Fab The part of an antibody molecule which
contains the antigen-combining site, consisting of a light chain and part
of the heavy chain; it is produced by enzymatic digestion.
Facilitated diffusion Protein-aided
transport of an ion or molecule across a membrane down its concentration
gradient. This type of transport is characterized by three properties:
(1) a rate faster than that predicted by passive diffusion through a phospholipid
bilayer according to Fick’s law; (2) ligand specificity (expressed by
Km); and (3) saturation (Vmax). The glucose
transporter is a well studied example of a protein that mediates facilitated
diffusion.
Factors B, P, D, H, and I Components of the
alternative complement pathway
Factor XII Initial factor in complete intrinsic
pathway sequence of reactions that results in blood clotting.
Factor XIIIa Activated plasma protein that
catalyzes cross-link formation between fibrin molecules to strengthen
blood clot.
Fc The portion of an antibody that is responsible
for binding to antibody receptors on cells and the C1q component of complement.
Fc receptors Surface molecules on a variety
of cells that bind to the Fc regions of immunoglobulins. They are antibody
class specific and isotype selective
Feedback inhibition Decrease in
the catalytic activity of one of the enzymes in a metabolic pathway caused
by binding of the ultimate product of the pathway. Usually, the inhibited
step is the first step in the pathway that does not lead to other products.
Fermenter Large-scale culture vessel, usually
applied to cells in suspension (for animal cells or microorganisms).
Ferritin Iron-binding protein that stores
iron in body.
Fertilization Fusion of a female
and male gamete (both haploid) to form a diploid zygote, which develops
into a new individual.
Fetus Period of mammalian development from
second month of intra-uterine life until birth.
Fibroblast A proliferating precursor cell
of the mature differentiated fibrocyte.
Fibroblastic Resembling fibroblasts, i.e.,
spindle shaped (bipolar) or stellate (multipolar) ; usually arranged in
parallel arrays at confluence if contact inhibited. Often used indiscriminately
for undifferentiated mesodermal cells regardless of their relationship
to the fibrocyte lineage. Implies a migratory type or cell with processes
exceeding the nuclear diameter by threefold or more.
Fibrinolytic system Cascade of plasma enzymes
that breaks down clots; also called thrombolytic system.
Fibronectin An extracellular multiadhesive
protein that binds to other matrix components, fibrin, and cell-surface
receptors of the integrin family. It functions to attach cells to the
extracellular matrix and is important in wound healing.
Field inversion gel electrophoresis (FIGE)
An electrophoresis technique for the separation of large DNA molecules.
Finite cell line A culture that has been
propagated by subculture but is only capable of a limited number of cell
generations in vitro before dying out.
Flagellum (pl. Flagella) Membrane-enclosed
locomotory structure extending from the surface of eukaryotic cells and
composed of a specific arrangement of microtubules, called an axoneme.
Usually there is only one flagellum per cell (as in sperm cells), and
its bending propels the cell forwards or backwards. Bacterial flagella
are much simpler structures containing a single predominant type of protein.
Fluorescence activated cells sorter (FACS)
A machine that analyses cells by flow cytometry and then allows them to
be sorted into different populations and collected.
Fluorescence in situ hybridization
(FISH) A hybridization technique that uses fluorochromes of
different colors to enable two or more genes to be located within a chromosome
preparation in a single in situ experiment.<
Follicular dendritic cells Antigen-presenting
cells present in the B-cell areas of lymphoid tissues which retain stores
of antigen.
Footprinting DNase technique for
identifying DNA regions that bind protein by digesting a radiolabeled
DNA sample with DNase in the presence or absence of a DNA-binding protein
and then subjecting the samples to gel electrophoresis. Because regions
of DNA with bound protein are protected from digestion, the patterns of
fragment bands from protected and unprotected samples will differ, permitting
identification of the protein-binding regions of the DNA.
Freund’s adjuvant An emulsion of aqueous
antigen in oil. Complete Freund’s adjuvant contains killed Mycobacterium
tuberculosis, while incomplete Freund’s adjuvant does not.
Free energy (G) A measure
of the potential energy of a system that is a function of the enthalpy
(H) and entropy (S).
Free-energy change (ΔG) The difference in the free energy of the product molecules
and of the starting molecules in a chemical reaction, which can be used
to predict the equilibrium of a reaction. A large negative value of ΔG
indicates that a reaction has a strong tendency to occur from left to
right, as written
