Cell: An Introduction
Do you know the egg of an ostrich is an example of the largest cell? And the cells which are present in our body are so small that can't be seen by the naked eye. What is the meaning of a cell? How these microscopic cells comprise our whole body. Do you know the types of cells and their functions? Do you know the different components of cells? Do you know the difference between plant cells and animal cells? Do you know bacterial cells are prokaryotic cells whereas human cells are eukaryotic cells? What is the difference between eukaryotic and prokaryotic cells? You will get answers of all these questions after reading this article. Human body cell structure is also explained below.
Cell Definition
The cell is the smallest functional and structural unit of all living organisms. All organisms are made of cells, a group of cells makes tissues, and a group of tissues makes organs.
What are the Types of Cells?
There are mainly two types of cells based on structure.
Eukaryotic cell
Prokaryotic Cells
These cells are found in lower or primitive organisms. These cells do not have a nucleus and the genetic material of these cells is suspended freely in the cytoplasm in a region called the nucleoid. These types of cells reproduce by asexual methods. The cell size is generally 0.1-0.5 micrometres. The hereditary material may be either DNA or RNA.
Eukaryotic Cells
These types of cells have true nuclei, and their size is between 10 and 100 micrometres. These cells can reproduce by both asexual and sexual methods. Eukaryotic cells involve animal cells, plant cells, fungi, and protists.
Structure of a Cell
The basic structure of a cell contains cell membranes, nuclei, cytoplasm, and various cell organelles.
All cell organelles are present in the cytoplasm of a cell.
Cytoplasm semifluid substance present between cell membrane and nucleus.
Different Parts of Cell and Functions
The following different parts of the cell and human cell function are explained below:
Nucleus - It is the main cell organelle and is also known as the master of the cell. It contains genetic material. The nuclear membrane is the outermost layer of the nucleus. Nuclear pores are present on the nuclear membrane to allow the movement of particles and molecules inside and outside of the cell.
Endoplasmic reticulum - Endoplasmic reticulum is also known as the palate particle in the name of discovery. It consists of membranes present inside the membrane.
It is of two types: Rough endoplasmic reticulum and smooth endoplasmic reticulum.
Rough endoplasmic reticulum - These are rough in appearance due to the presence of ribosomes on the surface of the endoplasmic reticulum. Rough endoplasmic reticulum synthesises protein and smooth endoplasmic reticulum is known as smooth because of an absence of ribosomes, which synthesise lipids, steroids, and other substances.
Mitochondria - These are sausage-shaped structures present in the cytoplasm. And synthesis of ATP molecules. It is also known as the powerhouse of the cell. It is a double membrane structure, an inner and outer membrane. Cristae are the fold of the inner membrane to increase the surface area. Matrix is the space present inside the inner membrane of mitochondria containing various types of enzymes and RNA.
Golgi Apparatus - These are the flattened and stacked pieces called cisternae and perform the functions of modifying, and packaging. It has two faces cis and trans. Various cisternae are held together by a matrix.
Lysosomes - These are membrane-bound organelles that contain a variety of enzymes that break biological polymers.
Human Cell Functions
The basic functions of the cell are given below:
Provide structural support.
Allow movement of substances inside and outside the cell.
Helps in reproduction through the process of meiosis and mitosis.
Cells contain mitochondria which help in energy production.
Help in the growth of organisms.
Cells of the Human Body
There are various types of cells in the human body depending on the structure and function they perform. Some examples of cells are provided below:
Blood Cells - There are different types of blood cells such as lymphocytes, leukocytes, and thrombocytes. Blood cells are produced from bone marrow.
Fat Cells - These cells contain or store fat droplets in the form of triglycerides. These are also known as adipocytes.
Nerve Cells - These cells comprise the whole nervous system. These are the basic units of the nervous system. Helps in the transmission of signals to and from the central nervous system. Contain a nucleus, cytoplasm, and some cell organelles.
Endothelial Cells - These cells form the innermost lining of the blood vessels. These cells make the new blood vessels.
Important Questions
1. Who discovered the cell?
Ans: The first dead cell was discovered by Robert Hooke in 1665 in the cork of bark. And first, the live cell was discovered by Leeuwenhoek.
2. What is the function cell?
Ans: The different functions of the cell are to provide structural support, convert food into energy, and also provide energy to various cells of the body. Cells also perform specialised functions for body cells.
3. What are cells made of?
Ans: Cells are made of various components: organic molecules, inorganic molecules, and water.
Interesting Facts
The ovum is the largest cell of the female human body.
A mature red blood cell does not have any nucleus.
The size of the longest neuron may be about 1m.
Plant cell does not rupture when placed over water.
Whenever there is damage to any organ of a pregnant woman, the foetus will send stem cells to regenerate the damaged organ.
Key Features
In this article, we studied cells, their types, and different examples of cells.
The cell is the structural and functional unit of living organisms.
There are mainly two types of cells: eukaryotic and prokaryotic.
Prokaryotes are the primitive type of cells whereas eukaryotes are the modern type of cells.
Important components of the cell are the plasma membrane, lysosomes, endoplasmic reticulum, mitochondria, etc.
The nucleus is known as the master of the cell.
Practice Questions
1. What is a cell mother?
2. Where do cells come from?
3. How many cells are in the human body?
4. Which organ is known as the mother of all cells?
5. Explain the human body cell structure.
6. What are different cell parts and functions?
FAQs on Parts of the Cell
1. Write the difference between plant cells and animal cells.
There are many differences between plant and animal cells. Some of the differences are given below:
Plant Cell | Animal Cell |
Plant cells are square or rectangular. | These are irregular in shape. |
The cell wall is present in a plant cell. | The cell wall is absent in an animal cell. |
Centrosomes are absent in plant cells. | These cells contain centrosomes. |
A very large vacuole is present in the centre of the cell and occupies most of the space of the cell. | Small and large numbers of vacuoles are present in an animal cell. |
The mode of nutrition in the plant is autotrophic. | In animal cell, mode of nutrition is heterotrophic. |
Cilla is absent in plant cells because they can't move from one place to another place. | Cilia and flagella are present in animal cells for mobility. |
Plastids are present in plant cells. | Animal cells do not contain plastids. |
2. What is cell theory?
Cell theory was given by shielding and Schwann and later extended by Rudolf Virchow in 1955. It states that:
All organisms are made of cells.
The cell is the basic and structural unit of life.
All new cells originate from pre-existing cells.
Cell theory is only valid for all living cells. Cell theory is not valid for viruses or lichens because viruses are not complete living cells, and lichens are symbiotic associations between algae and fungus.
3. Write various characteristics of the cell.
The following are the characteristics of a cell:
Each cell has one nucleus and various organelles.
The cell provides structural support and performs various types of functions.
The nucleus is the main part of the cell that controls various activities of the cell and also stores the genetic information of the cell.
Lysozyme is one of the organelles of the cell that digest unwanted substances in the cell.
Mitochondria is a double membrane-bound structure that acts as the powerhouse of the cell.
