1A: Chemistry for Biologists

Pearson Edexcel International AS Level Book 1

Anion

A negative ion that gains electrons

Cation

A positive ion that loses electrons

Ionic bonds

Bonds formed when atoms give or receive electrons and result in charged particles called ions

Covalent bonds

Bonds formed when atoms share electrons

Dipole

The separation of charge in a molecule when the electrons in covalent bonds aren’t evenly shared because an atom is more electronegative than the other

Polar molecule

A molecule containing a dipole

Dissociation

A chemical reaction in which a compound breaks down into smaller molecules, atoms or ions, when dissolved in a solvent.

Hydrogen bonds

A weak electrostatic attraction formed between the positive and negatively charged atoms of nearby water molecules as a result of the polar nature of water

Water

Medium in which all metabolic processes take place in cells and all substances are transported around the body

Cohesive

The attraction between the same molecules

Adhesive

The attraction between dissimilar molecules, atoms, surfaces, or substances

Monomer

A small molecule that is a single unit

Polymer

A long-chain molecule made up of many repeating monomers joined together by chemical bonds

Macromolecule

A very large molecule often formed by polymerisation

Starch

A long-chain polymer formed of glucose monomers used as an energy store in plants. The sugars produced by photosynthesis are rapidly converted into X, which can be broken down rapidly to release glucose when needed

Sucrose

A disaccharide formed by the joining of glucose and fructose by a 1,4-glycosidic bond

Glucose

A hexose sugar (monosaccharide)

Monosaccharide

A single sugar monomer

Disaccharide

A sugar made up of two monosaccharide units joined by a glycosidic bond, formed in a condensation reaction

Polysaccharide

A polymer consisting of long chains of monosaccharide units joined by glycosidic bonds

Triose sugar

A sugar with three carbon atoms

Pentose sugar

A sugar with five carbon atoms

Hexose sugar

A sugar with six carbon atoms

Ribose

A pentose sugar that is part of the structure of RNA

Deoxyribose

A pentose sugar that is part of the structure of DNA

Deoxyribonucleic aid (DNA)

A nucleic acid that is the genetic material in many organisms

Ribonucleic acid (RNA)

A nucleic acid which is the genetic material in some organisms and is involved in protein synthesis

Isomers

Molecules that have the same chemical formula, but different molecular structures

Condensation reaction

A reaction in which a molecule of water is removed from the reacting molecules as a bond is formed between them

Glycosidic bond

A covalent bond formed between two monosaccharides in a condensation reaction, which can be broken down by a hydrolysis reaction to release the monosaccharide units

Reducing sugars

Sugars that react with Blue Benedict’s solution and reduce the copper (II) ions to copper (I) ions giving an orangey-red precipitate

Non-reducing sugars

Sugars that do not react with Benedict’s solution

Oligosaccharides

Molecules with between 3 and 10 monosaccharide units

Hydrolysis

A reaction in which bonds are broken by the addition of a molecule of water

ATP

Adenosine triphosphate. The molecule that acts as a universal energy supply molecule in all cells

End products

the final products of a chemical reaction

Amylose

A complex carbohydrate containing only α-glucose monomers joined together by 1,4-glycosidic bonds so the molecules form long unbranched helix-shaped chains with a compact shape, making it good for storage

Amylopectin

A complex carbohydrate made up of α-glucose monomers joined by a 1,4-glycosidic bonds with some 1,6-glycosidic bonds so the molecules branch repeatedly. The branches result in many terminal glucose molecules, which can be easily hydrolyzed for use during cellular respiration or added to storage.

Glycogen

A complex carbohydrate with many α-glucose units joined by 1,4-glycosidic bonds with many 1,6-glycosidic bonds, giving it many side branches, and used for storage carbohydrate for animals and fungi.

Lipids

Monomolecules that contain carbon, hydrogen and oxygen atoms with a lower proportion of oxygen. They are important in cell membranes and as an energy store in many organisms. They include triglycerides, phospholipids and steroids. Lipids are non-polar and hydrophobic, insoluble in water

Triglycerides

Lipid that forms the main component of fats and oils.

Fatty acids

Organic acids with a long hydrocarbon chain

Glycerol

An important component of triglycerides

Ester bonds

Bonds formed in a condensation reaction between the carboxyl group (-COOH) of a fatty acid and one of the hydroxyl groups (-OH) of glycerol

Saturated fatty acids

A fatty acid in which the carbon atoms is joined to one next to it in the hydrocarbon chain by a single covalent bond

Unsaturated fatty acids

A fatty acid in which the carbon atoms in the hydrocarbon chain have one or more double covalent bonds in them

Monounsaturated fatty acid

A fatty acid with only one double covalent bond between carbon atoms in the hydrocarbon chain

Polyunsaturated fatty acid

A fatty acid with two or more double covalent bonds between carbon atoms in the hydrocarbon chain

Esterification

The process by which ester bonds are made

Haemoglobin

A red pigment that carries oxygen and gives the erythrocytes their colour

Amino acids

The building blocks of proteins consisting of an amino group (-NH2) and a carboxyl group (-COOH) attached to a carbon atom and an R group that varies between amino acids

Peptide bond

The bond formed by condensation reactions between amino acids

Dipeptide

two amino acids joined by a peptide bond

Polypeptide

A long chain of amino acids joined by peptide bonds

Disulfide bond

A strong covalent bond produced by an oxidation reaction between sulfur groups in cysteine or methionine molecules, which are close together in the structure of a polypeptide

Fibrous proteins

Proteins that have long, parallel polypeptide chains with occasional cross-linkages that produce fibres; they have little tertiary structure

Denaturation

The loss of the 3D shape of a protein, caused by changes in temperature or pH

Collagen

A strong fibrous protein with a triple helix structure

Globular proteins

Large proteins with complex tertiary and sometimes quaternary structures, folded into spherical, globular shapes

Hydrophobic

A substance that tends to repel water and that will not mix or dissolve in water

Hydrophilic

A substance with an affinity for water that will readily dissolve in or mix with water

Colloid

A suspension of molecules that are not fully dissolved

Prosthetic group

The molecule incorporated in a conjugated protein

Conjugated proteins

Protein molecules joined with or conjugated to another molecule called a prosthetic group

Lipoproteins

Conjugated proteins with a lipid prosthetic group

Glycoproteins

Conjugated proteins with a carbohydrate prosthetic group

Proteases

Protein-digesting enzymes

Sucrose (Source)

Stored in plants such as sugar cane

Sucrose (Components of Disaccharide)

Glucose + Fructose (1-2 glycosidic bond)

Lactose (Source)

Milk sugar (main carbohydrate found in milk)

Lactose (Component in Disaccharide)

Glucose + Galactose (1-4 glycosidic bond)

Maltose (Source)

Malt sugar (germinating seed - barley)

Maltose (Components in Disaccharide)

Glucose + Glucose (1-4 glycosidic bond)

Triglycerides (function)

Energy storage, insulation, buoyancy and protection