Chapter 5: The Lipids - Fats, Oils, Phospholipids, and Sterols

Comprehensive vocabulary flashcards covering the chemical structures, bodily functions, digestion, transport, health effects, and dietary sources of lipids from Chapter 5 of Nutrition Concepts & Controversies.

Lipids

A family of organic compounds soluble in organic solvents but not in water, comprising triglycerides (fats and oils), phospholipids, and sterols.

Energy Fuel (Lipid Function)

The role of fats providing $80$ to $90$ percent of the resting body's energy and much of the energy needed to fuel muscular work.

Triglyceride

The principal class of lipids found in both food and human body fat stores, composed of three fatty acids of differing lengths bound to one molecule of glycerol.

Point of Unsaturation

A site in a fatty acid carbon chain where hydrogen atoms are missing and a double bond is formed, introducing a bend or kink that prevents stacking and keeps oils liquid at room temperature.

Saturated Fatty Acid

A fatty acid whose hydrocarbon chain contains only single carbon-carbon bonds and holds the maximum possible number of hydrogen atoms; its straight chains stack tightly, making it solid at room temperature.

Monounsaturated Fatty Acid

A fatty acid possessing exactly one point of unsaturation (a single double bond) along its carbon chain, abundant in olive oil, canola oil, and avocado oil.

Polyunsaturated Fatty Acid (PUFA)

A fatty acid having two or more points of unsaturation (double bonds) in its carbon chain; this type of fat spoils most readily when exposed to oxygen.

Phospholipids

A class of lipids that are both fat- and water-soluble, functioning as emulsifiers in food and serving as the primary structural component of cell membranes.

Sterols

Lipids characterized by an interconnected ringlike structure, such as cholesterol and plant sterols, that serve as raw materials for making vitamin D, bile, and hormones.

Bile Emulsification

The process by which bile compounds—which have affinity for both fat and water—break large fat globules in the small intestine into small droplets that disperse into watery digestive juices so digestive enzymes can reach and digest them.

Lipoprotein

A transport vehicle assembled from an outer shell of phospholipids and proteins that encloses an inner core of insoluble triglycerides and cholesterol to move fats through watery body fluids.

Chylomicrons

Lipoproteins formed within intestinal cells that transport newly digested and absorbed lipids from the gut via the lymphatic system into the blood.

Low-Density Lipoproteins (LDL)

Larger, lighter lipoproteins rich in cholesterol that deliver lipids to tissues; elevated blood levels contribute to inflammation, atherosclerosis, and increased cardiovascular disease risk.

High-Density Lipoproteins (HDL)

Smaller, denser lipoproteins packaged with more protein that scavenge surplus cholesterol and other lipids from peripheral tissues and circulate them to the liver for excretion.

Ketosis

A metabolic condition that takes place when stored body fat is dismantled in the absence of sufficient carbohydrates, which are strictly required for complete fat oxidation.

Essential Fatty Acids

Polyunsaturated fatty acids that the body cannot synthesize and must obtain from the diet, serving as structural membrane parts and precursors to biologically active eicosanoids.

Eicosanoids

Biologically active lipid compounds synthesized from essential fatty acids that act as cellular signals modulating blood clotting, inflammation, and immune cell functions.

Linoleic Acid

An essential omega-6 polyunsaturated fatty acid found in poultry fat, nuts, seeds, and vegetable oils such as corn, cottonseed, safflower, soybean, and sunflower oils.

Linolenic Acid

An essential omega-3 polyunsaturated fatty acid found in nuts, seeds (chia, flaxseeds, walnuts), soybeans, and oils such as canola and flaxseed.

EPA and DHA

Long-chain omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid) found in enriched eggs, human milk, and marine seafood that promote vision, brain, and cardiovascular health.

Hydrogenation

A manufacturing chemical process that forces hydrogen atoms into unsaturated fatty acids, making liquid oils firmer, increasing shelf life by resisting oxidation, and elevating the smoke point.

Trans-Fatty Acids

Unusual fatty acids formed primarily as a byproduct of industrial hydrogenation that retain unsaturated bonds but adopt a rigid structure, raising harmful blood LDL cholesterol.

Acceptable Macronutrient Distribution Range (AMDR) for Fat

The recommended dietary intake range set by the Dietary Reference Intakes estimating that total fat should constitute $20\%$ to $35\%$ of daily energy.

Dietary Sources of Saturated Fat (U.S. Diet)

Food categories providing saturated fat in the average U.S. diet, led by sandwiches at $19\%$, desserts and sweet snacks at $11\%$, and rice, pasta, and grain-based dishes at $7\%$.

Satiety

The post-meal feeling of fullness and satisfaction mediated in part by dietary fats slowing digestive system mobility and stomach emptying.