Biology glossary

Amino acid

An amino acid is a small molecule that forms the basic unit of proteins.During protein synthesis, amino acids are linked together in a specific order determined by genetic information.There are twenty amino acids mainly used by cells to…

Biochimie

DNA

DNA (deoxyribonucleic acid) is a double helix-shaped molecule composed of nucleotides.Each nucleotide contains one nitrogenous base out of four types: adenine (A), thymine (T), cytosine (C), and guanine (G).These bases always pair (A wi…

Génétique

Allele

An allele is a different version of the same gene.Each individual has two alleles for a gene, one inherited from each parent, which can be identical or different.

Génétique

Dominant allele

A dominant allele is a version of a gene that can express itself in the phenotype when present in a single copy.In a heterozygous individual possessing one dominant allele and one recessive allele, the trait associated with the dominant…

Génétique

Recessive allele

A recessive allele is a version of a gene whose effect is generally masked by a dominant allele in a heterozygous individual.The trait associated with this allele is most often expressed when the individual has two recessive copies, tha…

Génétique

Antibiotic

An antibiotic is a substance used to kill or inhibit the growth of bacteria responsible for certain infections.

Microbiologie

Antibody

Antibodies are proteins produced by the body to recognize and neutralize microbes, such as bacteria or viruses.

Immunologie

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Antigen

An antigen is a foreign substance, such as a part of a microbe, that the body recognizes and against which it produces antibodies.

Immunologie

RNA

RNA (ribonucleic acid) is a molecule present in all cells that plays an essential role in the transmission and use of genetic information.It is made from DNA and is notably used to produce the proteins necessary for the functioning of c…

Biologie moléculaire

Artery

An artery is a blood vessel that carries blood from the heart to organs and tissues.Its wall is thick, elastic, and muscular to withstand the pressure produced by the heart's contractions.Most arteries carry oxygen-rich blood.The pulmon…

Système cardiovasculaire

ATP

ATP, or adenosine triphosphate, is a molecule used by cells to quickly store and transfer energy.This energy is contained in the bonds between its phosphate groups.When one phosphate group is detached, ATP becomes ADP and releases energ…

Métabolisme cellulaire

Bacterium

A bacterium is a microorganism made up of a single cell without a nucleus, capable of living in many environments (air, water, soil, human body).It reproduces rapidly by division.Some bacteria are essential for life, while others are ca…

Microbiologie

Biodiversity

Biodiversity is the variety of all living organisms, including different species of animals, plants, fungi, and microorganisms, as well as the variety of natural environments where they live.It also includes genetic diversity within eac…

Écologie

Biotope

A biotope is a natural environment with precise physical and chemical characteristics (such as temperature, water, soil) that enable certain living beings to live there.

Écologie

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Blastocyst

The blastocyst is an early stage of embryonic development in mammals. It appears a few days after fertilization and takes the form of a hollow structure made up of several cells.Its outer layer plays a key role in forming the placenta, …

Reproduction humaine

Genetic recombination

Genetic recombination refers to the mechanisms that create new combinations of alleles during sexual reproduction.It occurs notably during meiosis, thanks to the random distribution of parental chromosomes and exchanges of fragments bet…

Génétique

Blood capillary

A blood capillary is a microscopic vessel that connects the smallest arteries to the smallest veins.Its very thin wall is made of a single layer of cells, which facilitates exchanges between the blood and tissues.Oxygen and nutrients ca…

Système cardiovasculaire

Karyotype

A karyotype is an ordered display of all the chromosomes in a cell, generally arranged in pairs, by size, and according to their shape.It is made from chromosomes visible when they are highly condensed during cell division.The karyotype…

Génétique

Cell

A cell is the smallest living unit capable of autonomous function and constitutes the foundation of all living beings.It is bounded by a plasma membrane that protects the cell and controls exchanges with the outside.Inside, it contains …

Biologie cellulaire

Stem cell

A stem cell is a cell capable of multiplying and producing different types of specialized cells.When it divides, it can form a new stem cell or a cell that will differentiate to perform a specific function.Stem cells participate in embr…

Biologie cellulaire

Food chain

The food chain shows how energy and matter circulate in an ecosystem, moving from producers to consumers and then decomposers.Plants → Insects → Frog → Snake → OwlIn this chain:Plants are producers; they make their own food using sunlig…

Écologie

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Chloroplast

The chloroplast is a membrane-bound organelle found in green plant cells. It contains chlorophyll, a pigment that captures sunlight and allows the transformation of light energy into chemical energy during photosynthesis.
Inside the c…

Biologie cellulaire

Chromatid

A chromatid is one of the two identical copies of a chromosome after DNA duplication.The two chromatids of the same chromosome, called sister chromatids, are connected at a region called the centromere.During cell division, they separat…

Génétique

Chromosome

A chromosome is a thread-like, compact structure located in the nucleus of eukaryotic cells.It is made up of DNA wrapped around proteins called histones.Each chromosome carries many genes, which contain the instructions necessary for th…

Génétique

Contraception

Contraception includes all methods and means used to prevent pregnancy.It works by preventing the meeting of the sperm and the egg (fertilization), blocking the release of the egg (ovulation), or preventing the implantation of the embry…

Reproduction humaine

Cytoplasm

The cytoplasm is the gel-like substance, mainly composed of water, that fills the inside of the cell between the plasma membrane and the nucleus.It contains organelles, such as mitochondria or ribosomes, which perform various vital func…

Biologie cellulaire

Dictyosome

A dictyosome is a stack of flattened membrane sacs that form part of the Golgi apparatus.It receives proteins and lipids produced in the endoplasmic reticulum, then modifies, sorts, and directs them to their destination.These molecules …

Biologie cellulaire

Ecosystem

An ecosystem is a set formed by a natural environment, called biotope (with its physical characteristics such as soil, water, air), and by the community of living beings that inhabit it, called biocenosis.These living beings (plants, an…

Écologie

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Enzyme

An enzyme is a protein that acts as a biological catalyst.It speeds up chemical reactions in cells by lowering the energy required for them to occur, without being changed or consumed during the reaction.

Biochimie

Species

A species is a group of individuals that share common characteristics and can usually reproduce with each other to produce viable and fertile offspring.This definition is especially suited to organisms that reproduce sexually, but it do…

Écologie

Fertilization

Fertilization is the fusion of two reproductive cells, called gametes, which allows the formation of a single new cell. This cell, called a zygote, contains the genetic material from both parents and marks the beginning of the developme…

Reproduction humaine

Gamete

A gamete is a specialized reproductive cell that contains half the usual number of chromosomes of an organism.In animals, there are two types of gametes: the sperm (male gamete) and the ovum (female gamete).During fertilization, two gam…

Reproduction humaine

Gene

A gene is a segment of DNA that contains the information needed to make a protein or control a specific function within an organism.Genes determine hereditary characteristics, such as eye color or height.Each individual has two versions…

Génétique

Genome

The genome corresponds to all the genetic material of an organism or a cell. It contains genes, but also regions of DNA that do not directly code for proteins and may play a role in regulating their function.In humans, most of the genom…

Génétique

Genotype

The genotype corresponds to the set of alleles possessed by an individual, or more precisely, to the combination of alleles they have for one or several genes.The genotype contributes to the determination of observable traits, but its e…

Génétique

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Carbohydrate

A carbohydrate is an organic molecule primarily made up of carbon, hydrogen, and oxygen. Carbohydrates serve as an important energy source for cells.For example, glucose can be used during cellular respiration to produce ATP.Some carboh…

Biochimie

Helicase

A helicase is an enzyme capable of separating the two strands of a DNA molecule.It works by breaking the weak bonds that hold together the complementary bases of the double helix.This opening of the DNA is essential before replication, …

Biologie moléculaire

Red blood cell

A red blood cell, also called an erythrocyte, is a blood cell specialized in transporting respiratory gases.It contains a large amount of hemoglobin, a protein mainly able to bind oxygen in the lungs and release it in the organs.In huma…

Système cardiovasculaire

Heterozygote

An individual is heterozygous for a gene when they have two different alleles of that gene, one inherited from each parent.If one allele is dominant and the other is recessive, the trait associated with the dominant allele generally app…

Génétique

Homozygote

An individual is homozygous for a gene when they have two identical alleles of that gene, one inherited from their mother and the other from their father.For example, they may have two dominant alleles or two recessive alleles.In this c…

Génétique

Hormone

A hormone is a molecule produced by a gland or an organ in the body, released into the blood, and acts as a chemical messenger.It transmits information to other parts of the body to regulate important functions such as growth, reproduct…

Système endocrinien

Lipid

A lipid is an organic molecule generally poorly soluble in water. Lipids serve as a significant energy reserve and participate in forming cell membranes.Some lipids also play roles as thermal insulators, protect organs, or act as chemic…

Biochimie

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Lymphocyte

A lymphocyte is a type of white blood cell that participates in the body's immune defenses.B lymphocytes can produce antibodies capable of recognizing foreign elements.Some T lymphocytes destroy infected or abnormal cells, while others …

Immunologie

Meiosis

Meiosis is a special cell division that produces reproductive cells called gametes (sperm and eggs). It occurs in two successive stages resulting in four daughter cells, each containing half the number of chromosomes of the original cel…

Génétique

Plasma membrane

The plasma membrane is a thin layer that surrounds the cell and separates it from its environment.It controls the exchange of substances such as water, nutrients, and wastes between the inside of the cell and the outside, allowing the c…

Biologie cellulaire

Mitochondrion

The mitochondrion is an organelle found in most eukaryotic cells. It is surrounded by two membranes: a smooth outer membrane and an inner membrane folded into cristae, which increase its surface area.The mitochondrion is the main site o…

Biologie cellulaire

Mitosis

Mitosis is a cell division process that allows a diploid mother cell (2n), meaning it contains two copies of each chromosome, to divide into two identical daughter cells, which are also diploid (2n). Each daughter cell has the same numb…

Biologie cellulaire

Spinal cord

The spinal cord is a part of the central nervous system located inside the vertebral column.It transmits nerve messages between the brain and the rest of the body via nerves attached to it.It also participates in certain reflexes, allow…

Système nerveux

Genetic mutation

A genetic mutation is a lasting modification of the nucleotide sequence of DNA.It can occur spontaneously during DNA replication or be induced by certain agents, such as ultraviolet radiation or chemical substances.A mutation may produc…

Génétique

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Neuron

A neuron is a specialized cell of the nervous system responsible for the rapid transmission of information in the form of electrical and chemical signals.It consists of several parts: the cell body containing the nucleus, dendrites that…

Système nerveux

Nucleus

The nucleus is a structure present in eukaryotic cells that contains genetic material in the form of DNA.It is surrounded by a membrane called the nuclear envelope, which protects the DNA and controls exchanges between the nucleus and t…

Biologie cellulaire

Nucleotide

A nucleotide is the basic unit that composes DNA and RNA molecules. It consists of three components: a sugar, a phosphate group, and a nitrogenous base.In DNA, the nitrogenous bases are adenine, thymine, cytosine, and guanine.The sequen…

Biologie moléculaire

Organelle

An organelle is a specialized structure located inside a cell that performs a particular function. For example, mitochondria produce much of the energy used by the cell, while ribosomes participate in protein synthesis.Some organelles, …

Biologie cellulaire

Osmosis

Osmosis is a phenomenon where water diffuses through a semi-permeable membrane, meaning a membrane that allows water to pass but blocks certain dissolved substances.Water moves from an area where its concentration is high (dilute soluti…

Transports membranaires

Parasite

A parasite is an organism that lives at the expense of another living being, called the host, often causing it harm.The parasite uses the host's resources to feed, grow, or reproduce, which can weaken or make the host sick.

Microbiologie

Pathogen

A pathogen is a microorganism, such as a bacterium, virus, fungus, or parasite, capable of infecting a living organism and causing disease.These pathogens enter the body, multiply, and can damage cells or disrupt the normal functioning …

Microbiologie

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Phloem

Phloem is a vascular tissue in plants that transports elaborated sap.This sap mainly contains sugars produced in the leaves during photosynthesis, along with other organic substances.The phloem distributes these molecules to parts of th…

Biologie végétale

Photosynthesis

Photosynthesis is a process carried out by plants, algae, and certain bacteria that converts the sun's light energy into chemical energy stored in glucose. This process takes place in chloroplasts, using chlorophyll, a green pigment tha…

Métabolisme cellulaire

Protein

A protein is a molecule made of one or several chains of amino acids linked together. The order of amino acids determines the protein's shape and therefore its function.Proteins fulfill many roles in the organism: they can form structur…

Biochimie

Puberty

Puberty is a transition phase between childhood and adulthood during which the body undergoes physical and hormonal changes that allow the development of secondary sexual characteristics and the capacity to reproduce.In girls, this incl…

Reproduction humaine

Endoplasmic reticulum

The endoplasmic reticulum is an organelle made of a network of membranes located in the cytoplasm of eukaryotic cells.It exists in two forms. The rough endoplasmic reticulum has ribosomes on its surface and mainly participates in the sy…

Biologie cellulaire

Raw sap

Raw sap is a liquid mainly composed of water and mineral salts absorbed from the soil by the roots.It flows through the xylem vessels, typically from the roots to the leaves.The water it carries is involved especially in photosynthesis,…

Biologie végétale

Elaborated sap

Elaborated sap is a liquid rich in organic substances, especially sugars produced in the leaves during photosynthesis.It mainly flows through the phloem and distributes these molecules to different parts of the plant.The transported sug…

Biologie végétale

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Synapse

The synapse is the contact area between two neurons, or between a neuron and another cell (such as a muscle cell).It is at this site that information is transmitted from one cell to another using chemical signals called neurotransmitter…

Système nerveux

Vaccine

A vaccine is a biological product that stimulates the immune system to recognize and combat a pathogenic microorganism (virus, bacterium) without causing the disease. It contains inactivated or attenuated infectious agents or specific p…

Immunologie

Vacuole

A vacuole is a compartment surrounded by a membrane and filled mainly with water and dissolved substances.In plant cells, the large central vacuole stores water, ions, pigments, nutrients, or waste products.It also helps maintain the ri…

Biologie cellulaire

Vein

A vein is a blood vessel that returns blood from the organs to the heart.Its wall is generally thinner and less muscular than that of an artery because the blood pressure is lower.Many veins have valves that prevent blood from flowing i…

Système cardiovasculaire

Virus

A virus is an extremely small acellular microorganism that cannot live or reproduce independently. It consists of a core of nucleic acid, either DNA or RNA, surrounded by a protein coat called a capsid, and sometimes a lipid envelope.Th…

Microbiologie

Xylem

Xylem is a conducting tissue found in vascular plants.It mainly transports raw sap, composed of water and mineral salts absorbed by the roots, towards the stems and leaves.The movement of this sap is notably favored by transpiration fro…

Biologie végétale

Zygote

The zygote is the first cell of a new organism formed during fertilization by the fusion of two gametes.In humans, it results from the union of a spermatozoon and an oocyte.It possesses a complete set of chromosomes, half of which come …

Reproduction humaine

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