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Molecular Biology and Biochemistry Lecture 1 Summary

Molecular Biology and Biochemistry Lecture 1 Summary -...

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Molecular Biology and Biochemistry Lecture 1 Summary: By: Mak 1. Living organisms are mainly made up of water and macromolecules (carbohydrate, protein, lipid and nucleic acids). These molecules in cell keep on turning over (metabolism: chemical reactions occur in a cell at any one time; catabolism + anabolism). 2. Water: made up 70% of the cell; as the universal solvent (most metabolic reactions occur in aqueous solution). 3. Chemistry of water: Form extensive hydrogen bonding (maximum 4 hydrogen bond form between water molecules at solid state and 3.4 hydrogen bond in liquid state). 4. Physical properties of water: High specific heat capacity (maintain a constant temperature in environment and in living organism and provide/absorb energy during metabolic reaction); High melting and boiling point; High surface tension (capillary effect: cohesive and adhesive forces: for transportation of water within xylem in plant); Low viscosity (half life of hydrogen bond of water in liquid state is only 1 nanosecond); Solid state of water has lower density than liquid state 5. Chemical properties of water: A. Universal solvent for polar/ charged particles but poor solvent for non-polar molecules at room temperature (Reason: Like dissolve like; Due to high dielectric constant). Water is a poor solvent for non-polar solvent (Due to hydrophobic interaction enthalpy and entropy of water in system is favorable when lipid droplets cluster into a bigger droplet). Note that the dielectric constant of water changes with temperature and pressure. B. Chemically, water undergoes autoionization that produce hydronium and hydroxide ions which speeds up acid/base reactions and reactions involving protons. C. Proton jump: In water, H is
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