DIGESTION - WORKBOOK

Transcription

1 1. What is digestion? DIGESTION - WORKBOOK The physical and chemical breaking down of food into molecules small enough to move through intestinal cells. 2. What is the difference between digestion and absorption? Digestion is the breaking down of large molecules into smaller ones. Absorption occurs after digestion, and involves these small molecules moving across cell membranes and into the blood stream or lymph. 3. Compare the composition of the food we eat with the molecules that our cells actually use. Food is a mixture of large macromolecules of proteins, fats, nucleic acids, and polysaccharides. Our cells actually only use the small molecules which make up these macromolecules (amino acids, glucose, nucleic acids, glycerol, fatty acids). 4. How many teeth do adults have? What are the four types of teeth and their function? Adults have 32 teeth. Incisors for biting, canines for tearing, pre-molars for grinding, and molars for crushing. 5. What is a hydrolytic enzyme? What is the enzyme in saliva? What reaction does it catalyze? An enzyme that reacts water with a substrate to break it down. The enzyme in saliva is SALIVARY AMYLASE. It breaks starch down into the disaccharide MALTOSE. 6. Using a labeled diagram, explain why when you swallow food or liquid, it doesn't usually go up your nose and down your windpipe. The soft palate covers nasopharyngeal openings The trachea moves up and under the epiglottis PERISTALTIC waves move food down to the esophagus The soft palate keeps food from going up your nose and the epiglottis stops food from going down the trachea (wind pipe) 1

2 7. Describe the process of peristalsis in the esophagus. How can a combination of circular and longitudinal muscles cause this action? Circular muscles squeeze tubes, longitudinal muscles contract tubes to move food bolus along in a sequential fashion. 8. What are the functions of the stomach? Receives and temporarily stores food to be digested. Churns food to mechanically break it down, and produces pepsin which breaks proteins into peptides 9. What is gastric juice? Where is it produced? What is it composed of? What does it do? A digestive juice containing enzymes, and which is produced by glands in the stomach mucosal lining. Contains pepsinogen and HCl. Pepsinogen and HCl combine to produce Pepsin, a hydrolytic enzyme that breaks proteins into peptides 10. Give a one sentence description, using your own words, of the function of the following digestive components: Name Function 1. mouth receive and chew food, moisten with saliva, and start to digest starch. 2. pharynx Passageway for both air and food, leads to esophagus. 3. epiglottis Cover opening to larynx when swallowing. 4. cardiac sphinctor Muscle that encircles the esophagus at the stomach junction. Allows food into stomach, and also prevents constant vomiting. 5. esophagus Moves food from mouth to stomach through peristaltic action. 6. pepsinogen Protein precursor to pepsin, reacts with HCl to form pepsin. 11. How come, if your stomach is full of acid and protein-digesting enzymes, doesn't it digest itself? Thick mucus layer secreted by stomach wall protects it. 2

3 12. a) Majority of digestion takes place in this organ: The small intestine b) Structure of this organ: Long and convoluted b) Length of this organ: Very long / ~7m c) Three parts of this organ are called: duodenum, jejunum, and ilium 13. a) Length of the duodenum: A few inches b) What controls flow of material into the duodenum? Pyloric sphincter c) What is this material that enters the duodenum called? Chime / Chyme d) What is main role of duodenum in digestion? Inserts enzymes (amylase, trypsin, lipase, and nuclease), bile, and sodium bicarbonate (to neutralize acidic chime). e) What two organs produce secretions that end up in duodenum? Liver (gallbladder) and the pancreas 14. a) Liver produces what substance? Bile b) Where is this substance stored? The gall bladder 15. What does bile do? Bile emulsifies fat. Breaking large fat droplets into smaller fat droplets (mechanical) 16. a) What compound does pancreatic juice contain? Sodium Bicarbonate b) What does this substance do? It neutralizes the acidic chime. From ph 2 or 3 to ph 8 or 9 c) What 3 important enzymes does pancreatic juice contain (name and function)? Pancreatic Amylase: starch à maltose Trypsin: Protein à peptides Lipase: Lipids à fatty acids and glycerol 3

4 17. a) What produces the intestinal juices in the small intestine? Intestinal crypts or Intestinal glands b) Where are these glands located? Within/beside villi in the sm. Intestine (ilium and jejunum) c) Two important intestinal juice enzymes and their functions are (name and function): Maltase: Maltose à glucose Peptidase: Peptides à amino acids Nuclease: Nucleic acids à nucleotides 18. a) Draw a villus, and show the blood and lymph vessels within. 19. a) Where does absorption take place? Absorption of nutrients mainly in ileum, but jejunum too. Absorption of water in the lg. intestine. b) Where do sugars and amino acids go? Into your blood stream c) Where do glycerol and fatty acids go? Into the lacteal in your lymph system 4

5 20. List 6 functions of the liver Production of bile Glucose à Glycogen, and back again Destruction of old RBC Storing iron and vitamins Making plasma proteins Producing urea (from ammonia) Detoxifying metabolic wastes 21. Explain how the large intestine is structurally and functionally different from the small intestine. The large intestine is shorter and pouchier then the small intestine, and does not contain villi. The large intestine absorbs water from the stool and contains e.coli. This e.coli eat undisgestable food (such as fiber) and produces vitamins aa s and growth factors. The small intestine is long and convoluted, containing many villi for large surface area. The small intestine secrets enzymes into the intestinal tract and absorbs nutrients into the blood and lymph system. 22. What are the three main types of hormones regulating the digestive process? What do the do? DID NOT HAVE TO DO THIS QUESTION Gastrin High concentrations of protein in stomach cause release of gastrin Gastrin causes the stomach to release gastric juices Secretin and Cholecystokinin (CKK) Acid in duodenum (from chime), release Secretin. Fats release CKK These hormones cause increased secretions of pancreas and liver. 23. Trace the path of the blood from the small intestine to the heart. Small intestine à hepatic portal vein à liver à hepatic vein à vena cava à heart 5

6 Using the diagram above explain the following: 24) What does your body do when it senses a high blood sugar level? High blood sugar (glucose) stimulates your pancreas to release insulin. The insulin travels in your blood stream signaling your tissue cells to become more permeable to glucose (glucose is taken up by cells). Insulin also signals for the liver to convert glucose into glycogen for storage. This all helps to lower you bodies blood glucose levels. 25) What does your body do when it senses a low blood sugar level? Low blood sugar (glucose) stimulates your pancreas to release glucagon. This glucagon travels in your blood stream to your liver were it stimulates the liver to breakdown glycogen and release glucose into the blood. This increases your bodies blood glucose levels. 6

7 DIGESTO-MAN Draw and label all the digestive parts and enzymes Note: some descriptions are different in this diagram (enzymes called different things) 7