Cell biology

Cell biology explains how living matter is organized at the cellular level. A cell maintains an internal environment, exchanges materials with its surroundings, stores and expresses genetic information, and reproduces or enters specialized states. Prokaryotic cells, including bacteria and archaea, generally lack a membrane-bound nucleus, whereas eukaryotic cells contain a nucleus and extensive membrane-bound compartments.¹

The discipline grew from microscopy and cell theory. Robert Hooke used the word “cell” in 1665 after examining cork, while later observations by Antonie van Leeuwenhoek, Matthias Schleiden, Theodor Schwann, and Rudolf Virchow established that organisms are composed of cells and that cells arise from preexisting cells. Modern cell biology combines microscopy, biochemistry, genetics, electrophysiology, and quantitative modeling.

Cellular architecture divides work among specialized structures. The plasma membrane regulates transport and signaling; the cytoskeleton gives shape and supports movement; ribosomes synthesize proteins; and, in eukaryotes, the nucleus houses most genomic DNA. The endoplasmic reticulum, Golgi apparatus, endosomes, lysosomes, and related compartments move, modify, store, or degrade cellular materials.¹

Mitochondria generate much of the ATP used by eukaryotic cells and retain small genomes that reflect their evolutionary origin from bacterial endosymbionts. Chloroplasts perform photosynthesis in plants and algae and likewise possess bacterial-derived features.² Gene expression connects information to function: DNA is transcribed into RNA, and many RNAs are translated into proteins, although regulatory RNAs and epigenetic mechanisms add further layers of control.

Cells coordinate growth, metabolism, movement, and division through signaling networks. Receptors detect extracellular molecules or physical conditions, then activate intracellular pathways involving proteins such as kinases, G proteins, and transcription factors. Feedback allows cells to adapt while preserving stable internal conditions. The cell cycle duplicates DNA and distributes chromosomes, while mitosis supports growth and tissue maintenance; meiosis produces genetically varied reproductive cells in many eukaryotes.³

Cellular failure contributes to disease. Cancer can arise when mutations disrupt controls over proliferation, genome maintenance, cell death, or tissue invasion. Errors in protein folding, organelle function, metabolism, or immune signaling underlie many inherited and acquired disorders. Cell biology therefore supplies mechanisms and targets for therapies, including kinase inhibitors, antibodies, gene-based treatments, and drugs that alter intracellular trafficking or degradation.

Cells are not simply bounded bags of molecules; many organize reactions through biomolecular condensates that form without conventional membranes. These dynamic assemblies can concentrate RNA and proteins, although their functions and disease relevance remain active research topics.⁴ Membranes also carry electrical information: ion gradients across them power transport, enable neuronal signaling, and drive ATP production in mitochondria and chloroplasts.

Cell biology increasingly studies cells in their native neighborhoods. Single-cell sequencing can distinguish cell states within a tissue, while spatial methods preserve where those cells and molecules occur.⁵ Organoids, live-cell imaging, cryo-electron microscopy, and lineage tracing reveal transient states that bulk measurements can hide. Another boundary of the field is the microbiome, in which host cells interact continuously with vast communities of microbial cells, exchanging metabolites and signals that influence physiology.

Cell theory

The principle that organisms are composed of cells, that the cell is a basic unit of life, and that cells arise from preexisting cells.

Prokaryote

An organism whose cell generally lacks a membrane-bound nucleus, including bacteria and archaea.

Eukaryote

An organism whose cells contain a membrane-bound nucleus and other specialized compartments.

Organelle

A specialized structure within a cell, such as a mitochondrion, nucleus, or lysosome.

Apoptosis

A regulated form of cell death that helps shape tissues and remove damaged or unnecessary cells.