3D structureThe 3D structure of a protein depends on its amino acid sequence.
Amino acidBasic unit of a protein. Every protein is a succession of amino acids linked to one another. There are 20 different amino acids, each of which is symbolised by a letter: A (alanine), C (cysteine), D (asparagine), E (glutamine), F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y.
AntibioticAn antibiotic is a natural substance produced by bacteria or fungi for instance. Much like a chemical weapon, an antibiotic will act upon other species of bacteria or fungi by either killing them or slowing down their proliferation. Currently, many antibiotics are made in the laboratory and are therefore artificial.
AntibodyAn antibody is a protein that is produced by cells known as B lymphocytes, which are part of the immune system. Antibodies are found in different fluids (blood, saliva...). Their role is to detect the presence of foreign bodies, i.e. other proteins or bits of protein which belong to a virus for example. When this happens, a defence response, known as the immune reaction, is triggered off and the intruder is eliminated. Antibodies can also recognise cancer cells.
AntigenAn antigen is generally a sugar, a protein, or bit of protein, which belongs to something foreign which has entered our body (pollen, virus, bacteria...). Antigens are like flags which warn our body that there is an intruder. They are recognised by antibodies, and are at the heart of the immune reaction.
ATPEnergy-storing molecule of cells. In eukaryotes ATP is generally produced in the mitochondria.
BacteriaBacteria are unicellular micro-organisms that have no nucleus and can live in a variety of environments (air, soil, water, other organisms...). In common usage, 'bacteria' includes bacteria and archaea (formerly known as archaebacteria) that generally live in extreme conditions (high acidity and elevated temperatures for instance).
BiochemistryBranch of biology that studies chemical reactions in living organisms, such as the production of energy in cells, or the synthesis and degradation of lipids.
BioinformaticsBioinformatics is a field in the life sciences which uses computer programs, mathematics and statistics to store, analyse and visualise biological data such as DNA sequences (genomes), protein sequences or experimental results.
BiotechnologyField of science where techniques, which make use of living organisms (bacteria, yeast...) or some of their genes or proteins, are applied to the food industry, agriculture, pharmaceuticals and medicine.
bpAbbreviation of 'base pair', used to indicate the number of nucleotides that are found in a sequence of DNA or RNA.
CancerAbnormal proliferation of cells (tumour), caused by uncontrolled cell division.
CellThe cell is the smallest unit necessary for the constitution of a living being. The number of cells in a given species varies: bacteria are made up of only one cell, the common earthworm, C.elegans, is made up of about 1’000 cells, while you need 100’000 billion cells to make a human being.
ChannelProtein lodged in a cell's membrane that acts like a pore through which only certain small molecules are permitted to pass.
ChromosomeA chromosome is a more or less compactly wound thread of DNA, a little like a ball of wool. In some organisms, including humans, chromosomes appear in their popular 'X' form at the time of cell division, and dark and light horizontal bands alternate along their length when specific colourings are used. The topography of these bands is characteristic of a chromosome and used to identify it.
DatabankComputerised encyclopedia that organises data in a very structured way in order to store huge quantities of information as efficiently as possible (synonym: database).
DatabaseComputerised encyclopedia that organises data in a very structured way in order to store huge quantities of information as efficiently as possible (synonym: databank).
DNADNA is a chain of nucleotides that are linked to one another via chemical bonds. There are four different nucleotides: adenine, cytosine, guanine and thymine symbolised by A, C, G and T respectively. The order of nucleotides is very precise in DNA, and is the basis of genetic information. More often than not, DNA has a 'double helix' structure made up of two long strands. The strands are linked to each other via the nucleotides, where adenine (A) always binds to thymine (T), and guanine (G) to cytosine (C), rather like a twisted ladder.
DomainRegion of about 200 amino acids within a protein, which has a defined structure and a particular role. On average, one protein is made up of 2 to 3 different domains.
EnzymeAn enzyme is a protein which accelerates chemical reactions in an organism. As an example, proteases are enzymes that are able to sever other proteins, just like a pair of scissors.
EukaryotesEukaryotes are organisms whose cells have a nucleus in which the chromosomes are confined. Animals (humans included), plants and fungi are eukaryotes. Prokaryotes, on the other hand, do not have a nucleus and their chromosomes are ‘free’.
EvolutionDescribes the transformations undergone by living organisms (animals, plants and bacteria) as time goes by. Evolution is the consequence of gradual genetic changes. It drives the creation of new species from a common ancestor. The evolution of species can be represented by a phylogenetic tree.
FunctionThe role of a protein (or any other molecule) in a cell or an organism. As an example, amongst many other functions, proteins can be hormones, antibodies, enzymes or receptors.
GeneA gene is a piece of DNA. One gene can carry the recipe to make a protein, for example.
Genetic CodeThe genetic code is almost universal. It is used by Nature to convert (translate) a gene (sequence of nucleotides) into a protein (sequence of amino acids). One amino acid is encoded by 3 nucleotides (or 'codon').
Genetic illnessIllness of genetic origin (for example due to a defective gene), which can reappear in a family in successive generations.
Genetically modifiedA genetically modified organism is an organism (bacteria, animals, plants) whose genome has been altered. This usually involves adding one or more genes from an organism’s genome into another. Genetically modified organisms are used to study diseases, in drug design or for agricultural purposes for example.
GenomeThe sum of DNA found in one cell. As a rule, every cell in an organism has the same genome.
GenomicsDerived from 'genome', the field of genomics includes all the techniques used to study genomes.
HormoneMolecule produced by a gland and generally secreted into the blood so that it can reach the organ(s) it needs to act upon. As an example, insulin is a hormone produced by the pancreas, which regulates the level of sugar in blood. Certain hormones are proteins (insulin, EPO).
Immune systemAn organism’s defense system against infectious agents (fungi, bacteria, viruses) and defective cells (cancer).
LesionDamaged part of tissue caused by an illness, an infection or an accident.
LipidLipids are molecules that are also known as fatty acids or, more colloquially, fats.
LymphThe lymph is a fluid which is rich in proteins and immune cells. It circulates throughout our body, and soaks all our organs. The lymph plays an important role in the immune system's response.
MembraneEnvelope which defines a cell and its compartments (the nucleus and mitochondria for example). A membrane is mainly made out of lipids and proteins.
MetabolismThe sum of synthesis and degradation reactions that take place in a cell or an organism.
Micro-organismOrganism which is generally microscopic and has its own genetic information. For example: viruses, bacteria and unicellular fungi and algae.
MitochondriaCellular compartment or 'organelle'. Mitochondria are like tiny power plants that produce the energy an organism needs. The energy produced is called ATP.
Molecular BiologyA branch of biology which studies the molecules of living matter (DNA, proteins...).
MoleculeA molecule is an assembly of atoms.
MutationA mutation occurs when one or more nucleotides are modified in a DNA sequence. Such a mutation can involve changing the nucleotides identity, or the suppression or the addition of one or more nucleotides. When a mutation affects a gene, it can alter the corresponding protein's function and thus cause a disease. Mutations can happen spontaneously or be the result of chemical agents, such as UV radiation or a virus. It is estimated that about 10 mutations occur every time a cell divides. Mutations are the source of evolution.
Nervous systemThe nervous system is composed of billions of neurons that form a communication network between the different parts of an organism.
NeuronNeurons are cells which make up the greater part of the nervous system. Neurons transport and transmit nerve signals to other neurons.
NeurotransmitterNeurotransmitters are small molecules that transmit information from one neuron to another. These small chemical messengers are freed at the very tip of a neuron and cross a space – known as the synaptic cleft – to bind to receptors on a neighbouring neuron.
NucleotideBasic unit of DNA and RNA. Nucleotides are molecules symbolised by letters. In DNA, A is for adenine, T for thymine, G for guanine and C for cytosine. In RNA, T is replaced by U for uracile.
ParasiteAn organism that is dependent on another organism, or host. Without a host, a parasite cannot survive or reproduce. A few examples: tapeworms, Plasmodium falciparum which causes malaria, and viruses.
pbAbbreviation of 'base pair', used to indicate the number of nucleotides that are found in a sequence of DNA or RNA.
PeptideTerm used to designate either a protein composed of a small number of amino acids (about 50), or a protein fragment.
PheromoneChemical substance that acts as a messenger between individuals of the same species. In particular, certain pheromones play a role in sexual attraction.
PolymorphismThe sequence of a given gene can vary from one individual to another. These variations are called ‘polymorphisms’. Polymorphisms can sometimes give rise to a difference in the gene’s corresponding protein sequence. Depending on the environment, a polymorphism can be ‘neutral’ (i.e. involve no change in an individual), can predispose an individual to an illness or, on the contrary, it can become an advantage for those who carry it (resistance to a disease for example). In humans, it has been estimated that there is about 1 polymorphism every 1000 nucleotides.
ProkaryotesA prokaryote is an organism composed of only one cell, whose DNA is not confined to a nucleus – as opposed to eukaryotes. Bacteria and archaea are prokaryotes.
ProteinLike pearls in a necklace, a protein is a succession of amino acids that are linked to one another via chemical bonds. There are 20 different amino acids. Proteins are of variable length and fold into specific shapes – their 3D structure – which determine their function. Proteins are essential for a living being’s construction and activity.
Protein synthesisProcess which manufactures proteins in cells. Protein recipes are found in genes, which are photocopied to produce what is known as a messenger RNA (mRNA). Proteins are made by ribosomes. Ribosomes read the mRNA and then assemble the amino acids using the genetic code, thus synthesising a protein.
ProteomeA proteome designates the sum of proteins that are found in an organism, at a given time. Butterflies and caterpillars have exactly the same genomes, yet their proteomes are very different.
ProteomicsTerm which encompasses all the techniques used to study proteomes.
ReceptorA receptor interacts with other molecules or proteins. Besides other activities, receptors help messages enter a cell.
RibosomeA ribosome is a protein factory. It reads the information held in the messenger RNA and translates it into a protein, using the genetic code. Every cell has thousands of ribosomes.
RNARNA can be described as a photocopy of a piece of DNA. Its chemical composition is very close to that of DNA but is only made up of one strand. RNA acts as a 'messenger', and is essential in the synthesis of proteins. There are also other types of RNA which are not directly involved in protein synthesis.
SequenceOrder in which are linked the basic components of a macromolecule. A DNA sequence is a succession of nucleotides symbolized by letters: A, T, G and C (for example: CAAGGAAGTTTGGCAGAGGA). A protein sequence is a succession of amino acids symbolized by the following letters (20 different ones): A, C , D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y (for example: MALWMRLLPLLALLALW).
SequencingTechniques used to determine the order of nucleotides in DNA or amino acids in a protein.
Sex chromosomesEvery cell in the human body has two copies of each chromosome, i.e. 23 pairs of chromosomes. There is only one pair of chromosomes that determines an individual's gender. In girls, it is the XX pair of chromosomes while, in boys, it is the XY pair.
SugarsSugars are also known under the name of carbohydrates or, more rarely, glucids.
TissueSum of cells that contribute to a common function such as heart cells, liver cells and kidney cells. An organ is composed of different tissues. For example, skin is made up of three tissues: epidermis, dermis and hypodermis.
ToxinToxic substance produced by certain living organisms, in particular bacteria, snakes and insects.
VaccineA vaccine stimulates the immune system without provoking an actual infection. It leaves behind a ‘memory’ of itself, which allows a fast and effective restart of the immune system if the infectious agent is re-encountered. A vaccine either contains a micro-organism (virus or bacteria) that has been inactivated, or a protein or protein fragment which belongs to the infectious agent.
VirusParasitic micro-organism. A virus is composed of a protein shell which protects its genetic information (DNA or RNA).