Tamil Nadu HSE First Year Biochemistry key terms

The branch of science that studies the chemical substances and reactions occurring inside living organisms, explaining how molecules such as proteins, sugars and fats carry out life processes.

Any carbon-based compound produced by or essential to living cells, including carbohydrates, lipids, proteins and nucleic acids, each built from smaller repeating units.

A single small molecule that can join with identical or similar units to build a larger chain; examples include glucose, fatty acids and amino acids.

A large molecule formed when many monomers are linked together, such as starch from glucose units or a protein from amino acids.

A very large molecule of high molecular mass, usually built from hundreds or thousands of monomers, typical of proteins, nucleic acids and polysaccharides.

The complete set of chemical reactions in a cell, divided into breakdown pathways that release energy and building pathways that consume it.

The set of metabolic pathways that break larger molecules into simpler ones, releasing energy that is captured as ATP or as reduced coenzymes.

The set of metabolic pathways that build complex molecules from simpler precursors, requiring energy usually supplied by ATP and reducing power.

Adenosine triphosphate, the universal energy currency of cells; splitting its terminal phosphate bond releases usable energy for cellular work.

A covalent linkage whose hydrolysis releases an unusually large amount of free energy, as in the phosphate bonds of ATP or the thioester bond of acetyl-CoA.

A central two-carbon carrier molecule that feeds the citric acid cycle and serves as a starting unit for fatty acid synthesis and other biosynthetic routes.

The oxygen-independent pathway in the cytoplasm that converts one glucose molecule into two pyruvate molecules, with a net gain of two ATP and two NADH.

A cyclic series of mitochondrial reactions that oxidises acetyl groups to carbon dioxide while producing reduced coenzymes and a small amount of ATP.

The mitochondrial process in which electrons passed along the respiratory chain drive proton pumping, and the resulting gradient powers ATP synthesis.

The simplest sugar unit, a single polyhydroxy aldehyde or ketone that cannot be hydrolysed further, such as glucose, fructose or ribose.

A sugar made of two monosaccharide units joined by a glycosidic bond, for example sucrose, lactose or maltose.

A large carbohydrate built from many monosaccharide units, which may be a storage form such as starch or a structural form such as cellulose.

The covalent linkage formed between the anomeric carbon of one sugar and a hydroxyl group of another, joining sugar units into di- and polysaccharides.

A sugar that still has a free anomeric carbon able to reduce mild oxidising agents such as copper(II) ions, giving a positive Benedict's or Fehling's test.

One of two cyclic forms of a sugar that differ only in the arrangement at the anomeric carbon, labelled alpha or beta, as in alpha- and beta-glucose.

A long hydrocarbon chain ending in a carboxyl group; it may be saturated or contain one or more double bonds, and it is a building unit of lipids.

A fatty acid whose hydrocarbon chain has no carbon-carbon double bonds, so it is straight and packs tightly, as in stearic and palmitic acids.

A fatty acid containing one or more carbon-carbon double bonds; the kink at each double bond lowers melting point and keeps such fats liquid at room temperature.

A neutral lipid formed when one glycerol molecule is esterified with three fatty acid molecules; it is the main storage form of energy in adipose tissue.

The linkage produced when an acid reacts with an alcohol with loss of water, as between a fatty acid carboxyl group and a glycerol hydroxyl group in fats.

A lipid containing a phosphate group and two fatty acid tails on a glycerol or sphingosine backbone, forming the bilayer framework of cell membranes.

Describing a molecule that has both a water-loving polar region and a water-fearing nonpolar region, which makes it arrange itself at interfaces.

A molecule containing both an amino group and a carboxyl group on the same carbon; about twenty standard types are the building units of proteins.

A molecule carrying both positive and negative charges at the same time, the usual state of amino acids in neutral solution, giving them high solubility and characteristic behaviour.

The pH at which a molecule such as an amino acid or protein carries no net charge and therefore does not migrate in an electric field.

The amide linkage formed between the carboxyl group of one amino acid and the amino group of the next, with loss of water, forming the protein backbone.

The exact linear sequence of amino acid residues in a polypeptide chain, held together by peptide bonds and encoded by a gene.

Loss of a protein's three-dimensional shape and activity caused by heat, extreme pH or chemicals, without breaking the peptide bonds of the chain.

A biological catalyst, usually a protein, that speeds up a specific reaction by lowering its activation energy without being consumed itself.

The small pocket of an enzyme where substrate binds and catalysis occurs, formed by a few specific residues brought together by folding.

The minimum energy that reacting molecules must possess for a reaction to proceed; enzymes reduce it, so more molecules can react at a given temperature.

The temporary association formed when substrate occupies an enzyme's active site, from which product is released and the enzyme regenerated.

The substrate concentration at which an enzyme works at half its maximum rate; a low value indicates strong binding and high affinity for substrate.

The repeating unit of nucleic acids, made of a nitrogenous base, a five-carbon sugar and one or more phosphate groups.

The ring compound in a nucleotide; adenine, guanine, cytosine, thymine and uracil are the standard bases, and their order carries genetic information.

The specific hydrogen-bonded matching of adenine with thymine or uracil, and guanine with cytosine, that holds the two strands of DNA together.

A chain of nucleotides joined by phosphodiester bonds, forming one strand of DNA or RNA with a free phosphate end and a free hydroxyl end.

Separation of the two strands of the double helix by heat or alkali, breaking hydrogen bonds between base pairs but not the covalent backbone.

An organic micronutrient needed in small amounts for normal growth and health that the body cannot make in sufficient quantity and must obtain from food.

A small non-protein organic molecule that assists an enzyme, often by carrying electrons or chemical groups between reactions; many are derived from vitamins.

A non-protein substance, either an inorganic ion or an organic coenzyme, that an enzyme requires for activity and that binds to it.

The disease state produced by a prolonged lack of one or more vitamins in the diet, such as scurvy from vitamin C deficiency.

An inorganic element required by the body in small amounts, such as iron, calcium, iodine or zinc, needed for structural and regulatory roles.

A qualitative test in which a blue copper(II) solution turns green, yellow or brick red on heating with a reducing sugar, indicating its presence.

A separation technique in which components of a mixture distribute differently between a moving phase and a stationary phase, allowing their identification.

A technique that separates charged molecules such as proteins or DNA in a gel under an electric field, according to their charge and size.

A method of measuring how much light a solution absorbs at a chosen wavelength, used to estimate the concentration of coloured or ultraviolet-absorbing substances.