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64 Cards in this Set
- Front
- Back
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α helix |
A type of helical secondary structure inproteins that is stabilized by intrachain hydrogenbonds between every fourth residue along thehelix. The helix is right-handed, has a pitch of 3.6residues and 0.54 nm (5.4 Å) per turn. (B1) |
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abasic site |
A site in a nucleic acid chain that haslost the purine or pyrimidine base, but still has the sugar–phosphate backbone intact. (B1) |
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acceptor arm |
The region of a tRNA molecule that carries the CCA segment to which an amino acid is covalently attached. (B1) |
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acetyl CoA |
An acetyl group (CH3CO) covalently bound to the sulfur-containingcoenzyme A (CoA). (B1) |
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acetylcholine |
A small neurotransmitter molecule released at the nerve terminal in response to anelectrical impulse. (B3) |
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activators |
Proteins that activate transcription, usually by binding to specific DNA sequences in agene promoter. (B2) |
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active site |
The region of an enzyme that bindsthe reactant (substrate) molecule and catalyses itstransformation into product(s). The active site hasspecific groups arranged in just the right positionsto provide the substrate with an optimalenvironment for the reaction to occur. Onlyparticular compounds will have the correct groupsin the correct geometry to bind to the active site,and this is the origin of the substrate specificity ofenzymes. Enzyme catalysis involves the formationof an enzyme–substrate complex, which thenbreaks down into product(s). (B1) |
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active transport |
Transport of a substance acrossa biological membrane against its concentrationgradient. The energy required is provided, directlyor indirectly, by hydrolysis of ATP. (B1) |
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activin |
A signalling protein that induces celldifferentiation of cultured Xenopus mesoderm cellsin vitro. (B4) |
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adaptor proteins |
The term used to describeproteins that link different proteins of anintracellular signalling pathway together. Also usedto describe proteins that bind both to coat proteinsand to integral membrane proteins of a vesicle andstimulate vesicle assembly. (B3) |
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adenosine |
A nucleoside comprising adeninelinked to ribose or deoxyribose. (B1) |
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adenylyl cyclase |
An enzyme that catalyses theproduction of cyclic AMP from ATP. It is activatedor inhibited by activated G protein subunits, mostlyby different forms of Gα (Gαs stimulates and Gαiinhibits adenylyl cyclase). (B3) |
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A-DNA |
A-DNA is a right-handed helical DNAstructure. In A-DNA, the major and minor groovesare of similar dimensions and there are 11 bp perhelical turn (compared with 10 bp in B-DNA). (B1) |
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adrenalin |
A biogenic amine (modified aminoacid) that acts as a hormone and as a neurotransmitter.It is released from the adrenal gland. (B3) |
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affinity |
The binding strength of a single adhesionmolecule for its ligand. (B4) |
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aggregation |
The consequences of exposure ofhydrophobic areas of polypeptide chains or theirpartial degradation products in the aqueous cellenvironment, wherein they coalesce and eventuallyprecipitate within a cell. Aggregates are commonlyfound in human neurodegenerative diseases. (B2) |
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agonist |
A molecule that binds a receptor whichthen becomes activated and propagates the signal.It acts in the same way as a naturally occurringligand at a receptor, i.e. it mimics the action of theligand. (B3) |
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aliphatic |
Organic compounds that have anextended hydrocarbon chain structure, e.g. fattyacids. (B1) |
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alkene |
A hydrocarbon chain of varying length,containing a double bond between two carbonatoms. Such a compound is said to be unsaturated.(B1) |
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allosteric regulation |
In many proteins, thebinding of a particular ligand at one site affects theconformation of a second remote binding site, foranother ligand, on the same protein. This is animportant mechanism by which a protein’s bindingcapacity and/or its activity is regulated. (B1) |
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alternative splicing |
The splicing of differentcombinations of exons of a pre-mRNA that canresult in the synthesis of different polypeptides ormRNAs with different stabilities. Also calleddifferential splicing. (B2) |
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amino acid |
A compound that contains both anamino group, \NH2, and a carboxyl group,\COOH. There are about 20 naturally occurringamino acids, which are particularly important inliving organisms; these have the general formula:OH2N CH COH Rwhere R represents one of about 20 differentgroups (side-chains). Amino acids are the monomersfrom which proteins are synthesized. (B1) |
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amino acid radicals |
Free radicals formed whenan amino acid residue in a protein is oxidized by(i.e. loses an electron to) a free radical, e.g. themethionine radical, Met•. (B4) |
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aminoacyl synthases |
Enzymes that areresponsible for tRNA charging, i.e. the joining ofthe appropriate tRNA molecule to itscorresponding amino acid. There is one suchenzyme for each of the 20 amino acidsincorporated into proteins. (B2) |
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amphipathic |
Term describing molecules that arepart hydrophilic and part hydrophobic, e.g.membrane lipids. Synonymous with amphiphilic.(B1) |
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amyloidoses |
Diseases associated with theaccumulation of aggregated proteins calledamyloid fibrils or plaques. (B4) |
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anaphase A |
The subdivision of anaphase thatinvolves the initial poleward movement ofchromosomes on the spindle. (B2) |
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anaphase B |
The subdivision of anaphase duringwhich the spindle poles separate further apart,moving towards the cell cortex. (B2) |
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anaphase promoting complex (APC) |
Acomplex of proteins whose activation triggers thetransition from metaphase to anaphase. ActivatedAPC both stimulates the ubiquitination of cyclinsand the release of the inhibition on securin. (B2) |
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anaphase |
The phase of mitosis when sisterchromatids separate from each other and migratetowards the poles of the spindle. (B2) |
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anchorage dependence |
The requirement thatsome cells have, for attachment to the extracellularmatrix and/or other cells, in order to survive. (B4) |
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anchoring cell junctions |
Intercellular junctionspresent in many types of animal tissues that serveto hold the constituent cells to each other and to thesurrounding extracellular matrix. Adherensjunctions and desmosomes are anchoring junctionsbetween cells. Focal adhesions and hemidesmosomesare anchoring junctions between a cell andthe extracellular matrix. (B1) |
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aneuploid |
A deviation from the normal copynumber of chromosomes within a cell, resultingfrom an unequal segregation of chromosomesbetween the daughter cells before cell division (e.g.one chromosome too few or too many). (B2) |
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angiogenesis |
Induction of the de novo formationof blood vessels. (B4) |
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ankyrin |
An erythrocyte (red blood cell)membrane protein that links band 3 (a transmembraneprotein) with spectrin (the principlecomponent of the underlying cell cortex). (B1) |
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antagonist |
A molecule that binds a receptor butdoes not signal. As a result, it antagonizes, i.e.blocks the action of, a naturally occurring ligand ata receptor. (B3) |
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anti-apoptotic |
The term used to describe eventsor regulatory proteins that inhibit caspase activityand hence apoptosis. (B3) |
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anticodon arm |
The region of a tRNA moleculethat includes the base triplet that pairs with itspartner codon in the mRNA chain. (B1) |
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antigen presentation |
The presentation offragments of foreign material on MHC moleculesto T cells. (B3) |
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antigen processing |
The degradation of foreignmaterial which precedes antigen presentation to theT cell. (B3) |
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antiparallel helix |
Helical structure adopted bytwo complementary DNA chains where one strandruns 5′–3′, the other 3′–5′. (B1) |
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antiparallel β pleated sheet |
β pleated sheetstructure in which the polypeptide chains run inopposite directions. (B1) |
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antiport |
Transport of two different types of ionor polar molecules in opposite directions across abiological membrane, facilitated by a transporterprotein. (B1) |
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antisense |
The synthetic DNA or RNA strand thatis complementary to the sense or template strand.Synthetic antisense DNA and RNA can be used toblock gene expression. (B1) |
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Apaf-1 |
(apoptotic protease activating factor-1)A cytosolic adaptor protein that interacts withcytochrome c after its release from mitochondria.Apaf-1 has a nucleotide binding domain and aCARD domain, but usually exists in an inactive or‘closed’ form. Binding of cytochrome c andsubsequent binding of ATP to the nucleotidebinding domain changes the conformation of theprotein to an ‘open’ form, exposing the CARDdomain. Procaspase 9 is recruited by homotypicinteractions between its CARD domain and that ofApaf-1, forming the apoptosome. (B3) |
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apical domain |
One of two distinct regions of theplasma membrane in polarized cells such as gutepithelial cells. The apical domain is the exposedsurface, opposite to the basolateral domain. In gutepithelium the apical domain is next to the contentsof the intestine and is the site of absorption ofnutrients. (B1) |
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apoptosis (programmed cell death type I) |
Thecontrolled death (suicide) of a cell that is mediatedby the cell’s own proteins, the caspases.Programmed cell death occurs during developmentand in tissue homeostasis and also in response tosome exogenous factors and cellular stresses suchas oxidative stress. Apoptotic cells are removed byphagocytosis, so do not cause damage tosurrounding cells. (B3) |
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apoptosis initiating factor (AIF) |
A protein thatis released from mitochondria in response toapoptotic stimuli. Evidence suggests that AIF actsindependently of caspases and may have severalpro-apoptotic functions. In addition to translocatingto the nucleus, where it induces DNA condensationand DNA degradation, it has also been found tocause dissipation of the mitochondrial membranepotential when injected into normal cells in culture.(B3) |
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apoptosome |
A multiprotein structure that isformed if mitochondrial permeability iscompromised and cytochrome c is released. Thecytochrome c binds to cytosolic adaptor proteins(Apaf-1) forming a complex which recruits aninitiator procaspase (procaspase 9) to form theapoptosome. The close proximity of the initiatorprocaspase proteins in the apoptosome allows theirautoactivation, and the active initiator caspasesubsequently activates downstream effector procaspases.(B3) |
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aptamers |
Nucleic acid molecules that have beendeveloped to mimic the selective and tight bindingof other molecules such as antibodies. Selex(systematic evolution of ligands by exponentialenrichment) is utilized to identify suitable chains.The oligonucleotide chain is capable of bindingspecifically to a target, such as a protein surface,using hydrogen bonding and van der Waalsattractive forces along the nucleic acid chain andbackbone. (B1) |
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aromatic |
Organic compounds that containunsaturated hydrocarbon rings (typically 6C) thathave properties similar to benzene C6H6 (e.g. theamino acid tyrosine). (B1) |
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ARP complex |
An actin-related protein complexthat mediates the nucleation of new actin filaments.(B4) |
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ARS elements |
Autonomously replicatingsequence elements – short DNA segments thatconfer the ability to replicate upon small circularplasmid DNAs (serving as replication origins) inyeast cells. (B2) |
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astral microtubules |
These microtubules radiatefrom the microtubule organizing centre (MTOC)toward the cell cortex. The action of motor proteinson astral microtubules plays an important role inthe movement of the spindle poles in anaphase B.(B2) |
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asymmetric division |
Cell division that results inan unequal distribution of proteins or mRNAsbetween the two daughter cells. Asymmetric3 division can produce cells that are either unequal orequal in size. (B4) |
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ATP cap |
A cap of relatively stable actin-ATPmolecules found at the plus end of a growingmicrofilament. (B3) |
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attenuation |
A regulatory mechanism found insome prokaryotic operons that utilizes theavailability of an amino acid for translation toregulate its own biosynthetic pathways. (B2) |
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autocrine signalling |
Type of cellularcommunication in which a cell secretes a signallingmolecule that binds to and activates receptors on itsown surface. (B3) |
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autophagic cell death (programmed cell deathtype II) |
Type of cell death in which organelles aredigested by lysosomes. (B3) |
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autophagic vacuoles |
Cytoplasmic vacuoles withdouble membranes that are present in cellsundergoing autophagic cell death. They containfragments of organelles and other cellular ‘debris’.(B3) |
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autophagy |
The internalization and degradationof molecular debris by lysosomes. (B3) |
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autophosphorylation |
The self-phosphorylationof a kinase (e.g. CaM kinase II). Also used todescribe the phosphorylation of residues on anidentical molecule (for example, the enzymaticdomains of receptor tyrosine kinases phosphorylateeach other when activated by dimerization thatfollows ligand binding). (B3) |
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avidity |
The overall strength of cellularadhesiveness, which is determined by the densityand distribution of adhesion molecules in alocalized region of the plasma membrane, and bythe affinity of individual adhesion molecules. (B4) |
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axon guidance |
The guidance of the growth ofaxons to ensure that the correct connections aremade with target cells. (B4) |
