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3.1 Life’s molecular diversity is based on the properties of carbon A carbon atom can form four covalent bonds Allowing it to build large and diverse organic compounds Structural formula Ball-and-stick model H H Space-filling model H H C C H H Methane H H The 4 single bonds of carbon point to the corners of a tetrahedron. Carbon chains vary in many ways H H H C C H H H H H C C C H H H H H H Ethane Propane Carbon skeletons vary in length. H H C H H H H H H H H C C C C H H C C C H H H H H H H H Butane Isobutane Skeletons may be unbranched or branched. H H H H C C C C H H H H H H 1-Butene 2-Butene Skeletons may have double bonds, which can vary in location. H H H H H C C C C H H H H C H H C C H H C H C C H H C C H H C C C H H H C H H H Benzene Cyclohexane Skeletons may be arranged in rings. Hydrocarbons are composed of only hydrogen and carbon Functional groups help determine the properties of organic compounds – Functional groups are particular groupings of atoms • That give organic molecules particular properties OH O The four main classes of biological molecules are • • • • carbohydrates, lipids, proteins nucleic acids Monosaccharides are the simplest carbohydrates The monosaccharides glucose and fructose are isomers. H O H C C OH C O HO C H H H C OH HO C H H C OH H C OH H C OH H C OH H C OH H C OH H Glucose H Fructose Monosaccharides can also occur as ring structures Glucose O H C CH2OH H C OH HO C H H H C OH HO H C OH H C OH O H OH H H OH ring structure H Linear structure H O OH Simplified structure Cells link two single sugars (Monosaccharides) to form disaccharides. CH2OH O H H OH HO CH2OH O H H H H H OH Glucose HO OH H OH Glucose H2O CH2OH CH2OH H H H OH HO OH H O OH H H OH H H O O H H OH H H OH OH Maltose Cells link two single sugars (Monosaccharides) to form disaccharides. Cells link two single sugars (Monosaccharides) to form disaccharides. Cells make most of their large molecule by joining smaller organic molecules into chains called polymers by a dehydration reaction. H OH OH Short polymer OH H H Unlinked monomer Dehydration Dehydration reaction reaction H H H2O OH OH Longer polymer Polymers are broken down to monomers by the reverse process, hydrolysis. H2O H OH Hydrolysis H OH OH H Starch and glycogen are polysaccharides that store sugar for later use Cellulose is a polysaccharide found in plant cell walls Glucose monomer STARCH Starch granules in potato tuber cells 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 O O O O O O O O O O Cellulose fibrils in a plant cell wall Cellulose molecules O O CELLULOSE O O O O O O O O O O The orientation of the bond connecting the glucose monomers is different between starch and cellulose STARCH CELLULOSE Lipids •Fats are lipids that are mostly energy-storage molecules •Lipids are diverse compounds that consist mainly of carbon and hydrogen atoms linked by nonpolar covalent bonds C O CH2 CH2 CH2 CH2 CH2 Fatty acid CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 Fats, also called triglycerides, are lipids whose main function is energy storage Fats consist of glycerol linked to three fatty acids H H H H C C C O C O O C H O 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 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 CH3 CH CH2 CH2 CH2 CH2 CH2 CH2 CH3 There are different types of lipids with a variety of functions – Phospholipids are a major component of cell membranes – Waxes form waterproof coatings H H H – Steroids are often hormones H C C H C Phosphate Phospholipid O O O O P O C O C O O CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 Fatty acid CH CH2 CH2 CH2 CH2 CH2 CH2 CH3 There are different types of lipids with a variety of functions – Phospholipids are a major component of cell membranes – Waxes form waterproof coatings – Steroids are often hormones There are different types of lipids with a variety of functions – Phospholipids are a major component of cell membranes – Waxes form waterproof coatings – Steroids are often hormones Steroids There are different types of lipids with a variety of functions – Phospholipids are a major component of cell membranes – Waxes form waterproof coatings – Steroids are often hormones Steroids H3C CH3 CH3 CH3 CH3 HO Proteins – Proteins are essential to the structures and activities of life – A protein is a polymer constructed from amino acid monomers – Proteins are made from amino acids linked by peptide bonds Proteins Each protein has a different arrangement of a common set of 20 amino acid monomers. Proteins Each amino acid contains • • • An amino group A carboxyl group An R group, which distinguishes each of the 20 different amino acids H O H N C H C OH R Amino group Carboxyl (acid) group Proteins Each amino acid contains • • • An amino group A carboxyl group An R group, which distinguishes each of the 20 different amino acids Each amino acid has specific properties • H H H O N C H C H O N OH CH2 H H C H C CH N OH CH2 O C H OH CH2 OH C CH3 CH3 OH Leucine (Leu) Hydrophobic C Serine (Ser) O Aspartic acid (Asp) Hydrophilic Proteins Cells link amino acids together through peptide bonds Carboxyl group Peptide bond Amino group O N C R Amino acid O + OH N Dehydration reaction O C H N OH R Amino acid H2O C C O N C R R Dipeptide C OH Proteins Cells link amino acids together through peptide bonds Polypeptide Protein Groove A protein’s shape depends on four levels of structure – primary structure Leu Met Asn Pro Val Cys Gly Gly Thr Glu Ser Lys Lys Ala Val Leu Asp Ala Val Arg Amino acids Gly Pro Ser Val Ala Ile Arg Val His Phe Val A protein’s shape depends on four levels of structure – primary structure – secondary structure Amino acids Alpha helix Pleated sheet A protein’s shape depends on four levels of structure – primary structure – secondary structure – tertiary structure Groove A protein’s shape depends on four levels of structure – primary structure – secondary structure – tertiary structure – quaternary structure Polypeptide chain Collagen Nucleic acids Nucleic acids are information-rich polymers of nucleotides DNA and RNA Serve as the blueprints for proteins and thus control the life of a cell RNA and DNA are made up of very similar nucleotides. H H H N N N N OH O P N O CH2 ! O Phosphate group O H H N Nitrogenous base (A) O P N O CH2 O ! O H H N H H OH H N Phosphate group H H H N Nitrogenous base (A) H H H OH OH Sugar OH H Sugar RNA DNA The sugar and phosphate form the backbone for the nucleic acid or polynucleotide A T C G T Sugar-phosphate backbone Nucleotide DNA consists of two polynucleotides twisted around each other in a double helix. C A C T G C G TA C G A T A Base pair T GC T A A T TA RNA, by contrast is a single-stranded polynucleotide. C A C T G C G TA C G A T A Base pair T GC T A A TA T RNA consists of one polynucleotides twisted around itself. DNA and RNA have different functions: •DNA encodes information in the form of genes. •RNAs are both is both the messenger of information •RNAs also can have enzyme activity. C C G A G C T A T C G A A T A T A Base pair A T G C T T