To emulsify fats usually means to mix them with water-based liquids and a binding substance like bile salts or other compounds, which has important implications for cooking and digestion.
The adage "oil and water don't mix" is based on the characteristics of hydrophobic versus hydrophilic interactions. Fats are hydrophobic, which means they appear to avoid water and instead form large globules when mixed with a water-based liquid. However, this happens not because the fat molecules actively avoid water, but because the water molecules prefer to bond with each other rather than with the fats.
Water is a "polar" molecule, and fats are "non-polar. Emulsify fat means that you change the environment so the fat and water molecules can mix together more easily. Typically this requires you to add a compound, known as an emulsifier, which can serve as a bridge between the fat and water molecules. Emulsifiers typically have one end that is polar and one end that is non-polar.
Emulsifiers can be found in egg whites , mustard, gelatin and skim milk, and they're important for making mayonnaise and other foods that combine fats and water-based liquids. Emulsification of fats is also a critical part of digestion. This is the reason that a high intake of fiber is recommended to decrease blood cholesterol.
Foods high in fiber such as fresh fruits, vegetables, and oats can bind bile salts and cholesterol, preventing their absorption and carrying them out of the colon.
If fat malabsorption persists the condition is known as steatorrhea. Before the prepackaged food industry, fitness centers, and weight-loss programs, our ancestors worked hard to even locate a meal. They made plans, not for losing those last ten pounds to fit into a bathing suit for vacation, but rather for finding food. Today, this is why we can go long periods without eating, whether we are sick with a vanished appetite, our physical activity level has increased, or there is simply no food available.
Our bodies reserve fuel for a rainy day. One way the body stores fat involves the body transforms carbohydrates into glycogen that is in turn stored in the muscles for energy. When the muscles reach their capacity for glycogen storage, the excess is returned to the liver, where it is converted into triacylglycerols and then stored as fat.
In a similar manner, much of the triacylglycerols the body receives from food is transported to fat storehouses within the body if not used for producing energy. The chylomicrons are responsible for shuttling the triacylglycerols to various locations such as the muscles, breasts, external layers under the skin, and internal fat layers of the abdomen, thighs, and buttocks where they are stored by the body in adipose tissue for future use.
How is this accomplished? Recall that chylomicrons are large lipoproteins that contain a triacylglycerol and fatty-acid core. Capillary walls contain an enzyme called lipoprotein-lipase that dismantles the triacylglycerols in the lipoproteins into fatty acids and glycerol, thus enabling these to enter into the adipose cells.
Once inside the adipose cells, the fatty acids and glycerol are reassembled into triacylglycerols and stored for later use. Muscle cells may also take up the fatty acids and use them for muscular work and generating energy.
As the body calls for additional energy, the adipose tissue responds by dismantling its triacylglycerols and dispensing glycerol and fatty acids directly into the blood. Upon receipt of these substances the energy-hungry cells break them down further into tiny fragments.
These fragments go through a series of chemical reactions that yield energy, carbon dioxide, and water. Learning Objectives Summarize the steps in lipid digestion and absorption. Explain how lipids are used for energy and stored in the body. From the Mouth to the Stomach The first step in the digestion of triacylglycerols and phospholipids begins in the mouth as lipids encounter saliva. Going to the Bloodstream As stomach contents enter the small intestine, the digestive system sets out to manage a small hurdle, namely, to combine the separated fats with its own watery fluids.
Chylomicrons contain triglycerides, cholesterol, and other lipids; they have proteins on their surface. Together, they enable the chylomicron to move in an aqueous environment without exposing the lipids to water. Chylomicrons leave the absorptive cells via exocytosis, entering the lymphatic vessels. From there, they enter the blood in the subclavian vein.
Vitamins can be either water-soluble or lipid-soluble. Fat-soluble vitamins are absorbed in the same manner as lipids. It is important to consume some amount of dietary lipid to aid the absorption of lipid-soluble vitamins. Water-soluble vitamins can be directly absorbed into the bloodstream from the intestine.
Learning Objectives Explain the processes of digestion and absorption. Key Points In the mouth, carbohydrates are broken down by amylase into maltose a disaccharide and then move down the esophagus, which produces mucus for lubrication, but no digestive enzymes.
In the duodenum, disaccharides are broken down into monosaccharides by enzymes called maltases, sucrases, and lactases; the monosaccharides produced are then absorbed into the bloodstream and transported to cells to be used in metabolic pathways to harness energy.
In the stomach, proteins are broken down into peptides, which are then broken down into single amino acids that are absorbed in the bloodstream though the small intestine.
Lipids are digested mainly in the small intestine by bile salts through the process of emulsification, which allows lipases to divide lipids into fatty acids and monoglycerides. Monoglycerides and fatty acids enter absorptive cells in the small intestine through micelles; they leave micelles and recombine into chylomicrons, which then enter the bloodstream.
Fat-soluble vitamins are absorbed in the same manner as lipids; water-soluble vitamins can be directly absorbed into the bloodstream from the intestine. Key Terms chemical digestion : The process of enzymes breaking down food into small molecules the body can use.
Digestion and Absorption Digestion is the mechanical and chemical break down of food into small organic fragments. Carbohydrates The digestion of carbohydrates begins in the mouth. Starch and glycogen are broken down into glucose by amylase and maltase. Sucrose table sugar and lactose milk sugar are broken down by sucrase and lactase, respectively.
Protein A large part of protein digestion takes place in the stomach. Proteins are absorbed into the blood stream by the small intestine.
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