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CBSE Class 9 Notes Science Chapter 5 – The Fundamental Unit of Life

Last Updated : 10 May, 2023
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Notes of The Fundamental Unit Of Life of Class 9 Chapter 5: The fundamental unit of life is the cell. All living organisms are made up of fundamental building blocks which form the fundamental unit of life called cells. Whether it is a plant, animal, or microorganism; these basic units define all their structural and functional abilities. 


A cell is the underlying and essential unit of life. The investigation of cells from their essential construction to the elements of each and every cell organelle is called Cell Biology. Robert Hooke was the primary Biologist who found cells. All life forms are composed of cells. They might be comprised of a solitary cell (unicellular), or numerous cells (multicellular).

History of Cell

The prologue to cell started back in the year 1655 when a progressive perception was made by an English researcher Robert Hooke. This perception made him gigantic to the point that it proceeded to change the essential natural hypothesis and examination until the end of time. Anyway, how was the cell found?

Robert Hooke was inspecting a dried segment of the stopper tree utilizing an unrefined light magnifying lens. In this examination, he noticed various little chambers named the cells. From there on, over the course of the following 175 years, a few sorts of exploration were made which prompted the development of the cell hypothesis that we know today.

Cell Theory

The cell theory hypothesis expresses that the cell is the key primary and useful unit of living matter. In 1839 German physiologist Theodor Schwann and German botanist, Matthias Schleiden declared that cells are the “rudimentary particles of creatures” in the two plants and creatures and perceived that a few organic entities are unicellular and others multicellular. This hypothesis denoted an extraordinarily reasonable development in science and brought about restored regard for the living cycles that happen in cells.

Types of Cells

There are two cell types: prokaryotes and eukaryotes. Prokaryotic cells are normally single-celled and more modest than eukaryotic cells. Eukaryotic cells are normally tracked down in multicellular creatures, yet there are a few single-celled eukaryotes.

Prokaryotic Cell 

Eukaryotic Cell

The nucleus and nucleolus are absent Nucleus and nucleolus are present 
A single chromosome is present Multiple chromosomes are present 
Multiple chromosomes are present  Mitotic or meiotic cell division occurs 
Membrane-bound organelles can be seen  Membrane-bound organelles can be seen

Difference between Plant cells and animal cells

Plant cell 

Animal cell 

A rigid cell wall is present The cell wall is absent 
Larger size than animal cell   Smaller size than plant cell 
Plastids are present   Plastids are absent 
Centrosomes and centrioles are absent  Centrosomes and centrioles are present 
Vacuoles are large and permanent Vacuoles are small and temporary

Cell Structure

The cell structure includes individual parts with explicit capabilities fundamental for complete life’s cycles. These parts incorporate the cell wall, cytoplasm, core, and cell organelles. Peruse on to investigate more bits of knowledge on cell construction and capability.



Cell Membrane

  • The cell membrane upholds and safeguards the cell. It controls the development of substances all through the cells. It isolates the cell from the outer climate. The cell film is available in every one of the cells.
  • The cell membrane is the external covering of a cell inside which any remaining organelles, like the cytoplasm and core, are encased. It is additionally alluded to as the plasma layer.
  • By structure, it is a permeable film (with pores) that allows the development of specific substances through the cell. Other than this, the cell layer likewise shields the cell part from harm and spillage.
  • It frames the wall-like construction between two cells, as well as between the cell and its environmental factors.
  • Plants are stationary, so their cell structures are very much adjusted to safeguard them from outer elements. The cell wall assists with building up this capability.

Cell Wall

  • The cell wall is the most unmistakable piece of the plant’s cell structure. It comprises cellulose, hemicellulose, and gelatin.
  • The cell wall is available only in plant cells. It safeguards the plasma film and other cell parts. The cell wall is likewise the peripheral layer of plant cells.
  • It is an inflexible and firm design encompassing the cell film.
  • It gives shape and backing to the cells and safeguards them from mechanical shocks and wounds.


  • The cytoplasm is a thick, clear, jam-like substance present inside the cell layer.
  • The vast majority of the synthetic responses inside a cell occur in this cytoplasm.
  • The cell organelles, for example, the endoplasmic reticulum, vacuoles, mitochondria, and ribosomes, are suspended in this cytoplasm.


  • The core contains the inherited material of the cell, the DNA.
  • It conveys messages to the cells to develop, mature, gap, and bite the dust.
  • The core is encircled by the atomic envelope that isolates the DNA from the remainder of the cell.
  • The core safeguards the DNA and is a fundamental part of a plant’s cell structure.

Cell organelles

The cytoplasm of a cell carries different types of cell organelles that play an important function in the proper functioning of a cell. The different cell organelles are:

  • Nucleolus- The nucleolus is the site of the ribosome combination. Additionally, it is associated with controlling cell exercises and cell proliferation.
  • Nuclear layer- The nuclear layer safeguards the core by shaping a limit between the core and other cell organelles.
  • Chromosomes- Chromosomes assume a vital part in deciding the sex of a person. Every human cell contains 23 sets of chromosomes.
  • Endoplasmic Reticulum- The endoplasmic reticulum is engaged with the transportation of substances all through the cell. It assumes an essential part in the digestion of carbs, the union of lipids, steroids, and proteins.
  • Golgi Bodies- Golgi bodies are known as the cell’s mailing station, as it is associated with the transportation of materials inside the cell.
  • Ribosome- Ribosomes are the protein synthesizers of the cell.
  • Mitochondria- The mitochondrion is designated as “the force to be reckoned with in the cell. It is called so on the grounds that it produces ATP—the cell’s energy cash.
  • Lysosomes- Lysosomes safeguard the cell by immersing the unfamiliar bodies entering the cell and helping in cell recharging. Consequently, they are known as the cell’s self-destruction sacks.
  • Chloroplast- Chloroplasts are the essential organelles for photosynthesis. It contains a shade called chlorophyll.
  • Vacuoles- Vacuoles store food, water, and other waste materials in the cell.

Functions of a Cell

  • Structure and Support-Cells provide the structural basis of all organisms.
  • Growth-Cells are responsible for the growth of the organism.
  • Transport-Cells import the nutrients that are used in the different chemical processes which take place inside them. As a result of these processes, a waste product is produced. Cells then work to get rid of this waste. In this manner, small molecules such as oxygen, carbon dioxide, and ethanol pass through the cell membrane by diffusion. This method is known as passive transport. On the other hand, larger molecules, like proteins and polysaccharides, go in and out of the cell via active transport.
  • Energy Production-Organisms need the energy to perform different chemical reactions. In plants, the energy comes from the process of photosynthesis, while in animals the energy comes via respiration.
  • Metabolism-Cell is responsible for metabolism, including all the chemical reactions that take place inside an organism to keep it alive.
  • Reproduction-A cell helps in reproduction through the processes of mitosis (in more evolved organisms) and meiosis.

FAQs on Cell

Question 1: What is a cell?


The cell is the basic unit of life and it mainly consists of the nucleus, cytoplasm, and cell membrane.

Question 2: What is the study/research of cells called?


The study of cells or cell biology is called Cytology.

Question 3: What are the important cell organelles?


Ribosomes, Endoplasmic reticulum, Golgi apparatus, Chloroplasts, and Mitochondria are some of the organelles of the cell.

Question 4:  What are the types of cells?


There are two cell types: prokaryotes and eukaryotes.

Question 5: What is plasma membrane/cell membrane?


The plasma membrane or cell membrane is the membrane found in all cells that separate the interior of the cell from the outside environment.

Question 6: Name the organelles which show the analogy written as under


  • A powerhouse of the cell—— Mitochondria
  • Packaging and dispatching unit of the cell—— Golgi Body
  • Control room of the cell—— Nucleus
  • Suicidal/Digestive bag of the cell—— Lysosome
  • Transporting channels of the cell—— Endoplasmic Reticulum
  • Kitchen of the cell—— Chloroplast
  • Storage sacs of the cell—— Vacuole

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