Notes for NCERT Class 8 Science Chapter : Cell- Structural and Functional unit of Life |Reference Notes |

This chapter is part of NCERT book Science Class 8. If you are finding The Notes for ‘Cell’ Chapter; you have visited the right place to get the Reference Notes of Ch- Cell of NCERT Science book class 8. In this blog, we have written all the information about ‘Cell- structural and Functional Unit of Life’. This Notes is Full of Information as per Chapters and we have also written some basic or more information about ‘Human Cell’. We have also discussed your Doubt which was created when you were learning in Chapter. So, in this way It will become easy for you to learn and revise this ‘Cell’ Chapter. 

This Notes of ‘Cell’ Chapter helps you the most to read or revise your ‘Cell’ Chapter in reference and also takes only some time and Efforts to revise compared to reading the NCERT Book. Don’t think that, some information is not as per your NCERT book as because all the information and key points which are given in your Book are written and shot and referenced. Let’s get started to Explore your Class 8 NCERT chapter ‘Cell- Structural and Functional Unit of Life' in depth. Kindly, scroll down to get Notes of this chapter. 

Table of Content 

• How is Cell a basic unit of Living Organisms ? 

• Discovery of Cell ? 

• Types of Cell- by number and by Structure? 

• How to view a Cell in Microscope?

• View of a Animal Cell ? 

• Organelles of Cell Description? 

• How Cell Division Happens ? 

• Frequently Asked Questions ( FQA) 

How is Cell basic unit of Living Organisms? 

We know that any substance or thing consists of Molecules and Molecules is a group of Atoms. If the substance is non-living ; then, its basic unit is Atoms and It is the part of Physic Science. But, if the substance or Thing is living organisms; then, ‘Cell’ is a basic unit of Living Organism. This, part of living Science. So, in this Chapter we will describe the Basic unit of Living Organisms and part of living Science called ‘Cell’. 

Above para, we have learned that ‘Cell’ is the basic or smallest units of Living Organisms like- Human beings, Animal and Plants. Now, we will learned that How ‘Cell’ or smallest units becomes an organism? So, The Group of Cell is called tissue ; the Group of Tissue called Organs like - kidney, heart, Lungs etc.; The Group of Organs are called Organs System and Then, an Organ System creates Living Organisms. 

Who discovered Cell? 

The first Scientist who had discovered The ‘Cell’ was Robert Hook in 1665 AD. He had observed the wooden part of the Plant which had some small-scale units. So, he named it ‘Cell’ because it was likely a Prison and In England , Prison is also known as ‘Cell’. 

In 1670 AD, Antonie Van Leaunwooke observed ‘Cell’ in Animals and in 1838 AD, Mattias Jakod Schleden introduced a theory that “A Cell is the basic Unit of Plant”. But, In 1842 AD, Theodor Schwann declared finally that “A Cell is a Basic unit of all living Organism”. So, In this way, we have understood that A Cell is found in all living Organisms such as- human beings, Animals and Plants. Schleiden declared that a cell is only found in a Plants which was wrong ,as because A Cell is found in all living Organisms declared by Theodor Schwann 1842 AD. 

Types of Cell - By Number & Structure

 

By Number- You may have heard of Organisms such as - Amoeba, Paramecium, Bacteria, yeast etc. is also known as unicellular Organism. But Why? Because The number of ‘Cells’ in living Organisms is not the same at all. Some Living Organisms made of Single Cell or only One-Cell which are Called Unicellular or Microorganisms (As because, they can’t be seen by naked eyes. We can see Unicellular organisms using Microscope that’s why they are also called Microorganisms). The Examples of Unicellular or Microorganisms are bacteria, Amoeba, Paramecium etc. You may also have heard that human Beings are also known as Multicellular ; because A Organism made up of many Cells is called Multicellular such as - Human Beings, Animals, Plants. 

By Structure- A Cell’s Structure is not the same in all living Organisms. By Structure there are two types of Cell found in Living Organisms. They are- 

1. Prokaryotic Cell- A cell of an organism whose Nucleus is not bound by membrane and hereditary Material Called Genes (Group of DNA) is present in Cytoplasm. So, it is called a Prokaryotic Cell. Organisms which have Prokaryotic Cells are- Blue- Green Algae, bacteria, Nostoc etc. 

2. Eukaryotic Cell- A cell of an organism whose Nucleus is bounded by its Membrane and Hereditary Material called Genes is enclosed with Nucleus or present in Nucleus are called Eukaryotic Cell. Organisms having Eukaryotic Cells are - Human Beings, Animals and Plants. 

How to View a Cell using a Microscope? 

The Steps are given below to view a Cell of an Organisms using an Instrument called Microscope. 

1. Take a Slice of Onion because A Onion is also has ‘Cell’. 

2. Prepare a Slide, using some Dyes such as methylene Blue, Safranin or crystal Violet. 

3. Place it on the Glass Slide of Microscope. Then, zoom or using Objective Lens 

4. On the top of the Microscope, there would be an ocular or Eyepiece Lens, placing your eye to observe a ‘Cell’ of Onion. 

View of a Animal Cell 

The diagram given below is a view of Animal Cell. The living part of Cell or Substance which are present in Cell are called Organelles. Like - Nucleus, Lysosome, Endoplasmic Reticulum etc. We have also described all the organelles of Animals Cell. 

Cell Membrane - A cell is surrounded by a thin covering called the Cell Membrane / Plasma Membrane. It is responsible for giving shape to cells. 

Cell Wall- only present in Plants. It is an extraordinary layer above the cell Membrane.It provides skeleton protection to the Cells as plants do not have any skeleton support like human haves. It contains a large amount of Cellulose. 

Cytoplasm- is a jelly-like Fluid Found within the Cell Membrane. All organelles ( living part of a Cell is known as Organelles). Organelles under cytoplasm are- 

1. Nucleus

2. Golgi Apparatus

3. Mitochondrion

4. Vacuoles

5. Lysosome

6. Endoplasmic Reticulum

7. Centrosomes

8. Plastids 

Nucleus- It is referred to a brain of the Cell because It controls all organelles present in Cell. The Membrane of the Nucleus is known as Nuclear Membrane. 

Protoplasm inside the Nucleus is called Nucleoplasma.The Nucleoplasm contains thread-like substances called Chromosomes. The Chromosomes carry the hereditary Material called Genes which is responsible for transferring Parent’s Characteristics to Baby/ Offsprings. A non- Membrane spherical Structure is present in Nucleus is called Nucleolus. 

Golgi Apparatus / Bodies- It is made up of Sac-like structures called vesicles, which are responsible for the secretion of chemical substances as enzymes, hormones and proteins. 

Mitochondrion- is a rod-like or spherical Structure. This organelles oxides food to provide energy and thus, it is also known as the Powerhouse of the Cells. 

Vacuoles are sac-like structures enclosed by a membrane called tonoplast. They store water, food and waste substances. 

Lysosome- contains chemical substances called enzymes for digesting Cell Organelles. It is also known as Suicide Bag of Cell as they capability of bursting and destroying cell’s Organelles during Emergency. 

Endoplasmic Reticulum- This organelles is responsible for secretion of Fat and proteins. For Secretion of Fast and Proteins,it is divided in two part- 

1. Smooth ER- Responsible for Fat Secretions. 

2. Rough ER- Responsible for Protein Secretion. It also consists of Ribosome to strate it. 

Centrosomes- It is an Organelles, which is responsible for the Division of Cell. 

Plastids- This organelles is present only in Plant’s Cell. Plastids contain certains Pigments to Grow Plant, giving Colour, storing food etc. Certain Pigments are- 

1. Chloroplasts- Contains Green Pigments called Chlorophyll which helps plants make Food. 

2. Chromoplast- It gives Colour to Flower and food. 

3. Leucoplast- These are colorless and Store food in the form of carbohydrates, proteins and fat. 

How Cell Division Happens? 

When the Cell grows to a certain size; it starts dividing two or more than two cells. The new cell which would be formed is called daughter Cell and are exact copies of the Parent’s Cell. 

Chromosomes help to divide a cell into two cells. First, Nucleus will divide because it has the hereditary Material called Genes, for transferring characteristics from Parent’s Cell into Daughter’s Cell.  

Frequently Asked Questions (FAQ) 

1. Why is Nucleus called the Brain of a Cell? 

Nucleus is called the Brain of a Cell because it controls all the organelles of Cell and also carry the Hereditary Material called Genes. 

2. What is Genes? 

Group of DNA is called Genes. situated in the Nucleus of a Cell. 

3.  Why is the Cell Wall present in plants? 

Cell Wall present in plants Because, plants don't have skeleton support like humans have. The Cell Wall gives skeleton support to the Plant. 

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