CH:2 - Biological Molecules

Question 1

Macromolecule

Answer 1

A large molecule such as a polysaccharide, protein or nucleic acid.

Question 2

Polymer

Answer 2

A giant molecule made from many similar repeating subunits joined together in a chain; the subunits are much smaller and simpler molecules
known as monomers; examples of biological polymers are polysaccharides, proteins and nucleic acids.

Question 3

Monomer

Answer 3

A relatively simple molecule which is used as a basic building block for the synthesis of a polymer; many monomers are joined together by covalent bonds to make the polymer, usually
by condensation reactions; common examples
of monomers are monosaccharides, amino acids and nucleotides.

Question 4

Monosaccharide

Answer 4

A molecule consisting of a single sugar unit and with the general formula (CH2O)n.

Question 5

Condensation Reaction

Answer 5

A chemical reaction involving the joining together of two molecules by removal of a water molecule.

Question 6

Hydrolysis

Answer 6

A chemical reaction in which a chemical bond is broken by the addition of a water molecule; commonly used to break down complex molecules into simpler molecules.

Question 7

Disaccharide

Answer 7

A sugar molecule consisting of two monosaccharides joined together by a glycosidic bond.

Question 8

Glycosidic bond

Answer 8

A C–O–C link between two sugar molecules, formed by a condensation reaction; it is a covalent bond.

Question 9

Benedict’s test/reagent test

Answer 9

A test for the presence of reducing sugars; the unknown substance is heated with Benedict’s reagent, and a change from a clear blue solution to the production of a yellow, red or brown precipitate indicates the presence of reducing sugars such as glucose.

Question 10

Polysaccharide

Answer 10

A polymer whose subunits are monosaccharides joined together by glycosidic bonds.

Question 11

Glycogen

Answer 11

A polysaccharide made of many glucose molecules linked together, that acts as a glucose store in liver and muscle cells.

Question 12

Cellulose

Answer 12

A polysaccharide made from beta-glucose
subunits; used as a strengthening material in plant cell walls.

Question 13

Hydrogen Bond

Answer 13

A relatively weak bond formed by the attraction between a group with a small positive charge on a hydrogen atom (Hδ+) and another group carrying a small negative charge (δ−), e.g. between two –Oδ–Hδ+ groups.

Question 14

Ester bond/ester linkage

Answer 14

A chemical bond, represented as –COO– , formed when an acid reacts with an alcohol.

Question 15

Triglyceride

Answer 15

A type of lipid formed when three fatty acid molecules combine with glycerol, an alcohol with three hydroxyl (−OH) groups.

Question 16

Peptide Bond

Answer 16

The covalent bond joining neighbouring amino acids together in proteins; it is a C–N link between two amino acid molecules, formed by a condensation reaction.

Question 17

Polypeptide

Answer 17

A long chain of amino acids formed by condensation reactions between the individual amino acids; proteins are made of one or more polypeptide chains; see peptide bond.

Question 18

The different structures of PROTEINS?

Answer 18

Primary structure: The sequence of amino acids
in a polypeptide or protein.

Secondary structure: The structure of a protein
molecule resulting from the regular coiling or
folding of the chain of amino acids (an α-helix or
β-pleated sheet).

Tertiary structure: The compact structure of
a protein molecule resulting from the three-dimensional coiling of the chain of amino acids.

Quaternary structure: The three-dimensional
arrangement of two or more polypeptides, or of a
polypeptide and a non-protein component such as haem-, in a protein molecule.

Question 19

α-helix

Answer 19

A helical structure formed by a polypeptide chain, held in place by hydrogen bonds; an α-helix is an example of secondary structure in a protein.

Question 19

β-pleated sheet

Answer 19

A loose, sheet-like structure formed by hydrogen bonding between parallel polypeptide chains; a β-pleated sheet is an example of secondary structure in a protein.

Question 20

Haemoglobin

Answer 20

The red pigment found in red blood cells, whose molecules contain four iron atoms within a globular protein made up of four polypeptides; it combines reversibly with oxygen.

Question 21

Globular Protein

Answer 21

A protein whose molecules are folded into a relatively spherical shape, often has physiological roles and is often water-soluble and metabolically active, e.g. insulin, haemoglobin and enzymes.

Question 22

Sickle Cell Anaemia

Answer 22

A genetic disease caused by a faulty gene coding for haemoglobin, in which haemoglobin tends to precipitate when oxygen concentrations are low.

Question 23

Collagen

Answer 23

The main structural protein of animals; known as ‘white fibres’, the fundamental unit of the fibre consists of three helical polypeptide chains wound around each other, forming a ‘triple helix’ with high tensile strength.

Question 24

Fibrous Protein

Answer 24

A protein whose molecules have a relatively long, thin structure that is generally insoluble and metabolically inactive, and whose function is usually structural, e.g. keratin and collagen.

Question 25

Biuret Test

Answer 25

A test for the presence of amine groups and thus for the presence of protein; biuret reagent is added to the unknown substance, and a change from pale blue to purple indicates the presence of protein.