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1 Biology 12 DIGESTIVE SYSTEM ASSIGNMENT Part I. Vocabulary and Question Assignment 1. Explain why digestion of food in humans is called an extracellular process? Extracellular means outside the cell. Humans produce digestive enzymes inside cells but then secrete them into ducts or organs. Therefore, digestion occurs outside the cells (unlike single celled organisms like amoebas that use phagocytosis to engulf their food 2. What are the functions of the digestive system? To breakdown food, absorb nutrients and eliminate waste Mouth. 3. Distinguish between chemical and mechanical digestion. How is food mechanically digested in the mouth? Mechanical breaks food into smaller pieces while chemical actually changes the chemical composition of the substrate. Teeth…teeth mechanically break down food 4. Why is salivary amylase classed as a hydrolytic enzyme? It uses water to actually break apart the bonds and then OH- and H+ becomes part of the resulting products 5. Once again, what is the role of water in the digestion of starch or any nutrient polymer? Be specific…think biomolecules See above Pharynx 6. Identify the need for an epiglottis. It prevents food from going down the trachea (air pipe) Esophagus 7. Explain the term peristalsis. Is it a voluntary process? It is INvoluntary muscle contractions that pushes food down the esophagus 2 8. Where else does peristalsis occur in the digestive system? Why would peristalsis be a rather slow-acting set of muscle contractions in other parts of the digestive system? Stomach (churning), small intestine, lg intestine, rctum Slow process to allow for maximum nutrient absorption 9. Describe the structure and operation of a sphincter. Name the sphincter separating the stomach and esophagus Circular muscle will contract/ relax to allow food into the next part of the digestive system…cardiac sphincter Stomach 10. How is food mechanically digested in the stomach? churning 11. List 3 roles of HCl in the stomach. #1 Denature/ unravel proteins into polypeptides #2 Activate pepsinogen into pepsin #3 Create a pH 1.52.5 which is ideal for pepsin to work (basically a different way of saying #2) 12. What is meant by the term acid chyme? This implies a certain composition of food. Starch has started to breakdown into maltose, protein has started to breakdown into peptides and it would be acidic due to the HCl 13. Name the sphincter that separates the stomach and small intestine. pyloric 14. What enzyme is present in the stomach? What is its inactive form called? Pepsin…pepsinogen Small Intestine 15. 16. Would the emulsification of fat by bile salts be an example of chemical or physical (mechanical) digestion? Explain. Physical…just creates smaller droplets of fat What is the benefit of sodium bicarbonate (NaHCO3), being secreted by the pancreas into the small intestine? It neutralizes the acid pH coming from the stomach. Creates optimal pH for enzymes that work in the small intestine 3 17. What is the role of pancreatic juice? Water…transport of nutrients and to participate in hydrolysis Sodium bicarbonate…see above Trypsin, lipase, pancreatic amylase- all hydrolytic digestive enzymes 18. Insulin is made by the pancreas and secreted into the blood, not the intestine. Explain its importance to the body. Insulin will bind to liver protein receptors to cause glucose channels to open. Glucose enters liver and stores as glycogen. This will lower the blood sugar What is the general role of enzymes secreted from the duodenum? Hydrolytic enzymes used to catalyze chemical reactions (digestion) Why are ALL digestive enzymes described as hydrolytic? They use water to breakdown their substrates List 6 major roles of the liver. BRSPUD Bile production Red blood cell breakdown Blood sugar regulation Blood protein production Urea production Detoxification of the blood 19. 20. 21. Large Intestine 22. 23. 24. 25. What are the functions of the colon (= large intestine)? Conservation of water Fiber can help prevent constipation, explain how. Fibre holds onto water and prevents too much water being absorbed into the body What is the value of bacteria found in the large intestine? Breaks down indigestible material and releases vitamin K Explain what would happen to cause a person to have diarrhea Infection, food intolerance or stress can cause rapid contractions of the smooth muscle. This prevents water from being absorbed into the blood and is instead eliminated 4 Organ/Region PH Substrate Enzyme Origin of Enzyme Product or Products Mouth Starch Salivary amylase Salivary glands maltose Stomach Polypeptides Pepsin Stomach (gastric cells) peptides Small Intestine Duodenum (lumen) 8.0 Lipid (bile) lipase pancreas fatty acids and glycerol Small Intestine (sodium bicarbonate) 8.0 peptides Trypsin pancreas Smaller peptides Small Intestine 8.0 Starch Amylase Pancreas Maltose Small Intestine 8.0 (Smaller) Peptides Peptidase Small Intestine Amino Acids Small Intestine 8.0 Sucrose Sucrase Small intestine Fructose and Glucose Small Intestine 8.0 Maltose Maltase Small intestine glucose and glucose Absorbed by villus Small Intestine 8.0 Lactose Lactase Small Intestine Galactose and glucose