1 - Biological Molecules

1 - Biological Molecules

• the study of biological molecules is known as molecular biology

1.1 - introduction to biological molecules

Bonding and the formation of molecules:

• atoms share a pair of electrons in their outer shells
• as a result of this sharing, the outer shell of both atoms is filled and a molecule is formed

ionic bonding -

• ions with opposite charges attract to one another; this electrostatic attraction is known as an ionic bond
• ionic bonds are weaker than covalent bonds
• example : sodium chloride of Na+ and Cl-

• electrons within a molecule are not evenly distributed but tend to spend more time at one position
• the region where these electrons are distributed, is more negatively charged than the rest of the molecule

polar/polarised molecule: a molecule with an uneven distribution of charge

hydrogen bonding -

• when the negative region of one polarised molecule and the positively charged region of another attract each other and a weak electrostatic bond is formed between the two
•  each bond is individually weak, however they can collectively form important forces that alter the physical properties of molecules
• an example is - water

polymers - long chain of monomers sub-units

polymerisation - the process in which polymers are formed

• the monomers of a polymer are usually based on Carbon

polythene and polyesters - industrially produced

polysaccarides, polypeptides and polynucleotides - made naturally by living organisms

• the basic sub-unit of a polysaccaride is a monosaccaride or single sugar i.e glucose

polynucleotides -

• formed from mononucleotide sub-units

polypeptides -

• formed by linking together peptides that have amino acids as their basic sub-units

Condensation and Hydrolysis reactions:

• in the formations of polymers by polymerisation in organisms, each time a new sub-unit is attached a molecule of water is formed
• condensation reactions - reactions that produce water
• the formation of a polypeptide from amino acids = condensation reaction
• the reaction of a polysaccharide starch from the monosaccharide glucose = condensation reaction
• polymers can be broken down by through the addition of water
• hydrolysis reactions - when water molecules are used when breaking the bonds that link the sub-units of a polymer , splitting the molecule into its constiuent parts
• hydro = water
• lysis = splitting
• polypeptides can be hydrolysed to amino acids
• starch can be hydrolysed to glucose

Reactions between substances:

• nucleotides --> polynucleotides (nucleic acids) = condensation
• polynucleotides --> nucleotides = hydrolysis
• monosaccarides -->polysaccharides (carbohydrates) = condensation
• polysaccharides (carbohydrates) --> monosaccharides = hydrolysis
• fatty acids --> lipids = condensation
• lipids --> fatty acids = hydrolysis
• glycerol -->lipids = condensation
• lipids --> glycerol = hydrolysis
• amino acids --> polypeptides (proteins) = condensation
• polypeptides (proteins)--> amino acids = hydrolysis
  

metabolism - all the chemical processes that take place in living organisms 

the mole - the SI unit for measuring the amount of substance

1 mole = the same number of particles as there are in 12g of Carbon-12 atoms this number is the avogandro constant and is 6.022 x 10 to the power of 23

molar solution…