Biology (university) glossary
85 key terms from Biology (university), A to Z. Each is explained in one plain sentence and links to its free lesson.
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A
- Action potentialAnimal physiology
- A brief electrical signal travelling along a neuron.
- Active site and induced fitEnzymes and energy
- The active site is the pocket where the substrate binds.
- Active transportCell structure and membranes
- Moving a substance across a membrane against its concentration gradient, using energy (usually ATP).
- Adaptive immunityAnimal physiology
- The part of the immune system that learns.
- AlleleGenetics and inheritance
- One version of a gene.
- ATPEnzymes and energy
- Adenosine triphosphate, the cell's short-term energy carrier.
B
- BiodiversityEcology and the environment
- The variety of life: the number of species, the genetic variety within them and the variety of ecosystems.
C
- Calvin cycleRespiration and photosynthesis
- The second stage of photosynthesis, in the chloroplast stroma.
- CancerCell cycle, mitosis and meiosis
- Uncontrolled cell division caused by mutations in genes that control the cycle.
- Carbon cycleEcology and the environment
- Carbon moves between the air, living things, soil, oceans and rocks.
- Cell cycleCell cycle, mitosis and meiosis
- The ordered series of events from one cell division to the next.
- Cell cycle checkpointCell cycle, mitosis and meiosis
- A control point where the cell checks that conditions are right before moving on.
- Central dogmaDNA, transcription and translation
- Information in cells usually flows from DNA to RNA to protein.
- ChemiosmosisRespiration and photosynthesis
- Protons pumped across a membrane build a gradient, then flow back through ATP synthase, a molecular turbine that makes ATP.
- Citric acid cycleRespiration and photosynthesis
- A cycle in the mitochondrial matrix that fully oxidises the carbon from pyruvate to carbon dioxide.
- CRISPR-Cas9Gene regulation and biotechnology
- A gene-editing tool taken from bacterial defence against viruses.
- Crossing over and independent assortmentCell cycle, mitosis and meiosis
- Two sources of variation in meiosis.
- CytokinesisCell cycle, mitosis and meiosis
- The splitting of the cytoplasm after mitosis.
- CytoskeletonCell structure and membranes
- A network of protein fibres that gives a cell its shape, moves organelles and drives cell movement.
D
- DNA structureDNA, transcription and translation
- Two strands of nucleotides twisted into a double helix.
- Double circulationAnimal physiology
- Mammals pump blood through two loops.
E
- Ecological nicheEcology and the environment
- The role of a species in its environment: where it lives, what it eats, when it is active and how it interacts with others.
- Ecological successionEcology and the environment
- The gradual change in species over time in an area.
- Electron transport chainRespiration and photosynthesis
- A line of proteins in the inner mitochondrial membrane.
- Endomembrane systemCell structure and membranes
- A linked set of membrane compartments that make, sort and ship proteins and lipids.
- EndosymbiosisCell structure and membranes
- The idea that mitochondria and chloroplasts began as free-living bacteria swallowed by an ancestral cell.
- Energy couplingEnzymes and energy
- Using an energy-releasing reaction to drive an energy-needing one.
- Energy transferEcology and the environment
- Only part of the energy at one trophic level reaches the next.
- EnzymeEnzymes and energy
- A protein (sometimes RNA) that speeds up a reaction by lowering its activation energy.
- Enzyme inhibitionEnzymes and energy
- Competitive inhibitors bind the active site and block the substrate.
- Enzyme kineticsEnzymes and energy
- How reaction speed depends on substrate amount.
- Epigenetic modificationGene regulation and biotechnology
- Chemical tags on DNA or on the histone proteins it wraps around that change how active a gene is, without changing the DNA letters.
- Eukaryotic cellCell structure and membranes
- A cell whose DNA sits inside a nucleus and which has membrane-bound compartments called organelles.
- Evidence for evolutionEvolution and diversity of life
- Several independent lines point to common ancestry: fossils, homologous structures (the same bones used differently), DNA and protein similarity, and observed evolution such as antibiotic resistance.
F
- Feedback inhibitionEnzymes and energy
- The end product of a pathway switches off an early enzyme in that pathway.
- FermentationRespiration and photosynthesis
- Making ATP without oxygen by recycling NADH back to NAD+, so glycolysis can keep going.
- FitnessEvolution and diversity of life
- How many offspring an individual leaves that survive to reproduce, compared with others.
- Fluid mosaic modelCell structure and membranes
- The membrane is a double layer of phospholipids with proteins floating in it.
- Free energyEnzymes and energy
- The energy in a system that is available to do work, written as G.
G
- Gel electrophoresisGene regulation and biotechnology
- A method to sort DNA pieces by size.
- Gene flowEvolution and diversity of life
- The movement of alleles between populations when individuals or gametes move.
- Genetic codeDNA, transcription and translation
- Groups of three bases on mRNA (codons) specify an amino acid.
- Genetic driftEvolution and diversity of life
- Random changes in allele frequencies from one generation to the next, caused by chance.
- GlycolysisRespiration and photosynthesis
- The first stage of glucose breakdown.
H
- Hardy-Weinberg equilibriumEvolution and diversity of life
- A model for a population that is not evolving.
- HomeostasisAnimal physiology
- Keeping the internal conditions of the body within a narrow range, such as temperature, blood sugar and water level.
- HormoneAnimal physiology
- A chemical messenger made by an endocrine gland, carried in the blood, and acting on target cells with the right receptors.
I
- Incomplete dominance and codominanceGenetics and inheritance
- In incomplete dominance the heterozygote looks like a blend of the two homozygotes.
- Innate immunityAnimal physiology
- The body's fast, general defences present from birth: skin and mucus barriers, inflammation, and cells such as phagocytes that engulf germs.
L
- Lac operonGene regulation and biotechnology
- A group of bacterial genes switched on together to digest lactose.
- Lagging strandDNA, transcription and translation
- DNA polymerase only builds a new strand in one direction (5' to 3').
- Law of independent assortmentGenetics and inheritance
- Mendel's second law.
- Law of segregationGenetics and inheritance
- Mendel's first law.
- Light reactionsRespiration and photosynthesis
- The first stage of photosynthesis, in the thylakoid membranes of chloroplasts.
- Linked genesGenetics and inheritance
- Genes close together on the same chromosome tend to be inherited together.
M
- MeiosisCell cycle, mitosis and meiosis
- Two divisions that turn one diploid cell into four haploid cells, each with half the chromosomes.
- MetabolismEnzymes and energy
- All the chemical reactions in a living cell.
- MitosisCell cycle, mitosis and meiosis
- Division of the nucleus that produces two genetically identical daughter nuclei.
N
- Natural selectionEvolution and diversity of life
- Individuals in a population vary, some of that variation is inherited, and individuals with helpful traits leave more offspring.
- NephronAnimal physiology
- The working unit of the kidney.
- Nitrogen cycleEcology and the environment
- Nitrogen gas in the air cannot be used by most organisms.
- NondisjunctionCell cycle, mitosis and meiosis
- A failure of chromosomes to separate in meiosis.
- NucleusCell structure and membranes
- The organelle that stores DNA and controls which genes are used.
O
- OsmosisCell structure and membranes
- The movement of water across a selectively permeable membrane from lower solute concentration to higher solute concentration.
- Oxygen transportAnimal physiology
- Haemoglobin in red blood cells binds oxygen in the lungs, where oxygen is plentiful, and releases it in tissues, where oxygen is low.
P
- PedigreeGenetics and inheritance
- A family tree showing who has a trait.
- Phylogenetic treeEvolution and diversity of life
- A branching diagram showing evolutionary relationships.
- Point mutationDNA, transcription and translation
- A change in one DNA base.
- Polygenic traitGenetics and inheritance
- A trait controlled by many genes, often plus the environment.
- Polymerase chain reactionGene regulation and biotechnology
- PCR copies a chosen stretch of DNA millions of times.
- Population growthEcology and the environment
- With no limits, a population grows exponentially, faster and faster.
- Prokaryotic cellCell structure and membranes
- A small, simple cell with no nucleus.
R
- Recombinant DNAGene regulation and biotechnology
- DNA made by joining pieces from different sources.
- Redox reactionRespiration and photosynthesis
- A reaction where one substance loses electrons (oxidation) and another gains them (reduction).
- Restriction enzymeGene regulation and biotechnology
- A bacterial enzyme that cuts DNA at a specific short sequence.
- RNA splicingDNA, transcription and translation
- In eukaryotes the first RNA copy contains introns (non-coding stretches) and exons (coding stretches).
S
- Semi-conservative replicationDNA, transcription and translation
- DNA copies itself by unzipping.
- Sex-linked inheritanceGenetics and inheritance
- Genes on the X chromosome follow a different pattern in males (XY) and females (XX).
- SpeciationEvolution and diversity of life
- The formation of new species.
- SymbiosisEcology and the environment
- A close, long-term relationship between two species.
- SynapseAnimal physiology
- The gap between two neurons.
T
- TranscriptionDNA, transcription and translation
- Making an RNA copy of a gene.
- Transcription factorGene regulation and biotechnology
- A protein that binds DNA near a gene and helps or blocks RNA polymerase.
- TranslationDNA, transcription and translation
- Building a protein by reading mRNA.
- Trophic levelEcology and the environment
- A feeding level in a food chain: producers (plants and algae), primary consumers (herbivores), secondary consumers (carnivores that eat herbivores), and so on.