentration then the cell is known as hypertonic solution.