Answer to Question 1
Food manufacturers blend fat with watery ingredients by way of emulsification. For example, salad dressings separate to form two layersvinegar (water) on the bottom, oil on top. Other dressings, such as mayonnaise, are also made from vinegar and oil, but they never separate. The difference lies in a special ingredient of mayonnaise, the emulsifier lecithin in egg yolks. Lecithin, a phospholipid, blends the vinegar with the oil to form the stable, spreadable mayonnaise.
Answer to Question 2
Fat provides the majority of the energy needed to perform much of the body's muscular work. Fat is also the body's chief storage form for the energy from food eaten in excess of need. The storage of fat is a valuable survival mechanism for people who live a feast-or-famine existence: stored during times of plenty, fat enables them to remain alive during times of famine. Most body cells can store only limited fat, but some cells are specialized for fat storage. These fat cells seem able to expand almost indefinitelythe more fat they store, the larger they grow. Adipose (fat) tissue secretes hormones that help to regulate appetite and influence other body functions in ways critical to health. Additionally, fats protect the internal organs from shock, cushioning them with fat pads inside the body cavity. Fats insulate against temperature extremes by forming a fat layer under the skin and form the major material of cell membranes. Lipids are converted to other compounds, such as hormones, bile, and vitamin D, as needed.
A simplified food web from an African savannah ecosystem
The clotting process (coagulation).
A severe food shortage occurred in the Netherlands during the “Hunger Winter” of 1944–1945.
Hormones in the Digestive Process
Cultural food preferences often influence food choices.
Food Labels Provide Nutrient Content Information