A cell is the basic structural unit of an organism. The cell was first discovered by Robert Hooke, until then very little was known about the cell. Cells are assembled to make the body of an organism. Organisms made of more than one cell are known as multicellular organisms while single-celled organisms are known as unicellular organisms. The functions of organisms with a lesser number of cells are not affected by less number of cells. A single-celled organism like the amoeba respires, captures and digests food, grows, excretes and reproduces. Similar functions in a multicellular organism are carried out by groups of specialised cells forming different tissues. Tissues, in turn, form organs. A cell exhibits a variety of shapes and sizes. In class 8 science chapter 8, the various parts of a cell and their functions along with the comparison of plant and animal cells are discussed.
Parts of the Cell
A cell is composed of three basic components:
- Cell Membrane – Also known as plasma membrane separates cells from one another. It porous and allows the movement of materials both outward and inward.
- Cytoplasm – Jelly-like substance present between the nucleus and cell membrane Other organelles of cells are also present in the cytoplasm.
- Nucleus – It is the round dense body at the centre. The nucleus is composed of a nuclear membrane, nucleolus and chromosomes. It is the control centre of the activities of the cell. It also plays a major role in the inheritance.
Apart from these three basic components, a cell consists of other organelles such as Golgi bodies, ribosomes and mitochondria about which we will study in higher classes.
Comparison of Plant and Animal cells
Given below in a tabular column, the similarities and distinguishing features of plants and animal cells are given
|Part||Plant Cell||Animal Cell|
Plant cells differ from animal cells in having an additional layer around the cell membrane known as the cell wall. Apart from this, plastids containing chlorophyll known as chloroplast are found in plant cell only. Plant cells have a big central vacuole while animal cells have small vacuoles.
MCQ on Cell Structure And Function
- The functional unit of organisms is _____.
- A tissue is a group of _____.
- Hen’s egg is a _____.
- organ system
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