IAP family Intracellular protein inhibitors of apoptosis. Ig see immunoglobulin Ig superfamily Large family of proteins that contain immunoglobulin domains
or immunoglobulin-like domains. Most are involved in cell-cell interactions or
antigen recognition. image processing Computer treatment of images gained from microscopy that
reveal information not immediately visible to the eye. imaginal disc Group of cells that are set aside in the Drosophila embryo and
which will develop into an adult structure, e.g. eye, leg, wing. immature secretory vesicle Secretory vesicle that appears to have just
pinched off the Golgi stack. Its structure resembles that of a cisterna of the trans Golgi network. immortalization Production of a cell line capable of an unlimited number of
cell divisions. Can be the result of a chemical or viral transformation or of
fusion of the original cells with cells of a tumor line. immune response Response made by the immune system when a foreign
substance or microorganism enters its body. (See also innate immune response, adaptive immune response, primary immune response, secondary immune response.) immune system Population of lymphocytes and other white blood cells in the
vertebrate body that defends it against infection. immunoglobulin (Ig) An antibody molecule. Higher vertebrates have five
classes of immunoglobulin IgA, IgD, IgE, IgG, and IgM each with a
different role in the immune response. immunoglobulin domain (Ig domain) Characteristic protein domain of about
100 amino acids that is found in immunoglobulin light and heavy chains.
Similar domains, known as immunoglobulin-like (Ig-like) domains, are present
in many other proteins involved in cell cell interactions and antigen
recognition and define the Ig superfamily. immunogold electron microscopy Electron microscopy technique in which
cellular structures or molecules of interest are labeled with antibodies tagged
with electron-dense gold particles. These show up as black spots on the image. immunological memory Long-lived state that follows a primary immune
response to many antigens, in which subsequent encounter with that antigen
will provoke a rapid secondary immune response. immunoprecipitation Use of a specific antibody to draw the corresponding
protein antigen out of solution. The technique can identify complexes of
interacting proteins in cell extracts by using an antibody specific for one of the
proteins to precipitate the complex. in situ hybridization Technique in which a single-stranded RNA or DNA
probe is used to locate a gene or a messenger RNA molecule in a cell or tissue
by hybridization. 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 (in vitro), as opposed to in an organism (in vivo). (Latin for "in
glass.") in vivo In an intact cell or organism. (Latin for "in life.") induction In developmental biology, a change in the developmental fate of
one tissue caused by an interaction with another tissue. Such an interaction is
called an inductive interaction. inflammatory response Local response of a tissue to injury or
infection characterized by tissue redness, swelling, heat, and pain. Caused by
invasion of white blood cells, which release various local mediators such as
histamine. inhibitor of apoptosis family see IAP family inhibitory G protein (Gi) G protein that can regulate ion channels and inhibit
the enzyme adenylyl cyclase. inhibitory neurotransmitter Neurotransmitter that opens transmitter-gated
Cl or K+ channels in the postsynaptic membrane of a nerve or muscle cell
and thus tends to inhibit the generation of an action potential. initiation factor Protein that promotes the proper association of ribosomes
with messenger RNA and is required for the initiation of protein synthesis. initiator tRNA Special tRNA that intiates translation. It always carries the
amino acid methionine. innate immune response Immune response (of both vertebrates and
invertebrates) to a pathogen that involves the pre-existing defenses of the
body the innate immune system such as barriers formed by skin and
mucosa, antimicrobial molecules and phagocytes. Such a response is not
specific for the pathogen. inner membrane The innermost of two membranes surrounding an organelle.
In the mitochondrion, it encloses the matrix and contains the respiratory
electron transport chains. inner nuclear membrane The innermost of the two nuclear membranes. It
contains binding sites for chromatin and the nuclear lamina on its internal face. inositol phospholipids (phosphoinositides) One of a family of lipids
containing phosphorylated inositol derivatives. Although minor components of
the plasma membrane, they are important in signal transduction in eucaryotic
cells. insulator element DNA sequence that prevents a gene regulatory protein
bound to DNA in the control region of one gene from influencing the
transcription of adjacent genes. insulin Polypeptide hormone that is secreted by b cells in the pancreas and
helps regulate glucose metabolism in animals. integral membrane protein Protein that is held tightly in a membrane and can
only be removed by treatments that disrupt the lipid bilayer. integrin Member of a large family of transmembrane proteins involved in the
adhesion of cells to the extracellular matrix and to each other. intercalary regeneration Type of regeneration that fills in the missing tissues
when two mismatched parts of a structure are grafted together. interferon-g (IFN-g) Cytokine secreted by certain types of T cells after
activation, and which enhances the anti-viral response and macrophage
activation. interleukin Secreted peptide or protein that mainly mediates local interactions
between white blood cells (leucocytes) during inflammation and immune
responses. intermediate filament Fibrous protein filament (about 10 nm in diameter) that
forms ropelike networks in animal cells. One of the three most prominent types
of cytoskeletal filaments. intermembrane space (1) The subcompartment formed between the inner and
outer mitochondrial membranes. (2) The corresponding compartment in a
chloroplast. internal membrane Eucaryotic cell membrane other than the plasma
membrane. The membranes of the endoplasmic reticulum and the Golgi
apparatus are examples. interphase Long period of the cell cycle between one mitosis and the next.
Includes G1 phase, S phase, and G2 phase. intracellular signaling protein Protein that relays a signal as part of an
intracellular signaling pathway. It may either activate the next protein in the
pathway or generate a small intracellular mediator. intron Noncoding region of a eucaryotic gene that is transcribed into an RNA
molecule but is then excised by RNA splicing during production of the
messenger RNA or other functional structural RNA. inversion Type of mutation in which a segment of chromosome is inverted. ion channel Transmembrane protein complex that forms a water-filled channel
across the lipid bilayer through which specific inorganic ions can diffuse down
their electrochemical gradients. ion An atom that has either gained or lost electrons to acquire a charge; for
example Na+ and Cl . ionic bond Cohesion between two atoms, one with a positive charge, the other
with a negative charge. One type of noncovalent bond. ionophore Small hydrophobic molecule that dissolves in lipid bilayers and
increases their permeability to specific inorganic ions. iron-sulfur center Electron-transporting group consisting of either two or four
iron atoms bound to an equal number of sulfur atoms, found in a class of
electron-transport proteins. isoelectric point The pH at which a charged molecule in solution has no net
electric charge and therefore does not move in an electric field. isomers Molecules that are formed from the same atoms in the same chemical
linkages but have different three-dimensional conformations. isoprenoid (polyisoprenoid) Member of a large family of lipid molecules
with a carbon skeleton based on multiple five-carbon isoprene units. Examples
include retinoic acid and dolichol. isotope One of a number of forms of an atom that differ in atomic weight but
have the same number of protons and electrons, and therefore the same
chemistry. May be either stable or radioactive.
