Difference between Prokaryotic and Eukaryotic Cells
Cells are broadly classified into prokaryotic and eukaryotic types, forming the basic foundation of biology. Prokaryotes, such as bacteria, are simple cells that lack a true nucleus and membrane-bound organelles, while eukaryotes, including plants and animals, have a well-defined nucleus and specialized organelles. Understanding these differences is essential in Cell: The Unit of Life, making it a high-yield topic for Class 11 Biology and NEET.
This Story also Contains
- Introduction
- What are Prokaryotic Cells
- What are Eukaryotic Cells?
- Key Differences Between Prokaryotic and Eukaryotic Cells
- Prokaryotic vs Eukaryotic Cells Table (Comparison)
- Functions of Prokaryotic and Eukaryotic Cells
- Eukaryotic Cells NEET MCQs (With Answers & Explanations)
Introduction
Cells are the fundamental units of life, categorised into two main types, the prokaryotic and eukaryotic types of cells. Examples of prokaryotic cells include bacteria and archaea, which do not contain nucleus and membrane-bound organelles. While the plant, animal, and fungi cells and even some animal-like protists are the examples of eukaryotic cells, containing these structures.
The organism is a collection of a population of cells, and each cell has an independent capacity to perform basic activities. Prokaryotic cells are much smaller and simpler while eukaryotic cells are larger and structurally complex as they contain a nucleus along with several membrane bound organelles, each having a specific function. These differences show the variety of life forms and show how organisms can live in certain conditions/under certain conditions.
What are Prokaryotic Cells
In the term prokaryote, "pro" is derived from the Greek word meaning before or primitive, and "karyon," meaning nut or kernel, which refers to the nucleus. Therefore, “prokaryote” can be translated as “before the nucleus,” and this points to the fact that such organisms do not possess a real nucleus.
Characteristics
Prokaryotic cells are the simplest cells. Mostly unicellular organisms with no membrane-bound nucleus or organelle. They have following characteristics:
Simple structure: Prokaryotic cells are usually smaller and less complex; they are not enclosed by a membrane.
Lack of nucleus: The DNA is not surrounded by a nuclear membrane, but it is located at a particular site in the cell known as a nucleoid.
Absence of membrane-bound organelles: Cell organelles or structures like mitochondria, endoplasmic reticulum, Golgi apparatus, etc., are not found in prokaryotic cells.
Structure
The following describes the detailed structure of prokaryotic cells:
Cell Membrane: The prokaryotic cell membrane is made of the phospholipid layer that regulates the movement in and out of the cell substances.
Cell Wall: In bacteria, the cell wall is mainly constituted by peptidoglycan which provides mechanical support as well as a protection. In archaea, the composition may differ.
Nucleoid: It is an irregular structure within the cell housing the genetic material of the cell. It does not develop a membrane that surrounds it.
Cytoplasm: It is a jelly-like material that consists of water, enzymes, nutrients, waste products and gases. It contains the ribosomes and is the location of most of the cellular activities.
Ribosomes: Prokaryotic ribosomes are smaller, having a sedimentation value of 70S, which is made up of 50S and 30S parts. They are involved in the topology of hair and are also involved in protein synthesis.
External Structures
Flagella: Sensory and locomotive appendages in the form of long whips.
Pili and Fimbriae: It is used in attachment to various surfaces and conjugation-like hair-like structures.
Capsule: An outer skin-like structure that gives a protective tone as well as outer layer adhesion.
Examples (Bacteria, Archaea)
Bacteria: Some of the examples include Escherichia coli (E. coli) and Staphylococcus aureus.
Archaea: Some examples that can be taken under this category are Methanogens and Halophiles.
What are Eukaryotic Cells?
The term eukaryote is derived from the Greek words 'eu' meaning true and 'karyon' meaning nut or kernel, which refer to the nucleus. Therefore, such organisms possess a membrane-bound nucleus
Characteristics
Eukaryotic cells are complex, multicellular, or unicellular organisms characterised by the following features:
Complex structure: Eukaryotic cells are bigger, complex internal structure with one or many organelles depending on the cell's functions.
Presence of a true nucleus: The nucleus is surrounded by a double membrane called the nuclear envelope.
Membrane-bound organelles: Some of the structures found at the sub-cellular level including the mitochondria endoplasmic reticulum and the Golgi apparatus are enclosed in a membrane.
Structure
The following describes the detailed structure of eukaryotic cells:
Nucleus: The nuclear envelope is a two-layer membrane that surrounds the nucleus and has openings referred to as nuclear pores. The nucleolus is the part of the nucleus where the ribosome is synthesized.
Cell Membrane: The cell membrane acts as a protective barrier composed of phospholipid layered that has proteins that regulate the transport of molecules in and out of a cell along with acting as receptors.
Cytoplasm and Cytoskeleton: Cytoplasm is a semi-fluid mass composed of water, food materials, and other structures in the cell. The cytoskeleton is composed of protein fibers that give structural support and movement.
Mitochondria: Mitochondria of the cell, synthesize ATP through the process of cell respiration. These organisms have a double membrane and their DNA.
Endoplasmic Reticulum: Ribosome at studded on the rough endoplasmic reticulum; manufactures and modifies proteins
Golgi Apparatus: It modifies and sorts proteins and lipids and packs them for transportation
Lysosomes and Peroxisomes: Lysosomes have enzymes for breaking down macromolecules that are present in the food ingested by the organism. Peroxisomes emulsify fats and foreign materials as well as perform the detoxifying function
Vacuoles: These are big and membrane-bound structures consisting of reserve foods, and wastes, and mainly involved in the osmotic potential of a plant cell.
Chloroplasts (in plant cells): Sources of photosynthesis include chlorophyll and a double membrane.
Examples (Plants, Animals, Fungi, Protists)
Animals: Singly and multiply organized forms of life such as human beings, and animals.
Plants: Complex forms of organisms commonly include; trees and flowers.
Fungi: Yeasts, molds, mushrooms.
Protists: organisms such as amoebas, algae, or noncomplex organisms with one cell or a few cells.
Key Differences Between Prokaryotic and Eukaryotic Cells
The key differences between prokaryotic and eukaryotic cells are:
Nucleus
In prokaryotes, the nucleus is absent and instead a nucleoid is present. It is the region in the cytoplasm where the cell's DNA is located. It contains a single, circular chromosome and is responsible for transmitting genetic information.
In eukaryotes, the nucleus is one of the most important components. The nucleolus located in the nucleus of cells is involved in ribosome formation which has great involvement in protein synthesis.
Organelles
One of the distinguishing features of prokaryotic cells is that they lack membrane-bound organelles. Such membrane-bound organelles, typical in eukaryotic cells, such as mitochondria, endoplasmic reticulum, and Golgi apparatus, do not exist in prokaryotic cells. They carry out all their cellular activities either in the cytoplasm or at the membrane.
Ribosomes
Prokaryotic ribosomes are composed of an RNA and several proteins. They are smaller and have a sedimentation coefficient of 70S which further has 2 subunits of 50S and 30S.
Eukaryotic ribosomes can be free in the cytoplasm or attached to the rough endoplasmic reticulum. They are bigger and have a sedimentation coefficient of 80S which further has 2 subunits of 60S and 40S.
Cell Division (Binary Fission vs Mitosis/Meiosis)
Prokaryotic cells reproduce primarily through binary fission, an asexual process where a single cell divides into two genetically identical daughter cells. This simple and efficient mode of reproduction permits fast growth in these cells.
In eukaryotes, mitosis is the process of the formation of two alike daughter cells from one mother cell. Meiosis is the division that yields four genetically different daughter cells, which produce gametes.
Prokaryotic vs Eukaryotic Cells Table (Comparison)
This comparison talks about the differences between prokaryotic and eukaryotic cells, providing an overview of their structures and functions.
Feature | Prokaryotic Cells | Eukaryotic Cells |
Capsule | Present in some bacteria for protection and adhesion | Generally absent, though some eukaryotes have similar structures (e.g., slime layers) |
Nucleus | Absent; DNA in nucleoid region | Present; DNA enclosed within a nuclear envelope |
Size | Typically 0.1-5.0 µm | Typically 10-100 µm |
Organelles | No membrane-bound organelles | Membrane-bound organelles present (e.g., mitochondria, ER, Golgi apparatus) |
DNA Structure | Circular DNA | Linear DNA |
Ribosome Size | 70S (smaller) | 80S (larger) |
Cell Division | Binary fission | Mitosis and meiosis |
Cell Wall | Peptidoglycan (bacteria), varied in archaea | Cellulose (plants), chitin (fungi), absent in animal cells |
Membrane-bound Nucleus | Absent | Present |
Simple structures | Complex network of microtubules, microfilaments, and intermediate filaments | |
Mitochondria | Absent | Present |
Golgi Apparatus | Absent | Present |
Lysosomes | Absent | Present |
Peroxisomes | Absent | Present |
Vacuoles | Small or absent | Large central vacuole in plants; small vacuoles in animals |
Chloroplasts | Absent | Present in plants and some protists |
Pili/Fimbriae | Present for adhesion and conjugation | Absent |
Absent | Present in some eukaryotic cells for movement and sensory functions | |
Cytoplasmic Streaming | Absent | Present in plant and fungal cells |
Photosynthetic Apparatus | Present in some (e.g., cyanobacteria) | Present in chloroplasts of plants and algae |
Introns in Genes | Rare | Common |
Histones Associated with DNA | Absent (except in some archaea) | Present |
Minimal | Extensive (capping, splicing, polyadenylation) | |
Plasmids | Common | Rare, but present in some cases (e.g., yeast) |
Reproduction | Asexual, primarily binary fission | Sexual and asexual, involving mitosis and meiosis |
Functions of Prokaryotic and Eukaryotic Cells
Prokaryotic and eukaryotic cells have different functions:
Functions of Prokaryotic Cells (Decomposition, Nitrogen Fixation, Pathogenesis)
Decomposition: Prokaryotic cells are the chief decomposers in the ecosystem. They break down dead organic materials, thus recycling nutrients back into the environment. This in effect helps nutrients be retained in the soil, which maintains soil fertility and promotes plant growth, which is good for the whole ecosystem.
Nitrogen Fixation: Certain prokaryotes, such as cyanobacteria and rhizobia, can fix nitrogen. They change the atmospheric nitrogen to forms that are useful to plants. It is critical in agriculture to improve the health of soils besides improving productivity.
Pathogenesis: Several prokaryotic cells are pathogenic and cause various diseases in mammals, plants, and others. Escherichia coli and Mycobacterium tuberculosis are some of the bacteria that cause severe infection.
Functions of Eukaryotic Cells (Metabolism, Protein Synthesis, Cell Signalling)
Metabolism: Cellular respiration is the procedure of carrying out oxidative phosphorylation to generate ATP from glucose in the mitochondria. Photosynthesis is the conversion of light energy into chemical energy in the chlorophyll-containing pigmented organelles known as chloroplasts in plant cells.
Protein synthesis: Transcribing DNA to mRNA in the nucleus. At the ribosome, proteins are made using the information coded by the mRNA.
Cell signaling: Structures that comprise cells, tissues, and organs, which play a role in summoning other cells and molecules as well as in the overall regulation of cellular activities and the organism’s interaction with the surroundings.
Eukaryotic Cells NEET MCQs (With Answers & Explanations)
Important topics for NEET exam are:
Characteristics of Prokaryotic cells
Characteristics of Eukaryotic cells
Prokaryotic vs Eukaryotic Cells
Practice Questions for NEET
Q1. In eukaryotic cells , transcription and translation occurs in
Cytoplasm and nucleus respectively
Nucleus and cytoplasm respectively
Cytoplasm only
Nucleus only
Correct answer: 2) Nucleus and cytoplasm respectively
Explanation:
Transcription and Translation in Eukaryotic cell - Transcription occurs in the nucleus while translation takes place in the cytoplasm.
Hence, the correct answer is option 2) Nucleus and cytoplasm respectively.
Q2. Which of the following is not true of a eukaryotic cell?
Cell wall is made up of peptidoglycans
It has 80S type of ribosome present in the cytoplasm
Mitochondria contain circular DNA
Membrane bound organelles are present
Correct answer: 1) Cell wall is made up of peptidoglycans
Explanation:
The main building block of cell walls of eukaryotic plant cells is cellulose, a structural polysaccharide. It supports the cell's structure and shields it from mechanical stress from the outside by giving it strength and stiffness
Hence, the correct answer is option 1) Cell wall is made up of peptidoglycans.
Q3. Prokaryotic and eukaryotic cells generally have which of the following features in common?
Membrane - bounded nucleus
Cell wall made of cellulose
Ribosomes
Linear chromosomes made of DNA and protein
Correct answer: 3) Ribosomes
Explanation:
Eukaryotic cells have a more elaborate internal organization compared to prokaryotic cells. They are found in protists, plants, animals, and fungi. These cells contain a well-defined nucleus that houses the genetic material (DNA) and is surrounded by a nuclear membrane. Eukaryotic cells also possess various membrane-bound organelles, such as mitochondria, the endoplasmic reticulum, the Golgi apparatus, and, in plant cells, chloroplasts. This compartmentalization allows for more complex functions and greater specialization within the cell, contributing to the diversity and efficiency of eukaryotic organisms.
Hence, the correct answer is option 3) Ribosomes.
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Frequently Asked Questions (FAQs)
The first cells were identified by Robert Hooke in 1665 while using a microscope on a piece of cork and the word cell originated from the hole.
The cell theory as a concept was formulated by Schleiden and Schwann in the early 30s of the nineteenth century. Lastly, Rudolf Virchow proposed in 1855.
- Prokaryotic: No true nucleus which refers to the compartment of a bacterial cell encasing its DNA; instead it is found in the nucleoid region.
- Eukaryotic: This is located within a nuclear envelope which forms a true nucleus.
- Organelles :
- Prokaryotic: Non-membrane bound organelle is absent in its structure.
- Eukaryotic: Has membrane organelles such as the mitochondria, and endoplasmic reticulum.
- Size :
- Prokaryotic: Smaller. In a range of 1-10 micrometers.
- Eukaryotic: Coarser Graded (10-100 micrometers).
- DNA Structure :
- Prokaryotic: Circular DNA.
- Eukaryotic: Prokaryotic DNA is in the form of circular molecules while eukaryotic DNA is in the form of linear chromosomes.
- Reproduction :
- Prokaryotic: Binary fission.
- Eukaryotic: Cell division including mitosis and meiosis.
Animal Cells :
- Lack of cell walls.
- Have centrioles participate in the division of a cell.
- Contain lysosome for digesting the food particles.
- Lacks or possesses very small-sized vacuoles.
Plant Cells :
- They usually have cell walls primarily composed of cellulose.
- Zinc containing chloroplasts is required for photosynthesis.
- Ability to store substances in large cv and also maintain turgidity pressure.
- Plasmodesmata for intercellular exchange of information.
A prokaryotic cell is a single and simple-headed cell that has no true nucleus or membrane-bounded organelles. Prokaryotic cells are less complex their DNA is not bound in a membrane but is found in the nucleoid region. The example of Prokaryotic organisms includes bacterial and archaeal organisms.
A eukaryotic cell is a cell that contains a true nucleus that is enclosed by a nuclear membrane and several other membrane-bound organelles. Eukaryotic cells are much bigger than prokaryotic cells and can be a single or many-celled organism. Samples of eukaryotic organisms are animals, plants, fungi, and protists.