Cell biology is the academic discipline that studies the basic unit of living things, cells. Cells are the smallest independently functioning unit in the structure of an organism and usually consist of a nucleus surrounded by cytoplasm and enclosed by a membrane. Cell biology examines, on microscopic and molecular levels, the physiological properties, structure, organelles (such as nuclei and mitochondria), interactions, life cycle, division and death of these basic units of organisms. Cell biology research extends to both the great diversity of single-celled organisms, such as bacteria and the many specialized cells in multicellular organisms, such as animals and plants.
The field of cell biology traditionally has focused on questions concerning how the various organelles work and work together, how these cellular processes are regulated and how the various cells within the organism communicate with each other. Understanding the composition of cells and how cells work is fundamental to all the biological and medical sciences. Examining the similarities and differences between cell types is particularly important to the fields of cell and molecular biology, because the principles learned from studying one cell type can be generalized to other cell types. Research in cell biology closely is related to genetics, biochemistry, molecular biology and developmental biology.
The structures and functions within a cell often are compared to similar activities in a typical city. Mitochondria are the cell’s energy plants, plant chloroplasts are solar energy plants, chromosomes contain the original blueprints of the city, the endoplasmic reticulum represents the road system, Golgi apparatus is the post office and the nucleus is city hall. Proteins, however, participate in virtually every function of the cell city — in other words, they are the bricks and lumber, messengers, copy machines, waste recyclers and more. Every cell typically contains hundreds of different kinds of proteins that function together to generate the behavior of the cell. An important part of cell biology is investigation of molecular mechanisms by which proteins are moved to different places inside cells or secreted from cells.
Most proteins are synthesized by ribosomes in the cytoplasm. This process also is known as protein biosynthesis or protein translation. Some proteins, such as those to be incorporated in membranes (membrane proteins) are transported into the endoplasmic reticulum (ER) during synthesis and further processed in the Golgi apparatus. From the Golgi, membrane proteins can move to the plasma membrane or to other subcellular compartments, or they can be secreted from the cell. There is regular movement of proteins through these compartments. ER- and Golgi-resident proteins associate with other proteins but remain in their respective compartments. Other proteins pass through the ER and Golgi to the plasma membrane.
Most of the genetic information in the cell resides in the nucleus and is contained within the chromosomes (mitochondria also carry some DNA of their own). The study of the microscopically visible stages of cell division during mitosis and meiosis generally is considered part of cell biology, while the actual submicroscopic activity of DNA replication and protein synthesis is considered part of molecular biology.
Subdisciplines of Cell Biology
Active and Passive Transport
These are the movement of molecules into and out of cells.
This is how cells and tissues hold together.
This is the study of how cells duplicate themselves.
This is the regulation of cellular behavior by molecular signals from outside the cell.
These are the processes involved in creating and expending energy.
This is the study of the chemical processes and transformations in living organisms.
This is the study of the processes by which organisms grow and develop.
This is the science of genes, heredity and the variation of organisms.
This is the study of interactions of molecules among the various systems of a cell, including the interrelationship of DNA, RNA and protein synthesis and how these interactions are regulated.
This is the study of the architecture and shape of biological macromolecules — proteins and nucleic acids in particular — and what causes them to have the structures they have.