In this article, we discuss the notes of the chapter Cell Structure and Function with help of points and cover all the important topics, It is easy to revise and learn all the points, Chapter 8 Cell Structure and Functions Notes PDFs.
Cell Structure and Function Notes
1. Cell: The smallest structural and functional unit of an organism, which is typically microscopic and consists of cytoplasm and a nucleus enclosed in a membrane.
2. All organisms are made of smaller parts called organs.
3. Organs are made of still smaller parts. The smallest living part of an organism is a ‘cell’.
4. Cells were first observed in cork by Robert Hooke in 1665.
5. Cells exhibit a variety of shapes and sizes.
6. Number of cells also varies from organism to organism.
7. Some cells are big enough to be seen with the unaided eye. Hen’s egg is an example.
8. Some organisms are single-celled, while others contain a large number of cells.
9. The single cell of unicellular organisms performs all the basic functions performed by a variety of cells in multicellular organisms.
10. The cell has three main parts, (i) the cell membrane, (ii) cytoplasm which contains smaller components called organelles, and (iii) the nucleus.
11. Cell membrane: The basic component of a cell. The cytoplasm and nucleus are enclosed within a cell membrane. There is an outer thick layer in cells of plants called the cell walls.
12. Cytoplasm: The jelly-like substance present between the cell membrane and the nucleus. Various organelles present in the cytoplasm are:
(i) Mitochondria
(ii) Plastids (present only in plant cells)
(iii) Endoplasmic reticulum (ER)
(iv) Ribosome
(v) Lysosome
(vi) Vacuole
(vii) Golgi body
(viii) Centrosome (present only in the animal cells).
13. Nucleus: Nucleus is separated from the cytoplasm by a nuclear membrane. It is generally spherical in the centre of the cell.
14. Nuclear membrane: The nucleus is separated from the cytoplasm by a membrane called the nuclear membrane.
15. Nucleolus: Nucleus contains a still smaller round body known as nucleolus.
16. Chromosomes: The nucleus contains thread-like structures called chromosomes. These carry genes and help in the inheritance or transfer of character from the parents to the offspring
17. Cells without a well-organised nucleus, i.e. lacking nuclear membrane, are called prokaryotic cells.
18. Plant cells differ from animal cells in having an additional layer around the cell membrane termed cell wall.
19. Coloured bodies called plastids are found in plant cells only. Green plastids containing chlorophyll are called chloroplasts.
20. Plant cell has a big central vacuole unlike a number of small vacuoles in animal cells.
21. Size of cells: The size may be as small as a millionth of a metre or maybe as large as a few centimetres. The size of the cells has no relation with the size of the body of the animal or plant. It is related to its function.