LipidPrint - Our bodies receive nearly all of the energy...

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Our bodies receive nearly all of the energy they need from the oxidation of carbohydrates and lipids. Carbohydrates are a quick source of available energy, but lipids function mostly for energy storage. Lipid reserves in the fat depots of a 154 lb male containing 100,000 kcal of energy can maintain human body functions without food for 30-40 days as long as sufficient water is available. Lipids provide the sole source of energy in hibernating animals and migrating birds. Lipids are more compact and contain more energy per gram than glycogen, the stored for of carbohydrates. Body weight would increase approximately 110 pounds if glycogen replaced fat as the energy reserve in our bodies. Lipids are stored as fat throughout the body in specialized connective tissue called adipose tissue. Adipose tissue cells consist of fat globules in the form of triglycerides which can occupy up to 90% of the cell volume. Many cells contain phospholipids as a structural component in the bilayer of biological membranes. Other functions of lipids include providing a waterproof covering on plants and some animal bodies. Lipids and lipid derivatives serve as vitamins and hormones. Adipose tissue serves as a protective cushion and provides structural support to help prevent injury to vital organs such as the heart, liver, kidneys and spleen. Fat also insulates the body from heat loss and extreme temperature changes. Fat deposits under the skin may serve to generate
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heat in response to lower skin temperatures by being metabolized. Certain bile acids that are lipophilic or “lipid loving,” aid in making lipids soluble. When lipids are ingested as food, bile salts secreted into the small intestine emulsify them and the pancreatic enzyme pancreatic lipase breaks the lipids into fatty acids, glycerol or mono- and diglycerides. There is some debate about how lipids pass through the intestinal wall whether as fatty acids or glycerol. However, lipids and fatty acids are not soluble in blood and therefore react to water soluble proteins in the blood and are carried as lipoproteins and triglycerides in the blood and lymph. Once in the blood, lipids are absorbed by liver cells to provide energy for cellular functions. The liver is responsible for providing the proper concentrations of lipids in
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This note was uploaded on 04/21/2008 for the course BIOL 100 taught by Professor Lee during the Winter '07 term at San Diego State.

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LipidPrint - Our bodies receive nearly all of the energy...

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