2. Biological Molecules

Question 1

Monomer

Answer 1

A simple molecule which is used as a basic building block for polymer synthesis, usually by condensation reactions;
eg. monosaccharides, amino acids, nucleotides

Question 2

Polymer

Answer 2

A giant molecule made up of many repeating monomers;

eg. polysaccharides, proteins, nucleic acids

Question 3

Macromolecule

Answer 3

A large biological molecule;

eg. polysaccharides, proteins, nucleic acids

Question 4

Monosaccharide

Answer 4

A single sugar molecule with the general formula (CH2O)n

Question 5

Disaccharide

Answer 5

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

Question 6

Polysaccharide

Answer 6

A polymer consisting of many monosaccharides joined together by glycosidic bonds

Question 7

Primary structure

Answer 7

The sequence of amino acids in a polypeptide

Question 8

Secondary structure

Answer 8

The structure of a polypeptide chain resulting from the regular coiling or folding of the chain of amino acids, eg. an alpha-helix or beta-pleated sheet

Question 9

Tertiary structure

Answer 9

The complex 3D structure of a polypeptide formed after the folding of one secondary structure

Question 10

Quaternary structure

Answer 10

The structure formed when more than one polypeptide chains join together

Question 11

2 advantages of having a storage molecule that is highly branched

Answer 11

1. more compact/takes up less space

2. many terminals for attachment or removal of glucose

Question 12

Explain why cellulose is suitable as a component of plant cell walls.

Answer 12

• many hydrogen bonds form between cellulose MOLECULES, which are linear
• straight chain allows molecules lie parallel to each other
• molecules form microfibrils and fibres
• gives strength to cell wall to withstand turgor pressure and prevent cell bursting
• many gaps between fibres make cell wall permeable
• insoluble in water

Question 13

Describe the importance of water as an environment for the pond skater and the northern pike.

Answer 13

• high surface tension, pond skater can stand on water surface
• pond skater can get food from organisms that fall onto water
• high specific heat capacity, stable habitat for northern pike
• ice floats, so northern pike can survive beneath ice due to insulation
• good solvent, northern pike can get dissolved oxygen
• liquid, northern pike can move
• transparent, northern pike can see

Question 14

Explain how glycine plays an essential role in the structure of collagen. [3m]

Answer 14

• glycine is the amino acid with the smallest R group
• runs along the central axis of the helical polypeptide
• allows the triple helix to be tightly packed together
• allows hydrogen bonds to form between polypeptides

Question 15

Explain how the structure of a triglyceride is suited to its function as an energy storage molecule. [2m]

Answer 15

+ many C-H bonds
+ ref. to dense packing / large mass per unit volume
- ref. to role of hydrogens in oxidative phosphorylation
- bond energy released when bonds broken