Unit 1

• Water is a polar molecule: There is an uneven distribution of charge across the atoms. The       electron density is higher around oxygen
• Oxygen is more electronegative than hydrogen
• Water molecules react non- covalently: hydrogen bonding- partially negative oxygen forms an electrostatic bond with the partially positive hydrogen atom of another water molecule.

Properties:

1. Polarity of water enables it to act as a transport medium, and solvent form many essential chemical species which are polar and/ or charged
2. High latent heat of vaporisation enabling cells to provide a thermostable environment
3. Water molecules are cohesive(held together) as a result of the hydrogen bonds: - Key for support in tissue systems and acts as a lubricant e.g. mucus  

• Main respiratory substrate
• When broken down, it releases energy --> Energy released is captured by cells --> Energy enables cells to drive a whole range of processe

Monosaccharide: monomeric carbohydrate unit

Disaccharde: a sugar formed by the condensation of two monosaccharide units

Ogliosaccharide: a carbohydrate made up of a chain of few monosaccharide units

Polysaccharide: A carbohydrate consisting of a number of glucose molecules bonded together

• When two monosaccharides join together, they form a disaccharide. This happens in a condensation reaction in which a water molecule is released and a glycosidic bond is formed between the carbon 1 and carbon 4 atoms
• "Maltose" is made from two alpha glucose units

• An alpha- glucose polymer made up of alpha(1-->4) glycosidic linkages as well as alpha(1-->6) linkages.
• The alpha(1-->6) linkages make the polymer heavily branched
• Glycogen synthesis involves glucose condensation
• To mobilise the glucose, a phosphorolysis reaction takes place by which phosphate is added which attacks the alpha(1-->6) glycosidic linkages at the terminals. This reaction is catalysed by the enzyme glycogen phosphorolase
• Stored in the liver and muscle cells
• Glycogen is a useful biopolymer as it is: Insoluble- doesn't affect the water content of the cell and Highly Branched- Lots of glucose molecules can be stored in a more compact space

Primary roles in biological systems:

• Energy Storage (limitless)
• Cell Membranes
• Heat Insulation
• Internal Organ Shielding

Fats are stored in adipose tissues- Adipose cells consist of a nucleus and a large globule of fat

Fat molecules are non-polar making them hydophobic- They cannot interact with water

Excess carbohydrase can be converted into fat

Fats are also known as triglycerides (TG):

Structure of a triglyceride:

Glycerol is an alcohol and so has hydroxyl groups and fatty acids are carboxylic acids

The hydroxyl groups of the glycerol react with the carboxyls of three fatty acids in a condensation reaction (+elimination of water) to form ester linkages. As there are three links, this forms a triester.

Saturated Fatty Acids:

All the carbon-carbon bonds are single and there is the maximum number of hydrogen atoms in the chain. They tend to have higher boiling points- Mainly solid at room temp.

Unsaturated Fatty Acids:

Some of the carbon atoms have double bonds between them and therefore there is less room for hydrogen atoms in the chain. Mainly liquid at room temp.