As this unit focuses on products and processes related to curriculum units on acids and bases, this is also the knowledge background needed. Teachers must be able to choose household products, e.g. cleaners containing acids or bases. They must have general knowledge on the structures and properties of the substances, such as acidic acid, citric acid, or sodium hydroxide. Most important, they must consider all measures necessary for a safe realisation of students’ experiments, as described in the material. However, as this content knowledge is also very basic and can again be found in any chemistry textbook, no further explanations are needed at this point.
Precautionary measures are important for the experiments with bacteria and nutrient agar to prepare it sterile and its disposal.
For further information about hygiene around the home, Dr. Norbert Stelter (Henkel AG & Co. KGaA, Düsseldorf) suggests the following website:
http://www.ifh-homehygiene.org/IntegratedCRD.nsf/IFH_Home?OpenForm
Basic knowledge about bacteria, fungi and viruses
Bacteria are microorganisms existing in large numbers. Bacteria live nearly everywhere, for example in the air, on objects, or in the water. People need bacteria as they help them but they may also cause diseases. A lipid membrane and a cell wall surround cytoplasm of the cell of the bacterium. The cell wall type affects major characteristics of bacteria. Bacteria are prokaryotes and do not have a nucleus. They also lack other components compared to other cell types. The cytoplasm carries the bacteria’s genetic information in form of a circular chromosome which is to be found in the nucleoid. There are different cell morphologies and arrangements of bacteria, e.g. cocci or bacilli. Mostly, you can find a cell wall of peptidoglycan in bacteria which is essential for them to survive compared with fungi, which are eukaryotes and their cell walls are made up of chitin amongst others.
Sources:http://de.wikipedia.org/wiki/Bakterienhttp://en.wikipedia.org/wiki/BacteriaHans G. Schlegel (1992). Allgemeine Mikrobiologie. 7. überarb. Aufl.. Georg Thieme Verlag: Stuttgart. 22-26.
The function of proteins depends on its undisturbed molecular geometry. However, in the people’s digestive tract proteins are only degradable after their denaturation. This can happen via cooking or gastric acid. This is an important process for the hygiene of food as it destroys not only bacteria but also fungi. By adding strong acids or bases, organic solvents such as alcohol, heat or concentrated inorganic salts (e.g. NaCl) to proteins they are destroyed as they lose their secondary (local segments in a three-dimensional form with regular repeating patterns) and tertiary structure (three-dimensional structure of greater segments) which are altered but the primary structure (peptide bonds between amino acids) stays intact. The result of denaturation of living cells is disrupted activity of cells (disrupted covalent and Van-der-Waals interactions between side-chains of amino acids), they cannot fulfil its function any longer, or the death of cells.
While heating intra-molecular bonds are released by vibrational excitation. By applying alcohol or inorganic salts to proteins not only their secondary and tertiary structure are destroyed but also their primary and quaternary (protein subunits spatially arranged) structure may be destroyed or disrupted due to the competition of building hydrogen bond. Also surfactants may alter proteins as they disrupt the non-polar bonds which are directed inside the protein. Additionally, surfactants may impair the structure of lipid membranes.
Sources:http://www.chemieunterricht.de/dc2/wsu-bclm/kap_02a.htmWikipedia:http://de.wikipedia.org/wiki/Denaturierung_%28Biochemie%29http://en.wikipedia.org/wiki/Denaturation_%28biochemistry%29
Fungi are microorganisms that belong to group of eukaryotic organisms. They have cell walls made up of chitin (glucose-derivative, polymer of a N-acetylglucosamine). Fungal cells have a cell nucleus which is bounded by two membranes, the nuclear membrane, and which carries the chromosomal DNA.
Sources:http://en.wikipedia.org/wiki/FungusHans G. Schlegel (1992). Allgemeine Mikrobiologie. 7. überarb. Aufl.. Georg Thieme Verlag: Stuttgart. 169-172.
Bacteria and fungi are able to spoil materials like food or microbial sensitive products because they may multiply and metabolise substances in such goods. Some bacteria and fungi are known to cause illness either as infectious organisms or due to metabolism products. Thus, it is necessary in selected cases to actively fight microorganisms to prevent illness or spoilage of goods. This covers also the preservation of potentially sensitive goods (e.g. cosmetics, water based cleaners, and detergents, or water based paints). Measures to prevent infectious diseases in the private area are summarised under household hygiene. The correct and targeted application of cleansers and detergents support household hygiene.
Viruses are particles on the borderline between inanimate nature and real organisms. Viruses are characterised by the fact that they do not have their own metabolism and thus, viruses do not spoil materials like food or microbial sensitive products. Viruses are not able to multiply themselves. They capture living cells to force them to produce viruses. This is the reason why viruses cannot be cultivated on ordinary nutrient media. Some of them are highly infective and some of the most severe infectious diseases are caused by viruses.