1 Lipids Lipids are hydrophobic molecules Mostly C-H (non-polar) are the one class of large biological molecules that do not consist of polymers Uses: structure of cell membranes, energy source

Lipids Fats Phospholipids Steroids 2

3 Fats –Are constructed from two types of smaller molecules: single glycerol and three fatty acids Fatty Acid

4 Glycerol

5 ESTER LINKAGE

6 Saturated fatty acids –Have the maximum number of hydrogen atoms possible –Have no double bonds –Are solid at room temperature (e.g. animal fats) (a) Saturated fat and fatty acid Stearic acid Figure 5.12

7 Unsaturated fatty acids –Have one or more double bonds, causing a bend in its structure –Are liquids at room temperature (e.g. vegetable fats) (b) Unsaturated fat and fatty acid cis double bond causes bending Oleic acid Figure 5.12

Unsaturated Fats Monounsaturated fats (MUFA) –Have one double bond in their fatty acids 8 Polyunsaturated fats (PUFA) Have more than one double bond in their fatty acid chains

10

11 Phospholipids –Have only two fatty acids –Have a phosphate group instead of a third fatty acid

12 Phospholipid structure –Consists of a hydrophilic “head” and hydrophobic “tails” CH 2 O P O O O CH CH 2 OO C O C O Phosphate Glycerol (a) Structural formula (b) Space-filling model Fatty acids (c) Phospholipid symbol Hydrophobic tails Hydrophilic head Hydrophobic tails – Hydrophilic head CH 2 Choline + Figure 5.13 N(CH 3 ) 3

Micelles When phospholipids are added to water, they form micelles 13

14 Phospholipid Bilayer –Results in a phospholipid bilayer arrangement found in cell membranes Hydrophilic head WATER Hydrophobic tail Figure 5.14 Water and other polar and ionic materials cannot pass through the membrane except by the help of proteins in the membrane

15 Steroids –Are lipids that have a carbon skeleton consisting of four fused rings –Contain many different functional groups

16 One steroid, cholesterol –Is found in cell membranes –Is a precursor for some hormones HO CH 3 H3CH3C Figure 5.15

17 Nucleic Acids Nucleic acids store and transmit hereditary information There are two types of nucleic acids –Deoxyribonucleic acid (DNA) –Ribonucleic acid (RNA)

18 DNA –Stores information for the synthesis of specific proteins –Found in the nucleus of cells RNA –Reads information in DNA –Transports information to protein building structures within cell Function of DNA and RNA

19 The Structure of Nucleic Acids Nucleic acids (also called Polynucleotides) –Are polymers made up of individual nucleotide monomers (a) Polynucleotide, or nucleic acid 3’C 5’ end 5’C 3’C 5’C 3’ end OH Figure 5.26 O O O O

20 Each Nucleotide contains –Sugar + phosphate + nitrogen base Nitrogenous base Nucleoside O O OO OO P CH 2 5’C 3’C Phosphate group Pentose sugar (b) Nucleotide Figure 5.26 O

21 Nucleotide Monomers (c) Nucleoside components Figure 5.26 CH Uracil (in RNA) U Ribose (in RNA) Nitrogenous bases Pyrimidines C N N C O H NH 2 CH O C N H HN C O C CH 3 N HN C C H O O Cytosine C Thymine (in DNA) T N HC N C C N C CH N NH 2 O N HC N H H C C N NH C NH 2 Adenine A Guanine G O HOCH 2 H H H OH H O HOCH 2 H H H OH H Pentose sugars Deoxyribose (in DNA) Ribose (in RNA) OH CH Uracil (in RNA) U 4’ 5”5” 3’ OH H 2’ 1’ 5”5” 4’ 3’ 2’ 1’ Pyrimidines (single ring) Purines (double ring)

22 Nucleotide Polymers nucleotides linked by the–OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next Phosphodiester bond 3’C 5’ end 5’C 3’C 5’C 3’ end OH Figure 5.26 O O O O

23 Gene The sequence of bases along a nucleotide polymer –Is unique for each gene

24 The DNA Double Helix Have two polynucleotides that spiral around each other held together by hydrogen bonds between nitrogenous bases –A (adenine) will always bond with T (thymine – DNA only), or U (uracil – RNA only)  2 hydrogen bonds –C (cytosine) will always bond with G (guanine)  3 hydrogen bonds

25 The DNA double helix –Consists of two antiparallel nucleotide strands 3’ end Sugar-phosphate backbone Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand A 3’ end 5’ end New strands 3’ end 5’ end Figure 5.27