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Living organisms are made up of Cells that are the basic building unit of life. Almost every living organism found in the earth consists of cells. It is the functional, structural and biological unit of life. It's structure is like the structure of a honeycomb. It has a dual existence property which works as a building block and a distinct entity in the structure of living organisms.
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Keyterms: Cells, Living organisms, Cell Theory, Cell Division, Blood cells, Nerve cells, Fat cells
Read More: NCERT Solutions For Class 9 Science The Fundamental Unit of Life
Living Organisms and Cells
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All the living organisms in the world are made up of Cells and are the basic functional, structural and biological units of living organisms. It is the smallest unit of life. The cells were first discovered by the scientist Robert Hooke in 1665.
However, In 1839 two scientists named Matthias Jakob Schleiden and Theodor Schwann, stated that all the living organisms are composed of one or more living cells and are the structural as well as the functional unit of all the living organisms. This is also known as Cell Theory.
The process in which a single cell will produce many cells is known as Cell Division. Different organisms are made up of different types of cells such as unicellular or multicellular. The number of cells in animals and plants varies on the basis of their species whereas the human body alone shows various kinds of cells like blood cells, nerve cells, fat cells and many more.
The size and shapes of the cells depends upon their functions and structure. Some cells have fixed structure and perform a specific function, for example a nerve cell has tree shaped structures. Whereas, Amoeba is a different type of cell which changes its shape form to locomote.
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| Related Topics | ||
|---|---|---|
| Types of White Blood Cells | Centriole | Cytoskeleton |
| Cell Cycle and Cell Division | Difference Between Cytosol and Cytoplasm | Difference Between DNA and RNA |
Characteristics of Living Organisms
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Some of the key features of living organisms are given below
- All the living organisms move in some way or the other. For example, an animal has the ability to walk or, less obvious, a plant which moves with the movement of the sun.
- All living things eat foods for nutrition in some form to lead a healthy life.
- They respire. It is a chemical change within the cells which releases energy from food.
- Foods are eaten and digested in the body. They eliminate this through the excretory system of the body.
- All the living organisms have the ability to detect the changes in the environment.
- All living things grow. It is the most important aspect of living beings in which its cells develop.
- Living organisms reproduce either through asexual and sexual methods to pass the genetic information onto their offspring.
What are Cells Made Up Of?
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Cells are the basic building blocks of living organisms. Around two thirds of the cells are water and consist of cytoplasm. The cytoplasm is enclosed within a biological membrane, which is composed of biomolecules like proteins and nucleic acids.
Cytoplasm provides a definite structure to the body, takes nutrients from the foods, helps in breaking down the food molecules and converts the nutrients into energy which is used by our body to perform tasks. They also help in carrying out some specialized functions such as manufacturing the nerve cells, carrying out chemical reactions inside the body, producing blood cells, etc.
All of these functions require energy which is provided by the cells after breaking down food components.
Read More: Multicellular Organisms
Components of a Cell
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The structure of the cells of animals and plants are different. However, both of them consist of some common components such as a nucleus, mitochondria and the endoplasmic reticulum of the cell. Cells of living organisms primarily consist of the following components:
- Nucleus
- Cytoskeleton
- Endoplasmic reticulum
- Lysosomes
- Mitochondria
- Cytoplasm
- Secretory Vesicles
- Centriole
- Golgi Apparatus
- Ribosomes
- Plasma membrane
- Centrosome
- Peroxisome
Types of Cells
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Living Organism Cells are of two classifications:
- Eukaryotic Cells: The cells which have nucleus in the body are called Eukaryotic cells. It can be either single-celled or multicellular organisms.
- Prokaryotic Cells: The cells which do not contain a nucleus but a nucleoid region present in the body are called Prokaryotic cells. It can be found in single-celled organisms.
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| Chapter-Related Topics | ||
|---|---|---|
| Cell Biology | Fundamental Unit of Life | Cellular Organization |
| Plant Cell Model | Difference between Cell and Tissue | Nucleoplasm |
Things to Remember
- After the discovery of cells, various other microscopic organisms are discovered, some of which consist of single cells like amoeba and multicellular organisms.
- The cell membrane inside the body surrounds the cell and controls all the substances that go in and out of the cell.
- All the cells have three main parts which are the cell membrane, the nucleus, and the cytoplasm.
- The cells provide structure and function to the body, taking nutrients from foods, and converting those nutrients into energy.
- It also contains the body's genetic material and can make copies of themselves.
Previous Years’ Questions (PYQs)
- The Golgi complex participates in… (NEET 2018)
- Golgi apparatus is absent in… (AIIMS 2018)
- Mitochondria are called 'power houses' of the cell…
- The infoldings in mitochondria are known as… (KEAM 2010)
- Ribosomes are produced in… (JIPMER 2002)
- Continuity of cytoplasm from cell to cell is maintained… (COMEDK UGET 2012)
- Nucleolus is formed by… (CUCET 2006)
- The nucleolus is the site of the formation of…
- An outer covering membrane is absent over… (NEET 1992)
- During mitosis, ER and nucleolus begin to disappear at… (NEET 2010)
- Endoplasmic reticulum is in continuation with… (DUET 2009)
- The surface of the Endoplasmic Reticulum (ER) is covered with… (JKCET 2005)
Sample Questions
Ques. What is the longest cell? (1 Mark)
Ans. The nerve cells are the longest cells found in the human body. This is also called a neuron that is found in nervous systems. The size of the longest cell can be around three feets.
Ques. What is cell biology? (1 Mark)
Ans. It is the study of structure of the cells and functions and it revolves around the concept that the cell is the fundamental unit of living organisms. The cell study will provide you a detailed understanding of tissues and organisms that are composed of cells.
Ques. What are living organisms? (1 Mark)
Ans. Living things move, react to boosts, replicate and develop, respire, and are dependent upon their surroundings or environment. Most of the living organisms need food, water, light, temperatures within defined limits, and oxygen. Non-living things are generally the things that don't follow the latter things.
Ques. What is an example of a cell? (1 Mark)
Ans. A cell is characterized as the smallest unit of an organism with a nucleus. The unit of tissue of an animal muscle is an example of a cell. There is a small enclosed cavity or space, like a compartment in a honeycomb or inside a plant ovary or a region lined by veins in an insect's wing.
Ques. Which is the tallest cell in the human body? (1 Mark)
Ans. The Cerebellum's Granule Cell is the smallest cell in the human body that is between 4 micrometers to 4.5 micrometers long. The RBC 's size additionally discovered about 5 micrometers. The biggest one found in the human body is ovum. The ovum additionally called egg cell is the contraceptive cell in the female body.
Ques. What's in a human cell? (1 Mark)
Ans. The cells of a living organism consist of a nucleus and cytoplasm and is held inside the cell membrane, which directs what passes in and out. The nucleus contains chromosomes, which are the cell's hereditary material, and a nucleolus, which produces ribosomes.
Ribosomes produce proteins, which are packaged by the Golgi apparatus so that they can leave the cell. The cytoplasm consists of a fluid material and organelles, which could be considered the cell's organs. The endoplasmic reticulum transports materials within the cell. Mitochondria generate energy for the cell's activities. Lysosomes contain enzymes that can break down particles entering the cell. Centrioles participate in cell division.
Ques. What are the 2 types of cells? (4 Marks)
Ans. The cells are of two types namely eukaryotic and prokaryotic cells. The cells which have nucleus in the body are called Eukaryotic cells. The cells which do not contain a nucleus but a nucleoid region present in the body are called Prokaryotic cells.
Prokaryote Definition
Prokaryotes are unicellular organisms that lack membrane-bound structures, the most noteworthy of which is the nucleus. Prokaryotic cells tend to be small, simple cells, measuring around 0.1-5 μm in diameter.
Eukaryote Definition
Eukaryotes are organisms whose cells have a nucleus and other organelles enclosed by a plasma membrane. Organelles are internal structures responsible for a variety of functions, such as energy production and protein synthesis.
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