The chemical composition of biological systems

1. The chemical composition of biological systems (nucleic acids, proteins, lipids, sacharids)

2. 1. The proof of proteins in egg white and in yeast – biuret reaction • Material and methods: 3 test tubes, test tube rack, pipettes, mortar and pestle, destilled water, 10% KOH, 5% CuSO4, yeast (Saccharomyces cerevisiae), egg white. • 1, cca 0,5g of yeast is crushed in mortar with couple of drops of water, mass is moved to the test tube with 1,5cm3 of water. 2, To the second test tube, we pipette 1,5cm3 of destilled water. 3, To the third test tube, 0,5 cm3 of egg white is diluted with saline (1:20) and filled with destilled water to 1,5 cm3. • Then we add to all three test tubes 1 cm3 of KOH, mix, add few drops of CuSO4. We observe changes of color.

4. 2. The proof of the amylum grains in the potato cells and proof of sacharides in fruit • amylum-presence test • Material and methods: potato, filter paper, razor blade, Lugol‘s solution, microscope. • – piece of potate is rinsed with water, using the razor blade we cut thin slice and move it to microscope slide, we add drop of water. After short examination we add Lugol’s solution.

5. 2. The proof of amylum grains in potato cells and proof of sacharides in fruit • sacharides-presence test • Material and methods: fruit juice, Fehling’s reagent I. and II. • – we mix 1+1ml Fehling’s reagent and 2ml juice (1:1), we slowly heat the substance in water bath. We observe the change of color. t= cca 50°C +

6. 3. The observation of animal fat in subcutaneous tissue – lipid-presence test • Material and methods: animal subcutaneous fat, sudan III solution, microscope • – we cut thin slice from frozen bacon, we put in on microscope slide with drop of sudan III solution. We wait 5-10 minutes. After 10 minutes, we observe the slide under microscope.