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Chapter 4: Carbon

Chapter 4: Carbon. Carbon. Overview: Carbon—The Backbone of Biological Molecules All living organisms are made up of chemicals based mostly on the element carbon Organic chemistry is the study of carbon compounds. The Formation of Bonds with Carbon. Carbon has four valence electrons

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Chapter 4: Carbon

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  1. Chapter 4: Carbon

  2. Carbon • Overview: Carbon—The Backbone of Biological Molecules • All living organisms are made up of chemicals based mostly on the element carbon • Organic chemistry is the study of carbon compounds

  3. The Formation of Bonds with Carbon • Carbon has four valence electrons • This allows it to form four covalent bonds with a variety of atoms

  4. Name and Comments Space-Filling Model Molecular Formula Structural Formula Ball-and-Stick Model H (a) Methane CH4 C H H H H H (b) Ethane C C2H6 H C H H H H H (c) Ethene (ethylene) C C C2H4 H H Versatility of Carbon • The bonding versatility of carbon • Allows it to form many diverse molecules, including carbon skeletons

  5. Carbon (valence = 4) Nitrogen (valence = 3) Hydrogen (valence = 1) Oxygen (valence = 2) O H N C Common Bonding Partners of Carbon • The electron configuration of carbon • Gives it covalent compatibility with many different elements

  6. Which of the structures in this figure is an impossible covalently bonded molecule? A B C D E C

  7. H H C C C C H H C H H H H H H C H H H H H H H H H H H H C C C C C C C H H H H H H H H H H H H (a) Length H Ethane Propane H H H H H H H H H H H C C C C C C C C H H H H (b) Branching 2-methylpropane (commonly called isobutane) Butane H H H H C H (c) Double bonds H H C C C H H C C H H C C 1-Butene 2-Butene H H C C C (d) Rings Cyclohexane Benzene Molecular Diversity Arising from Carbon Skeleton Variation • Carbon chains • Form the skeletons of most organic molecules • Vary in length and shape

  8. Hydrocarbons • Hydrocarbons • Are molecules consisting of only carbon and hydrogen • The bonds between the C and H atoms are non-polar covalent • This makes hydrocarbons hydrophobic

  9. Fat droplets (stained red) 100 µm (b) Mammalian adipose cells (a) A fat molecule Hydrocarbons • Hydrocarbons • Are found in many of a cell’s organic molecules

  10. Isomers • Isomers • Are molecules with the same molecular formula but different structures and properties

  11. H H H C H H C H H H H H H H (a) Structural isomers H C C C C C H H C H C C H H H H H H H H H X X X C C C C (b) Geometric isomers X H H H CO2H CO2H C C (c) Enantiomers H H NH2 NH2 CH3 CH3 Isomers • Three types of isomers are • Structural • Geometric • Enantiomers

  12. H H H C H H C H H H H H H H (a) Structural isomers H C C C C C H H C H C C H H H H H H H H H X X X C C C C (b) Geometric isomers X H H H CO2H CO2H C C (c) Enantiomers H H NH2 NH2 CH3 CH3 Why are Enantiomeric isomers important? • Enzymes distinguish between enantiomers! Enzyme activity = 100 % Enzyme activity = 0 %

  13. Structure and Function • Subtle changes in structure can dramatically affect the molecule’s function

  14. The Functional Groups • Functional groups • Are the chemically reactive groups of atoms within an organic molecule • They behave consistently and characteristically, giving unique properties to the molecules possessing them.

  15. Six functional groups are important in the chemistry of life • Hydroxyl • Carbonyl • Carboxyl • Amino • Sulfhydryl • Phosphate

  16. FUNCTIONAL GROUP HYDROXYL CARBONYL CARBOXYL O O OH C C OH (may be written HO ) STRUCTURE In a hydroxyl group (—OH), a hydrogen atom is bonded to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. (Do not confuse this functional group with the hydroxide ion, OH–.) The carbonyl group( CO) consists of a carbon atom joined to an oxygen atom by a double bond. When an oxygen atom is double-bonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group (—COOH).  Functional Groups

  17. Ketones if the carbonyl group is within a carbon skeleton Aldehydes if the carbonyl group is at the end of the carbon skeleton NAME OF COMPOUNDS Alcohols (their specific names usually end in -ol) Carboxylic acids, or organic acids EXAMPLE H H H H O O C C H OH C C H C H C H OH H H H H C Ethanol, the alcohol present in alcoholic beverages H H Acetic acid, which gives vinegar its sour tatste Acetone, the simplest ketone H H O H C C C H H H Propanal, an aldehyde Functional Groups CARBONYL CARBOXYL HYDROXYL

  18. AMINO SULFHYDRYL PHOSPHATE O H SH N P OH O (may be written HS ) H OH In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygens carry negative charges; abbreviated P . The amino group (—NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton. The sulfhydryl group consists of a sulfur atom bonded to an atom of hydrogen; resembles a hydroxyl group in shape. Functional Groups

  19. OH O OH H H H H H O H C C C O P O N C C SH H C C HO H H H H O H H H Ethanethiol Glycine Glycerol phosphate Because it also has a carboxyl group, glycine is both an amine and a carboxylic acid; compounds with both groups are called amino acids. Functional Groups PHOSPHATE SULFHYDRYL AMINO

  20. OH CH3 Estradiol HO Female lion OH CH3 CH3 O Testosterone Male lion Effect of Different Functional Groups • Functional groups give organic molecules distinctive chemical properties

  21. Key Points of Chapter 4 • Organic chemistry is the study of carbon compounds • Carbon atoms can form diverse molecules by bonding to 4 other atoms • Functional groups are the parts of molecules involved in chemical reactions and behave chemically in expected manners

  22. Chapter 4 Essay Question • Discuss the biological importance of each of the following organic compounds in relation to cellular structure and function in plants and animals. • a. Carbohydrates • b. Proteins • c. Lipids • d. Nucleic acids

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