Biochemistry Vocab Words

Covalent Bond

A type of strong chemical bond in which two atoms share one or more pairs of valence electrons.

Hydrogen Bond

A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule.

Ionic Bond

A chemical bond resulting from the attraction between oppositely charged ions.

Specific Heat

The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1 degree C.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules.

Adhesion

The clinging of one substance to another, such as water to plant cell walls, in this case by means of hydrogen bonds.

Cohesion

The linking together of like molecules, often by hydrogen bonds.

Heat of vaporization

The quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state.

Hydrophobic

Having no affinity for water; tending to coalesce and form droplets in water.

Hydrophilic

Having an affinity for water.

pH scale

A logarithmic measurement scale from 0 to 14 that determines how acidic or basic an aqueous solution is based on its concentration of hydrogen ions (H+). A single proton with a charge of plus one.

H+ (hydrogen) ion

The dissociation of a water molecule leads to the generation of a hydroxide ion (with a charge of minus one) and a hydrogen ion (with a charge of plus one); in water, the hydrogen ion is not found alone but associates with a water molecule to form a hydronium ion.

Hydroxyl Group

A chemical group consisting of an oxygen atom joined to a hydrogen atom. Molecules possessing this group are soluble in water and are called alcohols.

Carboxyl Group

A chemical group present in organic acids and consisting of a single carbon atom double-bonded to an oxygen atom and also bonded to a hydroxyl group.

Carbonyl Group

A chemical group present in aldehydes and ketones and consisting of a carbon atom double-bonded to an oxygen atom.

Amino Group

A chemical group consisting of a nitrogen atom bonded to two hydrogen atoms; can act as a base in solution, accepting a hydrogen ion and acquiring a charge of plus one.

Phosphate Group

A chemical group consisting of a phosphorus atom bonded to four oxygen atoms; important in energy transfer.

Sulfhydryl Group

A chemical group consisting of a sulfur atom bonded to a hydrogen atom.

Polymer

A long molecule consisting of many similar or identical monomers linked together by covalent bonds.

Monomer

The subunit that serves as the building block of a polymer.

Condensation

A chemical reaction in which two molecules are covalently bonded to each other with the concurrent loss of a small molecule (broad category - any molecule).

Dehydration Reaction

A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule (specific subtype - water).

Hydrolysis Reaction

A chemical reaction that breaks bonds between two molecules by the addition of water; functions in disassembly of polymers to monomers.

Monosaccharide

The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also called simple sugars, monosaccharides have molecular formulas that are generally some multiple of C-H-subscript-2-O.

Glycosidic Linkage

A covalent bond formed between two monosaccharides by a dehydration reaction.

Polysaccharide

A polymer of many monosaccharides, formed by dehydration reactions.

Fatty Acid

A carboxylic acid with a long carbon chain. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form a fat molecule, also called triacylglycerol or triglyceride.

Triacylglycerol (scientific name) or Triglyceride (common name)

A lipid consisting of three fatty acids linked to one glycerol molecule; also called a fat or triglyceride.

Ester Linkage or Ester Bond

Condensation reaction (dehydration synthesis) between a hydroxyl group (–OH) of an alcohol and a carboxyl group (–COOH) of a carboxylic acid, releasing a molecule of water.

Phospholipid

A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head. Phospholipids form bilayers that function as biological membranes.

Steroid

A type of lipid characterized by a carbon skeleton consisting of four fused rings with various chemical groups attached.

Amino Acid

An organic molecule possessing both a carboxyl and an amino group. Amino acids serve as the monomers of polypeptides.

Peptide Bond

The covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a dehydration reaction.

Primary Structure

The level of protein structure referring to the specific linear sequence of amino acids.

Secondary Structure

Regions of repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bonding between constituents of the backbone (not the side chains).

Tertiary Structure

The overall shape of a protein molecule due to interactions of amino acid side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

Quaternary

The highest level of protein organization, formed when two or more separate polypeptide chains (called subunits) join together to create a single functional protein complex.

Denaturation

In proteins, a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive; in DNA, the separation of the two strands of the double helix. Denaturation occurs under extreme (noncellular) conditions of pH, salt concentration, or temperature.

DNA (deoxyribonucleic acid)

A nucleic acid molecule, usually a double-stranded helix, in which each polynucleotide strand consists of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of being replicated and determining the inherited structure of a cell’s proteins.

RNA (ribonucleic acid)

A type of nucleic acid consisting of a polynucleotide made up of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis, in gene regulation, and as the genome of some viruses.

Transfers genetic instructions from DNA to ribosomes for protein synthesis.

Nucleotide

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one to three phosphate groups.

Enzyme

A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most enzymes are proteins.

Activation Energy

The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation.

Catalyst

A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.

Substrate

The reactant on which an enzyme works.

Product

A material resulting from a chemical reaction.

Active Site

The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.

Cofactors

Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely and reversibly, along with the substrate, during catalysis.

Competitive Inhibitor

A substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics.

Non-Competitive Inhibitor

A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme’s shape so that the active site no longer effectively catalyzes the conversion of substrate to product.

Allosteric Site

A region on an enzyme, separate from the active site, where a regulatory molecule binds to change the enzyme's shape and turn its activity up or down.

Feedback Inhibition

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

Increase Polarity

An increase in polarity means a larger difference in electrical charge across a molecule or bond, caused by a greater difference in electronegativity between the bonded atoms.