a
actin filament:
Protein filament, about 7 nm thick, formed from a chain of globular actin molecules. A major constituent of the cytoskeleton of all eucaryotic cells and especially abundant in muscle cells.
anaphase:
Stage of mitosis during which the two sets of chromosomes separate and move away from each other. Composed of anaphase A (chromosomes move toward the two spindle poles) and anaphase B (spindle poles move apart).
angiogenesis:
Blood vessel formation which usually accompanies the growth of malignant tissue.
apoptosis:
see programmed cell death. A normal cellular process involving a genetically programmed series of events leading to the death of a cell.
ATP (adenosine 5-triphosphate):
Nucleoside triphosphate composed of adenine, ribose, and three phosphate groups; the principal carrier of chemical energy in cells. The terminal phosphate groups are highly reactive in the sense that their hydrolysis, or transfer to another molecule, takes place with release of a large amount of fee energy.
c
cancer:
Disease arising from mutant cells that escape normal controls on cell division and invade and colonize the tissues of the body.
cardiovascular disease:
Disease affecting the heart or blood vessels. Cardiovascular diseases include arteriosclerosis, coronary artery disease, heart valve disease, arrhythmia, heart failure, hypertension, orthostatic hypotension, shock, endocarditis, diseases of the aorta and its branches, disorders of the peripheral vascular system, and congenital heart disease.
cell:
The basic unit from which living organisms are made, consisting of an aqueous solution of organic molecules enclosed by a membrane. All cells arise from existing cells, usually by a process of division into two.
cell cycle:
Reproductive cycle of the cell: the orderly sequence of events by which a cell duplicates its contents and divides into two.
cell division:
Separation of a cell into two daughter cells. In eucaryotic cells it entails division of the nucleus (mitosis) closely followed by division of the cytoplasm (cytokinesis).
centrosome (cell center):
Centrally located organelle of animal cells that is the primary microtubule-organizing center and is duplicated to form the spindle poles during mitosis. In most animal cells it contains a pair of centrioles.
cytokinesis:
Division of the cytoplasm of a plant or animal into two, as distinct from the division of its nucleus (which is mitosis).
cytoplasm:
Contents of a cell that are contained within the plasma membrane but, in the case of eucaryotic cells, outside the nucleus.
cytoskeleton:
System of protein filaments in the cytoplasm of a eucaryotic cell that gives the cell a polarized shape and the capacity for directed movement. Its most abundant components are actin filaments, microtubules, and intermediate filaments.
d
dimorphism:
Having two different distinct forms of individuals within the same species or two different distinct forms of parts within the same organism. For plants, it could refer to different leaf types, flowers, etc. For animals, it could refer to different colouring, sizes, features, etc. Sexual dimorphism is a common case, where the two sexes have different shapes, sizes, etc. from each other.
dynein:
Member of a family of large motor proteins that undergo ATP-dependent movement along microtubules. Dynein is responsible for the bending of cilia.
e
endoplasmic reticulum (ER):
Labyrinthine, membrane-bounded compartment in the cytoplasm of eucaryotic cells, where lipids are secreted and membrane-bound proteins are made.
endothelial cell:
A thin, flattened cell; a layer of them lines the inside surfaces of body cavities, blood vessels, and lymph vessels, making up the endothelium.
endothelium:
A layer of cells (called endothelial cells) that lines the inside surfaces of body cavities, blood vessels, and lymph vessels.
epithelium:
Sheet of cells covering or lining an external surface or cavity.
eucaryote:
(Also eukaryote.) Living organism composed of one or more cells with a distinct nucleus and cytoplasm. Includes plans, animals, fungi and protozoa; excludes bacteria (prokaryotes).
extracellular matrix:
Complex network of polysaccharides (such as glycosaminoglycans or cellulose) and proteins (such as collagen) secreted by cells. A structural component of tissues that also influences their development and physiology.
f
fibroblast:
Common cell type, found in connective tissue, that secretes an extracellular matrix rich in collagen and other macromolecules. Migrates and proliferates readily in wound repair and in tissue culture.
fungal infections:
An infection caused by the presence of a fungus. For instance, Candidiasis, also called thrush, is a fungal, or yeast, infection caused by Candida albicans or consider a yeast, Cryptococcus neoformans, that is responsible for causing cryptococcosis infection.
G
G1 phase:
Gap 1 phase of the eucaryotic cell cycle, between the end of Cytokinesis and the start of DNA synthesis.
G2 phase:
Gap 2 phase of the eucaryotic cell cycle, between the end of DNA synthesis and the beginning of mitosis.
Golgi apparatus:
Membrane bound organelle in eucaryotic cells, where the proteins and lipids made in the endoplasmic reticulum are modified and sorted. (Named after its discoverer, Camillo Golgi.)
i
in vitro:
Term used by biochemists to describe a process taking place in an isolated cell-free extract. Also used by cell biologists to refer to cells growing in culture. (Latin for in glass.)
in vivo:
In an intact cell or organism. (Latin for in life.)
intermediate filament :
Fibrous protein filament (about 10nm in diameter) that forms ropelike bundles in animal cells. Often provides tensile strength to withstand tension applied to the cell from outside.
k
kinesin:
One of the types of motor proteins that use the energy of ATP hydrolysis to move along microtubules.
l
lipid:
Organic molecule, generally containing hydrocarbon chain(s), that is insoluble in water but dissolves readily in nonpolar organic solvents. One class the phospholipids, forms the structural basis of biological membranes.
lysosome:
Intracellular membrane-bounded organelle containing digestive enzymes. The interior of a lysosome is strongly acidic, and its enzymes are active at an acid pH.
M
M phase:
Period of the eucaryotic cell cycle during which the chromosomes are condensed and the nucleus and cytoplasm divide.
meiosis:
Special type of cell division by which eggs and sperm cells are made involving reduction from a diploid (double) to a haploid (single) chromosome set. Two successive nuclear divisions with only one round of DNA replication generate four haploid cells daughter cells from the initial diploid cell. (From Greek, meiosis, diminution.)
membrane:
Thin sheet of lipid molecules and associated proteins that encloses all cells and forms the boundaries of many eucaryotic organelles.
metaphase:
Stage of mitosis at which chromosomes are firmly attached to the mitotic spindle at its equator but have not yet segregated toward opposite poles.
metastasis:
The spread of cancer from one part of the body to another. Cells in the metastatic (secondary) tumor are like those in the original (primary) tumor.
microtubule:
Long, stiff, cylindrical intracellular structure, 20 nanometers in diameter, composed of the protein tubulin; one of the major components of the cytoskeleton, used by eucaryotic cells to regulate their shape and control their movements.
mitochondrion (plural mitochondria):
Membrane-bounded organelle, about the size of a bacterium, that carries out oxidative phosphorylation and produces most of the ATP in eucaryotic cells.
mitosis:
Division of the nucleus of a eucaryotic cell, involving condensation of the DNA into visible chromosomes. (From Greek, mitos, a thread, referring to the threadlike appearance of the condensed chromosomes.)
mitotic spindle:
Array of microtubules and associated molecules that forms between the two poles of a eucaryotic cell during mitosis and serves to move the duplicated chromosomes apart.
motility:
The ability to move spontaneously.
motor protein:
Protein such as myosin or kinesin that uses energy derived from ATP hydrolysis to propel itself along a protein filament.
myofibril:
Long, highly organized contractile bundle of actin, myosin, and other proteins in the cytoplasm of a muscle cell; contracts by a sliding-filament mechanism.
myosin:
Motor protein that uses ATP to drive movements along actin filaments. Myosin II is a large protein that forms the thick filaments of skeletal muscle. Smaller myosins, such as myosin I, are widely distributed, and responsible for many actin-based movements within cells.
n
neurodegenerative:
A type of neurological disease marked by the loss of nerve cells.
nuclear envelope:
Envelope surrounding the nucleus in a eucaryotic cell. It consists of two lipid bilayer membranes an outer and an inner and is perforated by nuclear pores.
nucleolus:
Structure in the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled.
nucleus:
(1) In a eucaryotic cell, the major organelle, containing DNA organized into chromosomes. (2) In an atom, the massive central body composed of neutrons and protons.
o
oncogene:
Gene that makes a cell cancerous. Typically a mutant form of a normal gene (proto-oncogene) involved in the control or cell growth or division.
oncology:
The study of cancer.
organelle:
A discrete structure or subcompartment of a eucaryotic cell specialized to carry out a particular function; especially a cellular substructure that is visible in the light microscope. Examples include mitochondria and the Golgi apparatus.
p
peroxisome:
Small membrane-bounded organelle that uses molecular oxygen to oxidize organic molecules. Contains some enzymes that produce hydrogen peroxide and others that degrade hydrogen peroxide (H2O2).
phagocytosis:
The process by which particulate material is engulfed by a cell. Prominent in predatory protozoa, such as Amoeba proteus, and in certain specialized cells of multicellular animals such as macrophages. (From Greek, phagein, to eat.)
phenotype:
The observable character of a cell or an organism.
plasma membrane:
Membrane that surrounds a living cell.
programmed cell death (apoptosis):
Normal benign process of cell suicide, in which the cell shrinks, dissolves its contents, and activates phagocytosis by neighboring cells.
prometaphase:
Stage of mitosis that precedes metaphase.
prophase:
First stage of mitosis during which the chromosomes are condensed but not yet attached to a mitotic spindle. Also a superficially similar stage in meiosis.
S
S phase:
Period of a eucaryotic cell cycle in which DNA is synthesized.
sarcomere:
Repeating unit of a myofibril in a muscle cell, about 2.5 mm long, composed of an array of overlapping thick (myosin) and thin (actin) filaments.
secretory vesicle:
Membrane-bound organelle in which molecules destined for secretion are stored prior to release. Sometimes called secretory granule because darkly staining contents make the organelle appear as a small dense object.
spindle pole:
One of the pair of centrosomes in a cell undergoing mitosis. Microtubules radiating from these centrosomes form the mitotic spindle.
systemic fungal infection:
An infection of the bloodstream or organs of the body caused by the presence of a fungus. For instance, candidemia, a bloodstream infection of the fungus Candida albicans.
t
telophase:
Final stage of mitosis in which the two sets of separated chromosomes decondense and become enclosed by nuclear envelopes.
tubulin:
Protein from which microtubules are made.
tumor:
An abnormal mass of undifferentiated cells within a multicellular organism. They can interfere with vital body functions and absorb nutrients needed elsewhere. They can be malignant (cancerous), which means they will grow rapidly and spread to other parts of the body or cause more tumors to form elsewhere, or be benign, which means that they will generally grow much more slowly and stay put in one area.
v
vesicle:
Small, membrane-bounded, spherical organelle in the cytoplasm of a eucaryotic cell.
