Write Notes on Chapter Cell Structure and Functions Class 8th
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Answer:
Notes Chapter 8 Cell Structure and Functions
All organisms are the combination of different parts, i.e., called organs.
Roots, stems, leaves and flowers are the organs of plants.
Hands, feet, legs, heart, kidney etc. are the organs of animals.
All organs are made up of tissues which in turn are made up of cells.
Though organisms differ in shape and size, these are all made up of a basic unit called cells.
Cells present in living organism, differ in numbers, shape and size.
Bacteria (PPLO) has the smallest cell size of 0.1 microns. Ostrich egg has the largest cell size of 170 mm.
The shape of cells varies from spherical, cuboidal, columnar to long and branched types.
Some cells have an irregular shape, i.e., Amoeboid shape, in case of amoeba.
There are unicellular organisms (bacteria) as well as multicellular organisms (plants and animals).
Each cell has smaller components, called organelles. Some of these are common to different cell types. Each organelle has its own specific function.
The single cell of unicellular organisms performs all the basic functions, i.e., performed by a variety of cells in multicellular organisms.
The cell has three main parts:
the cell membrane
cytoplasm which contains smaller components called organelles, and
the nucleus.
Nucleus is separated from the cytoplasm by a nuclear membrane.
Nucleus acts as a control centre for all the activities of the cell.
Nucleus contains some smaller spherical body, i.e., nucleolus and threadlike structure, i.e., chromosomes.
The chromosomes carry genes that help in inheritance or transfer of characters from parents to the offspring.
Nucleoplasm is the liquid material of the nucleus.
Cells without a well-organised nucleus, i.e., lacking a nuclear membrane, Eire called prokaryotic cells.
Plant cells differ from animal cells in having an additional layer around the cell membrane termed as the cell wall.
Coloured organelle, i.e., called plastids, are found in the plant cells only. Green plastids containing chlorophyll are called chloroplasts.
Plant cell has a big central vacuole unlike a number of small vacuoles in animal cells
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Explanation:
cells have many structures inside of them called organelles . these organelles are like the organs in a human and they help the cell stay alive each organelle has its own specific function to help the cell survive the nucleus of a euarkaryotic cell directs the cells activities and stores dNa .
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