CBSE Class 9 Answered
Cell is the basic structural and functional unit of a living organism. They join to form tissues, which in turn group to form organs and systems. The various systems collaborate to form the organism.
Cells perform various functions according to the tissue in which they are present. So cardiac muscle cells contract rapidly and rhythmically througout life, nerve cells are able to transmit impulses, red blood cell can carry the respiratory gases etc. But all cells are capable of carrying out certain basic functions such as nutrition, respiration,growth and reproduction. These functions are essential for the survival of cells and are made possible by the various organelles present in each cell.
Cells reproduce by cell division (binary fission/mitosis or meiosis). This helps in maintaining the required number of cells in the body.
Cells are capable of metabolic activities which includes taking in raw materials, building cell components, converting energy, molecules and releasing by-products. The functioning of a cell depends upon its ability to extract and use chemical energy stored in organic molecules. This energy is released and then used in metabolic pathways.
The cell contents are contained within the plasma membrane, which is semi-permeable and allows entry and exit of only certain molecules.
Cells carry out protein production using the DNA, RNA and ribosomes present within the cell.
The genetic material present within the nucleus is concerned with the transmission of hereditary characters from the parent to the offspring.
Cells can take in nutrients and convert these nutrients into energy. The generation of energy is done by the mitochondria of cell.
Cells can secrete cell products such as enzymes, hormones, mucus etc.