In biology, a cell is the smallest living structure which functions as a living unit, also known as the smallest building block of life. The term "cell" was penned by Robert Hooke, who observed and studied the cells of cork microscopically in the late 17th century. What he observed reminded him of monastery cells. There are unicellular (single cell) organisms, such as bacteria, some algae and some fungi (yeasts); and there are multicellular organisms, such as plants and [animal|[animals]]. Cells do differ significantly in physical, functional and biochemical characteristics depending on whether they are from prokaryotes or eukaryotes, from plants or animals, or where they are located within the organism's body.
The structures of Eukaryotic and Prokaryotic cells are featured in photos below on this page. You will also find sections also on the differences between Eukaryotes and Prokaryotes and how plant and animal cells differ. This page also includes miscellaneous facts about cells and links that will help you further understand cell biology and structure. On the right of this page, there is a list of external links that can help you find out more about cells, like the Virtual Cell Tour, animations and microscopy links.
Different Characteristics of Cell Types.
Differences between the basic types of cells:
- Eukaryote - has cellular DNA in a nucleolus within a nuclear membrane, it is 10-100 micrometers in diameter, has cellular organelles, such as mitochondria, liposomes, ribosomes, reproduce by either mitosis or meiosis.
- Prokaryote - cellular DNA is diffused within the cell cytoplasm, it is from 1-10 micrometers in diameter, it has no cellular organelles except ribosomes, almost always single-celled and reproduce by binary fission. http://microbiology.suite101.com/article.cfm/prokaryotic_and_eukaryotic_cells
Differences between plant and animal cells (both are Eukaryotes):
- Plants - have rigid cell walls made of cellulose, chloroplasts for photosynthesis, a large central vacuole, cells manufacture sugar for their energy metabolism from carbon dioxide via photosynthesis
- Animals - do not have rigid cell walls, only membranes, cells break down sugar for energy and waste carbon dioxide. http://www.differencebetween.net/science/difference-between-animal-and-plant-cells/<ref>
Eukaryotic Cell Structures
Cell organelles contained within a eukaryotic cell are illustrated. The mitochondria is the site of cellular respiration for the cell, generating cell energy. The golgi complex secretes lipids for cell membranes and other processes. The nucleus contains the cell DNA. Lysosomes contain lysozyme enzymes which help the cell to recycle proteins. Ribosomes can be found on the surface of the endoplasmic reticulum and the cell cytoplasm (the clear cellular fluid between the organelles). Ribosomes which are important for cellular protein synthesis. The endoplasmic reticulum is a tubular network which is attached to the nuclear membrane and it makes a network in the cell cytoplasm for compartmentalization of the cell and the transport of cell metabolites. There are smooth and rough (with ribosomes) types of endoplasmic reticulum. In plant cells, there are also chloroplasts which harvest light energy to make glucose.
Bacterial (Prokaryotic) Cell Structure
The components of a bacterial cell are illustrated. All bacteria have the cellular DNA dispersed in the cytoplasm, ribosomes, cell membranes, a cell wall and a capsule. Some bacteria do not have flagellae, some have a single flagellum, and some have multiple flagellae. Not all bacteria have pili, but bacterial pathogens do, and the pili allow them to attach to host cells.
External Links on Cell Structure and Function
- Virtual cell tour - Downloadable cell structure files and on the site there are lists of questions to evaluate your understanding of the material. http://www.ibiblio.org/virtualcell/
- Inside the Cell - Several illustrated chapters and some animations of cell structure and function from the National Institute of General Medical Sciences. Great resource with some up-to-date information! http://publications.nigms.nih.gov/insidethecell/chapter1.html
- Animated presentation of cell structure, components and function. Detailed, including DNA, photosynthesis, diffusion, cell membranes, and many other aspects of cell biology. http://www.johnkyrk.com/
- Virtual electron microscope - Different types of cells are shown at various magnfications mostly using scanning electron microscopy. Some external structures of insects and fungi are also shown. http://school.discoveryeducation.com/lessonplans/interact/vemwindow.html
- Virtual light microscope - tool for learning how a light microscope works. Examples of various types of cells can be viewed and the viewer can operate the virtual light microscope under simulated conditions.
References
Fast Facts
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'''Structure'''
Rigid (plants and prokaryotes), flexible membrane (animals)
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'''Function of cell'''
Compartmentation of metabolism, protection from environmental stresses, reproduction
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'''Origin of name'''
Latin "cellula," small room
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'''Largest cell'''
Ostrich egg
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Modern cell theory
1. All cells come from pre-existing cells. 2. The cell is the basic unit of life. 3. All living things come from one or more cells.
