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LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 4 Carbon and the Molecular Diversity of Life 碳與生命的分子 多樣 Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc. Overview: Carbon: The Backbone of Life • Living organisms consist mostly of carbonbased compounds • Carbon is unparalleled in its ability to form large, complex, and diverse molecules 碳架構的有機分子豐富多樣的有機分子世界 • Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds 豐富生命的 蛋白、核酸、碳氫子分等均為碳化合物 © 2011 Pearson Education, Inc. Figure 4.1 Concept 4.1: Organic chemistry is the study of carbon compounds • Organic chemistry is the study of compounds that contain carbon 有機化學乃以碳為主架構的化合物研究 • Organic compounds range from simple molecules to colossal ones • Most organic compounds contain hydrogen atoms in addition to carbon atoms 有機化合物結合許多氫原子於碳上 © 2011 Pearson Education, Inc. • Vitalism 生機論, the idea that organic compounds arise only in organisms, was disproved when chemists synthesized these compounds有機分子組成有機體 • Mechanism is the view that all natural phenomena are governed by physical and chemical laws 所有自然現象均有其 物理或化學法則 © 2011 Pearson Education, Inc. Organic Molecules and the Origin of Life on Earth • Stanley Miller’s classic experiment demonstrated the abiotic synthesis of organic compounds無機化合物可以經 由化學反應組成有機分子 • Experiments support the idea that abiotic synthesis of organic compounds, perhaps near volcanoes, could have been a stage in the origin of life 海底火 山可能是生命起源處 © 2011 Pearson Education, Inc. Figure 4.2 EXPERIMENT “Atmosphere” CH4 Water vapor Electrode Condenser Cooled “rain” 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 電子特性決定分子 鍵結數目與型式 © 2011 Pearson Education, Inc. The Formation of Bonds with Carbon • With four valence electrons, carbon can form four covalent bonds with a variety of atoms • This ability makes large, complex molecules possible 碳原子為有機分子骨架,組構大份子 • In molecules with multiple carbons, each carbon bonded to four other atoms has a tetrahedral shape • However, when two carbon atoms are joined by a double bond, the atoms joined to the carbons are in the same plane as the carbons 雙鍵可使份子形成ㄧ平面 © 2011 Pearson Education, Inc. Figure 4.3 Name and Comment Molecular Formula (a) Methane CH4 (b) Ethane C2H6 (c) Ethene (ethylene) C2H4 Structural Formula Ball-andStick Model Space-Filling Model • The electron configuration of carbon gives it covalent compatibility with many different elements • The valences of carbon and its most frequent partners (hydrogen, oxygen, and nitrogen) are the “building code” that governs the architecture of living molecules • 碳原子可與許多其他原子結合形成許多有 機分子 © 2011 Pearson Education, Inc. Figure 4.4 Hydrogen (valence 1) Oxygen (valence 2) Nitrogen (valence 3) Carbon (valence 4) • Carbon atoms can partner with atoms other than hydrogen; for example: – Carbon dioxide: CO2 – Urea: CO(NH2)2 © 2011 Pearson Education, Inc. Figure 4.UN01 Urea Molecular Diversity Arising from Carbon Skeleton Variation • Carbon chains form the skeletons of most organic molecules • Carbon chains vary in length and shape 碳為骨架的有機分子,可變化無窮的有機分子 © 2011 Pearson Education, Inc. Figure 4.5 (c) Double bond position (a) Length Ethane Propane (b) Branching Butane 1-Butene 2-Butene (d) Presence of rings 2-Methylpropane (isobutane) Cyclohexane Benzene Figure 4.5a (a) Length Ethane Propane Figure 4.5b (b) Branching Butane 2-Methylpropane (commonly called isobutane) Figure 4.5c (c) Double bond position 1-Butene 2-Butene Figure 4.5d (d) Presence of rings Cyclohexane Benzene Hydrocarbons 碳氫化合物 • Hydrocarbons are organic molecules consisting of only carbon and hydrogen • Many organic molecules, such as fats, have hydrocarbon components • Hydrocarbons can undergo reactions that release a large amount of energy碳氫化 合物蘊含大量能量 © 2011 Pearson Education, Inc. Figure 4.6 Nucleus Fat droplets 10 m (a) Part of a human adipose cell (b) A fat molecule Isomers 異構物 • 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 – Enantiomers are isomers that are mirror images of each other © 2011 Pearson Education, Inc. Figure 4.7 (a) Structural isomers 直鏈 支鏈 (b) Cis-trans isomers 順式 反式 cis isomer: The two Xs are on the same side. trans isomer: The two Xs are on opposite sides. (c) Enantiomers CO2H CO2H 左旋 右旋 H NH2 CH3 L isomer NH2 H CH3 D isomer Figure 4.7a (a) Structural isomers Figure 4.7b (b) Cis-trans isomers cis isomer: The two Xs are on the same side. trans isomer: The two Xs are on opposite sides. Figure 4.7c (c) Enantiomers CO2H H CO2H NH2 CH3 L isomer NH2 H CH3 D isomer 鏡像異構物活性不同 • 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 © 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 Asthma Fig. 4-UN9 L-dopa D-dopa Concept 4.3: A few chemical groups are key to the functioning of biological molecules • Distinctive properties of organic molecules depend on the carbon skeleton and on the molecular components attached to it • A number of characteristic groups can replace the hydrogens attached to skeletons of organic molecules • ㄧ群小分有子機分子提供生物活性 © 2011 Pearson Education, Inc. The Chemical Groups Most Important in the Processes of Life • Functional groups are the components of organic molecules that are most commonly involved in chemical reactions The number and arrangement of functional groups give each molecule its unique properties 官能基是化學分子進行化學反應處 亦提供分子特性 © 2011 Pearson Education, Inc. Figure 4.UN02 Estradiol Testosterone • The seven functional groups that are most important in the chemistry of life: – Hydroxyl group 羥基 – Carbonyl group 羰基 – Carboxyl group 羧基 – Amino group 氨基 – Sulfhydryl group 硫氫基 – Phosphate group 磷酸基 – Methyl group 甲基 © 2011 Pearson Education, Inc. Figure 4.9-a CHEMICAL GROUP Hydroxyl Carbonyl Carboxyl STRUCTURE (may be written HO—) NAME OF COMPOUND Alcohols (Their specific names usually end in -ol.) Ketones if the carbonyl group is within a carbon skeleton Carboxylic acids, or organic acids Aldehydes if the carbonyl group is at the end of the carbon skeleton EXAMPLE Ethanol Acetone Acetic acid Propanal FUNCTIONAL PROPERTIES • Is polar as a result of the electrons spending more time near the electronegative oxygen atom. • Can form hydrogen bonds with water molecules, helping dissolve organic compounds such as sugars. • A ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal. • Ketone and aldehyde groups are also found in sugars, giving rise to two major groups of sugars: ketoses (containing ketone groups) and aldoses (containing aldehyde groups). • Acts as an acid; can donate an H+ because the covalent bond between oxygen and hydrogen is so polar: Nonionized Ionized • Found in cells in the ionized form with a charge of 1 and called a carboxylate ion. Figure 4.9-b Amino Sulfhydryl Phosphate Methyl (may be written HS—) Amines Organic phosphates Thiols Cysteine Glycine • Acts as a base; can pick up an H+ from the surrounding solution (water, in living organisms): Nonionized Ionized • Found in cells in the ionized form with a charge of 1+. Glycerol phosphate • Two sulfhydryl groups can react, forming a covalent bond. This “cross-linking” helps stabilize protein structure. • Contributes negative charge to the molecule of which it is a part (2– when at the end of a molecule, as above; 1– when located internally in a chain of phosphates). • Cross-linking of cysteines in hair proteins maintains the curliness or straightness of hair. Straight hair can be “permanently” curled by shaping it around curlers and then breaking and re-forming the cross-linking bonds. • Molecules containing phosphate groups have the potential to react with water, releasing energy. Methylated compounds 5-Methyl cytidine • Addition of a methyl group to DNA, or to molecules bound to DNA, affects the expression of genes. • Arrangement of methyl groups in male and female sex hormones affects their shape and function. Figure 4.9a Hydroxyl STRUCTURE (may be written HO—) EXAMPLE Ethanol Alcohols (Their specific names usually end in -ol.) NAME OF COMPOUND • Is polar as a result of the electrons spending more time near the electronegative oxygen atom. FUNCTIONAL PROPERTIES • Can form hydrogen bonds with water molecules, helping dissolve organic compounds such as sugars. Figure 4.9b Carbonyl STRUCTURE Ketones if the carbonyl group is within a carbon skeleton NAME OF COMPOUND Aldehydes if the carbonyl group is at the end of the carbon skeleton EXAMPLE Acetone Propanal • A ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal. • Ketone and aldehyde groups are also found in sugars, giving rise to two major groups of sugars: ketoses (containing ketone groups) and aldoses (containing aldehyde groups). FUNCTIONAL PROPERTIES Figure 4.9c Carboxyl STRUCTURE Carboxylic acids, or organic acids NAME OF COMPOUND EXAMPLE • Acts as an acid; can FUNCTIONAL PROPERTIES donate an H+ because the covalent bond between oxygen and hydrogen is so polar: Acetic acid Nonionized Ionized • Found in cells in the ionized form with a charge of 1– and called a carboxylate ion. Figure 4.9d Amino STRUCTURE Amines NAME OF COMPOUND EXAMPLE • FUNCTIONAL PROPERTIES Acts as a base; can pick up an H+ from the surrounding solution (water, in living organisms): Glycine Nonionized • Ionized Found in cells in the ionized form with a charge of 1. Figure 4.9e Sulfhydryl STRUCTURE Thiols NAME OF COMPOUND • Two sulfhydryl groups can react, forming a covalent bond. This “cross-linking” helps stabilize protein structure. FUNCTIONAL PROPERTIES • Cross-linking of cysteines in hair proteins maintains the curliness or straightness of hair. Straight hair can be “permanently” curled by shaping it around curlers and then breaking and re-forming the cross-linking bonds. (may be written HS—) EXAMPLE Cysteine Figure 4.9f Phosphate STRUCTURE Organic phosphates EXAMPLE • FUNCTIONAL Contributes negative charge to the molecule PROPERTIES of which it is a part (2– when at the end of a molecule, as at left; 1– when located internally in a chain of phosphates). • Molecules containing phosphate groups have the potential to react with water, releasing energy. Glycerol phosphate NAME OF COMPOUND Figure 4.9g Methyl STRUCTURE Methylated compounds EXAMPLE • Addition of a methyl group FUNCTIONAL PROPERTIES to DNA, or to molecules bound to DNA, affects the expression of genes. • Arrangement of methyl groups in male and female sex hormones affects their shape and function. 5-Methyl cytidine NAME OF COMPOUND ATP: An Important Source of Energy for Cellular Processes • One phosphate molecule, adenosine triphosphate (ATP), is the primary energy-transferring molecule in the cell • ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups • 能量載體 © 2011 Pearson Education, Inc. Figure 4. UN04 Adenosine Figure 4. UN05 Reacts with H2O Adenosine Adenosine ATP Inorganic phosphate ADP Energy The Chemical Elements of Life: A Review • The versatility of carbon makes possible the great diversity of organic molecules • Variation at the molecular level lies at the foundation of all biological diversity © 2011 Pearson Education, Inc.