Two Groups of Organisms: All living organisms are categorized as either prokaryotes or eukaryotes, distinguished by cellular structure.
Prokaryotes: Unicellular, no nucleus or membrane-bound organelles, includes bacteria and archaea, smaller and simpler.
Eukaryotes: Often multicellular, has a nucleus and membrane-bound organelles, includes animals, plants, fungi, algae, protozoans, larger and more complex.
Comparing Prokaryotes and Eukaryotes
Evolution: Eukaryotes are believed to have evolved from prokaryotes about 2.7 billion years ago through endosymbiosis.
Endosymbiosis: Led to development of mitochondria and other organelles.
New Research: Suggests prokaryotic bacteria may perform endocytosis, challenging previous understanding.
Key Differences
Nucleus:
Prokaryotes: Absent, DNA is bundled in the nucleoid, not membrane-bound.
Eukaryotes: Present, stores genetic information.
Organelles:
Prokaryotes: No membrane-bound organelles.
Eukaryotes: Contains various membrane-bound organelles.
DNA Structure:
Prokaryotes: Generally circular, but can also be linear in some cases.
Eukaryotes: Linear DNA.
Cell Structure:
Prokaryotes: Unicellular.
Eukaryotes: Mostly multicellular, some unicellular.
Similarities
Shared features of both cell types include DNA, plasma membrane, cytoplasm, and ribosomes.
Transcription and Translation
Prokaryotes: Transcription and translation are coupled; translation begins during mRNA synthesis.
Eukaryotes: Transcription occurs in the nucleus, mRNA exits, and translation occurs in the cytoplasm.
Prokaryotes
**Features: **
Nucleoid: Contains DNA.
Ribosome: Protein synthesis.
Cell Wall: Structure and protection.
Cell Membrane: Separates cell from environment.
Capsule: Protection and attachment.
Pili and Flagella: Movement and DNA transfer.
Examples: Bacteria, archaea.
Organelles: No nucleus or mitochondria.
Eukaryotes
Features:
Nucleus and Nucleolus: Stores and produces genetic material.
Plasma Membrane and Cytoskeleton: Encloses cell and maintains shape.
Cell Wall: Present in some eukaryotes like plants.
Ribosomes and Mitochondria: Protein synthesis and energy production.
Cytoplasm and Cytosol: Fill the cell and contain organelles.
Endoplasmic Reticulum, Vesicles, and Vacuoles: Organelles for protein maturation, transport, and storage.
Other Organelles: Golgi apparatus, chloroplasts, lysosomes (in many eukaryotes).