Water

Properties of 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.

 

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Carbohydrates

- 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

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Monosaccharides

- 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

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Disaccharides

- 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)

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Polysaccharides

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