- ABC transporters
- ATP-binding cassette transporters. A large family of proteins which characterized
by conserved ATP-binding domains and clusters of membrane spanning alpha-helices
(i.e., integral membrane protein) believed to form a transmembrane pore. The
individual members of the family display a wide spectrum of substrate (i.e.,
- actin filaments (microfilaments)
- Filament formed by the polymerization of globular actin proteins. A major
cytoskeletal element found in all eukaryotic cells. Actin
filaments are also involved in the generation of contractile force through
associations with myosin.
- A general term used to describe proteins found on the suface of cells that are involved in cell-cell interactions or interactions of the cell with the substratum. Often contain domains that are involved in protein-protein interactions.
- amino acid
- The basic building block of proteins. Amino acids are
joined together chemically into long linear polymers to form proteins and
- A non-photosynthetic plastid found in Plasmodium and other apicomplexa.
Plastids are cytoplasmic organelles bound by 2-4 membranes,
contain their own DNA and often contain photosynthetic pigments. Chloroplasts
of plants are examples of plastids. The apicoplast is characterized by three-to-four
membranes, a 35 kb circular DNA and no pigments.
- Adenosine triphosphate. The primary source of energy for cells. The third
phosphate is hydrolyzed by enzymes called ATPases resulting
in the formation of ADP (adenosine diphosphate) and phosphate. The energy
stored in the hydrolyzed phosphate bond is captured and used to carry out
a function associated with that particular ATPase.
- Also referred to as 'constructive' metabolism. It is the process of converting
simple molecules to more complex molecules. An example include the de novo
synthesis of precursors, or building blocks, used for the synthesis of macromolecules
such as proteins and nucleic acids. The assembly of the precursors into macromolecules
would also be an example of anabolism. The antonym is catabolism.
- Bacteria-like organisms that that exhibit many unique features as well as
features typical of either prokaryotes or eukaryotes.
Their rRNA sequences are distinctly different from both
eubacteria and eukaryota (see 3-domain
tree of life).
- band 3
- A multipass integral membrane protein which functions
as an anion transporter. Band 3 also functions as an attachment site for the
spectrin-actin submembrane cytoskeleton of erythrocytes.
- Also referred to as 'destructive' metabolism. It is the opposite of anabolism
and involves breakdown of molecules into simpler components. For example,
the breakdown and oxidation of glucose to carbon dioxide and the capture of
the released energy in the form of ATP is a catabolic process.
Catabolism also includes the breakdown of macromolecules into their monomeric
- Structure composed of DNA and proteins representing the
basic hereditary unit. The long DNA molecule is packaged into compact structure
found within the nucleus.
- Heme proteins serving as electron carriers in electron transport chains
involved in respiration. See also oxidative phosphorylation.
- Filamentous structures which are responsible for cell shape. The three major
cytoskeletal systems are actin filaments (also called
microfilaments), microtubules and intermediate filaments
(only found in multicellular organisms). Microfilaments and microtubules are
also capable of generating force and movement through associated motor
- A subcellular structure found on the surface of many diverse protozoa that
is involved in feeding via an endocytic pathway.
- Deoxyribonucleic acid. DNA encodes all the information necessary for synthesizing
proteins and can be duplicated by the cell, and therefore
is the hereditary material of life (see Central
- Uptake of material into a cell by invagination of the plasma
membrane and the formation of a membrane-bound vesicle. Pinocytosis is
the uptake up external fluid material (i.e., 'cell drinking') and is distinguished
from phagocytosis which involves taking up large particulate matter or other
cells (i.e., 'cell eating'). The uptake of specific substances is accomplished
through receptor-mediated endocytosis. Exocytosis is the
opposite of endocytosis.
- A protein that catalyzes a biochemical reaction. Enzymes
are often parts of metabolic pathways that involve the conversion a molecule
into another molecule. [See diagrammatic example of metabolic
- epidermal growth factor (EGF)-like module
- A small structural domain, or motif, within a protein. The EGF-like domain
is characterized by spacing of cysteine residues which form disulfide bonds
(see Protein Structure).
- An organism in which the cells are compartmentalized. In particular, the
cells have a distinct nucleus and cytoplasm. The eukaryotes, prokaryotes
(= bacteria) and archaea make up the three
major domains of life.
- The export of substances from cells mediated by the fusion of secretory
vesicles with the plasma membrane. The contents of vesicles
are released following membrane fusion. Endocytosis is
the opposite of exocytosis.
- Refers to actin-myosin complex and associated proteins that is found between the inner membrane complex and the plasma membrane of the invasive stages of apicomplexan parasites and that provides the force for gliding motility and cell invasion.
- glutathione (GSH)
- A tripeptide (g-L-glutamyl-L-cysteineylglycine)
which participates in many redox reactions within cells.
GSH functions in many metabolic processes as well as in detoxifying ROI.
- Single pass integral membrane proteins exposed on the
- glycosylphosphatidylinositol (GPI) anchor
- A complex glycolipid covalently attached to the C-terminal end of a protein.
The fatty acid chains of the lipid are imbedded in the lipid bilayer of the
membrane and anchor the protein to the membrane.
- A prosthetic group found associated with many proteins. Heme-containing
proteins typically function in electron transfers (eg., cytochromes) or binding
oxygen (eg., hemoglobin). Heme is composed of an iron atom
and protoprophyrin IX.
- An abundant protein found in erythrocytes that functions in the transport
of oxygen to the tissues and the removal of carbon dioxide from the tissues.
Hemoglobin is a tetramer consisting of 2 alpha-globin chains and 2 beta-globin
chains. A heme group is associated with each of the 4 globin chains.
- A waste product formed by the malaria parasite as a byproduct of hemoglobin
degradation. It is also known as the malaria pigment. Free heme
groups are covalently linked through a carboxylic group and the iron into
a dimer which is identical to b-hematin. These
dimers form an insoluble substance through a biomineralization or biocrystallization
- Genes with similar sequences due to common ancestory. Homologs can be classified
as orthologs or paralogs. Genes
with sequence similarities not due to common ancestory are analogs.
- immunoglobulin (Ig) superfamily
- Proteins which have one or more Ig-like domains. The domain is about 100
amino acids and exhibits a characteristic structure stabilized by a disulfide
bond. Most members of the family mediate cell-cell recognition or antigen
recognition in the immune system. Members outside of the immune system include
other cell adhesion molecules and various growth factor receptors.
- inner membrane complex
- A double membrane lying underneath the plasma membrane of the invasive stages of Apicomplexan parasites composed of flattened vesicles running the length of the parasite and supported by sub-pellicular mictrotubules.
- integral membrane protein
- Proteins which pass through the lipid bilayer of the membrane.
Integral membrane proteins can have a single transmembrane domain or multiple
- Any molecule that binds to a specific site on a protein or other macromolecule.
Most often used in the context of receptors.
- A subcellular organelle characterized by acidic pH
and hydrolytic enzymes.
- A double layer of lipid molecules and associated proteins (see
Figure) which define subcellular compartments or enclose the cell. Types
of proteins associated with membranes are: integral membrane
proteins, peripheral membrane proteins and GPI-anchored
- Long cylindrical structures composed of proteins called tubulins. Microtubules
function as cytoskeletal elements, a major component of
cilia and flagella, and the mitotic spindle. Motor proteins
are involved in microtubule based motility.
- A doubled-membrane organelle that carries out electron
transport and oxidative phosphorylation and produces most
of the ATP in eukaryotic cells. The inner membrane is often
folded into numerous cristae.
- motor proteins
- Cytoskeletal proteins involved in the generation of
force. Motor proteins function by converting the chemical energy released
from the hydrolysis of ATP into mechanical energy. Myosin
functions as an actin-filament associated motor protein
and kinesin and dynein are microtubule associated motor
- moving junction
- Refers to the complex of adhesins from the parasite bound to the receptors on the host cell and anchored to the glidesome that is moved from the anterior of the parasite to the posterior of the parasite during gliding motility and cell invasion of apicomplexan parasites.
- Prominent membrane-bound organelle in eukaryotic cells
containing the DNA organized into chromosomes.
- A subcellular compartment which carries out a particular function(s).
- Homologous genes that perform the same functions
in different species.
- oxidative phosphorylation
- The enzymatic phosphorylation of ADP to ATP coupled to
electron transport in the mitochondria. Electrons derived from TCA
cycle intermediates flow down a series of electron-carrier proteins (i.e.,
cytochromes) until finally being transferred to molecular
oxygen. The available free energy derived from the electrons, as they move
to successively lower energy levels, is captured in the phosphate bond of
- Homologous genes that are the result of gene duplication
within an evolutionary lineage (eg., species) which may or may not have similar
- also called polypeptide. A linear polymer of amino acids
similar to a protein. Generally refers to a shorter polymer
than a protein, which are either natural cellular products or products resulting
from the degradation of proteins by proteases.
- peripheral membrane protein
- Proteins that associate with the outer surfaces of the membrane
lipid bilayer through non-covalent interactions with integral
membrane proteins or the polar groups of the lipids.
- plasma membrane
- The outermost membrane(s) of a cell.
- Organisms with cells lacking a well-defined membrane enclosed nucleus as
well as other membrane bound organelles. They include bacteria and cyanobacteria.
See also eukaryote.
- An enzyme that hydrolyses the peptide bond between amino
acids of a protein. Also called peptidase. Endopeptidases cleave within the
polypeptide chain. The specificity of cleavage is determined by the amino
acids near the scissile (i.e., hydrolyzed) bond. Exopeptidases remove amino
acids either one or two at a time from the ends of the polypeptide chain.
Exopeptidases are either amino-peptidases or carboxy-peptidases depending
upon the specificity for either the N-terminus or the C-terminus, respectively.
Proteases are grouped into 4 major classes depending on their mechanism: serine,
cysteine (or thiol), aspartic (or acid), and metallo.
- The major macromolecular constituent of cells. Responsible for cellular
structure and function. Composed of a linear
polymer of amino acids folded into a unique 3-dimensional structure.
See also peptide.
- Parasitophorous vacuolar membrane. A membrane surrounding intracellular
parasites. In the case of apicomplexa it is formed during parasite entry.
See merozoite invasion for more information
on the PVM and its formation.
- A protein that binds a specific ligand. Cell-surface
receptors are generally integral membrane proteins with a receptor-binding
domain exposed on the extracellular side.
- redox reactions
- refer to oxidation-reduction reactions. Oxidation is the loss of electrons
and reduction is the gain of electrons. Redox reactions proceed with the transfer
of electrons from an electron donor (i.e., reducing agent) to an electron
acceptor (i.e., oxidizing agent). Electron donors and acceptors function as
conjugate reductant-oxidant pairs:
electron donor « e- + electron acceptor
- After gaining an electron, the oxidant becomes the reductant and can be recycled by donating its electron and visa versa. Electrons will tend to flow from electronegative donors such as NADH to more electropositive acceptors such as cytochromes and ultimately oxygen. The transfer of electrons can also be mediated by a hydrogen atom in which case the dehydrogenation equals oxidation and hydrogenation equals reduction.
- Ribonucleic acid. The primary function of RNA involves the decoding of information stored in DNA by directing the synthesis of proteins (see Central Dogma). The 3 types of RNA are: messenger (mRNA), ribosomal (rRNA), and transfer (tRNA). The mRNA is transcribed from DNA and encodes the information necessary for the synthesis of proteins. The rRNA are a component of ribosomes, the organelle responsible for translating mRNA into protein. The tRNA decodes the genetic code and transfers the appropriate amino acid to the growing polypeptide chain.
- reactive oxygen intermediate. Highly reactive forms of oxygen (eg., hydrogen peroxide, super oxide, hydroxyl radical) capable of doing cellular damage.
- secretory vesicle
- A membrane-bound organelle in which molecules destined for export are stored prior to their release, or exocytosis.
- Cell adhesion proteins that recognize specific carbohydrate groups. Some selectins mediate the initial binding of neutrophils (white blood cells) to endothelial cells during the inflammatory response.
- spectrin-actin submembrane cytoskeleton
- Cytoskeletal elements associated with the erythrocyte membrane as peripheral membrane proteins. Spectrin proteins and short actin filaments form a 2-dimensional network on the cytoplasmic side of the erythrocyte plasma membrane. Other proteins are involved in the attachment of this network to band 3 and glycophorin.
- tricarboxylic acid (TCA) cycle
- A biochemical pathway of respiration in which acetyl residues are oxidized to carbon dioxide and hydrogen atoms via a cyclical series of enzymatic reactions. The hydrogen atoms--or more precisely, their equivalent electrons--are utilized in electron transport and oxidative phosphorylation.