BIOLOGY 12: CHAPTER 12 - REVIEW WORKSHEET KEY DIGESTIVE SYSTEM A. CHAPTER REVIEW 1. i) Ingestion = food is taken in, mechanically and chemically digested ii) Digestion = extracellular of breaking down food so it can be absorbed iii) Absorption = cells take up small molecules iv) Elimination = indigestible materials pass out of digestive compartment 2. The skeletal muscle and the taste buds of the tongue contribute to the formation of the bolus. Lips & cheek = enclose mouth. Taste buds = sense of taste, sends electrical impulses to brain when food is present Roof of mouth = separates oral cavity from nasal cavity above Tonsils = protect against infection Salivary glands = provide salivary amylase to break down starch into maltose 3. The soft palate/uvula blocks the nasal cavity, while the epiglottis prevents food from entering the trachea. 4. starch + H2O salivary amylase maltose 5. The opening to the larynx is called the glottis, which is covered when the trachea moves up by the epiglottis. 6. a) i) Mucosa (mucous membrane layer) = secretes digestive enzymes & mucus ii) Submucosa (submucosal layer) = loose connective tissue that has blood vessels & lymph vessels iii) Muscularis = 2 layers of smooth muscle for peristalsis; inner circular muscle is covered by outer longitudinal muscle iv) Serosa (serous membrane) = very thin membrane that secretes serous fluid which lubricates organs of abdominal cavity, so slide against each other instead of sticking b) Label the layers in the diagram. 1
7. Peristalsis. 8. Caused when gastric juice from stomach escapes upward into esophagus. 9. Expands to store food (2L), secretes (3L a day) gastric juices and mixes it with food to digest it, absorbs alcohol. Chime is a soupy nutrient broth that is made from churning food b/w 2-6 hours ready to leave stomach. 10. Ulcer = open sore in lining of stomach; frequently caused by bacterial infection. 11. Write the chemical reaction that occurs in the stomach. protein + H2O pepsin peptides 12. Digestion of all 4 biological molecules and absorption of nutrient monomers. Converts maltose into glucose, peptides into amino acids, nucleotides into base+sugar+phosphate, fat droplets into fatty acid + glycerol. Sodium bicarbonate neutralizes the acidity of chime. 13. fat bile salts fat droplets starch + H2O pancreatic amylase maltose protein + H2O trypsin peptides fat droplets + H2O nucleic acid + H2O lipase nuclease nucleotides fatty acids + glycerol 2
14. Villi in the small intestine are finger-like projections on the wall that is supplied by blood capillaries and lacteals. Microvilli are microscopic appendages on the epithelial cells of the villi to increase surface area. 15. maltose + H2O maltase glucose peptide + H2O peptidase amino acid nucleotide + H2O nucleosidase base + sugar + phosphate 16. Small nutrient monomers are absorbed through mainly active transport as well as facilitated diffusion, they enter the vessels of the villus (blood capillaries and lacteal). 17. Absorbs water, salts, and vitamins; temporarily stores indigestible material. Wider than small intestine, but shorter than small intestine. 18. a) Which associate organ of the large intestine plays a role in immunity? Appendix b) What is the term used to refer to the inflammation of this organ? Appendicitis c) What is the term used to refer to surgical removal of this organ? Appendectomy 19. Over 99% of bacteria in the colon are classified as anaerobic, because they die in the presence of oxygen. 20. Bacteria in the large intestine break down indigestible material and produces vitamins. HIGH coliform(non-pathogenic intestinal) count in lake water means that there is a significant amount of feces in the water, which means there is a greater possibility that disease-causing bacteria is also present. 21. Food poisoning can cause diarrhea by irritating the intestinal wall from eating contaminated food. Nerve stimulation can cause diarrhea as nervous stress stimulates intestinal walls to increase peristalsis. Dangerous to a person s health because can dehydrate body of water, and water loss can cause imbalance of salt in blood, which affects heart contraction. 22. Makes stool slippery so it can slide through more easily. 23. Exocrine function = secretes pancreatic juice via pancreatic duct. 24. Endocrine function = secretes hormones insulin and glucagon directly into bloodstream. Insulin is secreted when glucose in blood is HIGH, glucagon is secreted when blood glucose is LOW. 25. Bile = bile pigment bilirubin (yellow-green color), and bile salts (derived from cholesterol); produced in liver, and stored in gallbladder. 3
26. As blood passes through liver, it removes the poisonous substances and detoxifies them. Also removes nutrients and works to keep blood contents constant. 27. Deamination = to break down excess amino acids. Excess amino groups are deaminated to glucose and urea in the liver. Excreted by kidneys. Write out the reaction of urea production. 2NH3 + CO2 NH2 C NH2 Ammonia ll O Urea 28. Liver produces bile fat emulsification; acts as gatekeeper b/w blood and food; detoxifies blood by removing & metabolizing poisonous substances; stores iron & vitamins A, D, E, K; makes plasma proteins; maintains blood sugar at 0.1%; deaminates excess amino acids to glucose & urea; removes worn-out RBC s; regulates blood cholesterol. 29. Haemolytic jaundice = RBC s have been broken down in abnormally large amounts. Obstructive jaundice = bile ducts are blocked or liver cells are damaged. 30. Hep A = usually from fecal-contaminated drinking water. Hep B = usually from sexual contact, or spread by blood transfusions/ contaminated needles. Hep C = usually from contact with infected blood. 31. Lactose intolerance = these people do not produce enzyme lactase to break down lactose. Drinking milk will cause them to have diarrhea, gas, cramps. 32. Nutrient = monomers the body requires to function. Balanced diet = bulk should be grains, vegetables & fruits, minimal meat and fats & sweets should be eaten sparingly. 33. Essential amino acid = amino acids the body CANNOT produce. Complete protein source = source that provides all 20 aa s like meat. Incomplete protein source = source that by itself, supplies us with aa s but does not have at least one essential aa. 34. Simple carbs = empty calories b/c only contribute to energy needs and weight gain w/o supplying any other nutritional requirements. 35. Insoluble fibre = has laxative effect, and may guard against colon cancer by limiting time cancer-causing substances are in contact with intestinal wall. Soluble fibre = combines w/ bile acids and cholesterol in intestine and prevents them from being absorbed. 36. i) Choose poultry, fish or dry beans and peas as protein source. ii) Broil, boil or bake rather than frying. iii) Eat non-fat or low-fat foods. iv) Limit intake of butter, cream, hydrogenated oils, shortenings, and tropical oils (coconut and palm oils) 4
37. LDL is bad b/c carries cholesterol from liver to body cells. HDL is good b/c carries cholesterol to liver, which converts it to bile salts. 38. Vitamins = organic compounds that body cannot produce in adequate amounts, needed as parts for coenzymes in metabolic pathways. 39. Harm body by donating extra electron to DNA, proteins, enzymes, or lipids found in PM; donations most likely damage cellular molecules, thereby leading to disorders, perhaps even cancer. 40. Body uses vitamins C, E, and A, or antioxidants to defend against free radicals. 41. Osteoclasts are more active than osteoblasts = osteoporosis. Women can i) consume more calcium and other vitamins daily ii) Estrogen replacement therapy and exercise iii) Stop drinking more than 9 cups of caffeinated coffee per day and smoking B. COMPLETION AND SHORT ANSWER QUESTIONS 1. The stomach is directly connected to the esophagus above and the small intestine (2 words) below. 2. The major food molecule digested in the stomach is proteins, which is hydrolyzed by the enzyme pepsin. The enzyme s inactive form is called pepsinogen. 3. Among its chemical aspects, every digestive enzyme has a preferred ph. 4. Before fats are digested by the enzyme lipase, they are first emulsified by bile salts. 5. Pancreatic juices enter the small intestine (duodenum) by way of the pancreatic duct and contain digestive enzymse for the digestion of EVERY type of food. 6. The liver first receives the products of digestion by means of the hepatic portal vein; any excess glucose is stored as glycogen. 7. The secretion of digestive juices is controlled generally by both hormones and the nervous system. 8. Surface area in the small intestine is increased greatly by the presence of villi and microvilli. 9. There are 8 essential amino acids required by adults. 10. There are 2 essential fatty acids required by adults. 5
11. Complete the following table. HORMONE PRODUCTION SITE TRIGGER/CAUSE OF RELEASE AFFECTED ORGAN(S) ACTION OF AFFECTED ORGAN GASTRIN Gastric glands protein Stomach Secretion of gastric juice (pepsin & HCl) Duodenal wall Secretion of gastric juice Stomach, small intestine Inhibits gastric juice secretion SECRETIN Duodenal wall Acid (HCl) Pancreas Pancreatic Juice (enzymes) Duodenal wall Protein and Fat Pancreas, gall Enzymes & Bile bladder GASTRIC INHIBITORY PEPTIDE (GIP) CHOLECYSTOLKININ (CCK) 12. Vitamins are portions of coenzymes, which are necessary for cellular metabolism. 13. Answer the following questions about the digestive tract. a) In which part of the digestive tract are nutrient molecules absorbed? Small intestine. b) The absorbed nutrient molecules enter what vein associated with the liver and intestine? Hepatic portal vein. c) In which specific part of the digestive tract does pancreatic juice enter? Duodenum. d) In which specific part of the digestive tract does bile enter? Duodenum. e) The three accessory organs that do NOT contain food are the pancreas, liver, and gall bladder. f) What parts of the digestive tract do NOT have ducts entering them and do NOT secrete digestive juices? Esophagus and Large Intestine. 14. Carbohydrate Digestion (starch) Starch digestion begins in the mouth, Here, the ducts empty saliva from the salivary glands. There are three pairs of these glands, named parotid glands, sublingual glands, and submandibular glands. The saliva from these glands contains the enzyme salivary amylase, and this enzyme breaks down starch to the disaccharide maltose. Starch will continue to be broken down in the small intestine. Here, a duct empties from the pancreas. Pancreatic juice contains the enzyme pancreatic amylase, which breaks down starch to the disaccharide maltose. Starch digestion is completed when this disaccharide is broken down to glucose, a monosaccharide that can be absorbed by intestinal villi. The enzyme 6
that converts maltose to glucose is called maltase, and this enzyme is secreted by epithelial cells of the intestinal villus. 15. Protein Digestion (meat) Protein digestion begins in the stomach. The gastric glands line the wall of the stomach. They secrete the enzyme pepsinogen, which is converted into its active form pepsin by hydrochloric acid; this enzyme breaks down protein into peptides. In the pancreas (gland), another enzyme called trypsin acts on protein in the small intestine breaking down protein into peptides. Protein digestion is completed when peptides are broken down to amino acids, molecules small enough to be absorbed by intestinal villi. This is achieved by the enzyme peptidase, which is produced by the epithelial cells of the intestinal villus. 16. Fat Digestion (butter) Fat is first emulsified by bile, a substance made by the liver and stored in the gall bladder (gland). The secretions in this gland enter the small intestine by way of the bile duct. After the fat has been emulsified, it is broken down by the enzyme lipase, which is found in pancreatic juice. Fats are broken down to glycerol and fatty acids, molecules small enough to be absorbed by intestinal villi. After resynthesis (~repackage) into lipoprotein droplets, fats enter the lacteals, which are part of the lymphatic system. 17. Path of Food. a) Food consists of the large organic molecules proteins, carbohydrates and fats. In the mouth, the only type of food digested are carbohydrates (starch) The mouth has a neutral ph of 7. The food passes down the long tube called the esophagus. A rhythmic contraction called peristalsis pushes the food along. b) After passing through a sphincter (circular muscle), the food enters the stomach. Here the primary food acted on is proteins. This organ has a(n) acidic ph of 2. The food is now called chyme which passes through another sphincter into the duodenum, which is the first section of the small intestine. 7
c) Two ducts enter this organ; they are the common bile duct from the gallbladder and the pancreatic duct from the pancreas. Bile contains an emulsifier that divides fat into fat droplets. Pancreatic juice contains enzymes that act on carbohydrates, proteins and fats. Lining the walls of the intestine are villi with microvilli on the apical surface of each cell. The epithelial cells produce enzymes that finish digestion by converting maltose to glucose and peptides to amino acids. Thus the small nutrient molecules that are absorbed by villi are amino acids and sugars, which enter the hepatic portal vein. Glycerol and fatty acids enter the lacteals. d) The hepatic portal vein takes the nutrients to the liver, an organ of homeostasis. For example, this organ stores glucose as glycogen and always keeps the blood glucose level constant. This organ can also remove amino groups from amino acids and convert the amino groups to urea a nitrogenous waste product. 18. What happens to a person who takes in more calories/energy than needed? Weight gain. C. DIGESTIVE ENZYME ACTIVITY For each combination of substances below, decide whether digestion will or won t occur. If it does not, provide a reason why. (Hint: remember to consider optimum ph of the enzyme) 1. trypsin, NaHCO3, egg white - warm gently Yes 2. salivary amylase, water, egg white warm gently No, wrong substrate. 3. pepsin, HCl, egg white freeze No, wrong temperature. 4. pancreatic amylase, HCl, starch heat to boiling No, wrong ph and temperature. 5. lipase, NaHCO3, fats warm gently No, bile salts are absent. 6. maltase, HCl, maltose warm gently No, wrong ph. 7. peptidases, fat, HCl warm gently No, wrong ph and substrate. 8
8. pepsin, HCl, egg white warm gently Yes. 9. trypsin, starch, water warm gently No, wrong substrate and ph. 10. HCl, egg white, water, warm gently No, needs enzyme pepsin. 9