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92 Cards in this Set
- Front
- Back
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Active site |
The region of an enzyme that binds the reactant, or substrate, molecule and catalyses its transformation into product(s). The active site has specific groups arranged in just the right positions to provide the substrate with an ideal environment for reaction. Only particular compounds will have the correct geometry to bind to the active site, and this is the origin of the substrate specificity of enzymes. Enzyme catalysis involves the formation of an enzyme-substrate complex which then breaks down into product(s). (B4, B5) |
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Anaphase |
The phase of mitosis in which the chromatid pairs formed during replication separate, so that each chromatid becomes a chromosome in its own right. One member of each pair is drawn to one end of the cell, and its partner is drawn to the other end. (B5) |
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Animalia |
The formal name for the animal kingdom, one of four kingdoms within the domain Eukarya. (B5) |
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Archaea |
A domain consisting of prokaryotic organisms; there are two such domains, the other being Bacteria. (B5) |
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asexual reproduction |
A form of reproduction in which an individual organism produces offspring without combining part of its genetic material with part of that of another individual. Compare with sexual reproduction. (B5) |
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autosome |
A chromosome other than a sex chromosome; autosomes are paired in a diploid cell. (B5) |
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autotroph |
An organism that makes its own carbon-based material starting with carbon dioxide. An autotroph is also known as a primary producer. Almost all plants are autotrophs; they convert carbon dioxide into carbon-based material by photosynthesis. Compare with heterotroph. (B5) |
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Bacteria |
A domain consisting of prokaryotic organisms; there are two such domains, the other being Archaea. (B5) |
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biodiversity |
A term used to encompass all the species living on Earth, or a specified part of it, at any time; sometimes used to encompass ecosystem diversity as well. (B5) |
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biopolymere |
A polymer found in biological material; a naturally occurring polymer. The commonest are proteins, polysaccharides and nucleic acids. (B4, B5) |
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carnivore |
An organism that obtains its carbon-based materials by consuming living or recently killed animals, either in whole or in part, i.e. a type of heterotroph. Compare with herbivore. (B5) |
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cell |
The smallest unit of an organism that is capable of showing the three attributes of life. The three main components of a eukaryotic cell are the cell membrane, the cytoplasm and the nucleus. A prokaryotic cell does not possess a nucleus. A multicellular organism consists of more than one cell (usually many more). A specialised cell is one which specialises in the performance of a particular function. (B5) |
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cell cycle |
The repeated alternation of cell growth and cell division characteristic of all organisms. (B5) |
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cell division |
The part of the cell cycle in which a single cell splits into two progeny cells; cell division follows mitosis and entails the production of a new cell membrane which divides the original cell’s cytoplasm between the two progeny cells. The term cell division is sometimes used loosely to include mitosis. (B5) |
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cell membrane |
The structure that separates the rest of a cell from the cell’s external environment. The cell membrane is selectively permeable in that it can, to some extent, control which substances pass through it. (B5) |
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cell wall |
The structure that occurs outside the cell membrane of the cells of most plants, fungi and bacteria, and helps to maintain a rigid cell shape. In plants this is made of fibres of cellulose. (B5) |
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centromere |
The point of attachment of one chromatid to its partner to make up a single chromosome. (B5) |
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character |
A term used in biology to mean a characteristic or trait of an organism or species. (B5) |
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chloroplast |
Plant cell organelle in which photosynthesis takes place. The layers of membranes within chloroplasts contain chlorophyll and are the site of the light reactions of photosynthesis. The dark reactions of photosynthesis occur in the stroma, which surrounds the internal chloroplast membranes. (Not all plant cells contain chloroplasts). (B5) |
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chromatid |
One of a pair of identical DNA molecules (with associated protein molecules). Between replication and the anaphase stage of mitosis, each chromosome in a cell consists of two chromatids joined together at a centromere. (B5) |
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chromosome |
A structure composed of the genetic material of a cell (the DNA) and protein molecules. A chromosome may be an autosome or a sex chromosome. During the replication phase of the cell cycle, the DNA in each chromosome is copied so that each of the progeny cells eventually contains an identical set of chromosomes (and hence genetic material) to that of the parent cell. In a eukaryote, chromosomes are normally contained within the nucleus. (B5) |
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clade |
A group of species derived from the same common ancestor. (B5) |
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coenzyme |
A small organic molecule that works with an enzyme in some reactions. It binds to the active site of the enzyme, and transfers small groups of atoms (e.g. 2H, acetyl) to the substrate – or else picks up small groups of atoms as they are removed from the substrate. Examples are NAD, NADP and coenzyme A. (B5) |
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cytoplasm |
All those parts of a cell enclosed by the cell membrane, other than the nucleus. (B5) |
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cytosol |
The gel-like liquid that remains when rough endoplasmic reticulum andmitochondria (and chloroplasts, in plant cells) and other subcellular structures have been removed. (B5) |
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dehydrogenation |
An oxidation reaction in which a substance is oxidised by the removal of (usually two) hydrogen atoms from an organic molecule. In the cell, dehydrogenation reactions are catalysed by specific enzymes. (B5) |
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diploid |
A diploid cell is one in which each autosome has a similar-looking partner.Compare with haploid. (B5) |
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DNA |
Abbreviation for deoxyribonucleic acid. The class of molecules that carries the genetic information of organisms and is thus the genetic material. DNA is a polymer whose monomers are nucleotides, which consist of three component parts joined by covalent bonds: a phosphate group, a sugar (deoxyribose) and a base. There are four different bases in DNA: adenine (A), guanine (G), cytosine (C) and thymine (T). Nucleotides joined together form polynucleotides. Each DNA molecule consists of two polynucleotide chains intertwined to form a characteristic double helix. DNA molecules are by far the largest known molecules in living organisms; some have relative molecular masses of many billions! DNA carries the genetic information of the cell, coded as a sequence of nucleotides (and hence a sequence of bases). (B5) |
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domain |
The broadest level in the scheme of taxonomic classification; three domains are recognised: Archaea, Bacteria and Eukarya. (B5) |
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endosymbiotic hypothesis |
A proposal that provides a unifying concept to account for the evolutionary relationships of all cell types. It suggests that the earliest eukaryotic cells had only a nucleus. Mitochondria and chloroplasts were originally free-living bacteria which moved into the eukaryotic ‘host’ cells. Eventually the bacterial partners became completely integrated into and dependent on the host cells. (B5) |
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enzyme-substrate complex |
The one-to-one complex that is formed when the substrate binds to the active site of an enzyme by weak bonds. Once the complex is formed, catalysis occurs, the product is released and the enzyme is regenerated. (B5) |
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Eukarya |
The domain that includes all except prokaryotic organisms (which belong to either Archaea or Bacteria). (B5) |
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eukaryote |
An organism in which each cell typically contains a nucleus in which genetic material is found. Eukaryotic organisms are members of the domain Eukarya. Compare with prokaryote. (B5) |
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fatty acid |
A long-chain carboxylic acid produced from fats by hydrolysis. (B4, B5) |
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fibrous protein |
Protein that has an elongated, roughly linear shape, in which long fibres may be wound round one another like a rope. They form structural materials providing support, e.g. collagen, muscle proteins, keratin. (B5) |
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Fungi |
The formal name for the fungi kingdom, one of four kingdoms within the domain Eukarya. A fungus (the singular of fungi) is a heterotroph and a typical fungus is a multicellular organism. (B5) |
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gametes |
A haploid cell capable of fusing with another gamete in sexual reproduction to give rise to a diploid zygote. (B5) |
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glycerol |
An alcohol which condenses with three fatty acid molecules to give a triacylglycerol. (B5) |
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globular protein |
Protein that is usually coiled into broadly spherical shapes. The precise globular structure arises directly from the primary structure of the polypeptide as a consequence of the formation of weak interactions between specific functional groups (R groups) of amino acids. Globular proteins have more specialised roles than fibrous proteins, acting as cell receptors or enzymes, for example. (B5) |
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glycosidic linkage |
The covalent bond joining adjacent sugars in a polysaccharide. It is formed by a condensation reaction. (B5) |
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growth |
Increase in size of an organism or cell; one of the three attributes of life. (B5) |
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growth I |
A phase of the cell cycle in which the cell increases in size before replication of its DNA. (B5) |
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growth II |
A phase of the cell cycle in which the cell increases in size following replication of its DNA. (B5) |
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haploid |
A haploid cell is one in which each autosome does not have a similar-looking partner. Compare with diploid. (B5) |
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heterotroph |
An organism that cannot manufacture its own carbon-based materials starting from carbon dioxide and therefore feeds on other organisms. A heterotroph is also known as a consumer. Compare with autotroph. (B5) |
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higher-order structure |
The three-dimensional folding pattern of a biopolymer, such as proteins. The shape of each biopolymer is unique and arises as a consequence of a particular arrangement of weak bonds, e.g. between amino acid R groups. Thus the primary structure of a biopolymer determines its higher-order structure. (B5) |
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hydrophilic |
Term describing a molecule or functional group that forms hydrogen bondswith water molecules and thus readily dissolves in water. Literally means ‘water-loving’. (B5) |
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hydrophobic |
Term describing a molecule or part of a molecule that is unable to interact with charges on water molecules and therefore does not dissolve in water. Literally means ‘water-fearing’. (B5) |
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interphase |
The collective term for the three phases of the cell cycle known as growth I, replication and growth II. (B5) |
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kingdom |
The level of taxonomic classification between domain and phylum, e.g. the kingdom Animalia is part of the domain Eukarya and comprises all the animals. (B5) |
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lipid |
One of a varied group of hydrophobic organic compounds, insoluble in water and soluble in hydrophobic solvents. Lipids are the fatty components of living organisms; solid lipids are referred to as fats, and liquid lipids as oils. (B5) |
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metaphase |
A phase of mitosis in which each chromosome becomes aligned across the middle of the cell. (B5) |
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mitochondria (singular: mitochondrion) |
Organelles that occur in most eukaryotic cells, and vary in size and shape. They have an outer membrane and an internal, highly folded membrane within them. The TCA cycle and the link reaction occur in the matrix. Electron transport and oxidative phosphorylation occur at the inner membrane. (B5) |
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mitosis |
The type of cell division that takes place during growth and during repair of parts of the body. Mitosis produces diploid progeny cells, in each of which every chromosome is identical to a chromosome possessed by the parent cell. Mitosis occurs in a sequence of stages, termed prophase, metaphase, anaphase and telophase. (B5) |
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monophyletic |
A monophyletic group consists of species that share recent common ancestors (and therefore have similar features) and are closely related to each other. A monophyletic group is called a clade. An example of a monophyletic group is the primates. (B5) |
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monosaccharide |
A sugar that cannot be hydrolysed to anything simpler and which is a sweet, water-soluble carbon compound with several hydroxyl (OH) groups. Common monosaccharides are glucose, fructose and ribose. (B4, B5) |
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NAD (nicotinamide adenine dinucleotide) |
A coenzyme that carries hydrogen atoms. Its reduced form is written as NAD.2H. It is used in reactions of catabolism such as those of the glucose oxidation pathway. (B5) |
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nucleic acid |
A biopolymer in which the monomers are nucleotides. There are two types of nucleic acid: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).(B5) |
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nucleus (plural: nuclei) |
In biology, a component of a eukaryotic cell surrounded by a nuclear membrane; the nucleus contains chromosomes, each chromosome consisting of DNA (the cell’s genetic material) and protein molecules. (B5) In chemistry and physics, the core of an atom. It contains nearly all of the atomic mass and is positively charged. With the exception of the hydrogen nucleus, which is a single proton, nuclei consist of protons and neutrons.(B4, B7) |
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organelle |
A membrane-bound structure within a cell. The most important organelles are the chloroplasts, mitochondria and the nucleus. (B5) |
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ova |
The female sex cell or gamete. (B5) |
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parsimony |
The principal that the least complex explanation for any phenomena is generally thought to be correct. (B5) |
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phylogenetic tree |
A diagrammatic illustration of the evolutionary relationship between taxonomic groups. (B5) |
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phylogeny |
The evolutionary history of a group of organisms. (B5) |
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phylum (plural: phyla) |
The level of taxonomic classification between kingdom and class. For example, the phylum Chordata (mostly animals with backbones) is part of the kingdom Animalia (animals) and comprises several classes including Mammalia (mammals) and Aves (birds). (B5) |
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Plantae |
The formal name for the plant kingdom, one of four kingdoms within the domain Eukarya. (B5) |
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polymorphic |
A species is described as polymorphic if it consists of a number of ‘types’ with distinctive morphology. (B5) |
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population |
A group of organisms belonging to the same species which live in a defined place. (B5) |
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primary structure |
(of a biopolymer). The sequence of specific amino acids in a protein, or of sugars in a polysaccharide, or of nucleotides in a nucleic acid. (B4, B5) |
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progeny cells |
The cells produced by cell division of a previously existing parent cell. (B5) |
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Prokarya |
The two prokaryotic domains (Archaea and Bacteria). (B5) |
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prokaryote (adjective: prokaryotic) |
An organism comprising a single cell (with a few exceptions) in which the DNA is not contained within a nucleus. Prokaryotes are members of either the domain Archaea or the domain Bacteria. Compare with eukaryote. (B5) |
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prophase |
The phase of mitosis in which chromosomes can first be seen in the cytoplasm of the cell, the nuclear membrane which normally surrounds the nucleus having disappeared. During prophase, each chromosome consists of a chromatid pair attached at a centromere. (B5) |
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Protoctista |
The formal name for the kingdom of the organisms known informally as protoctists; one of four kingdoms within the domain Eukarya. (B5) |
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replication |
A phase of the cell cycle between growth I and growth II during which the DNA molecules within the nucleus are copied. (B5) |
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reproduction |
reproduction |
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reproductive isolation |
Under normal circumstances, sexual reproduction occurs only between members of the same species, i.e. there is usually reproductive isolation between species. Reproductive isolation is therefore often used as a defining characteristic of species that reproduce sexually. However, since some interbreeding between species may occur in certain circumstances, reproductive isolation is a relative, not absolute, term. It is a situation where gene flow, between two populations or two species, does not take place, or at least is reduced to a very low level. (B5) |
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respiration |
The sum of all the chemical reactions by which an organism breaks down simple organic carbon compounds (i.e. in food) to release energy. In most organisms, respiration is accompanied by consumption of oxygen and production of carbon dioxide and water. In respiration the energy stored in organic compounds is released in a series of very small, highly controlled steps, as part of the process of metabolism. (B1, B5) |
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ribosomes |
Small, roughly spherical objects free in the cytosol of prokaryotes and attached to the surface of rough endoplasmic reticulum in eukaryotes. The structures on which proteins are synthesised during translation. (B5) |
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rough endoplasmic reticulum |
Membrane material organised into sack-like or sheet-like structures with a granular appearance due to small, roughly spherical objects attached to its surface. These are the ribosomes – the structures on which proteins are synthesised. (B5) |
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selective permeable |
The cell membrane is said to be selectively permeable in that it can, to some extent, control which substances pass through it. (B5) |
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sex chromosomes |
In many diploid species, sex chromosomes help determine the sex of the individual organism; human females have a matching pair of X chromosomes, while human males have one X and one Y chromosome which do not match. Compare with autosome. (B5) |
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sexual dimorphism |
A specific type of polymorphism in which the two sexes have strikingly different forms, e.g. elephant seals, peafowl, sparrowhawks. (B5) |
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sexual reproduction |
A form of reproduction in which part of the genetic material of each of two individuals is combined in their offspring. A haploid male gamete fuses with a haploid female gamete in the process of fertilisation. Compare withasexual reproduction. (B5) |
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species |
A group of organisms that are similar to one another in appearance and/or behaviour, and that differ in some way from other closely-related groups of organisms. There is usually a significant degree of reproductive isolation between species that reproduce sexually. The species is the level of taxonomic classification immediately below genus. The second part of an organism’s scientific label identifies it as belonging to a particular species within its genus. For example, the domestic cat is uniquely identified by the scientific label Felis catus (which can be abbreviated to F. catus, providing there is no ambiguity) in contrast to other species within the genus Felis, such as the wild cat (F. silvestris). (B5) |
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spermatozoon (plural: spermatozoa) |
A haploid gamete produced by a male animal through meiosis. (B5) |
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substrate |
The specific molecule which binds to the active site of a named enzyme and undergoes a chemical reaction. (B5) |
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telophase |
The phase of mitosis in which a complete set of chromosomes (i.e. one member of each chromosome pair) gathers at one end of the cell and an identical set gathers at the other end, prior to cell division. (B5) |
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thermal denaturation |
The loss of catalytic activity by an enzyme when raised above its optimum temperature; a consequence of the breakdown in higher-order structure due to the disruption of weak interactions and the associated change in shape of the active site. (B5) |
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triacylglycerol (TAG) |
A water-insoluble lipid (fat) formed by the condensation of one molecule of glycerol with three molecules of long-chain fatty acids. (B4, B5) |
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weak interaction |
ionic interaction hydrogen bonds hydrophobic interactions |
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zygote |
The diploid cell produced when a haploid male gamete fuses with a haploid female gamete in the process of fertilisation. (B5) |
