Water

- Water is a dipolar molecule 

- Hydrogen bonds form between the oxygen of one water molecule and the hydrogen of another.

-The slightly negatively charged oxygen and slightly positively charged hydrogen are joined by the hydrogen bonds.

- Water molecules therefore tend to be attracted to each other by hydrogen bonds and this attraction is called Cohesion.

-Cohesion is responsible for surface tension which helps organisms in following ways:

1. Enables aquatic insects to walk on water e.g. Skaters

2. It aids capillarity in the xylem vessel

-Surface tension occurs when water molecules are attracted to each other but not attracted to different molecules, surfaces or air.

-Water requires lots of energy to break the hydrogen bonds. This is why water has such high melting and boiling points.

- Contain carbon, hydrogen and oxygen

-They are largest group of organic componds in living organisms

-Groups of carbohydrates

Monosaccharides- simple sugars

Disaccharides- double sugars

Polysaccharides- complex sugars

- General formula of (CH2O)n.

-Glucose is the most common monosaccharide and there are two forms we need to know: Alpha glucose and Beta glucose

- They are isomers so they have same chemical formula but different properties

-Hexoses - C6H12O6

-They are single units

-They are soluble in water

-They lack glycosidic bonds

- Two monosaccharides joined by condensation reaction where water is given out.

-The monosaccharide are joined by covalent bonds called glycosidic bonds

-The general formula is (C5H10O5)n

Maltose - Alpha glucose + Alpha glucose

Sucrose - Alpha glucose + Fructose

Lactose - Alpha glucose + Galactose

- Condensation reaction join together (H2O released)

-Hydrolysis reactions split apart (H2O issued)