Difference between Prokaryotic and Eukaryotic Cells

Cells are the fundamental units of life, categorised into two main types: asexual and the two broad categories of cells, namely the prokaryotic and eukaryotic types of cells. Thus, the bacteria and archaea, called prokaryotic cells, do not contain a nucleus and membrane-bound organelles, while the plant, animal, and fungi cells and even some animal-like protists, called eukaryotic cells, contain these structures. This knowledge of cellular differences is crucial for biology students and applies to medicine, research, and biotechnology.

The organism is a collection of a population of cells, and each cell has having independent capacity to perform basic activities such as metabolic and reproductive mechanisms. Prokaryotic cells are much smaller and comparatively simpler not having a nuclear membrane and organelia while eukaryotic cells are larger and structurally complex; they contain a nuclear membrane along with several organelia 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.

Detailed Comparison Table: Prokaryotic vs. Eukaryotic Cells

This comparison talks about the differences between prokaryotic and eukaryotic cells, providing an overview of their structures and functions.

Prokaryotic Cells

In the previous discussion of the derivation of the term "prokaryote," it is now understood that "pro" is derived from the Greek word meaning before, 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.

It is a category of the simplest cells, mostly unicellular organisms with no membrane-bound nucleus or membrane-bounded organelle. They are characterized by their simple structure, which includes: They are characterised by their simple structure, which includes:

• Simple structure: Prokaryotic cells are usually smaller and less complex than eukaryotic cells; 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.

Detailed Structure of Prokaryotic Cells

The following describes the detailed structure of prokaryotic cells:-

• Cell Membrane: The prokaryotic cell membrane or the cell membrane is made of the phospholipid layer that regulates the movement in and out of the cell substances to support homeostasis.
• Cell Wall: In bacteria, the cell wall is mainly constituted by peptidoglycan which plays the role of giving mechanical support as well as a protection function. In archaea, the composition may differ, but it doesn’t have peptidoglycan inside of it.
• Nucleoid: The organelle is nucleoid which is an irregular structure within the cell housing the genetic material of the cell. It does not develop a membrane that surrounds it.
• Cytoplasm: Cytoplasm can be described as a jelly-like material of the cell 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 of smaller size compared to the eukaryotic ribosomal ribosomes and have 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.

Functions of Prokaryotic Cells

• Binary fission: The application of a type of asexual reproduction whereby a cell of an organism splits into two genetically similar cells.
• Metabolism: Prokaryotic cells have multiple strategies of energy metabolism that are known as aerobic and anaerobic respiration, fermentations, and photosynthesis.
• Genetic variation: It is done through conjugation (transfer of genetic material between bacteria), transformation (taking of foreign DNA), and transduction which is the transferring of genetic material through a bacteria virus.

Examples of Prokaryotic Cells

• 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.

Eukaryotic Cells

• About the term “eukaryote”

The term eukaryote is derived from the Greek words 'eu' (true) and 'karyon' (nut or kernel), which refer to the nucleus. Therefore, such organisms possess a membrane-bound nucleus

• Definition and Characteristics

Eukaryotic cells are complex, multicellular, or unicellular organisms characterised by the following features:

• Complex structure: Rather than having a simple structure, eukaryotic cells are a lot bigger, having a 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 which is located outside the nucleus.
• 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.
• 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 ribosome is synthesized. Chromatin contains the DNA and protein that condenses to form chromosomes during cell division.

Diagram: Structure of a Nucleus

• Cell Membrane: The cell membrane as a protective barrier is composed of phospholipid layered that has proteins that regulate the transport of molecules in and out of a cell along with acting as receptors.

Diagram: Cell Membrane Structure

• Cytoplasm and Cytoskeleton: Cytoplasm is a semi-fluid mass in the cell composed of water, food materials, and any other structures in the cell. The cytoskeleton is composed of protein fibers (microfilament, intermediate filament, micro thread) that give structural support, shape cytoplasm, and well as movement.

• Organelles

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: Golgi apparatus changes 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: 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.

Diagram: Various Organelles in Eukaryotic Cells

• Functions of Eukaryotic Cells

• Cell division: 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.
• 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.
• Examples of Eukaryotic Cells
• 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, moulds, mushrooms.
• Protists: organisms such as amoebas, algae, or noncomplex organisms with one cell or a few cells.