Biology IB Topic 2_ Molecular Biology.pdf - Topic 2 Molecular Biology Vitalism and Molecular Biology ● ● ● Theory of vitalism living organisms

Biology IB Topic 2_ Molecular Biology.pdf - Topic 2...

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Topic 2: Molecular Biology Vitalism and Molecular Biology Theory of vitalism - living organisms were composed of organic chemicals that could only be produced in living organisms Theory of vitalism was falsified by a series of discoveries, including a method of synthesizing urea artificially Living organisms are governed by the same chemical and physical forces as in non-living matter Synthesis of Urea Urea is present in human urine According to theory of vitalism, urea could only be made in living organisms because it was an organic compound 1828, German chemist Friedrich Wohler synthesized urea artificially by using silver isocyanate and ammonium chloride Atoms and Molecules Atom - single particle of an element, consists of a positively charged nucleus surrounded by a cloud of negatively charged electrons Molecule - group of two or more atoms held together by covalent bonds Covalent bonds are relatively strong, so molecules can be stable Intermolecular forces - weaker bonds that form between molecules Main types of molecules used by living organisms: carbohydrates, lipids, proteins, and nucleic acids Metabolism Metabolism - web of all enzyme catalyzed reactions in a cell or organism Anabolism - synthesis of complex molecules from simpler molecules Condensation reactions (water is produced) Catabolism - breakdown of complex molecules into simpler molecules Hydrolysis reactions (water molecules are split) Polarity of Water Covalent bonds form when two atoms share a pair of electrons In some cases, the nucleus of one of the atoms is more attractive to the electrons, so the electrons are not shared equally A part of the molecule has a slight positive charge and another part has a slight negative charge, making the molecule polar Water molecules are polar Hydrogen Bonding in Water Hydrogen bond - bond forms between the positive pole of one water molecule and the negative pole of another
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Solubility in Water Hydrophilic substances - attractive to water and form bonds with water molecules Ionic compounds and substances with polar molecules are hydrophilic Many hydrophilic substances dissolve in water because their ions are more attracted to water than to each other Hydrophobic substances - water molecules are more strongly attached to each other than to the nonpolar molecules Hydrophobic substances are insoluble in water Transport in Blood Blood transports a variety of substances Most substances are transported in the blood plasma Mode of transport depends on its solubility in water Sodium chloride is soluble in water and is transported dissolved in the plasma as sodium and chloride ions Glucose and amino acids are polar and so can be transported dissolved in the plasma Oxygen is nonpolar, amount that dissolves in plasma is insufficient, red blood cells are needed with hemoglobin to which oxygen binds
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