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

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

Glycerol Glycerol is a 3 carbon alcohol

ESTER LINKAGE Ester linkage – formed by the dehydration (condensation) of a carboxyl group from the fatty acid to the hydroxyl group of glycerol

(a) Saturated fat and fatty acid 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

(b) Unsaturated fat and fatty acid 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 Polyunsaturated fats (PUFA) Have more than one double bond in their fatty acid chains

Saturated fats – solid at room temperature, unsaturated – liquid at room temperature

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

(a) Structural formula (b) Space-filling model Phospholipid structure Consists of a hydrophilic “head” and hydrophobic “tails” CH2 O P CH C Phosphate Glycerol (a) Structural formula (b) Space-filling model Fatty acids (c) Phospholipid symbol Hydrophobic tails Hydrophilic head Hydrophobic tails – Hydrophilic head Choline + Figure 5.13 N(CH3)3

Micelles When phospholipids are added to water, they form micelles

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

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

One steroid, cholesterol Is found in cell membranes Is a precursor for some hormones HO CH3 H3C Figure 5.15

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

Function of DNA and RNA DNA RNA 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

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

Each Nucleotide contains Sugar + phosphate + nitrogen base Nitrogenous base Nucleoside O O O P CH2 5’C 3’C Phosphate group Pentose sugar (b) Nucleotide Figure 5.26

(c) Nucleoside components Nucleotide Monomers CH Uracil (in RNA) U Ribose (in RNA) Nitrogenous bases Pyrimidines C N O H NH2 HN CH3 Cytosine Thymine (in DNA) T HC NH Adenine A Guanine G HOCH2 OH Pentose sugars Deoxyribose (in DNA) 4’ 5” 3’ 2’ 1’ (c) Nucleoside components Pyrimidines (single ring) Purines (double ring) Deoxyribose (carbon 2  no oxygen), Ribose (carbon 2 has an oxygen – hydroxyl group) Figure 5.26

Nucleotide Polymers 3’C 5’ end 5’C 3’ end OH Figure 5.26 O 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

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

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 http://www.youtube.com/watch?v=l-hrLs03KjY&feature=related

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 5’ end New strands Figure 5.27