Are complimentary to each other not identical gc 3 h

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Unformatted text preview: phate-sugar-phosphate-sugar-phosphate-… linear chain with nitrogenous bases to the side 10 Biological Chemistry Nucleic Acids — linear polymers complementary base pairing • DNA is “doublestranded ” – Two polymers held together by hydrogen-bonding between bases Condensation of sugars and phosphates form polymer “backbone ” Complementary base pairing in DNA Bases form side groups — not involved in formation of polymer complementary base pairing • C pairs only with G • A pairs only with T dsDNA Structure H N N N H N Sugar O H CH 3 N N O Sugar Thymine (T) Adenine (A) \ the sequence of Each pair = 1 purine + 1 pyrimidine N • A=T (2 H-bonds) • bases in the two strands are complimentary to each other (not identical). G≡C (3 H-bonds) H O N N H N Figure 16.8 N H N N Sugar H O N N H Guanine (G) Sugar DNA ’s complementary base sequence Cytosine (C) 4. Lipids — Include Fats and Cholesterol • Used for: Fatty Acids •Long C 8–16 hydrocarbon “tail ” = non-polar = hydrophobic = “fatty ” •Carboxyl “head” = acid fi “ Fatty Acid ” – Energy storage, insulation, steroids, vitamins • Subunit: • Saturated : all C-C single bonds – fatty acids • Macromolecule: – Two hydrogens on each carbon (not a polymer — subunits attached to a different carbon backbone) – triglycerides & phospholipids – sphyngolipids – waxes Cholesterol, a modified fatty acid Heyer • Unsaturated : chain contains double bonds – Causes rigid kinks in chain 11 Biological Chemistry Triglycerides Saturated fat forms solids at room temp (animal fat) • Tri = three; glyceride = on glycerol • Formed by dehydration synthesis of fatty acid side-chains linked onto glycerol – One fatty acid on the glycerol = monoglyceride = acyl-glycerol – Two fatty acids on the glycerol = diglyceride = diacyl-glycerol [DAG] – Three fatty acids on the glycerol = triglyceride = triacyl-glycerol [TAG] • Storage form of lipids Animal fat is a mixture of triglycerides with >50% of fatty acids saturated. Unsaturated fats are liquid at room temp (vegetable oil) Phospholipids • Used to make cell membranes – Plasma membrane – Cell membranes • Phosphate: – Hydrophilic “head ” • 2 Fatty acid chains: – Hydrophobic “tail ” Plant oil is a mixture of triglycerides with <15% of fatty acids saturated. Hydrophilic heads Isolated activity compartments Phospholipid Bilayer Hydrophobic tails • Hydrophilic “heads” associate together – Form outer layer of cell membrane • Hydrophobic “tails”associate together – Form inner layer of cell membrane – Keep water soluble molecules from crossing membrane • Form double layer of cell membranes Heyer • Cell membrane • Organelle membranes 12...
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