Keywords

Adhesion

The property of molecules binding to other molecules of a different substance.

Alpha helix

A protein secondary structure - coiling of a polypeptide chain to form a right-handed spiral held in place by hydrogen bonds.

Amino acids

Monomer of polypeptides.

Amphoteric

A molecule that can act as an acid or a base.

Benedict’s test

A biochemical test for the presence of reducing sugars.

Beta pleated sheet

A folded protein secondary structure held in place by hydrogen bonds.

Biuret’s test

A biochemical test for the presence of proteins.

Carbohydrates

Family of molecules that includes starch, glycogen, cellulose and glucose - often used as an energy source, energy store or in the formation of glycoproteins.

Cohesion

The property of molecules binding to other molecules of the same type.

Condensation reaction

A type of chemical reaction in which two molecules are joined together by a covalent bond to form a larger molecule, releasing a molecule of water.

Denaturation

An irreversible change in the tertiary structure of a protein molecule. It leads to loss of function in most proteins.

Disaccharide

A molecule consisting of two monosaccharide sugars joined by a glycosidic bond.

Disulfide linkage

A covalent bond formed between the sulfur atoms in two cysteine amino acid residues.

Ester bond

A bond formed in a condensation reaction between the -OH group of a carboxylic acid and an -OH group of an alcohol.

Fibrous protein

A protein with a relatively long, thin structure, which is insoluble in water and metabolically inactive, often having a structural role within the organism.

Globular protein

A protein with a relatively spherical structure, which is soluble in water and often having metabolic roles within the organism.

Glycosidic bond

Covalent bond formed when monosaccharides are joined together in condensation reaction.

Hydrogen bond

A weak electrostatic attraction between the partially positively charged and partially negatively charged atoms in polar molecules.

Hydrolysis reaction

A reaction in which a large molecule is broken down into two smaller molecules, by the addition of water and the breaking of a covalent bond.

Ionic bond

Electrostatic attraction between oppositely charged ions.

Latent heat of vapourisation

The amount of heat required to enable a molecule to separate from other molecules around it - turning a liquid into a vapour.

Monomers

Small molecules of the same general type that are joined in condensation reactions to form a polymer.

Monosaccharides

Monomer of polysaccharides.

Non-reducing sugar

Disaccharides (e.g. sucrose) that do not reduce other molecules.

Peptide bond

The covalent bond formed when amino acids are joined together in condensation reactions.

Polar molecule

Hydrophilic molecule with an unequal distribution of charge.

Polymer

A large molecule made by covalently joining many similar small molecules together in a condensation reaction.

Polypeptide

A polymer consisting of many amino acid monomers covalently bonded together by peptide bonds.

Polysaccharide

Polymer formed from many repeated condensation reactions joining many monosaccharide monomers together.

Primary structure

The sequence of amino acids found in a polypeptide held together by peptide bonds.

Prosthetic group

A non-protein group covalently attached to a polypeptide.

Protein

A large molecule composed of one or more polypeptide chains.

Qualitative test

A test that reveals the presence or absence of a substance but not its numerical quantity.

Quantitative test

A test that gives readings and recordings that are numerical.

Quaternary structure

Level of protein structure where a protein consists of more than one polypeptide chain.

Reducing sugars

Sugar molecules including all monosaccharides and some disaccharides that can reduce other molecules.

Saturated fatty acid

Only contains single C-C covalent bonds.

Secondary structure

The regular coiling or folding parts of a polypeptide chain due to the formation of hydrogen bonds between the C=O and NH groups in the polypeptide backbone. Includes alpha helix and beta pleated sheet.

Specific heat capacity

The amount of energy required to make substance change temperature.

Steroids

A class of non-polar lipid molecules e.g. cholesterol, testosterone.

Tertiary structure

The overall 3D shape of a polypeptide formed as a result of interactions between the amino acid side chains (R groups).

Triglyceride

Most common lipid in the body, containing three fatty acids and a glycerol molecule. They are entirely hydrophobic and form large droplets inside cells.

Unsaturated fatty acid

Contains one or more C=C double bond.