Cell versus protoplasm: revisionist history

The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the nucleus-first hypothesis, the ancestral prokaryote first evolved a membrane to enclose DNA and form the nucleus. Conversely, the mitochondria-first hypothesis suggests that the nucleus was formed after endosymbiosis of mitochondria.
Contrary to the endosymbiont theory, the eukaryote-first hypothesis proposes that the simpler prokaryotic and...

Protists are diverse eukaryotic microorganisms that lack the specialized tissues of plants and animals and the chitinous cell walls of fungi. Their early divergence within Eukarya resulted in structural, functional, and ecological diversity. They are classified into supergroups such as Archaeplastida, Excavata, Amoebozoa, Rhizaria, Alveolata, and Stramenopiles, determined through genetic analysis and structural similarities.Structural and Functional AdaptationsProtists have various adaptations...

Prokaryotic and eukaryotic cells represent two fundamental types of cellular organization, differing significantly in structure, complexity, and function. These distinctions underpin the biological diversity seen across domains of life.Prokaryotic Cell CharacteristicsProkaryotic cells, exemplified by bacteria and archaea, are structurally simple and lack membrane-bound organelles, including a nucleus. Their genetic material consists of a single, circular DNA molecule in the nucleoid region,...

The organs in a multicellular organism’s body are made up of tissues formed by cells. To work together cohesively, cells must communicate. One way that cells communicate is through direct contact with other cells. The points of contact that connect adjacent cells are called intercellular junctions.

In a multicellular organism, cells must communicate to work together in a coordinated manner. One way that cells communicate is through direct contact with other cells. The points of contact that connect adjacent cells are called intercellular junctions.
Intercellular junctions are a feature of fungal, plant, and animal cells. However, different types of junctions are found in different kinds of cells. Intercellular junctions found in animal cells include tight junctions, gap junctions, and...

The present-day mitochondrial and chloroplast genomes have retained some of the characteristics of their ancestral prokaryotes and also have acquired new attributes during their evolution within eukaryotic cells. Like prokaryotic genomes, mitochondrial and chloroplast genomes neither bind with histone-like proteins nor show complex packaging into chromosome-like structures, as observed in eukaryotes. Unlike mitotic cell divisions observed in eukaryotic cells, mitochondria and chloroplasts...