Lipids Biochemistry PDF

LIPIDS Monomer is the fatty acid Class includes fats, oils, and waxes Classified by their hydrophobic nature (DO NOT DISSOLVE IN WATER) Long term energy storing molecule, lipids have double the energy per gram than carbs.  4 TYPES OF LIPIDS 1) FATTY ACID - Long...

LIPIDS Monomer is the fatty acid Class includes fats, oils, and waxes Classified by their hydrophobic nature (DO NOT DISSOLVE IN WATER) Long term energy storing molecule, lipids have double the energy per gram than carbs.  4 TYPES OF LIPIDS 1) FATTY ACID - Long hydrocarbon chain with a carboxyl group on the end 2) FATS AND OILS - lipids used to store energy ( Formed from the combining of 3 fatty acids + a glycerol) 3) Phospholipids- composes the cell membrane bilayer 4) Steroids- differ from other lipids in structure but are classified as a lipid because they are insoluble in water examples : cholesterol progesterone Serve as hormones (compounds secreted in one tissue with effects elsewhere in the body)  Chemical Structures of the 4 Important Subgoups of Lipids: ▪Fatty acids ▪Triglycerides (fats) ▪Phospholipids ▪Sterols (or steriods) Lipid Subgroups: Fatty Acids Saturated = fully hydrogenated (hydrogen at every position), straight chain Unsaturated = double/ triple bonds where hydrogen is missing, kink or bent structure at the point of double/ triple bonds Saturated Fatty Acids Fats with saturated fatty acids are saturated fats. ○ Most animal fats are saturated. ○ Saturated fats are solid at room temperature. ○ A diet rich in saturated fats may contribute to cardiovascular disease (atherosclerosis) through plaque deposits. Unsaturated Fatty Acids Fats with unsaturated fatty acids are unsaturated fats. ○ Plant and fish fats, known as oils, are liquid are room temperature. The kinks provided by the double bonds prevent the molecules from packing tightly together. Also includes MUFA’s (monounsaturated FA’s) one double bond and PUFA’s (polyunsaturated FA’s) more than one double bond.  Triglycerides (aka FATS) Animals store energy in the form of fats. One glycerol bonds with 3 FA’s (through dehydration synthesis) to form a triglyceride. 2 FA’s- diglyceride, 1 FA - monoglyceride Stored in fat cells in adipose tissue (unlimited capacity for growth).  The major function of fats is long term energy storage in adipose cells (humans/mammals). – A gram of fat stores more than twice as much energy as a gram of a polysaccharide. – Plants use starch for energy storage when mobility is not a concern but use oils for seed dispersal as they are lighter Fat also functions to cushion vital organs. A layer of fats can also function as insulation. – This subcutaneous layer is especially thick in whales, seals, and most other marine mammals Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  Glycerol consists of a three-carbon skeleton with a hydroxyl group attached to each. A fatty acid consists of a carboxyl group attached to a long carbon skeleton, often 16 to 18 carbons long. Fig. 5.10a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  The many nonpolar C-H bonds in the long hydrocarbon skeleton make fats hydrophobic. In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triglyceride. Fig. 5.10b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  Glycerol + 3 FA’s = Triglyceride Glycerol glycerol + fatty acid----🡪 monoglyceride + ____  Phospholipids Phospholipids are major components of cell membranes  Phospholipids have two fatty acids attached to glycerol and a phosphate group at the third position. – The phosphate group carries a negative charge. – Additional smaller groups may be attached to the phosphate group.  The interaction of phospholipids with water is complex. – The fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head. Fig. 5.12 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  When phospholipids are added to water, they self-assemble into aggregates with the hydrophobic tails pointing toward the center and the hydrophilic heads on the outside. – This type of structure is called a micelle. Fig. 5.13a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  At the surface of a cell phospholipids are arranged as a bilayer. – Again, the hydrophilic heads are on the outside in contact with the aqueous solution and the hydrophobic tails form the core. – The phospholipid bilayer forms a barrier between the cell and the external environment. They are the major component of membranes. Fig. 5.12b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  Steroids Cholesterol and certain hormones Steroids are lipids with a carbon skeleton consisting of four fused carbon rings. – Different steroids are created by varying functional groups attached to the rings. Fig. 5.14 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings  Steroids con’t Cholesterol, an important steroid, is a component in animal cell membranes. Cholesterol is also the precursor from which all other steroids are synthesized. Many of these other steroids are hormones, including the vertebrate sex hormones. Hormone-compounds secreted in one tissue with effects elsewhere in the body)  While cholesterol is clearly an essential molecule, high levels of cholesterol in the blood may contribute to cardiovascular disease. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings