Definitions (Biological molecules): Foundations in Biology: Biology OCR A Level

Adhesion

A property of water molecules that creates an attraction between them and surfaces that they are in contact with.

Amino acid

The monomers containing an amino group (NH2), a carboxyl group (COOH) and a variable R group that make up proteins.

Amylopectin

A branched polysaccharide made up of alpha glucose monomers joined by α-1,6 glycosidic bonds that makes up starch along with amylose.

Amylose

An unbranched polysaccharide made up of alpha glucose monomers joined by α-1,4 glycosidic bonds that makes up starch along with amylopectin.

Anions

An ion with a negative charge.

Benedict’s test

A biochemical test used to detect the presence of a reducing sugar in a solution and distinguish between solutions of different reducing sugar concentrations.

Biuret test

A biochemical test that produces a purple colour when it is added to a solution containing protein.

Cations

An ion with a positive charge.

Cellulose

A linear polysaccharide that is the main component of the cell wall in plants and is made up of many beta glucose molecules joined by β-1,4 glycosidic bonds.

Chromatography

A technique used to separate different molecules in a solution by their different properties.

Cohesion

A property of water molecules that creates an attraction between them which causes them to stick together.

Collagen

A type of fibrous protein that provides strength to many different cell types and makes up connective tissues.

Condensation reaction

A type of reaction that joins two molecules together with the formation of a chemical bond involving the elimination of a molecule of water.

Conjugated protein

A protein with a prosthetic group bound to it.

Elastin

A type of fibrous protein that allows tissues and structures like blood vessels to stretch and return to their original shape.

Fibrous protein

A class of long chain proteins that are generally insoluble in water and typically have structural roles.

Globular protein

A class of spherical shaped proteins that are generally water soluble and typically have metabolic roles.

Glucose

A hexose monosaccharide that is the main respiratory substrate in eukaryotes.

Glycogen

A highly branched polysaccharide that is used as the main energy storage molecule in animals and is made up of alpha glucose monomers joined by α-1,4 glycosidic bonds.

Haemoglobin

A type of conjugated globular protein used to transport oxygen that is made up of four polypeptide chains each containing a haem prosthetic group.

Hexose monosaccharide

A simple sugar that contains 6 carbon atoms.

Hydrogen bond

A type of weak bond formed between an electropositive hydrogen and an electronegative atom like oxygen or nitrogen.

Hydrolysis

Breaking a chemical bond between two molecules involving the use of a water molecule.

Insulin

A globular protein hormone that is made in the pancreas in response to detection of high glucose levels in the blood.

Iodine test

A biochemical test that produces a blue/black colour when it is added to a solution containing starch.

Keratin

A type of fibrous protein that provides strength to hair and nails.

Lactose

A disaccharide made of a molecule glucose and galactose joined by a glycosidic bond.

Lipid emulsion test

A biochemical test that produces a cloudy emulsion when performed on lipids.

Maltose

A disaccharide made of two molecules of glucose joined by a glycosidic bond.

Monomer

An individual unit that can be bonded to other identical monomers to make a polymer.

Monomers

The smaller units from which larger molecules are made.

Pentose monosaccharide

A simple sugar that contains 5 carbon atoms.

Phospholipid

A type of amphipathic lipid made from a molecule of glycerol bonded to two fatty acid molecules and a phosphate group.

Polymer

A molecule made from many repeating monomers joined together.

Polymers

Molecules made from a large number of monomers joined together.

Primary structure

The individual sequence of amino acids in a protein.

Quaternary structure

A structure only applicable to proteins with multiple polypeptide chains that describes the interactions of the different chains.

Ribose

A pentose monosaccharide which composes the backbone of RNA.

Saturated fatty acid

A type of fatty acid molecule containing only single bonds between the carbon atoms.

Secondary structure

The local interactions of the amino acids in the polypeptide chain.

Solvent

A liquid that solutes can dissolve in to form a solution

Starch

A polysaccharide used for energy storage in plants that is made up of alpha glucose joined together in the forms of amylose and amylopectin.

Sucrose

A disaccharide made of a molecule glucose and fructose joined by a glycosidic bond.

Tertiary structure

The way that the whole protein folds to make a three dimensional structure.

Triglyceride

A type of lipid formed from a molecule of glycerol joined by ester bonds to three fatty acid molecules.

Unsaturated fatty acid

A type of fatty acid molecule containing at least one double bond in the carbon chain.