Review Each small organic molecule can be a unit of a large organic molecule called a macromolecule. Small organic molecules can serve as monomers, the subunits of polymers.

There are four types of biological macromolecules Carbohydrates Lipids Proteins Nucleic acids

What Are Lipids? All lipids contain large chains of nonpolar hydrocarbons (chains of carbon and hydrogen) Most lipids are therefore hydrophobic and water insoluble

What Are Lipids? Lipids are diverse in structure and serve in a variety of functions Energy storage Waterproofing Membranes in cells Hormones

Types of Lipids Triglycerides Waxes Phospholipids Sterols

Page 21: Triglycerides Fats and oils Formed by condensation reactions 3 fatty acids + glycerol  triglyceride

A fatty acid is a long chain of mostly carbon and hydrogen atoms with a –COOH group (“carboxyl”) at one end.

The hydrocarbon chain can vary in length … from 4 to about 24 carbons long, depending on the type of fatty acid. (in humans, 16 and 18 are the most common)

Fats and oils used for long-term energy storage Fats and oils possess a high density of stored chemical energy

Saturated Fatty Acids Saturated fatty acids have mostly single C-C bonds in the fatty acid chains Saturated fats are typically solid at room temperature Saturated fats are often from animal sources

Unsaturated Fatty Acids Unsaturated fats have one or more C=C double bond in the fatty acid chain Unsaturated fats are typically liquid at room temperature, because kinks in the tails prevent tight packing Unsaturated fats are often from plant sources

Cis-unsaturated fatty acids Page 22 Most naturally occurring unsaturated fatty acids occur in the cis- confirmation Cis is a Latin word meaning "on the same side” Causes a kink in the fatty acid chain

Trans-unsaturated fatty acids Most fatty acids in the trans configuration (trans fats) are not found in nature and are the result of human processing Trans is a Latin word meaning "across", "on the opposite side" Causes a straight fatty acid chain (even though it is unsaturated)

What's the problem with trans fatty acids? Trans fatty acids increase LDL cholesterol levels, and reduce HDL cholesterol levels. In other words, trans fatty acids are detrimental to cardiac health.

Which foods contain trans fatty acids? Margarines High-fat baked goods Any product for which the label says "partially hydrogenated vegetable oils" (which, it sadly appears, includes virtually all processed foods.)

Types of Lipids Fatty Acids Fats Phospholipids Waxes Sterols

Glucose Glycogen Fat Page 23: Carbs vs. fats Our body uses three main sources of energy: Glucose Glycogen Fat Can’t be stored Carbohydrates Long term storage

Types of Lipids Fatty Acids Fats Phospholipids Waxes Sterols

Phospholipids They are formed by attachment of two fatty acids plus a phosphate group to a glycerol. They are the main structural components of membranes.

Types of Lipids Fatty Acids Fats Phospholipids Waxes Sterols

Waxes Waxes are composed of long hydrocarbon chains and are strongly hydrophobic Waxes are highly saturated and solid at room temperature Waxes form waterproof coatings Leaves and stems of plants Fur in mammals Insect exoskeletons Used to build honeycomb structures Figure: 19-2 part a Title: Viral structure and replication part a Caption: (a) A cross section of the virus that causes AIDS. Inside, genetic material is surrounded by a protein coat and molecules of reverse transcriptase, an enzyme that catalyzes the transcription of DNA from the viral RNA template after the virus enters the host cell. This virus is among those that also have an outer envelope that is formed from the host cell's plasma membrane. Spikes made of glycoprotein (protein and carbohydrate) project from the envelope and help the virus attach to its host cell.

The frozen ropes in this image represent the wax on the surface of Asparagus! The tube-like structures are called stomatal chimneys. They are composed of wax.

Types of Lipids Fatty Acids Fats Phospholipids Waxes Sterols

Sterols Sterols have a backbone of four carbon rings Cholesterol is a component of cell membranes and can be modified to form sex hormones (testosterone and estrogen).

Cholesterol: a steroid