What is a Cell? Discovery of Cell, Characteristics of Typical Cell

Have you ever wondered what we are made of? How does our body function as this tireless machine from the time we are born till the time we die? You must have.
The interesting thing is that a small insect or even smaller Amoeba is performing the same basic activities that a huge organism like us humans is performing. This is because we have the same functional units in our bodies which are the cells. Yes! The superheroes- cells
Cells are the basic structural and functional unit of life. According to Cell theory, each and every living being is composed of one or more kinds of cells. Come let us learn some more about cells.

Table of contents

• Introduction to cell
• Discovery of cell
• Types of organisms based on the number of cells
• Division of labour
• Characteristics of typical cell
• Practice problems
• FAQs

Introduction to cell

The word ‘cell’ originates from the Latin word ‘cellula’ which means ‘hollow spaces or tiny compartments’. The structural and functional unit of life is called a cell. It contains certain structures inside to support and conduct basic life processes and performs a variety of functions in a living being. Cells are able to multiply and divide and constitute the entire body of a living organism. Hence, they are considered as the building blocks of our body.The study of structure, function, multiplication and behaviour of cells is called Cell biology or Cytology.

Discovery of Cell

The history of scientific discoveries related to cells continued for more than a few centuries. The scientists who discovered various features and structural components of a cell are listed below along with their work.

Robert Hooke (1665)

He was the first person to observe dead cork cells. The cells were so named because they reminded him of cells in a monastery. The cells of the cork resembled a honeycomb structure. He wrote the book Micrographia in which he mentioned details of his observation through the lens. 

Anton Von Leeuwenhoek (1674)

He was the first to observe living cells. He saw bacteria and protozoa under his microscope lens and named those as ‘animalcules’. He scraped out the plaque between his teeth and observed it under the microscope.

Robert Brown (1831)

He was the first to discover a plant nucleus.The term ‘nucleus’ was coined by him.

Matthias Schleiden (1838)

Being a German botanist, Schleiden examined a large number of plants. He observed that plants are composed of different types of cells which form tissues in them.

Theodore Schwann (1839)

Being a British zoologist, Schwann studied different types of animal cells. He reported that cells possess a thin outer layer which is nowadays referred to as the Plasma membrane. He concluded that the plant cells are unique due to the presence of a cell wall. Finally he put forward his theory that stated that bodies of animals and plants are composed of cells and their products.

Rudolf Virchow (1855)

He added on to the cell theory given by Schleiden and Schwann. He was the first one to explain that cells are formed from the pre-existing cells (Omnis cellula-e-cellula).

Types of organisms based on the number of cells

Organisms can be classified into two types on the basis of cell number present in their body:

• Unicellular organisms
• Multicellular organisms

Unicellular organisms

The body of such organisms is composed of a single cell. The single cell can perform all basic life processes. Hence, it can be called a complete functional unit which is capable of undergoing respiration, excretion, digestion, interactions with the environment, etc. Hence, each unicellular organism is mostly capable of independent existence.

Multicellular organisms

The bodies of such organisms are made up of more than one cell.The number of cells in multicellular organisms usually correlates with the size of the organism. Specialised cells are grouped together into tissues, tissues into organs and organs into organ systems which perform different physiological functions. These cells then interact with one another to maintain life.

Division of labour

Division of labour is the term used to describe the distribution of functions among different parts of the body or a cell to ensure the conduction of life processes. This aids in the survival of an individual.

In a living being, this can be seen in different tissues of an organ as well as in different organelles of a cell. Thus it can be observed in both unicellular and multicellular organisms.

In Unicellular organisms 

Since unicellular organisms are made up of a single cell, the distribution of work for maintaining life occurs at the cellular level. Each cell organelle performs a specific function to ensure the survival of the cell.The control of these functions is done by certain signalling machinery and genetic material. 

In Multicellular organisms

In multicellular organisms generally billions or trillions of cells are present. All the cells that perform similar functions are categorised as a tissue. Tissues of cells performing similar functions are grouped together to form organs. The organs involved to achieve a particular function form the organ system. Each and every organ system is involved in performing specific physiological functions.

There are many functions that a living body performs, all of which are possible because of the distribution of work among different organ systems.

Characteristics of a Typical Cell

Cells are the structural units of life as they comprise the basic structural entity of a living organism. A cell contains various smaller entities inside it, known as cell organelles, which perform various cellular activities for the survival of the cell. The life processes happening inside an organism are ultimately maintained by its constituent cells. Hence, the cell is also called the functional unit of life.
Every living cell contains genetic material (in the form of nucleic acids) which acts as the most essential part. This is because the genetic material is the hereditary material that gets transferred to the daughter cells after cell division. Cells maintain homeostasis to keep the organism alive.
Some cells can remain functional even after they die such as ‘xylem vessels’ in plants and ‘horny cells’ in animals. The activities of any cell can be regulated in two ways-

1. By the flow of genetic information
2. By the flow of hormonal information
 

Practice problems of Cell

1. Which of the following is not a unicellular organism?

a) Amoeba
b) Yeast
c) Bacteria
d) Kelps

Solution: Amoeba, yeast and bacteria are unicellular organisms made up of a single cell but kelps are multicellular algae composed of millions of cells.
Thus, the correct option is d.

2. Find the correct pair.

a. Robert Brown - Stated that all cells arise from pre-existing cells.
b. Theodore Schwann - Gave the theory that both plants and animals are made up of cells.
c. Rudolf Virchow - First discovered plant nucleus.
d. Anton von Leeuwenhoek - First discovered dead cork cells

Solution: Theodore schwann  stated that bodies of animals and plants are composed of cells and their products.
Robert Brown first discovered the plant nucleus.
Rudolf Virchow stated that all cells arise from pre-existing cells.
Anton von Leeuwenhoek was the first scientist to observe living cells under the microscope. Robert Hooke first discovered cells by observing dead cork cells under a microscope.
Thus, the correct answer is b.

FAQs of Cell

Question 1. What is the composition of a typical cell?

Answer. All cells are primarily made up of organic molecules such as nucleic acids, proteins, carbohydrates, and lipids. Cells contain certain structures inside to support and conduct basic life processes and perform a variety of functions in a living being.

Question 2. How does a cell function for the survival of organisms?

Answer. Cells are the structural and functional units of life. They derive energy from food and carry out specialised functions. Cells also contain the body's hereditary material DNA. Cells have many cell organelles, each with a different function which makes the cells capable of performing basic life processes such as digestion of food, respiration, excretion, etc. In unicellular organisms, a single cell carries out all these functions whereas in multicellular organisms the cells are grouped into specialised tissues which perform specific functions for the organism.

Question 3. Write down 5 characteristics of a typical cell.

Answer. characteristics of a cell are following-

• Cells are a structural unit of life as they comprise the basic structural entity of a living organism.
• A cell contains various smaller entities inside it, known as cell organelles, which perform various cellular activities for the survival of the cell. 
• The life processes happening inside an organism are ultimately maintained by its constituent cells. Hence, the cell is also called the functional unit of life.
• Every living cell contains genetic material (in the form of nucleic acids) which acts as the most essential part. This is because the genetic material is the hereditary material that gets transferred to the daughter cells after cell division.
• Cells maintain homeostasis to keep the organism alive.

Question 4. What do you understand by division of labour in a cell?

Answer: Division of labour is the term used to describe the distribution of functions among different parts of the body or a cell to ensure the conduction of life processes. This aids in the survival of an individual.

In a living being, it can be seen in different tissues of an organ as well as in different organelles of a cell. Thus it can be observed in both unicellular and multicellular organisms.

Question 5. Who was the first person to discover cells?

Answer: Robert Hooke was the first person to observe dead cork cells. The cells were so named because they reminded him of cells in a monastery. The cells of the cork resembled a honeycomb structure. 

Question 6. What is cytology?

Answer: The study of structure, function, multiplication and behaviour of cells is called as Cell biology or Cytology.

Related Topics to What is a Cell in Biology

• Differences between Prokaryotic and Eukaryotic Cell Difference
• Cell
• Eukaryotic cells 
• Mitochondria
• Cell Envelopes and Cell Membranes
• Animal Cell
• Plant Cell
• Prokaryotic Cells
• Types of Cells
• Endomembrane System

NCERT Class 11 Biology Chapters