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This chapter explores the different molecules found in cells, including enzymes, proteins, carbohydrates, and nucleic acids, and their structural variations. It also discusses the importance of functional groups in organic compounds.
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Chapter 3 0 The Molecules of Cells
Model of amilk-digestingenzyme Unnumbered Figure p.32 0
Space-fillingmodel Structuralformula Ball-and-stickmodel H H H C H C H H H Methane H The 4 single bonds of carbon point to the corners of a tetrahedron. H H H H H C C C C C H H H H H H H H H Ethane Propane Carbon skeletons vary in length. H C 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 Butane Isobutane Skeletons may be unbranched or branched. H H H H H H H H C C C H H C C C H C C H H H H H 1-Butene 2-Butene Skeletons may have double bonds, which can vary in location. H H H C C H H H H C C C C H H H C C H C C H H C H H C H H H Benzene Cyclohexane Skeletons may be arranged in rings. Figure 3.1 Variations in carbon skeletons
OH Estradiol HO Female lion OH O Testosterone Figure 3.2 Differences in the functional groups of male and female sex hormones (carbons and their attached hydrogens omitted) Male lion
H H OH OH OH OH H H Short polymer Short polymer Unlinked monomer Unlinked monomer H2O Dehydration reaction Dehydration reaction H H OH OH Longer polymer Longer polymer Figure 3.3A Building a polymer chain
H2O H OH Hydrolysis H OH H OH Figure 3.3B Breaking a polymer chain
Figure 3.4A Bees with honey, a mixture of two monosaccharides
H O H H C OH C H OH C C O HO C H C HO H H OH C C H OH H OH C C OH H C H OH C H OH H H Glucose Fructose Figure 3.4B Structures of glucose and fructose
CH2OH 6 CH2OH C O 5 H O O H H H H H C C 1 4 OH H OH H OH HO OH OH C C 2 3 H OH H OH Simplified structure Structural formula Abbreviated structure Figure 3.4C Three representations of the ring form of glucose
CH2OH CH2OH O O H H H H H H OH H H OH O OH H OH HO H OH H OH Glucose Glucose H2O CH2OH CH2OH O O H H H H H H OH OH H H O HO OH H H OH OH Maltose Figure 3.5 Disaccharide formation
Glucose monomer STARCH Starch granules in potato tuber cells O O O O O O O O O O O Glycogen granules in muscle tissue GLYCOGEN O O O O O O O O O O O O O Cellulose fibrils in a plant cell wall CELLULOSE O O OH O Cellulose molecules O O O O OH O O O O O O O O O O O O O O O O Figure 3.7 Polysaccharides
Figure 3.8A Water beading on the naturally oily coating of feathers
H H H H C C H C OH OH OH Glycerol HO C O H2O CH2 CH2 CH2 CH2 CH2 Fatty acid CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 Figure 3.8B A dehydration reaction linking a fatty acid to glycerol
H H H H H C C H C O O O C O C O C O CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH CH2 CH2 CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 CH3 CH3 Figure 3.8C A fat molecule
H3C CH3 CH3 CH3 CH3 HO Figure 3.9 Cholesterol, a steroid
H O H C C N H OH R Amino group Carboxyl (acid) group Figure 3.12A General structure of an amino acid
H H H H H H O O O N C C N C C N C C OH OH H H H OH CH2 CH2 CH2 CH OH C CH3 CH3 OH O Leucine (Leu) Serine (Ser) Aspartic acid (Asp) Hydrophobic Hydrophilic Figure 3.12B Examples of amino acids
Peptide bond Carboxyl group Amino group H H Dehydration reaction H O H H H O O O H N C C + N C C N C C N C C H OH OH H OH H H R R R R H2O Amino acid Amino acid Dipeptide Figure 3.12C Peptide bond formation
Polypeptide chain Collagen Unnumbered Figure page 44
Figure 3.14 Protein Structure Levels of Protein Structure Leu Met Asn Val Pro Ala Val Ile Arg Primary structure Cys Val Lys Phe Ala Glu His Gly Val Ser Lys Thr Val Gly Pro Ala Val Asp Arg Leu Gly Ser Amino acids Hydrogen bond O H H O C C C N N H C O C C C R N C C N H H H O N C C O C C C N O H H C N C N O H C H C H C N N C N O C O N H N C H O O C R C C O C O H H H C C O Secondary structure C N H O N C C C N C H C C O O H N C C O N H C C H H N H N O O N C C N C O C H N H N C C H O C O C C N H C C C N O H C O Alpha helix Pleated sheet Tertiary structure Polypeptide (single subunit of transthyretin) Transthyretin, with four identical Polypeptide subunits Quaternary structure
Figure 3.15 Linus Pauling with a model of the alpha helix in 1948
H H N N N H OH N H N O P O CH2 Nitrogenous base (A) O O H H Phosphate group H H H OH Sugar Figure 3.16A A nucleotide
Nucleotide A T C G T Sugar-phosphate backbone Figure 3.16B Part of a polynucleotide
C A T C G G C A T C G T A A Base pair G C T A A T A T Figure 3.16C DNA double helix T
H2O Dehydration … … OH + H H H Hydrolysis Short polymer Monomer Longer polymer H2O Unnumbered Figure page 48
C Unnumbered Figure page 48
CH2OH O O HOCH2 H H H H H H OH HO O HO CH2OH H OH OH H Sucrose Unnumbered Figure page 49
H O H N C C OH H CH2 OH Unnumbered Figure page 49
Enzyme A Enzyme B Rate of reaction 0 20 40 60 80 100 Temperature (C) Unnumbered Figure page 49