Monday, 18 October 2010

Chemical Composition of Living Things




The matter is made of atoms. There are about 115 different types of atoms, one per each type of element. Elements are the simplest substances.

· Atoms bond together making more complex substances like molecules. Some molecules are made of few atoms, whereas others are made of a lot of them.

· What are bioelements?: They are the elements which living things are made of. Living things are mainly composed of Carbon, Hydrogen, Oxygen, Nitrogen, Sulphur and Phosphorus.

· What are biomolecules?: They are the compounds, so they are made of atoms of bioelements bonded together. They are the building blocks of life. They are 2 groups:

· Inorganic biomolecules: They are not exclusive to living beings. However, they are essential for life.

o Water (H2O) is the most abundant substance in living things. It makes up about 65 % of your body. It is present in tissues, organs, blood and even in your teeth. It is used to carry out all chemical reactions. It is also needed to transport substances and to regulate body temperatures.

Mineral salts form the solid structure of living things, such as skeletons. Mineral salts are also involved in chemical reactions; They are necessary for the transmission of nervous impulses.

· Organic Biomolecules: They are exclusive to living beings. There are four types:

o Carbohydrates are the most abundant organic compounds. They are colourless, crystalline substances, with sweet taste, which dissolve in

water. Most are responsible for storing and transporting energy, as Glucose, Sucrose and Starch. However, others are structural, for example, cellulose.



o Lipids are insoluble in water. Lipids perform many different functions. For example, fats and oils are used for storing energy.

o Proteins are macromolecules (large biomolecules), with very complex structures, made up of chains of smaller molecules called amino acids. The most important functions or proteins are: to give structure to the cells, for example, collagen in the skin; to transport substances around the body, for example haemoglobin

; to regulate chemical reactions, for example, enzymes.

o Nucleic Acids are macromolecules also. They are two types:

§ Dexoyribonucleic acid (DNA) stores all the information necessary for the functioning and development of living things.DNA is found in the cell nucleus.

§ Ribonucleic acid (RNA), participates in the synthesis of protein. RNA is found in the cytoplasm.

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