The Chemistry of Biology. What are living things made up of?
All living things including humans are made up of chemical substances. These chemical substances are both organic and inorganic substances.
Organic substances include: Carbohydrates, Fats and Oils (lipids), Proteins,
Inorganic substances include: Salts and Water
The main functions of these substances include:
Each substance has certain jobs to do. These are their main jobs.
- Carbohydrates: carbohydrates give energy; one of the best known carbohydrates is sugar of which there are several different types.
- Fats and Oils (lipids): Fats and lipids also give us energy. They is a lot of fat under the skin where it helps to keep warm and oils on the surface can help make the body water proof.
- Proteins: Proteins help to build the body. They form important structures like muscles and tendons and are also important as enzymes which are important in the digestion and other processes.
- Salts: Salts help to make the tissues and organs in the body work properly.
- Water: Water provides a fluid in which other substances can move about the body and react together within the cells.
How are these complex substances constructed?
- All carbohydrates contain carbon, hydrogen and oxygen. One of the simplest is glucose which is a type of sugar. Its chemical formula is C6H12O6. This shows that the molecule contains 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms.
- Glucose molecules can be linked together to form more complex carbohydrates, for example starch and glycogen. Their function is to store energy for use when it is needed.
- Fats and oils are complex substance too. Their molecules are made up of two parts: glycerol and fatty acids. Like carbohydrates, fats and oils contain carbon hydrogen and oxygen atoms.
- Proteins are amongst the most complex substances found in living things. They contain nitrogen as well as carbon, hydrogen, oxygen and sulphur too. A protein molecule may consist of one or more chains of chemical building blocks called amino acids. Sulphur helps cross-link the amino acid chains. Some proteins are solid, others are in solution. Muscle is a solid protein, where as egg white is a soluble protein.
- Proteins may combine with other molecules and form even more complex substances. For example, they combine with nucleic acids such as DNA to form nucleoproteins.
Substances like proteins and starch, which are made up of lots of smaller molecules joined together are called polymers. Proteins are polymers of amino acids: starch, glycogen and cellulose are polymers. Natural polymers are very important in living organisms and some of them have practical uses. Paper, for example is made from cellulose. These polymers wont dissolve in water, in other words, they are insoluble. However, the chemicals they are composes of – amino acids and glucose for example – are soluble.
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This article is in continuation with our previous article on Biology Structure of Cell