NCERT Solutions for Class 8 Science Cell Structure and Functions
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In this article, we will discuss the Cell, its structure, and its function. (Class 8 Science Cell Structure and Functions)
Cell
We, living things carry out our basic functions with the help of different sets of organs. The structural unit of an organ is called Cell.
As the walls are important while building a house, the same is the role of cell to form an organism.
Variations in cells
All living organism like plants, animals, and humans are made up of cell. The smallest structural and functional unit of an organism is called a cell.
Variations in Number
The basis on the composition of cells organism is classified as
- Unicellular Organism-Organism made up of a single cell are called unicellular organism. Allvigorousactions like feeding, movement, respiration, and reproduction. are performed by the single-cell organism Example –
- Multicellular organism – Organism whose body consists of many cells are called multicellular organism. Organism grouped to perform particular functions.
Variations In shape
Different cells, carrying out different functions, exist in different shapes. They can be disc-shaped, polygonal, rectangular, branched, or even irregular.
- Nerve cells carry messages between different parts of the body to the brain or spinal cord.
Nerve cells
- Muscle cells help in movement through contraction and expansion.
Muscle cells
- Skin cells cover a large area, they are flat and broad in shape.
Skin cells
Variation in size
Most of the cells are microscopic and cannot be seen with the naked eye. Cell size may vary from a micrometer to few centimeters.
Prokaryotic and Eukaryotic Cells
Cells that not have a well-defined nucleus surrounded by a nuclear membrane are called prokaryotic cells. Example -Bacteria
Cells that have a well-defined nucleus are called eukaryotic cells.
Structure of a cell
- Cell membrane–A cell membrane is the outermost covering of a cell, which protects the cell and separates it from other cells. Plants cell have an additional layer outside the cell membrane is called the cell wall.
- Cytoplasm –A jelly-like substance present within the cell membrane is called cytoplasm. Many Living membrane-bound bodies having definite shape and functions within the cytoplasm is called cell organelles.
- Golgi apparatus –Membrane-bound, fluid-filled sacs stacked together are called Golgi apparatus. It is used for packaging, transporting fats, and protein. Lysosomes are created with this.
- Vacuole –Vacuoles are fluid-filled space enclosed by a membrane. Its main function is to store excess water, useful minerals, pigments, and many other substances.
- Lysosomes – They are made up of chemical substances called enzymes and are responsible for digesting cell, a variety of intra and extracellular materials.
- Endoplasmic reticulum –It is an interconnected network of tubules and channel. Its responsibility is to synthesize, storage, and transport of cell products.
- Ribosomes–They are small granular structure found in the cytoplasm. Their major function is protein synthesis.
- Mitochondria– They are double membrane-bound bodies usually spherical or rod-shaped.
- Plastids- They are present in plant cells only. They contain a certain pigment that has a specific role in plant functioning,
- Centrosomes –They are present only in animal cells.
- Nucleus-Nucleus is called as the brain of the cell. It is a spherical body surround by a double membrane called nuclear membrane. Nuclear pores are the pores on the membrane.
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