Distinguish between autotrophic and heterotrophic nutrition. (b) What role does the liver and pancreas play in: (i) Food digestion (ii) Metabolism of absorbed products (c) State the fate of the end products of liquid digestion

a) • Autotrophic nutrition is a mode of nutrition where organisms produce their own food from simple inorganic substances (like carbon dioxide and water) using light energy (photosynthesis) or chemical energy (chemosynthesis). Examples include plants and algae. • Heterotrophic nutrition is a mode of nutrition where organisms obtain food by consuming other organisms or organic matter, as they cannot synthesize their own food. Examples include animals, fungi, and most bacteria. b) i) Role of the liver and pancreas in food digestion: • Liver: Produces bile, which is stored in the gallbladder. Bile is released into the small intestine where it emulsifies fats, breaking large fat globules into smaller ones. This increases the surface area for the action of lipase enzymes. • Pancreas: Produces pancreatic juice, which contains a variety of digestive enzymes, including pancreatic amylase (for carbohydrates), pancreatic lipase (for fats), and proteases like trypsin and chymotrypsin (for proteins). It also produces bicarbonate to neutralize the acidic chyme from the stomach, creating an optimal environment for these enzymes. ii) Role of the liver and pancreas in metabolism of absorbed products: • Liver: Plays a central role in metabolizing absorbed nutrients. It converts absorbed monosaccharides (like fructose and galactose) into glucose, stores excess glucose as glycogen (glycogenesis), and can release glucose from glycogen (glycogenolysis). It also synthesizes and breaks down lipids and proteins, deaminates amino acids, and forms urea for excretion. • Pancreas: Its endocrine function involves producing hormones insulin and glucagon from the islets of Langerhans. Insulin promotes the uptake of glucose by cells and its conversion to glycogen or fat for storage, thus lowering blood glucose. Glucagon stimulates the liver to release stored glucose, raising blood glucose levels. These hormones are crucial for regulating the metabolism of absorbed carbohydrates. c) The end products of lipid digestion are fatty acids and glycerol. These are absorbed into the epithelial cells of the small intestine. Inside these cells, they are re-esterified to form triglycerides. These triglycerides are then packaged with cholesterol and proteins into lipoprotein particles called chylomicrons. The chylomicrons are too large to enter the capillaries directly, so they are absorbed into the lacteals (lymphatic capillaries) within the intestinal villi. From the lacteals, they travel through the lymphatic system and eventually enter the bloodstream via the thoracic duct, delivering lipids to various body tissues for energy or storage. What's next?