LIPIDS Diverse group of organics Insoluble in water Will dissolve in nonpolar solvents MAJOR GROUPS FATS PHOSPHOLIPIDS STEROIDS

Fats Store Large Amounts of Energy COMPONENTS of a FAT: GLYCEROL: A 3-Carbon Alcohol FATTY ACID (Carboxylic Acid) *Carboxyl at one end attached to a hydrocarbon chain *Carboxyl end has acid properties *Usually contains a long C skeleton with an even number (Most have 16-18C’s) *Nonpolar C-H bonds make the chain hydrophobic

LIPID FORMATION Enzyme catalyzed condensation reactions link glycerol to fatty acids by an Ester Linkage: ESTER LINKAGE: Bond formed between a hydroxyl group and a carboxyl group TRIACYLGLYCEROL (Triglyceride) A fat composed of three fatty acids bonded to a glycerol by ester linkages

The Making of a Triglyceride

! Insoluble in water Variation is due to fatty acid composition Fat Characteristics Insoluble in water Variation is due to fatty acid composition Fatty acids can be the same or different, including different lengths, and have C=C double bonds in different places

Saturated and Unsaturated Fats No double bonds between C’s in fatty acid tail C’s bonded to max # of H’s (saturated w/H) Usually solid at room temp. Most animal fats UNSATURATED FATS: One or more double bonds between C’s in fatty acid tail Tail kinks at each C=C, so molecules are spread out more Usually liquid at room temp. Most plant fats

FAT FUNCTIONS Energy Storage: 1 Gram of fat=2X energy of 1 Gram of Polysaccharide!!! More compact energy storage Cushions mammal’s organs Insulates against heat loss

PHOSPHOLIPIDS Glycerol, 2 fatty acids, a phosphate group, and usually a small chemical group attached to the phosphate.(Campbell 5.12) Phosphate is negatively charged Variable group is usually charged or polar Can be diverse Aren’t truly hydrophobic or hydrophilic (Hydrocarbon tails are hydrophobic, polar head is hydrophilic) Are major components of cell membranes: Form a bilayer due to reaction of hydrophobic tails A MICELLE or phospholipid cluster forms spontaneously in water

STEROIDS Lipids which have 4 fused carbon rings with various functional groups attached Cholesterol is an important steroid: Precursor to many other steroids including sex hormones and bile acids Common component of animal cell membranes Can contribute to artherosclerosis

CHOLESTEROL