What is a cell? What variations do the cells of organisms show?
A cell is the structural and functional unit of an organism. Each cell contains a fluid called the cytoplasm, which is enclosed by a membrane. Also present in the cytoplasm are several biomolecules like proteins, nucleic acids and lipids.
Variation in the shape of cells is as follows:
(i) Generally, cell’s shapes are rounded, spherical or elongated. Some types of cells are long and pointed at both ends. They exhibit spindle shapes. Some types of cells are branched like the nerve cell or a neuron, which receives and transfers messages for helping to control and coordinate the working of different parts of the body.
(ii) Components of the cell are enclosed in a membrane. This membrane provides shape to the cells of plants and animals. The cell wall is an additional covering over the cell membrane in plant cells. It gives shape and rigidity to these cells.
Variation in size of cells is as follows:
(i) The cell’s size in living organisms may be as small as a millionth of a meter (micrometre or micron) or maybe as large as a few centimetres.
(ii) Most of the cells are microscopic in size and are not visible to the naked eye. They need to be enlarged or magnified by a microscope for seeing.
(iii) The smallest cell is 0.1 to 0.5 micrometre in bacteria. The largest cell measuring 170 mm ×130 mm, which is the egg of an ostrich.
(iv) The size of the cells has no relation with the size of the body of the animal or plant.
A cell is the structural and functional unit of an organism. Each cell contains a fluid called the cytoplasm, which is enclosed by a membrane. Also present in the cytoplasm are several biomolecules like proteins, nucleic acids and lipids.
Variation in the shape of cells is as follows:
(i) Generally, cell’s shapes are rounded, spherical or elongated. Some types of cells are long and pointed at both ends. They exhibit spindle shapes. Some types of cells are branched like the nerve cell or a neuron, which receives and transfers messages for helping to control and coordinate the working of different parts of the body.
(ii) Components of the cell are enclosed in a membrane. This membrane provides shape to the cells of plants and animals. The cell wall is an additional covering over the cell membrane in plant cells. It gives shape and rigidity to these cells.
Variation in size of cells is as follows:
(i) The cell’s size in living organisms may be as small as a millionth of a meter (micrometre or micron) or maybe as large as a few centimetres.
(ii) Most of the cells are microscopic in size and are not visible to the naked eye. They need to be enlarged or magnified by a microscope for seeing.
(iii) The smallest cell is 0.1 to 0.5 micrometre in bacteria. The largest cell measuring 170 mm ×130 mm, which is the egg of an ostrich.
(iv) The size of the cells has no relation with the size of the body of the animal or plant.
