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Chapter 4 Carbon and the Molecular Diversity of Life PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Organic Chemistry • Although cells are 70–95% water, the rest consists mostly of carbon-based compounds • Carbon is unparalleled in its ability to form large, complex, and diverse molecules • Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 4-2 EXPERIMENT “Atmosphere” Water vapor CH4 Electrode Condenser Cooled water containing organic molecules H2O “sea” Sample for chemical analysis Cold water Concept 4.2: Carbon atoms can form diverse molecules by bonding to four other atoms • Electron configuration is the key to an atom’s characteristics • Electron configuration determines the kinds and number of bonds an atom will form with other atoms • With four valence electrons, carbon can form four covalent bonds with a variety of atoms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Valences • Valence: Number of covalent bonds an atom will usually form. • Usually equal to the number of electrons needed to complete the outermost shell. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 4-3 Name (a) Methane (b) Ethane (c) Ethene (ethylene) Molecular Formula Structural Formula Ball-and-Stick Model Space-Filling Model Hydrocarbons • Major components of petroleum. • Many organic compounds have regions that consist only of these. – Ex. Fats have long hydrocarbon tails that are nonpolar attached to a polar head. • Store a relatively large amount of energy. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hydrocarbons Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Role of Hydrocarbons in Fat: Triglycerides •Black = carbon •Gray = hydrogen •Red = oxygen (A)Triglycerides are fat molecules consists of a headpiece and 3 hydrocarbon tails – the tails store energy and account for the hydrophobic behavior of fats. (B)Mammalian adipose cells stockpile fat molecules as a fuel reserve. Isomers • Isomers are compounds with the same molecular formula but different structures and therefore different properties: – Structural isomers – Geometric isomers – Enantiomers Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Structural Isomers • Differ in the covalent arrangement of their atoms. • May also differ in the location of double bonds. – As the carbon skeleton increases in size, the number of possible isomers increases tremendously. • Differ in covalent partners & possibly location of double bonds: butane and isobutane Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Geometric Isomers • Have the same covalent partnerships, but differ in their spatial arrangements. • Arise from the inflexibility of double bonds – will not allow the atoms they join to rotate freely about the bond axis (unlike single bonds). • Differ in arrangement about a double bond. • This slight difference in shape can dramatically affect the biological activity of the molecules. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Enantiomers • Molecules that are mirror images of each other. • Usually, these “right-handed” and “left-handed” versions of the same molecule allow for one to be biologically active and the other inactive. – Ex. Thalidomide • Differ in spatial arrangement around an asymmetric carbon. – Results in molecules that are mirror images, like left and right hands. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Pharmacological Importance of Enantiomers • Two enantiomers of a drug may not be equally effective (and in some cases, produce harmful effects). – Thalidomide was prescribed for pregnant women in the late 50’s – a drug that was a mixture of two enantiomers. • One enantiomer reduced morning sickness • The other caused severe birth defects Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 4-8 Drug Condition Ibuprofen Pain; inflammation Albuterol Effective Enantiomer Ineffective Enantiomer S-Ibuprofen R-Ibuprofen R-Albuterol S-Albuterol Asthma Fig. 4-7 Pentane 2-methyl butane (a) Structural isomers cis isomer: The two Xs are on the same side. (b) Geometric isomers (c) Enantiomers trans isomer: The two Xs are on opposite sides. Functional Groups • Functional groups are the components of organic molecules that are usually involved in chemical reactions. – Each group behaves consistently from one organic molecule to another. – The number and arrangement of functional groups help give each molecule its unique properties. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Functional Groups • The seven functional groups that are most important in the chemistry of life: – Hydroxyl group – Carbonyl group – Carboxyl group – Amino group – Sulfhydryl group – Phosphate group – Methyl group Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Text pg. 6465…KNOW THE CHART! A Comparison of Functional Groups • Two molecules differ mainly in the attachment of functional groups to a common carbon skeleton. – These subtle variations in molecular architecture (shaded in blue and pink) influence the development of the anatomical and physiological differences between female & male vertebrates. – Sexuality has a biological basis in variations of molecular architecture! Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings ATP: An Important Source of Energy for Cellular Processes • One phosphate molecule, adenosine triphosphate (ATP), is the primary energytransferring molecule in the cell • ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings ATP: An Important Source of Energy for Cellular Processes You should now be able to: 1. Explain how carbon’s electron configuration explains its ability to form large, complex, diverse organic molecules. 2. Distinguish among the three types of isomers: structural, geometric, and enantiomer. Discuss the biological importance of isomers. 3. Identify the 7 main functional groups and the characteristics of each. 4. Explain how ATP functions as the primary energy transfer molecule in living cells. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings