{"id":125,"date":"2017-09-04T04:34:35","date_gmt":"2017-09-04T04:34:35","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/general-science\/?page_id=125"},"modified":"2017-09-21T14:29:53","modified_gmt":"2017-09-21T14:29:53","slug":"biochemical-basis-of-life","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/general-science\/biochemical-basis-of-life\/","title":{"rendered":"Biochemical Basis of Life"},"content":{"rendered":"
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Workshop Index<\/a>\u00a0Next Lesson \u27a1<\/a><\/div>\n

<\/p>\n

Biochemical Basis of Life<\/h1>\n

Objective<\/h4>\n

We will now cover the biology content in more depth; starting with the building blocks of life, organic molecule. We will review the types of organic molecules, what they are composed of, and how they function in living organisms. The biochemical basis of life is fundamental to all other aspects of biology and the life sciences.<\/p>\n

Previously Covered<\/h4>\n

We have just covered the most important aspects of Physics in depth. The last lessons covered electromagnetism and optics, the properties of waves, light, and the electromagnetic spectrum.<\/p>\n

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Organic Molecules<\/h3>\n

As we understand the universe, all matter is fundamentally composed of atoms. Depending upon the numbers of protons, neutrons, and electrons, an atom can be any one of at least 259 known elements (with perhaps half a dozen more yet to be discovered). Of these 259 elements, only about a dozen are important for life \u2014 and the molecules formed by these elements are called organic<\/abbr> molecules. Organic chemistry is one of the most important and complex disciplines within chemistry and overlaps considerably with biochemistry and biology. Living things are composed primarily of organic molecules.<\/p>\n

Organic molecules are those that have a carbon skeleton with hydrogen and\/or other functional group<\/abbr> attached. Because carbon has four valence electrons, it tends to form covalent bonds<\/abbr> with up to four other atoms. Coincidentally, the energy used by living things is usually stored in the covalent bonds of organic compounds.<\/p>\n

Hydrocarbons or alkyls are the simplest organic compounds, containing only carbon and hydrogen. Alkanes are saturated hydrocarbons, meaning there are no carbon double bonds present. Methane, shown below, is an example of an alkane. Alkenes<\/strong>, on the other hand, are characterized by having a double bond; they are unsaturated hydrocarbons. The degree of saturation of a hydrocarbon influences its reactivity and shape. Below is also shown an example of a simple alkene, ethene.<\/p>\n

\"Methan<\/center><\/p>\n

Examples of Alkanes<\/p>\n

The functional groups attached to carbon compounds determine the reactivity and classification of more complex organic molecules. Classes of organic compounds are often represented by the functional group bonded to a generic organic group that can vary among the amino acids. These generic organic groups are sometimes represented as an R. Likewise, there are other symbols for specific types of functional groups.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Methyl Group<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Single carbon alkyl<\/li>\n
  • Component of fatty acid chains<\/li>\n
  • Insoluble in water<\/li>\n
  • Common component in many organic molecules (including biodiesel)<\/li>\n<\/ul>\n<\/td>\n
\"Methyl<\/td>\n<\/tr>\n
Ether Group<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Oxygen bonded to two alkyl groups<\/li>\n
  • Are of very low chemical reactivity.<\/li>\n
  • They should not be confused with similar compounds:\n
      \n
    • The aromatic rings with an oxygen<\/li>\n
    • Compounds that have oxygen bonded to a sulfur or nitrogen, like esters, acetyls, aminals, and anhydrides.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/td>\n
\"Ether<\/td>\n<\/tr>\n
Hydroxyl Group<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Simple:OH group common to many organic molecules<\/li>\n
  • Present in alcohols, sugars, and amino acids<\/li>\n
  • Highly reactive with other compounds and usually short-lived<\/li>\n
  • Important in atmospheric chemistry to oxidize otherwise noxious gases<\/li>\n<\/ul>\n<\/td>\n
\"Hydroxyl<\/td>\n<\/tr>\n
Phenols<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Hydroxyl groups bond to an aromatic hydrocarbon (ring)<\/li>\n
  • Some phenols are germicidal<\/li>\n
  • Some are endocrine disruptors (they mimic animal sex hormones)<\/li>\n
  • Similar to alcohols, but the hydroxyl group is bonded to a saturated carbon<\/li>\n<\/ul>\n<\/td>\n
\"Phenol<\/td>\n<\/tr>\n
Sulfhydryl Group<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Sulfur analog of hydroxyl group<\/li>\n
  • Functionally similar to alcohols<\/li>\n
  • Form disulfide bonds in some amino acids<\/li>\n
  • Can be important in biological catalysts<\/li>\n
  • Molecules with these are called thiols<\/li>\n
  • They have relatively low boiling points and solubility<\/li>\n<\/ul>\n<\/td>\n
\"Sulfhydryl<\/td>\n<\/tr>\n
Carbonyl Group<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Present in sugars, amino acids, and nucleotides<\/li>\n
  • Water soluble<\/li>\n
  • Because of the molecule\u2019s polarity, it is highly reactive<\/li>\n
  • Present in many other types of functional groups like aldehydes, ketones, carboxyls, esters, amides, and anhydrides.<\/li>\n<\/ul>\n<\/td>\n
\"Carbonyl<\/td>\n<\/tr>\n
Aldehydes<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Carbonyl group bonded with a hydrogen on one side, at the end of a carbon backbone<\/li>\n
  • React to form more complex molecules<\/li>\n
  • Include odors of cinnamon, vanilla, and rancid butter<\/li>\n<\/ul>\n<\/td>\n
\"Aldehydes<\/td>\n<\/tr>\n
Ketones<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Carbonyl group attached in the middle of a carbon backbone<\/li>\n
  • Good solvents or polymers<\/li>\n
  • The carbonyl group is polar, making ketones very polar compounds<\/li>\n
  • Are more volatile than alcohols and carboxyl acids<\/li>\n<\/ul>\n<\/td>\n
\"Ketones<\/td>\n<\/tr>\n
Carboxyl Group<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Associated with organic acids<\/li>\n
  • Present in amino acids and fatty acids<\/li>\n
  • Very polar and water soluble<\/li>\n
  • Act as acids by ionizing by giving up H+ ions in solution<\/li>\n
  • Vinegar is a common example<\/li>\n<\/ul>\n<\/td>\n
\"Carboxyl<\/td>\n<\/tr>\n
Esters<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Formed by the reaction between an alcohol and an acid<\/li>\n
  • An alkyl group replaces an H on the organic acid and water is condensed<\/li>\n
  • Because of their distinctive odors, they are often used in flavorings and fragrances<\/li>\n
  • Fruit odors and aspirin are examples<\/li>\n<\/ul>\n<\/td>\n
\"Esters<\/td>\n<\/tr>\n
Amine Group<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Nitrogen-based derivatives of ammonia<\/li>\n
  • Present in amino acids and nucleotides<\/li>\n
  • Can act as relatively strong bases<\/li>\n
  • Water soluble<\/li>\n
  • Acts as a weak base in solution by attracting protons to produce an ionized form<\/li>\n<\/ul>\n<\/td>\n
\"Amine<\/td>\n<\/tr>\n
Phosphate Group<\/strong><\/td>\n<\/tr>\n
\n
    \n
  • Found in DNA, RNA, ATP, and many proteins and phospholipids<\/li>\n
  • Water soluble and acidic<\/li>\n
  • High-energy bonds<\/li>\n
  • Often a limiting resource in most biological systems<\/li>\n<\/ul>\n<\/td>\n
\"Phosphate<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Making and Breaking<\/h3>\n

Complex organic macromolecules called polymers<\/strong> are formed from simple organic monomers<\/strong>. Living things are composed primarily of only four kinds of organic polymers: carbohydrates, lipids, proteins, and nucleic acids. Each type of these macromolecules is made of a distinctive combination of organic monomers. Organic monomers undergo dehydration synthesis<\/strong> (also called condensation reaction) to produce complex polymers. In a condensation reaction, one monomer loses an H+<\/sup> ion and the other loses an OH–<\/sup>; to create water (H2<\/sub>O) and a new bond linking the formerly two molecules into one. In the opposite reaction, called hydrolysis<\/strong>, polymers are broken down into monomer subunits by the addition of water.<\/p>\n

\"Common<\/center><\/p>\n

Common dietary sources of carbohydrates<\/p>\n

Carbohydrates are standard energy storing molecules and are commonly called sugars and starches. The monomers of carbohydrates are called monosaccharides or sugars. They produce polymers called polysaccharides or starches by forming glycosidic bonds. There are several classes of carbohydrates that we will discuss in detail later.<\/p>\n

\"Lipid<\/center><\/p>\n

Example of lipid structures<\/p>\n

Lipids typically contain long fatty acid<\/abbr> chains, are non-polar, and water insoluble. Fats, like triglycerides and oils, are lipids composed of glycerol bonded to fatty acid chains. Other lipids, such as steroids, contain distinctive ring structures and can have powerful biological properties.<\/p>\n

Proteins have several levels of structure, but all proteins are composed of amino acid<\/abbr> monomers joined by peptide bonds<\/abbr> in dehydration synthesis reactions. Proteins are very important in controlling metabolism in their action as enzymes.<\/p>\n

The monomers of the nucleic acids DNA and RNA are called nucleotides. Nucleotides form phosphodiester bonds<\/abbr> in dehydration synthesis reactions to form the DNA backbone. Another important nucleotide in all living things is called adenosine triphosphate<\/abbr> (ATP).<\/p>\n

ATP is a very important molecule in living things. It is often called the energy currency of the cell. It is composed of a pentose sugar called ribose, an amine called adenine, and three phosphate groups. The line of phosphates contains very high-energy bonds that are easily broken. Energy is transferred by dehydration synthesis reactions by making and breaking high-energy bonds in ATP.<\/p>\n

Examples of dehydration synthesis reactions for three of the four main classes of organic macromolecules are shown below.<\/p>\n

\"Carbohydrate\"Lipid
\n\"Nucleic<\/center><\/p>\n

Dehydration synthesis in a nucleic acid<\/p>\n

Hydrolysis reactions for each type of macromolecule are the opposite process of that shown above. In hydrolysis, water is split by hydrolytic enzymes, breaking it into an H atom and an OH group. These react to form simple monomers when the molecular bonds of the polymer are broken.<\/p>\n

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Question<\/h4>\n

What is formed by the dehydration synthesis of sucrose?<\/p>\n

    \n
  1. Glucose and fructose<\/li>\n
  2. Monosaccharides<\/li>\n
  3. Water<\/li>\n
  4. Cellulose<\/li>\n<\/ol>\n

    Reveal Answer<\/a><\/p>\n

    The correct answer is C. Dehydration synthesis builds complex molecules from simple ones, and water is produced as a by-product.<\/p>\n<\/section>\n

    Lesson Objective<\/h4>\n

    In this lesson, we will review the kinds and properties of carbohydrates.<\/p>\n

    Previously Covered<\/h4>\n