Explain the processes that fat molecules undergo starting from the duodenum until it is finally used by body cells.
Answer:
• Lipid digestion begins in the duodenum.
• Bile salts produced by the liver emulsify fats into lipid droplets.
• Pancreas secretes pancreatic juice which contains lipase into the duodenum.
• Lipase hydrolyses lipid droplets to fatty acids and glycerol.
• Lipid + water → Glycerol + fatty acids
• Absorption of fatty acids and glycerol occurs in the small intestine.
• In the epithelial cells of villi, the condensation of fatty acid and glycerol forms lipid.
• Lipid droplets are absorbed into the lacteals of villi.
• Lipid is transported from the lacteal by the lymphatic system into the thoracic duct and finally enters the blood flow through the left subclavian vein.
• Assimilation occurs in the cells.
• Cells use lipids to form the complex compounds of the plasma membrane.
A teenager had the following for his breakfast.
Explain what happens to the final digested products of his breakfast in his body cells.
Answer:
• Bread contains carbohydrate. The digestion of carbohydrate produces glucose.
• Glucose is transported to body cells and the liver to be oxidised during cellular respiration to yield energy.
• Excess glucose is converted into glycogen for storage.
• The final product of butter is fatty acids and glycerol.
• Lipid is oxidised to produce energy.
• Some of the lipids are stored in adipose tissues.
• The final product of proteins (egg and milk) is amino acids.
• Amino acids are carried to body cells for enzyme synthesis and repair of damaged tissues.
• Apple and milk provide vitamin and mineral salts.
• Vitamins such as vitamin B are used as cofactors. Generally, vitamins and mineral salts maintain optimum health.
• Apple also provides undigested fibre that facilitates defaecation.