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Ans. A cell is the smallest unit of life that can carry out all the processes necessary for living organisms. It is often referred to as the basic building block of life.
Q. What are the types of cells?
Ans. Cells can be broadly categorized into two main types: prokaryotic cells (which lack a nucleus, like bacteria) and eukaryotic cells (which have a nucleus, like plant and animal cells). Eukaryotic cells can be further divided into plant cells and animal cells.
Q. What is the structure of cells?
Ans. A typical cell consists of three main parts: the cell membrane (which encloses the cell), the nucleus (which contains the genetic material), and the cytoplasm (the fluid that fills the cell and contains organelles).
Q. What is an example of a cell?
Ans. One example of a cell is a red blood cell, responsible for transporting oxygen throughout the body. Another example is a nerve cell, which plays a crucial role in sending signals within the nervous system.
Q. What is the definition of a cell?
Ans. A cell is defined as the basic structural and functional unit of all living organisms, capable of performing life processes.
Q. What are the main functions of a cell?
Ans. Cells provide structure, transport substances, produce energy, facilitate growth, synthesize proteins, communicate with other cells, and aid in reproduction.
Q. What is the meaning of cell?
Ans. The term "cell" comes from the Latin word "cella," meaning "small room," reflecting its small size and fundamental role in biology.
Q. How many cells are in the human body?
Ans. The human body is estimated to contain over 30 trillion cells, with a variety of types and functions working together to maintain life.
What is Cell? Discovery, Types, Structure, Function, MCQs
Cell, This article provides comprehensive details of cell structure, definition, types, functions, cell theory, and related MCQs with answers.
Krati Saraswat3 Jun, 2025
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The cell is the smallest living organism and the basic unit of life on Earth. Together, trillions of cells make up the human body, each performing essential functions to sustain life. Cells are composed of three main parts: the membrane, which controls what enters and exits the cell; the nucleus, which contains genetic material ( DNA ); and the cytoplasm, where various cellular processes occur.
Cell is essential for the NEET Exam , as it forms the foundation for topics in biology, including genetics, physiology, and cell biology, all of which are integral to the NEET syllabus .
What is Cell?
A cell is the basic unit of life in all living organisms. It is like a tiny building block that makes up every part of our body, performing specific tasks to keep us alive and functioning. Cells can be compared to small factories, where essential processes like energy production and growth take place.
Discovery of Cell
Cells were first observed by Robert Hooke in 1665 with the aid of a compound microscope. While examining thin slices of cork, he noticed numerous small structures, which he named cellula. Hooke’s findings were published in his book Micrographia. Following Hooke’s discovery, Anton van Leeuwenhoek in Holland made significant advancements using his microscope. Leeuwenhoek crafted his own lenses, resulting in a microscope that was more powerful than those of his contemporaries, and comparable to modern light microscopes. Through his observations, Leeuwenhoek became the first person to see human cells and bacteria.
Cell Theory
Cell theory is a basic scientific principle in biology that states that cells are the fundamental units of all living tissues. This theory was first introduced by German scientists Theodor Schwann and Matthias Jakob Schleiden in 1838. They proposed that all plants and animals are made up of cells, which was a significant advancement in understanding biology and led to increased focus on the processes happening within cells.
By the early 1800s, scientists had already observed cells from various organisms. Based on these observations, Schwann and Schleiden concluded that cells are the essential building blocks of all living things. Later, around 1850, German doctor Rudolf Virchow studied cells under a microscope and noticed that cells divide to form new cells. From this, he proposed that living cells arise only from other living cells. The combined ideas of Schwann, Schleiden, and Virchow established cell theory, which is a foundational concept in biology. Cell theory includes three main points:
All organisms are made of one or more cells.
All life functions occur within cells.
All cells come from pre-existing cells.
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Types of Cells
Cells are classified into two main types based on their structure and complexity: prokaryotic cells and eukaryotic cells.
They do not have a true nucleus or membrane-bound organelles.
The genetic material (DNA) floats freely in the cytoplasm instead of being enclosed in a nucleus.
Examples of prokaryotic cells include bacteria and Archaea.
Eukaryotic Cell
Eukaryotic cells are more complex and have a true nucleus that contains the genetic material (DNA) within a nuclear membrane.
They also have organelles surrounded by membranes, such as mitochondria, endoplasmic reticulum, and Golgi apparatus, each with specific jobs.
Eukaryotic cells are found in plants, fungi, protists, and animals.
Different Shape and Size of Cell
Cells come in various sizes and shapes, reflecting their different roles in the body. For example, they can be disc-shaped, square, long and thin, or even irregular. The size of cells can also vary; the smallest cells, called mycoplasmas, are just 0.3 micrometers long, while the largest single cell is the ostrich egg. In humans, red blood cells are about 7 micrometers in diameter, while nerve cells are among the longest. The shape of a cell often relates to what it does in the body.
Structure of Cell
A cell is composed of various parts, each performing a unique function essential for the cell's survival and proper functioning. These components work together to maintain the life processes of the cell. A typical cell has three main parts: the cell membrane, the nucleus, and the cytoplasm, within which lie organelles responsible for specific tasks. Below are the key components of a cell:
Cell Membrane: The cell membrane encloses the cell, separating its internal environment from the external. It regulates the passage of substances in and out of the cell and consists of a double layer of phospholipids with proteins that provide support, act as channels, and function as receptor sites.
Nucleus and Nucleolus : The nucleus , surrounded by a nuclear membrane, contains DNA and controls cell activities. The nucleolus inside the nucleus is where ribosomes are formed. Together, they determine the cell’s function and structure.
Cytoplasm : The cytoplasm is a gel-like fluid where chemical reactions occur, and it supports the organelles. It facilitates cell functions such as growth and replication.
Cytoplasmic Organelles : Organelles like mitochondria , ribosomes , endoplasmic reticulum, Golgi apparatus, and lysosomes, each have distinct roles, including energy production, protein synthesis, and waste breakdown.
Mitochondria : Mitochondria are often called the "powerhouses" of the cell because they produce energy by breaking down food molecules. This energy is used for various cell functions.
Endoplasmic Reticulum (ER) : The endoplasmic reticulum is a network of membranes that helps transport materials throughout the cell.
Golgi Apparatus: The Golgi apparatus is responsible for packaging and distributing proteins and other materials within the cell. It modifies proteins and prepares them for transport to their final destination.
Lysosomes : Lysosomes are small organelles that contain enzymes used to break down waste materials and worn-out cell parts. They help in keeping the cell clean.
Vacuoles : Vacuoles are storage sacs within the cell that hold water, nutrients, and waste products. Plant cells have large central vacuoles, which also help maintain the cell’s shape by storing water.
Chloroplasts : Chloroplasts are present only in plant cells and certain algae. They contain a green pigment known as chlorophyll and are essential for photosynthesis, the process that allows plants to create their food using sunlight.
Differences Between Animal and Plant Cell
Animal and plant cells differ in structure and function, reflecting their roles in different organisms. While both are eukaryotic cells, they exhibit several key differences, such as the presence of a cell wall, plastids, and vacuole size, which distinguish plant cells from animal cells.
Difference Between Animal and Plant Cell
Animal Cell
Plant Cell
Animal cells are generally smaller in size.
Plant cells are usually bigger than animal cells..
The cell wall is absent.
Plant cells have a rigid cell wall made of cellulose and hemicellulose surrounding the plasma membrane.
Except for protozoans like Euglena, animal cells do not contain plastids.
Plastids (chloroplasts, chromoplasts, and leucoplasts) are present in plant cells.
Animal cells contain one highly complex and well-developed Golgi apparatus.
Plant cells contain multiple simpler units known as dictyosomes.
Animal cells have centrosomes and centrioles.
Plant cells lack centrosomes and centrioles.
Vacuoles are smaller and more numerous.
Vacuoles are larger but fewer in number (1-3).
The nucleus is usually located in the center.
The nucleus is often positioned towards the periphery.
Function of Cell
Cells perform essential functions that are vital for the survival and maintenance of all living organisms. Each cell type has specialized roles, working together to ensure the organism's overall health and functionality.
Support : Cells provide structure and support to the organism. They maintain shape and protect internal components.
Transportation of Substances : Cells regulate the movement of nutrients, gases, and waste materials in and out through the cell membrane, ensuring homeostasis.
Energy Production : Cells generate energy through processes like cellular respiration (in animals) and photosynthesis (in plants), which are essential for cellular activities.
Growth and Development : Cells undergo division (mitosis and meiosis) to facilitate growth, repair tissues, and produce gametes for reproduction.
Protein Synthesis: Cells synthesize proteins based on the instructions from DNA, playing a crucial role in metabolism, immune response, and cell signaling.
Reproduction : Cells reproduce to form new cells, either through mitosis (asexual reproduction) for somatic cells or meiosis for gametes, contributing to genetic diversity.
Metabolism: Cells carry out various chemical reactions to convert nutrients into energy and building blocks for growth and repair.
MCQs of Cell
Q1. Which of the following was first examined under a microscope that later led to the discovery of cells?
Honeycomb.
Cork.
Drosophila.
Dead leaves
Q2. What is a cell?
Smallest and advanced unit of life.
The smallest and basic unit of life.
The largest and basic unit of life.
Largest and advanced unit of life
Q3. Who gave the final shape to the cell theory?
Antony Von Leeuwenhoek.
Matthias Schleiden.
Rudolf Virchow.
Theodore Schwann
Answers of MCQs’s Cell
Ans1 . Cork, Ans2 . Smallest and basic unit of life., Ans3 . Rudolf Virchow Physics Wallah (PW) offers theNEET Online Coachingin India, designed to make quality education accessible to all aspiring medical students. With a focus on breaking down financial barriers, PW is dedicated to empowering students nationwide to excel in the NEET exam and achieve their dreams of a medical career.
