Freshman Year Biology 118 Notes

Freshman Year Biology 118 Notes - Chapter 4 Carbon 4.1 Most...

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Chapter 4 – Carbon 4.1 Most organic compounds contain hydrogen in addition to carbon. Because of carbon’s versatility, a variety of different organic molecules can be constructed. 4.2 The electron configuration determines the kinds of bonds that an atom can form. Carbon has 6 electrons. 4 are valence electrons. Carbon forms single or double covalent bonds. Four major components of organic molecules are carbon, hydrogen, oxygen, and nitrogen. CO 2 is considered inorganic even though it contains carbon. Carbon chains form the skeleton of most organic molecules. The skeletons can be straight, branched, or arranged in close rings. Hydrocarbons are organic molecules that only contain carbon and hydrogen. Hydrocarbons are the major component of petroleum. Hydrocarbons are not prevalent in most living organisms. Fats have long hydrocarbon tails. Carbon-hydrogen linkages are nonpolar and therefore do not dissolve in water. Hydrocarbons can undergo reactions that release a lot of energy. Isomers are variations of the architecture of organic molecules. The compounds have the same numbers of the same elements but their structures are different. Structural isomers differ in the covalent arrangements of their atoms. They can also differ in the location of double bonds. Cis-trans isomers or geometric isomers have covalent bonds to the same atoms but the atoms differ in spatial arrangement. This is due to the inflexibility of double bonds. Enantiomers are mirror images of each other and differ in shape because of a carbon that is attached to four different atoms. Usually only one of these enantiomers is biologically active.
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Our cells are composed of 70-90% water. Most of the rest consists of carbon-based components. Proteins, DNA, and carbohydrates are all made of carbon. Carbon does not form ionic bonds because it would have to gain or lose four electrons. When carbon forms four single bonds, the angles form a tetrahedron. Variations in carbon skeletons provides molecular diversity. Isomers have different properties. There are a few functional groups that are frequently attached to the skeletons of the organic molecules. The functional groups can replace hydrogens bonded to the carbon skeleton of a hydrocarbon. There are 7 functional groups that are important to life. 1. Hydroxyl Made up of a hydrogen bonded to an oxygen. OH or HO. It is found in alcohols. It has a polar covalent bond that dissolves in water. Ex. ethanol 2. Carbonyl Carbon double bonded to an oxygen. CO. Can be found at the end of a carbon skeleton (aldehyde) or within a skeleton (ketone). Hydrophilic. Ex. Acetone (ketone). Propanal (aldehyde) 3. Carboxyl An oxygen is double bonded to a carbon that is double bonded to an OH group. COOH. Found in carboxylic acids. The hydrogen can dissociate producing a weak acid. Hydrophilic. Ex. Acetic acid 4. Amino A nitrogen bonded to two hydrogen atoms and the carbon skeleton. NH 2 .
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