Molecular-Biology-Q2-Week-2-Chapter-4-The-Chemistry-of-Life

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  • Living organisms are composed of about 25 chemical elements

    • Matter is composed of chemical elements

    • An element cannot be broken down to other substances by ordinary chemical means

  • Life requires about 25 chemical elements

    • Oxygen, carbon, hydrogen, and nitrogen make up about 96% of the human body

    • Calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium account for most of the remaining 4%

    • Trace elements are essential, but only in minute quantities

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  • Elements can combine to form compounds

    • Compounds are substances containing two or more elements in a fixed ratio

    • Compounds are more common than pure elements

  • Most compounds in living organisms contain carbon, hydrogen, oxygen, and nitrogen

  • Sodium chloride and vitamin A are both classified as compounds because they contain two or more elements in a fixed ratio

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  • Carbon is unparalleled in its ability to form large, diverse molecules

  • Carbon-based molecules are called organic compounds

  • Carbon atoms can form up to four covalent bonds, allowing molecules to branch in multiple directions

  • Methane and other compounds composed of carbon and hydrogen are called hydrocarbons

  • Hydrocarbons can have different structures, including chains, rings, and double bonds

  • Compounds with the same formula but different structures are called isomers

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  • Functional groups determine the properties of organic compounds

  • Functional groups are groups of atoms that participate in chemical reactions

  • Five important functional groups are hydroxyl, carbonyl, carboxyl, amino, and phosphate

  • Functional groups are polar and make compounds hydrophilic and soluble in water

  • Examples of organic compounds with functional groups include alcohols, aldehydes, ketones, carboxylic acids, amines, and organic phosphates

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  • Compounds that are female and male sex hormones in humans and other vertebrates

    • Differ mainly in the functional groups attached to their carbon skeletons

    • Different actions of these molecules on many targets in the body produce contrasting features of females and males

    • Sexual differences have their biological basis in variations in functional groups

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  • Formation of polymers and monomers

    • Cells make a huge number of large molecules from a small set of small molecules

    • Four main classes of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids

    • Macromolecules are very large molecules composed of thousands of covalently bonded atoms

    • Many macromolecules are polymers of smaller molecules called monomers

    • Cells make most of their large molecules by joining smaller organic molecules into chains called polymers

    • A polymer is a large molecule consisting of many identical or similar molecular units strung together

    • Units that serve as the building blocks of polymers are called monomers

    • Living cells make a vast number of different polymers, with proteins alone having about a trillion different kinds in nature

    • Proteins are built from 20 kinds of amino acids, while DNA is built from 4 kinds of nucleotides

    • Variety of polymers accounts for the uniqueness of each organism

    • Monomers used to make polymers are essentially universal

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  • Isomers

    • Compounds that contain the same number of atoms but differ in the way the atoms are arranged

  • Types of isomers

    • Geometric isomers

      • Result from restricted rotation, usually due to a double bond

      • Cis isomers have the same types of atoms on the same side of the molecule, while trans isomers have them on the opposite side

      • Geometric isomers require different atoms or groups attached to one end of the double bond

    • Structural isomers

      • Also known as constitutional isomers

      • Differ in the connectivity of atoms in molecules

      • Can be formed by hydrocarbons with at least four carbon atoms

      • Three types: skeletal, positional, and functional group isomers

    • Enantiomers

      • Non-superimposable mirror images of each other

      • Have the same chemical bonds but completely opposite three-dimensional structures

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  • Isomers

    • Organic compounds with the same molecular formula but different structural formulas

    • Isomers may differ in the arrangement of atoms

  • Example: Ethanol and dimethyl ether

    • Same molecular formula (C2H6O2) but different structural formulas

    • Called constitutional isomers

    • Have different properties due to differences in how the atoms are