SECTION C: LONG ANSWER QUESTIONS [30 MARKSI 16. Discuss the physiological functions of dietary fibres in human health 17. Classify the lipids and describe their functions 18. Explain selenium as non-metallic element in human nutrition. [15 Marks [15 Marks [15 Marks

<br /> 16. Dietary fibers play several important roles in human health. They are found in plant-based foods and are not digested by the human body. Instead, they pass through the digestive system relatively intact, providing bulk and aiding in regular bowel movements, which helps prevent constipation. Additionally, dietary fibers can help lower blood cholesterol levels by binding with bile acids in the intestine, which are then excreted. This process forces the body to use up more cholesterol to produce more bile acids, thereby reducing the level of cholesterol in the blood. Furthermore, fibers can slow the absorption of sugars, helping to control blood sugar levels, which is particularly beneficial for individuals with diabetes. <br /> 17. Lipids are a diverse group of organic compounds that are insoluble in water but soluble in nonpolar solvents. They can be classified into several categories: <br /> a. Triglycerides: These are the main form of stored energy in animals and humans. They are composed of one glycerol molecule bonded to three fatty acid chains. <br /> b. Phospholipids: These are major components of cell membranes. They have a phosphate group in their structure, which makes them attracted to water (hydrophilic), while the fatty acid tails are repelled by water (obic). This unique structure allows them to form bilayers in cell membranes, providing a barrier between the cell's internal and external environments. <br /> c. Steroids: These are characterized by a core structure of four fused carbon rings. They play various roles, including serving as hormones (like testosterone and estrogen) and contributing to cell membrane structure (like cholesterol). <br /> d. Waxes: These are long-chain fatty acids esterified to long-chain alcohols. They are used by many organisms to coat surfaces, providing protection and reducing water loss. <br /> Each class of lipids has specific functions in the body, including energy storage, structural roles, and signaling. <br /> 18. Selenium is a non-metallic element that plays a crucial role in human nutrition. It is an essential trace mineral that is incorporated into proteins to make selenoproteins. These selenoproteins have various functions, including antioxidant activity, thyroid hormone metabolism, and immune function. One of the most well-known roles of selenium is its involvement in glutathione peroxidase, an enzyme that helps protect cells from oxidative damage by reducing hydrogen peroxide and organic hydroperoxides. Selenium is vital for maintaining the integrity of cell membranes and preventing cellular damage caused by free radicals. The recommended dietary allowance (RDA) for selenium varies by age, sex, and life stage, but it is generally around 55 micrograms per day for adults. Foods rich in selenium include nuts, seeds, meat, and fish.