Cell: The Unit of Life, Cell theory, Prokaryotes, Eukaryotes

Cell: The Unit Of Life

Edited By Irshad Anwar | Updated on Oct 03, 2024 02:53 PM IST

The most fundamental, structural, and functional unit of all living beings is the cell. A cell is a structure that contains organelles that perform essential processes for the cell to survive. Organisms are divided into two classes based on the number of cells in their bodies: unicellular and multicellular organisms. Not all cells, however, are the same. The cell is the smallest, fundamental unit of life and is sometimes referred to as the "building blocks of life." Cells are capable of self-sustaining existence and executing vital life tasks. From an exam point of view, the cell is considered one of the most important biology chapters. It carries a weightage of 10 -12% in the entrance exams like NEET, Paramedical and Pharmacy.

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This Story also Contains

What is a Cell?
Cell and its Organelles
Characteristics of Cells
Cell Theory
Types of Cells
Tips, Tricks, and Strategies to Prepare for Cell
Types of Questions Asked on Cell
Weightage of Cell in Different Entrance Exams
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What is a Cell?

The most fundamental, structural, and functional unit of all living beings is the cell. A cell is a structure containing organelles that perform essential processes for the cell to survive. Not all cells, however, are the same. Cells are capable of self-sustaining existence and executing vital life tasks. All creatures, including plants and animals, are made up of one or more cells, each of which originates from a previous cell. Some of the basic essential information about cells is discussed below:

Cells can perform all the essential life activities such as growth metabolism and reproduction on their own.
Cells have different organelles responsible for different functions. These organs are the nucleus mitochondria ribosome and many others. Each one of them has its specific role to play inside our body.
All the cells come from pre-existing cells. This is cell theory.
Unicellular organisms contain single cells while multicellular organisms have specialized cells working together for every mechanism taking place in the body.
The cell membrane is one of the important organelles present and responsible for the exchange of materials between the cell and its environment.
The genetic material of the cell is DNA which is present in the nucleus and has all the essential instructions for cellular functions and reproduction.

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Cell and its Organelles

Some of the basic features of cells and their organelles are discussed below:

Aspects	Explanation
Basic Composition	Made up of various organelles which are responsible for various tasks like energy production and waste control of the cell.
Self- Sustaining	Performs its metabolic functions and response activity to environmental change.
Cell Origins	All cells arise from pre-existing cells. The process of formation of new cells takes place through cell division.
Different types of Cell	Based on the origin and development cells are divided into two types. Prokaryotic cells Eukaryotic cells
Nucleus	Contains DNA and has direct control of all cellular activities such as growth and reproduction.
Mitochondria	Known as the powerhouse of the cell as it produces energy (ATP) through cellular respiration.
Ribosomes	Responsible for protein synthesis and is one of the essential components for cellular functions and growth.
Endoplasmic Reticulum	Helps in the transportation of protein (Rough ER) and lipids (Smooth ER).
Golgi Apparatus	Also known as the packaging unit of the cell. It is responsible for modifying, sorting and packaging of proteins for transportation and various secretions in the body.
Cell Membrane	Regulates the movement of substances both inside and outside of the cell. Responsible for maintaining homeostasis of the cell.
Lysosomes	Is responsible for breaking down cellular waste and debris.
Plant Cell	Contains cell organelles like cell wall chloroplast and a large central vacuole.
Animal Cell	Absence of cell wall and chloroplast. Contains smaller vacuoles and centrioles.

Characteristics of Cells

The following are some of the most important properties of cells

Characteristics	Description
Structural support	Provides basic structure and support to the organism which helps and formation of tissues and organ
Division of Organelles	Cell organelles are separated by a membrane which ensures efficient smooth functioning of the mechanism inside the cell.
Nucleus	The nucleus of a cell contains DNA. DNA is responsible for directing cell reproduction growth and all its metabolic activity.
Cytoplasm and organelles	The cytoplast of the cell has organelles which include a single nucleus and are responsible for various important functions in the cell.
Mitochondria	Mitochondria is known as the powerhouse of the cell. It is responsible for ATP synthesis through cellular respiration.
Endoplasmic reticulum	The endoplasmic reticulum is responsible for the packaging of proteins and lipids.

Cell Theory

This scientific hypothesis states that all living entities are made up of cells and that new cells are generated from pre-existing cells. It was first postulated by Matthias Schleiden and Theodor Schwann. Even though Schleiden and Schwann proposed the hypothesis, numerous renowned scientists have added to it, elevating it from a theory to a commonly acknowledged fact.

Types of Cells

Cells are comparable to factories in that they have various workers and departments working toward a shared goal. Distinct types of cells have different purposes. There are two types of cells based on their cellular structure:

The basic difference between both types of cells is described below in the table:

Key Features	Prokaryotic cell	Eukaryotic cell
Nucleus	DNA floats freely in the cytoplasm. Therefore the nucleus is absent.	Present (The DNA is tightly packed within a membrane-bound nucleus)
Size	0.1-5 µm in diameter	10-100 µm in diameter
Complexity	Simple structure	More Complex
Membrane bound Organelles	Absent	Present in organelles like mitochondria, the plasmic reticulum and the Golgi complex.
Cell division	Binary fission ( asexual mode of reproduction)	Mitosis and meiosis ( both sexual and asexual reproduction)
Examples	Bacteria and unicellular organisms	All the multicellular organisms.
Ribosomes	Smaller (70s Ribosomes)	Larger (80s ribosomes)
Cell Wall	Present (Bacterial cell walls are made up of peptidoglycan)	Present in plants and fungi ( made up of cellulose or chitin)
Metabolism	Simple metabolic process	Complex metabolic process with more Energy Production.
DNA Structure	Circular DNA	Organized chromosomes with linear DNA

Tips, Tricks, and Strategies to Prepare for Cell

It's hard to remember everything in a single go. We made the entire problem easy. Some of the tricks regarding Cell are given below which you can use to memorize the important points.

CELL: Important Organelles

NEMGRLCV

N: Nucleus
E: Endoplasmic Reticulum (ER)
M: Mitochondria
G: Golgi Apparatus
R: Ribosomes
L: Lysosomes
C: Chloroplasts (only in plant cells)
V: Vacuoles

Classification of Cell Functions

SGPDER

S: Structure (cell membrane, cell wall)
G: Genetic Control (nucleus, DNA)
P: Protein Synthesis (ribosomes, ER)
D: Digestion & Waste Removal (lysosomes)
E: Energy Production (mitochondria, chloroplasts)
R: Regulation (cell membrane)

Types of Questions Asked on Cell

During the preparation of the exam, there are different types of questions asked about Cells in different forms. The table given below contains the different patterns of questions asked in different exams.

Exam Type	Types of Questions Asked
CBSE	Definition of cells. Characteristics of cells. Cell organelles function.
NEET	Cell and its evolution. Cell organelles and their mechanisms. Differences between Prokaryotic and Eukaryotic. DNA, Nucleus and chromosomes.
Paramedical	Basics of cell. Cell theory and its importance. Role of different organelles and their mechanisms.

Weightage of Cell in Different Entrance Exams

It is important to keep weightage of the topic in mind throughout the preparation. The weightage of Cell in different exams is mentioned below in the table: