What is a cell?

cell_cartoonA cell is a basic unit of life, everyone knows that. It is the smallest particle our very body is made up of. Each cell fulfills a specific purpose. Its structure is out of shape in animals and humans. In plants, cells are rigid and are commonly rectangular or are of similar shape.

What is the Protoplasm?

The Cytoplasm, the Plasma membrane and the Nucleus of the cell are altogether known as the protoplasm of a cell.

The Organelles found in a Cell:

Plasma Membrane:

This is an animal cell. The outside purple layer in the figure is called the plasma membrane which is semi permeable to specific substances such as food cell which has been cut into small cells by digestive system. It lets in small particles to strengthen it for chemical reactions. It basically is the protective barrier of the cell.


The inner part contains a gelatin substance consisting of mainly water and other minerals which create the cytoplasm. Inside the cytoplasm many chemical reactions occur which helps in everyday activities. Inside the cytoplasm other structures are also found.

Mitochondria and ATP:

The mitochondrion (plural – mitochondria) is an oval shaped structure which is mitochondriafigure1.jpginvolved in cell respiration.

Its structure contains outer membrane, inner membrane, Cristae, and the matrix as in figure 1.

It releases energy from food molecules and stores it in Adenosine Triphosphate (ATP).

It is a coenzyme. Think of it as storage. The energy it stores is taken from it when need by the cell by breaking it down.

 The Vacuole and Centrioles:

The animal cell also contains small bits of vacuole compared to large vacuoles found in plants. These don’t last long and only contains water and food substances.

A pair of small structures found in cell is called centrioles which bring about cell division.

The Nucleus:

The next thing found in a cell is the nucleus. It is the brain of the cell which guides the cell and commands it to do different activities. It includes three main structures. The outer layer is covered with the membrane which is called the nuclear envelop which forms a barrier between the cytoplasm and the contents of the nucleus. Inside its membrane is found the chromatin which contains hereditary information. The chromatin is a thread like structure which is made up of protein and deoxyribonucleic acid (DNA). It has hereditary materials inherited from our parents.


Ch1C1This is a detailed structure of the nucleus.

The nucleus of a cell also contains the nucleolus which builds up protein.

All the structures found in the nucleus including the nuclear envelop forms the nucleoplasm (the protoplasm of the nucleus).

This completes the study of all the main structures found in the animal cell.

Plant cells:

plant_cellThe shape of the plant cells are different compared to the animal cells. The plant cells also have a few additional organelles not found in animal cells as animals and humans do not need such organelles for survival.

The plant cells have large vacuoles compared to the small vacuoles found in animal cells. The vacuoles are filled with cell sap containing dissolved substances including water, amino acids, minerals etcetera. The vacuoles are enclosed with the membrane called the tonoplast.

The membrane of the plant cell is further protected by the rigid Cell Wall. The cell wall is made of cellulose. It protects the cell from injury. This structure is also not found in animal cells.

The chloroplast of the cell combines Carbon dioxide (Co2) and oxygen as well as absorb solar power to form sugar. In other words the chloroplast helps plants produce its own food.

The centrioles are such organelles which are missing in most of the plant cells.

These are the main organelles found in a plant cell.

Tissues, Organs and Organ systems:

A cell does not carry out all the heavy duty work all by itself. As we all know that cells forms a group with other cells which serve the same purpose. These groups are known as tissues.

Examples of tissues in animals and humans are:

  • Nervous Tissue
  • Epithelial Tissue                                                                                              ec19dfb80ab59a5fc080b354fc937d78
  • Adipose Tissue
  • Muscle Tissue

Examples of tissues in plants are:

  • Vascular Tissue
  • Epidermal Tissue
  • Ground Tissue
  • Meristematic Tissue

Tissues further join together with another tissue with the same nature and purpose and form a group called the organ.

The most common examples of organs in animals are:

  • Stomach                                                                                             h9991275_001
  • Liver
  • Heart
  • Skin
  • Pancreas and many more.

Example of plant organs:

  • Leaves
  • Stems
  • Flower
  • Root

The organs are further grouped together into organ systems. Each organ system has organs working together to achieve the same purpose. There are 11 Organ systems in a human body.

Common examples of organ systems in animals are:

  • Digestive system                                                                                           K-digestive-275x267-enIL
  • Respiratory system
  • Excretory system

Examples of plant organ systems are:

  • Shoot system
  • And the Root system


When new cells are produced they may change their function and form new kinds of tissues. This process of change is known as Differentiation.

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