Full corse notes ENG

Pagina 1

1 BIOMOLECULES 1. CARBOHYDRATES 2. LIPIDS: non polar, hydrophobic molecules made of fatty acid (block building of lipids) 3. NUCLEIC ACID: DNA and RNA 4. PROTEINS 2 WATER PROPERTIES In the prebiotic era the ultraviolet rays of sun have favored reactions between inorganic molecules (H2O) present in the atmosphere by forming organic compounds, like aminoacids AAs the block buildings of proteins. Water is a polar molecule with a negative pole (O) and a positive one (H). They are linked by a covalent bond (0.0965 nm). Water molecules interact each other thanks to hydrogen bond between atoms of opposite electronegativity (O -H), the distance is 0.177 nm. The physical state of water depends on the number of H-bonds between molecules: in the ice state, each molecule performs 4 H-bonds. Solubilisation in water is possible only for charged (ions) or polar molecules (hydrophilic compounds). The hydratation of biomolecules is possible thanks to the interactions between ionized carboxyl groups and H of water or between protonated amine groups and O of water. PROTEINS They are present in all living systems. They are made of 20 AAs combined in a different way so the properties, size and complexity depend on the composition. AMINO ACID: the building blocks of proteins. The main structure of AAs is characterized by a central Calfa connecting a N -terminus, a C -terminus, an H and R which is different for each AAs and confers chemical feature to AAs. In physiological conditions (pH = 7.4), the amino acid is in a Zwitterion state characterized by electrical conducibility, high solubility in water, high melting and boiling points. In this state, the amino group is protonated, while the carboxyl grou p is deprotonated. The Zwitterion state is an isoeletric state (uncharged). The pH of…