A molecule that has both hydrophobic and hydrophilic regions.
Arabidopsis thaliana
A small flowering plant used as a model for plant molecular biology and development.
archaebacteria
One of two major groups of prokaryotes; many species of archaebacteria live in extreme conditions similar to those prevalent on primitive Earth.
ATP (adenosine 5′-triphosphate)
An adenine-containing nucleoside triphosphate that serves as a store of free energy in the cell.
bacteriophage
A bacterial virus.
retrovirus
A virus that replicates by making a DNA copy of its RNA genome by reverse transcription.
bright-field microscopy
The simplest form of light microscopy in which light passes directly through a cell.
Caenorhabditis elegans
A nematode used as a simple multicellular model for development.
callus
An undifferentiated mass of plant cells in culture.
cell line
Cells that can proliferate indefinitely in culture.
cell wall
A rigid, porous structure forming an external layer that provides structural support to bacteria, fungi, and plant cells.
chloroplast
The organelle responsible for photosynthesis in the cells of plants and green algae.
confocal microscopy
A form of microscopy in which fluorescence microscopy is combined with electronic image analysis to obtain images with increased contrast and detail.
cyanobacteria
The largest and most complex prokaryotes in which photosynthesis is believed to have evolved.
cytoskeleton
A network of protein filaments that extends throughout the cytoplasm of eukaryotic cells. It provides the structural framework of the cell and is responsible for cell movements.
density-gradient centrifugation
A method of separating particles by centrifugation through a gradient of a dense substance, such as sucrose or cesium chloride.
differential centrifugation
A method used to separate the components of cells on the basis of their size and density.
differential interference-contrast microscopy
A type of microscopy in which variations in density or thickness between parts of the cell are converted to differences in contrast in the final image.
Drosophila melanogaster
A species of fruit fly commonly used for studies of animal genetics and development.
electron tomography
A method used to generate three-dimensional images by computer analysis of multiple two-dimensional images obtained by electron microscopy.
embryonic stem (ES) cell
A stem cell cultured from an early embryo.
endoplasmic reticulum (ER)
An extensive network of membrane-enclosed tubules and sacs involved in protein sorting and processing as well as in lipid synthesis.
endosymbiosis
A symbiotic relationship in which one cell resides within a larger cell.
epithelial cell
A type of cell that forms sheets (epithelial tissue) that cover the surface of the body and line internal organs.
equilibrium centrifugation
The separation of particles on the basis of density by centrifugation to equilibrium in a gradient of a dense substance.
erythrocyte
A red blood cell.
Escherichia coli (E. coli)
A species of bacteria that has been extensively used as a model system for molecular biology.
eubacteria
One of two major groups of prokaryotes, including most common species of bacteria.
eukaryotic cell
A cell that has a nuclear envelope, cytoplasmic organelles, and linear chromosomes.
fibroblast
A cell type found in connective tissue.
fluorescence microscopy
Type of microscopy in which molecules are detected based on the emission of flourescent light.
fluorescence recovery after photobleaching (FRAP)
A method used to study the movement of proteins within living cells.
fluorescence resonance energy transfer (FRET)
A method used to study protein interactions within living cells.
freeze fracture
Method of electron microscopy in which specimens are frozen in liquid nitrogen and then fractured to split the lipid bilayer, revealing the interior faces of cell membranes.
glycolysis
The anaerobic breakdown of glucose.
Golgi apparatus
A cytoplasmic organelle involved in the processing and sorting of proteins and lipids. In plant cells, it is also the site of the synthesis of cell wall polysaccharides.
granulocyte
A type of blood cell involved in inflammatory reactions.
green fluorescent protein (GFP)
A protein from jellyfish that is commonly used as a marker for fluorescence microscopy.
hydrophilic
Soluble in water.
hydrophobic
Not soluble in water.
lymphocyte
A blood cell that functions in the immune response. B lymphocytes produce antibodies and T lymphocytes are responsible for cell mediated immunity.
lysosome
A cytoplasmic organelle containing enzymes that break down biological polymers.
macrophage
A type of white blood cell specialized for phagocytosis.
metal shadowing
An electron microscopic technique in which the surface of a specimen is coated with a thin layer of evaporated metal.
mitochondria
Cytoplasmic organelles responsible for synthesis of most of the ATP in eukaryotic cells by oxidative phosphorylation.
monocyte
A type of blood cell involved in inflammatory reactions.
multi-photon excitation microscopy
A form of fluorescence microscopy in which the specimen is illuminated with a wavelength of light such that excitation of the fluorescent dye requires the simultaneous absorption of two or more photons.
neuron
A nerve cell specialized to receive and transmit signals throughout the body.
nucleus
The most prominent organelle of eukaryotic cells; contains the genetic material.
oxidative metabolism
The use of molecular oxygen as an electron acceptor in the breakdown of organic molecules.
peroxisome
A cytoplasmic organelle specialized for carrying out oxidative reactions.
phase-contrast microscopy
A type of microscopy in which variations in density or thickness between parts of the cell are converted to differences in contrast in the final image.
phospholipid
One of a family of molecules that are the principal components of cell membranes, consisting of two hydrocarbon chains (usually fatty acids) joined to a polar head group containing phosphate.
photosynthesis
The process by which cells harness energy from sunlight and synthesize glucose from CO2 and water.
plasma membrane
A phospholipid bilayer with associated proteins that surrounds the cell.
primary culture
A cell culture established from a tissue.
prokaryotic cell
A cell lacking a nuclear envelope and cytoplasmic organelles (bacteria).
pseudopodium
An actin-based extension of the plasma membrane responsible for phagocytosis and amoeboid movement.
resolution
The ability of a microscope to distinguish objects separated by small distances.
ribosome
A particle composed of RNA and proteins that is the site of protein synthesis.
RNA world
An early stage of evolution based on self-replicating RNA molecules.
Saccharomyces cerevisiae
A frequently studied budding yeast.
scanning electron microscopy
See electron microscopy.
transmission electron microscopy
See electron microscopy.
ultracentrifuge
A centrifuge that rotates samples at high speeds.
vacuole
A large membrane-enclosed sac in the cytoplasm of eukaryotic cells. In plant cells, vacuoles function to store nutrients and waste products, to degrade macromolecules, and to maintain turgor pressure.
velocity centrifugation
The separation of particles based on their rates of sedimentation.
video-enhanced microscopy
The combined use of video cameras with the light microscope to allow the visualization of small objects.
Xenopus laevis
An African clawed frog used as a model system for developmental biology.
yeast
The simplest unicellular eukaryotes. Yeasts are important models for studies of eukaryotic cells.
zebrafish
A species of small fish used for genetic studies of vertebrate development.
