Cell Biology and Evolution: Key Concepts in Genetics, Organelles, and Domains of Life

Cell Theory

All living things are made of cells, the cell is the basic unit of life, and cells arise from preexisting cells.

Central Dogma

Flow of genetic information: DNA → RNA → Protein.

RNA World Hypothesis

Early life was based on RNA, which could both store genetic information and catalyze reactions.

Ribozymes

RNA molecules with enzymatic activity (e.g., peptide bond formation in ribosomes, RNA splicing).

Domains of Life

Bacteria, Archaea, Eukarya.

Bacteria

The most diverse domain, found in nearly all environments; include species like E. coli.

Archaea

Prokaryotes with unique membrane lipids; often live in extreme environments; more closely related to eukaryotes.

Eukaryotes

Organisms with nuclei, membrane-bound organelles, and a cytoskeleton.

Endosymbiotic Theory

Mitochondria and chloroplasts originated from bacteria engulfed by ancestral eukaryotes.

Evidence for Endosymbiosis

Double membranes, circular DNA, ribosomes similar to bacteria, independent division.

Prokaryotic Cells

Lack nuclei and organelles, have circular DNA in a nucleoid, often with plasmids and cell walls.

Photosynthetic Bacteria

Capture energy from sunlight (e.g., Anabaena can fix nitrogen and perform photosynthesis).

Nucleus

Organelle containing most of the cell's DNA; information storage center.

Mitochondria

Double-membrane organelles that generate ATP; originally endosymbionts.

Chloroplasts

Double-membrane organelles in plants/algae that capture light energy; contain thylakoids with chlorophyll.

Cytoskeleton

Dynamic network of proteins responsible for cell shape, structure, and movement.

Endocytosis

Import of materials into the cell via vesicles.

Exocytosis

Export of materials out of the cell via vesicles.