Biology Terms

Abiotic – nonliving, inanimate, characterized by the absence of life; of inorganic matter.

Activation energy – The energy required to complete a chemical reaction.

Aerobic: living or occurring only in the presence of oxygen.

Amino acid – The “building blocks” of proteins.

Amino sugar – A sugar molecule with an amine group attached instead of one of its hydroxyl groups.

Anatomy: Anatomy is a branch of natural science which deals with the structural organization of living things. Anatomy is the study of the structure and relationship between body parts.

Antibiotic: any substance that can destroy or inhibit the growth of bacteria and similar microorganisms.

Antibody – A protein produced by the immune system meant to incapacitate and tag foreign bodies for disposal.

Antigen – A protein attached to the surface of a foreign body which can be recognized by proteins on immune cells.

Apoptosis – Programmed cell death that occurs in multicellular organisms, preceded by distinct changes to the morphology and biochemistry of the cell. Common during development and also used to prevent disease.

ATP – The “energy currency” of the cell. The chemical bonds in the ATP molecule store energy that can be used to accomplish life functions.

Binary fission – The method by which bacteria reproduce asexually through dividing.

Biodiversity – Large variety of organisms.

Biofilm: a thin film of mucus created by and containing a colony of bacteria and other microorganisms.

Biome – A large, naturally occurring community of life forms. Biomes can be thought of as “types of ecosystems.” Rainforest, tundra, savanna, temperate forest, and temperate grassland are examples of biomes.

Bioremediation: the use of biological organisms, usually microorganisms, to remove contaminants, especially from soil or polluted water.

Biotechnology: the use of living organisms (especially microorganisms) in industrial, agricultural, medical, and other technological applications.

Biotic factor – A living element of an ecosystem, such as a plant, animal, or bacteria. Biotic and abiotic factors together make up an ecosystem.

Biotransformation: the changes (both chemical and physical) that occur to a substance (especially a drug) by the actions of enzymes within an organism.

Capillary action – The mechanism by which trees draw water up through their roots to feed their leaves.

Carbon cycle: the physical cycle of carbon through the earth’s biosphere, geosphere, hydrosphere, and atmosphere that includes such processes as photosynthesis, decomposition, respiration and carbonification.

Cell membrane – A membrane made up of phospholipids, and which separates from the inside of a cell from the outside.

Cellular respiration – Energy from nutrients is converted into ATP.

Chemosynthetic: Using chemical reactions as energy source. Eg: Nitrosomonas Bacteria.

Chemotroph – An organism that obtains energy mainly from carbon dioxide and from other inorganic chemicals through a process called chemosynthesis

Chloroplast: an organelle found in the cells of green plants and photosynthetic algae where photosynthesis takes place.

Classification: Grouping of organisms into categories on the basis of similarities & differences.

Coenzyme – A complex enzyme contains a non-protein part, called a prosthetic group or co-enzymes. Co-enzymes are very essential for the biological activities of the enzyme.

Cohesion – The tendency of molecules to stick to other molecules like themselves.

Convergent evolution – Occurs when unrelated life forms evolve very similar solutions to environmental problems.

Conjugation: the temporary fusion of organisms, especially as part of sexual reproduction.

Crista: cristae (singular crista) are the internal compartments formed by the inner membrane of a mitochondrion.

Cyanobacteria: photosynthetic prokaryotic microorganisms, of phylum Cyanobacteria, once known as blue-green algae.

Digestion: the process in the alimentary canal by which food is broken up physically, as by the action of the teethand chemically, as by the action of enzymes, and converted into substance suitable for absorption and assimilation into the body.

Ecosystem – A biological community of organisms and their environment. “Ecosystem” and “biome” are very similar terms, although “biome” usually refers to a specific type of ecosystem such as a rainforest, tundra, etc.


Electron Transport Chain(ETC):

The sequence of reactions whereby the reduced forms of the coenzymes are reoxidized by molecular O2 known as electron transport chain

The chain has principle electron carriers

  • NADH dehydrogenase.
  • Succinate dehydrogenase.
  • Coenzyme Q.
  • Cytochromes b2, bH, b560, c1, c, a, & a3 and iron sulphur proteins.

Each of them functions as a redox system with its prosthetic group or metal ions changing alternatively to reductant and oxidant – forms during electron transport.

Energy Pyramid – A graphic illustration which is used to show how energy flows through an ecosystem. These pyramids typically have plants, which efficiently and directly harvest sunlight, at the “bottom” and the top predator at the top, with herbivores and intermediate prey species in the middle.

Endomembrane: all the membraneous components inside a eukaryotic cell, including the nuclear envelope, endoplasmic reticulum, and Golgi apparatus

Endosymbionts – Organisms that live within other organisms.

Endosymbiosis: when one symbiotic species is taken inside the cytoplasm of another symbiotic species and both become endosymbiotic

Eukaryotic cell – A relatively large cell with a true nucleus and organelles.

Evolution – The process that changes populations of organisms over time, adapting them to the environment

Enzyme – are protein catalyst produced by a cell and responsible ‘for the high rate’ and specificity of one or more intracellular or extracellular biochemical reactions.

Fermentation – an anaerobic biochemical reaction, in yeast, for example, in which enzymes catalyze the conversion of sugars to alcohol or acetic acid with the evolution of carbon dioxide.

Genotype – The alleles present at a specific locus in the DNA, which give rise to phenotypes through the production (or lack of production) of protein.

Glycolysis – The breakdown of glucose by enzymes, releasing energy and pyruvic acid. It also knows as “Embden-Meyerhof-Parnas” or “EMP pathway”.

Halophiles: Organism living in salty areas.

Hydrolysis – Breaking a bond in a molecule and splitting it into smaller molecules through a reaction with water.

Identification: Correct description of an organism prior to nomenclature.

Immune System – A system of cells in an organism which work together to find and destroy foreign bodies that might cause harm.

Inorganic – Molecules containing little carbon not made in living organisms.

Kinase – An enzyme that transfers a phosphate group from ATP to another molecule.

Krebs (citric acid) cycle – the sequence of reactions by which most living cells generate energy during the process of aerobic respiration. It takes place in the mitochondria, using up oxygen and producing carbon dioxide and water as waste products, and ADP is converted to energy-rich ATP. It is also known as TriCarboxylic Acid (TCA) cycle.

Legume – a large family of herbs, shrubs, and trees that bear nodules on the roots that contain nitrogen-fixing bacteria

Macronutrient – a chemical element or substance (such as potassium or protein) that is essential in relatively large amounts to the growth and health of a living organism.

Micronutrient: a mineral, vitamin, or other substance that is essential, even in very small quantities, for growth or metabolism.

Mitochondria – An important organelle in animal cells which efficiently extracts energy from sugars.

Mitosis – The process by which a eukaryotic cell divides.

Mutation – When DNA polymerase makes a mistake and places the wrong nucleic acid in a DNA chain.

Nitrogen cycle: the natural circulation of nitrogen, in which atmospheric nitrogen is converted to nitrogen oxides and deposited in the soil, where it is used by organisms or decomposed back to elemental nitrogen.

Nitrogen fixation: the conversion of atmospheric nitrogen into ammonia and organic derivatives, by natural means, especially by microorganisms in the soil, into a form that can be assimilated by plants.

Nomenclature: Scientific naming of organisms

Nucleoid – the irregularly-shaped region within a prokaryote cell where the genetic material is localized

Nutrition: Nutrition, nourishment, or aliment, is the supply of materials – food – required by organisms and cells to stay alive. In science and human medicine, nutrition is the science or practice of consuming and utilizing foods.

Organelle – A specialized structure within a cell that performs a specific function.

Organic – Molecules synthesized in living organisms that contain many carbon-carbon bonds.

Osmosis: Osmosis is a type of diffusion that, in biology, is usually related to cells. Diffusion is when molecules or atoms move from an area of high concentration to an area of low concentration. Osmosis is when a substance crosses a semipermeable membrane in order to balance the concentrations of another substance. In biology, this is usually when a solvent such as water flows into or out of a cell depending on the concentration of a solute such as salt. Osmosis happens spontaneously and without any energy on the part of the cell.

Osmotic pressure– the hydrostatic pressure exerted by a solution across a semipermeable membrane from a pure solvent.

Oxidative Phosphorylation:

Oxidative phosphorylation is the process in which ATP is formed as a result of the transfer of electrons from NADH or FADH 2to O 2 by a series of electron carriers. This process, which takes place in mitochondria, is the major source of ATP in aerobic organisms. For example, oxidative phosphorylation generates 26 of the 30 molecules of ATP that are formed when glucose is completely oxidized to CO2 and H2O.

Pathogen– any organism or substance, especially a microorganism, capable of causing diseases, such as bacteria, viruses, protozoa, or fungi.

Peroxisome: a eukaryotic organelle that is the source of the enzymes that catalyze the production and breakdown of hydrogen peroxide and are responsible for the oxidation of long-chain fatty acids.

Phagocytosis: the process where a cell incorporates a particle by extending pseudopodia and drawing the particle into a vacuole of its cytoplasm

Phenotype – The physical manifestation of the DNA, expressed in terms of protein

Pilus – a hairlike appendage found on the cell surface of many bacteria

plague – an epidemic or pandemic caused by any pestilence.

Plankton: Plants floating passively in water current.

Plasmid – a circle of double-stranded DNA that is separate from the chromosomes, which is found in bacteria and protozoa

Plastid: any of various organelles found in the cells of plants and algae, often concerned with photosynthesis

Polarity – A property of some molecules where one part of the molecule has a slight positive charge, while another has a slight negative charge.

Polymer – A large molecule made up of many repeated units.

Polymerase – An enzyme used to bind monomers into polymers, or smaller molecules into large ones.

Prokaryotic cell – A relatively small cell with no true nucleus and no organelles except for ribosomes.

Protein – A protein is a structure made of one or more long chains of amino acids.

Proteoglycan – A protein that has been glycosylated.

Ribosome – One of the first cellular machines, capable of producing proteins from RNA molecules and amino acids.

Signal transduction – The transmission of signals from a cell’s outside to its inside.

Sodium-potassium pump – An important transport protein which uses about 20-25% of all ATP in the human body. It illustrates the importance of ATP because of what happens if this pump runs out of fuel.

Species: Group of Individual organisms with fundamental similarities (with capacity of interbreeding).

Systematics: Branch of biology dealing with taxonomy along with the evolutionary relationship between organisms.

Taxon: Concrete biological object or category of classification.

Taxonomy: Study of Identification, nomenclature and classification of organisms.

Telomere: either of the repetitive nucleotide sequences at each end of a eukaryotic chromosome, which protects the chromosome from degradation

Thallus: Plant body without true stem, root & Leaf.

Thylakoid: a folded membrane within plant chloroplasts from which grana are made, used in photosynthesis

Tissue: An aggregation of morphologically similar cells and associated intercellular matter acting together to perform specific functions in the body. There are four basic types of tissue: muscle, nerve, epithelial, and connective.

Transduction – horizontal gene transfer mechanism in prokaryotes where genes are transferred using a virus

Transformation – the alteration of a bacterial cell caused by the transfer of DNA from another, especially if pathogenic.

Vaccine – A serum containing antigens of a certain disease, meant to train the immune system to fight off an infection.

Vacuole: a large, membrane-bound, fluid-filled compartment in a cell’s cytoplasm

Zoonosis – an animal disease that can be transmitted to humans.