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CAMPBELL BIOLOGY Outline TENTH EDITION Reece • Urry • Cain • Wasserman • Minorsky • Jackson 4 I. Organic compounds II. Bonding with Carbon III. Isomers IV. Functional Groups Carbon and the Molecular Diversity of Life Dr Burns NVC © 2014 Pearson Education, Inc. Organic Compounds What is organic We think of organic produce “natural” In chemistry organic refers to molecules that have a carbon backbone, covalently bound to each other Early chemists thought of organic as coming from plants and animals and inorganic coming from minerals Overview: Carbon: The Backbone of Life Living organisms consist 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 © 2011 Pearson Education, Inc. Figure 4.1a Carbon Carbon has four valence electrons. It needs eight electrons to be stable So, carbon can form up to four covalent bonds. Carbon can bond to four other atoms or groups of atoms, making a large variety of molecules possible. 1 Carbon compounds Molecule Carbons can link together to form a backbone – many other elements can bond to this backbone (a) Methane Carbon – carbon bonds are strong (b) Ethane Molecular Formula Structural Formula Ball-and-Stick Model Space-Filling Model CH4 C2H6 Carbons can form single, double or triple bonds. (c) Ethene (ethylene) Carbons can form chains or rings C2H4 Figure 4.5 Hydrocarbons Hydrocarbons are organic molecules consisting of only carbon and hydrogen (c) Double bond position (a) Length Ethane Propane (b) Branching 1-Butene 2-Butene Many organic molecules, such as fats, have hydrocarbon components (d) Presence of rings Hydrocarbons can undergo reactions that release a large amount of energy 2-Methylpropane (isobutane) Butane Cyclohexane Figure 4.6 Benzene Isomers Nucleus Fat droplets Isomers are compounds with the same molecular formula but different structures and properties Structural isomers have different covalent arrangements of their atoms Cis-trans isomers have the same covalent bonds but differ in spatial arrangements 10 μm (a) Part of a human adipose cell (b) A fat molecule Enantiomers are isomers that are mirror images of each other 2 Animation: Isomers (a) Structural isomers Pentane 2-methyl butane (b) Cis-trans isomers cis isomer: The two Xs are on the same side. trans isomer: The two Xs are on opposite sides. (c) Enantiomers CO2H CO2H C H C NH2 NH2 H CH3 L isomer CH3 D isomer Structural Isomers Molecule have different arrangement of their carbon skeleton but still have the same molecular formula: Enantiomers Cis-trans Isomers Have the same arrangement of atoms but the spatial arrangement of the atoms are different. An example is cis vs trans arrangements across a double bond (cis = large groups are on same side, trans = large groups on opposite side Enantiomers Isomers that are mirror images of each other Must be a chiral molecule – where a carbon is bonded to four different molecules Referred to as: + or – R or L 3 Why do we care Why do we care The function of a protein is determined by its shape. Biological organisms usually synthesize only one form. Usually only one form of an isomer is active in biological systems. However, chemical synthesis usually produces equal amounts of the two enantiomers Enantiomers are important in the pharmaceutical industry Two enantiomers of a drug may have different effects Usually only one isomer is biologically active Differing effects of enantiomers demonstrate that organisms are sensitive to even subtle variations in molecules Animation: L-Dopa Right-click slide / select “Play” © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Figure 4.8 Drug Condition Ibuprofen Pain; inflammation Albuterol Effective Enantiomer Ineffective Enantiomer S-Ibuprofen R-Ibuprofen R-Albuterol S-Albuterol Example: The drug albuterol (e.g., Proventil®) contains equal amounts of two enantiomers. Another more expensive drug is levalbuterol (Xopenex®) it only contains the active form of the drug, it has fewer side effects Asthma 4 Functional Groups This is an example of what kind of isomer? Cis-trans Enantiomers Structural None of the above 25% 25% 25% 25% Functional groups are the components of organic molecules that are most commonly involved in chemical reactions e ab ov ur a th e St ru ct tio m er s an eo N on e of En G l The number and arrangement of functional groups give each molecule its unique properties m et ric 1. 2. 3. 4. © 2011 Pearson Education, Inc. Functional Groups Groups of atoms; determines the types of chemical reactions and associations Estradiol Testosterone 1. 2. 3. 4. 5. 6. 7. Polarity Hydroxyl Carbonyl Carboxyl Amino Sulfhydryl Phosphate Methyl Chemical Group Hydroxyl group (—OH) Compound Name Examples Alcohol Ethanol Carbonyl group ( Remember that C-H and C-C bonds are non polar C=O) Ketone Aldehyde Acetone Carboxyl group (—COOH) Carboxylic acid, or organic acid Amino group (—NH2) Amine Sulfhydryl group (—SH) Thiol Phosphate group (—OPO32−) Organic phosphate Methyl group (—CH3) Methylated compound Propanal Acetic acid S, N, and O are electronegative atoms and can make a molecule more polar. Glycine Cysteine Polar and ionic functional groups are hydrophilic, and strongly associate with water Glycerol phosphate 5-Methyl cytosine 5 Properties of functional Groups 1. Hydroxyl – polar, can form hydrogen bonds 2. Carbonyl – polar, can form hydrogen bonds 3. Carboxyl – very polar, weakly acidic and can ionize to become -COO- + H+ Important in amino acids 5. Sulfhydryl – also called thiol, polar, important in proteins, can form strong S-S bonds that stabilize structure 6. Phosphate – polar and weakly acidic. Can dissociate to –PO4-2 4. Amino - Polar and weakly basic, can accept a H+ to become –NH3+ Properties of functional Groups Important in nucleic acids and some lipids 7. Methyl – nonpolar hydrocarbon Important in amino acids and nucleic acids Figure 4.9aa Figure 4.9ab Carbonyl group ( Hydroxyl group (—OH) C=O) Ethanol, the alcohol present in alcoholic beverages (may be written HO—) Polar due to electronegative oxygen. Forms hydrogen bonds with water. Compound name: Alcohol Figure 4.9ac Acetone, the simplest ketone Propanal, an aldehyde Sugars with ketone groups are called ketoses; those with aldehydes are called aldoses. Compound name: Ketone or aldehyde Figure 4.9ad Carboxyl group (—COOH) Amino group (—NH2) Acetic acid, which gives vinegar its sour taste Acts as an acid. Compound name: Carboxylic acid, or organic acid Ionized form of —COOH (carboxylate ion), found in cells Glycine, an amino acid (note its carboxyl group) Ionized form of —NH2, found in cells Acts as a base. Compound name: Amine 6 Figure 4.9ba Figure 4.9bb Sulfhydryl group (—SH) Phosphate group (—OPO32−) Glycerol phosphate, which takes part in many important chemical reactions in cells Cysteine, a sulfurcontaining amino acid (may be written HS—) Two —SH groups can react, forming a “cross-link” that helps stabilize protein structure. Compound name: Thiol Figure 4.9bc Contributes negative charge. When attached, confers on a molecule the ability to react with water, releasing energy. Compound name: Organic phosphate Carboxyl functional groups are: Methyl group (—CH3) 5-Methyl cytosine, a component of DNA that has been modified by addition of a methyl group 1. 2. 3. 4. Polar Acidic Nonpolar Polar and acidic 25% 25% 25% 25% ic c ac id po la r ci di an d on Po la r N A Po la r Affects the expression of genes. Affects the shape and function of sex hormones. Compound name: Methylated compound Important Concepts Read Chapters 5 for next lecture Know the vocabulary of the lecture Understand the importance of carbon in organic molecules What are the different types of isomers? Be able to identify examples of each type of isomer. What are the structure and the properties of the common functional groups? 7