top of page

Discover the Fascinating World of Cells: An Introduction to the Fundamentals of Life for CBSE Class 9 Students

The fundamental unit of life is an important concept for students studying CBSE Class 9 Science. To help students understand this concept, a PDF download has been developed which explains the structure and function of the fundamental unit of life. The PDF provides information on the different components of cells, their functions, and how they interact with each other to form a living organism. It also explains the importance of cell division and how it helps in maintaining life. With this resource, students can gain a better understanding of the fundamental unit of life and its significance.

Our website offers a range of PDF downloads for CBSE Class 9 Science students. These PDFs provide in-depth information about the fundamental unit of life. With our PDF downloads, students can easily access and study the material at their own pace, and from any location. Our PDFs are designed to be comprehensive and user-friendly, making it easier for students to grasp the fundamentals of this important topic.

CHAPTER 5 FUNDAMENTAL UNIT OF LIFE CELL

Cell

It is a basic, structural and functional unit of life. First discovered by Robert hook in 1665.

Cell theory

  • All living things are composed of cell.

  • Cells are the basic unit of structure and function in living things.

  • New cells are produced from existing cells.

human cells images

Types of organisms on the basis of number of cells

Unicellular organisms

  • Made of one cell

  • Single cell performs all life function (eat, reproduce, rid waste, move

  • Example – amoeba, bacteria

Multicellular organisms

  • Made of more than one cell

  • Specialized cell performs different life function (nerve cells)

  • Example – humans.

Types of cells

Prokaryotic cell

  • Size generally small (1 – 10 µm) 1µm = 10^-6 m

  • Nuclear region: Nucleus is not well defined and known as nucleoids

  • Single chromosome

  • Membrane bound cell organelles absent

Eukaryotic cell

  • Size generally large (5 – 100 µm)

  • Nuclear region: well, define and surrounded by a nuclear membrane

  • More than one chromosome

  • They have membrane bound organelles

prokaryotic cell

Living organisms

Prokaryotes

  • Oldest cell type small and simple

  • lack nucleus

  • lack organelles

  • single cells

Eukaryotes

  • Evolve from prokaryotes, larger and more complex.

  • Contain nucleus

  • Contain organelles

  • Single cells or multicellular

Both have DNA, have ribosomes, have cytoplasm, have plasma membrane.

Eukaryotes

Plant cell

  • Cell wall present

  • Plastid’s present

  • They have large central vacuole

Animal cell

  • Cell wall absent

  • Plastids absent

  • They have small vacuole

plant cell digram
animal cell digram

Nuclease

  • It was discovered by Robert brown.

  • They are also called brain of the cell

Structure

  • Double membrane (nuclear envelope)

Function

nuclease digram

  • Control center of the cell.

  • Store hereditary information (DNA).

  • Makes RNA and protein.

  • Makes ribosomes (nucleolus)

The nucleus contains chromosomes, which are visible as rod shaped structure only when the cell is about to divide. Chromosomes contain information for inheritance of features from parents to next generation in the form of DNA (Deoxyribose nucleic acid) molecules.

Cell wall

Function

Provides support and protection for the cell.

Structure

  • Lies outside the cell membrane

  • Found in plant, algae, fungi and many bacteria.

  • Not found in animal cell.

Plasma membrane or cell membrane

Function

Physical barrier for the cell, separates internal and external environments, selective permeability.

Location

  • Surrounding the cell, outer surface

Cytoplasm

Structure

  • Fluid between cell membrane and organelles.

  • Contain water, salt, organic compounds.

Function

  • Aids in movement

Semi permeable membrane

​Example - plasma membrane

Osmosis

The prosses of movement of water inside or outside the cell through P.M. (S.P.M.)

Diffusion

The prosses of movement of substances inside or outside the cell through P.M. (S.P.M.). Example - oxygen, carbon dioxide, etc.

Plasmolysis

​Plasmolysis is the shrinking of the cytoplasm of a plant cell in response to diffusion of water out of the cell and into a high salt concentration solution. During plasmolysis, the cell membrane pulls plasmolysis, the cell membrane pulls away from the cell wall.

Some important cell organelles

  1. Endoplasmic reticulum

  2. Golgi apparatus

  3. Lysosomes

  4. Mitochondria

  5. Plastids

  6. Vacuoles

Endoplasmic reticulum

The endoplasmic reticulum (ER) is a large network of membrane bound tubes and sheets. It looks long tubular or oblong bags (vesicles).

There are two types of ER, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER).

The ribosomes, which are present in all active cells, are the sites of protein manufacture.

  • The SER helps in the manufacture of fat molecules or lipids.

  • Some of these proteins and lipids help in building the cell membrane. This process is known as membrane biogenesis.

  • Some other proteins and lipids function as enzymes and hormones.

endoplasmic reticulum digram

Golgi apparatus

First described by Camillo Golgi.

Structure

  • It consists of a system of membrane bound vesicles arranged approximately parallel to each other in stacks called cisterns.

  • These membranes often have connection with the membrane of ER.

Function

  • The material synthesized near the ER is packaged and dispatched to various targets inside and outside the cell through the Golgi apparatus.

  • Its function includes the storage, modification and packaging of product in vesicles.

  • In some cases, complex sugars may be made from simple sugar in the Golgi apparatus.

  • The Golgi apparatus is also involved in the formation of lysosomes.

Lysosomes

  • Structurally, lysosomes are membrane – bound sacs filled with digestive enzymes. These enzymes are made by RER.

  • Lysosomes are a kind of waste disposal system of cell. Lysosomes help to keep the cell clean by digesting any foreign material as well as worn out cell organelles.

  • Lysosomes break them up as they contain powerful digestive enzymes.

  • When the cell gets damaged, lysosomes may burst and the enzymes digest their own cell. Therefore, lysosomes are also known as suicide bags of a cell.

Mitochondria

Structure

  • Mitochondria have two membranes covering instead of just one.

  • The outer membrane is very porous while the inner membrane is deeply folded.

  • Mitochondria are known as the power house of the cell.

Function

  • The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine triphosphate) molecules. ATP is known as the energy currency of the cell.

  • Mitochondria are strange organelles in the sense that they have their own DNA and ribosomes. Therefore, mitochondria are able to make some of their proteins.

mitochondria

Plastids

​They are present only in plant cells. There are two types of plastids chromoplast (colored plastid) and leucoplasts (white or colored plastid).

Chloroplast

  • Plastids containing the pigment chlorophyll are known as chloroplasts.

  • Chloroplasts are important for photosynthesis in plant.

  • The internal organization of the plastids consists of numerous membrane layers embedded in a material called the stroma.

  • Like the mitochondria, plastids also have their own DNA and ribosomes.

Vacuoles

Structure

  • Vacuoles are storage sacs for solid or liquid contents.

  • Vacuoles are small sized in animal cell while plant cells have large vacuoles.

Function

  • The plant cell vacuoles are full of cell sap and provide turgidity and rigidity to the cell.

  • It stores important substance like amino acids, sugars, various organic acid and some protein.

  • Some unicellular organisms have food vacuoles, while some other have specialized vacuoles to expel excess water and waste.

PDF DOWNLOAD FREE 

Sing Up/Login Required

You have to sign up to download the PDF. You will get the PDF of the full chapter.

Click Here

Direct Download

To download the PDF you just have to click on the button. You will get the PDF of HALF chapter.

Click Here
bottom of page