Biological Molecules F212

4 Funtions of water to living organisms

• Reactant and important in chemical reactions
• Water is a Solvent so many substances dissolve in it
• Water Transports substances as it is a liquid and a solvent
• Water helps with Tempurature Control it has a high specific heat capacity

Water Moleclule Structure

1) 2-Hydrogen joined to 1-Oxygen by Shared Electrons covalent bonding holds these together

2) Shared Negative electrons are pulled towards the oxygen

3) Unshared negative electrons give it a slight negative charge (delta minus)

4)This is why water  is Polar(attraction between molecules of the same type) it has a slightly positive charge at the end where the hydrogen ions sit, and a negative charge on the opposite side to where the oxygen is situated

5) This attraction is called Hydrogen bonding and gives water its useful properties such as a high heat capacity as hydrogen bonds absorb lots of energy

Hydrogen Bonds give water High Latent Heat of Evaporation

• It takes alot of energy to break a hydrogen bond
• High Latent Heat of Evaporation lots of energy uis used when it evaporates
• This is useful to organisms as it cools things

Water Polarity makes it a good solvent

• most biological reactions are ionic (They are made from a positive and negatively charged ion)
• the positive end of a water molecule is attracted to the negative ion vice versa
• This means ions will be completely surrounded by water molecules (dissolve)
• Therefore waters Polarity makes it a useful Solvent

Proteins are made from long chains of Amino Acids

• A dipeptide is where two amino acids are joined together
• A polypeptide is more than two amino acids joined together
• A protein is made up of one or more polypeptide

Amino Acids have Different Variable Groups

• All amino acids have a carboxyl group(-COOH) and an amino group(-NH2) attached to a carbon atom. 
• The Variable Group is represented as an "R" on a diagram (situated above the carbon atom)
• This is the reason amino acids differ from each other

Amino Acids are joined by Peptide Bonds

• They are linked together to create dipeptides and polypeptides
• A molecule of water is released during the reaction (Condensation Reaction)
• The reverse  of the reaction adds water to break the bond (Hydrolysis)

Proteins Have 4 Structural Levels

Primary  - A sequence of Amino Acids in a Polypeptide Chain

Bonds: Peptide bonds between amino acids

Secondary - Hydrogen bonds form between the (AA)* in the chain, causes it co turn into an alpha-Helix or a Beta Pleated Sheet

Bonds:Hydrogen Bonds

Tertiary - Coiled and folded further, more bonds in the polypeptide chain.sometimes take a globular shape, Protiens made from 1 polypeptide chain forms thier 3-D structure

Bonds: Ionic (bonds) interactions, Disulfide Bonds, Hydrophobic and Hydrophilic interactions, Hydrogen Bonds

Quaternary Structure - made of several polypeptide chains held together by bonds, Quaternary structure is the way polypeptide chains are assembled e.g haemoglobin is made of 4 polypeptide chains

Bonds: Determined by the tertiary structure