CHEMISTRY OF FOOD DIGESTION : Answer Key
1. Endergonic rxns require energy from an outside source to build bonds.
Exergonic rxns release energy overall
2. From eating food: the exergonic reactions of breaking the bonds of the macrmolecules
3. Life requires energy and nutrients at a very fast rate. The reactions alone, without a catalyst, would not occur quickly enough
4. Proteins
5. Many people circled the entire enzyme. Realize it is just the notched portion of the dark, bottom molecule (the enzyme).
6. pH, concentration, temperature
7. a – starches being broken into simple sugars: The graphed line is decreasing, indicating a decrease in Free Energy. Remember, “free energy” really means usable energy – potential energy that can be used – which is stored in the form of bonds. If the “free energy” is lowered, that means there are less bonds, which must mean the compound has gotten smaller.
8. Physical (mechanical) vs. Chemical (intracellular vs. extracellular would make sense too). Similar: Both break nutrients down to increase the surface area. Mechanical is just separation of macromolecules without breaking any bonds (remember that atoms are tiny). Chemical is breaking bonds of the compounds to yield smaller compounds (not really the individual atoms yet though).
9. Break down food into smaller parts so that it can be taken into our body to be used as energy in later reactions involving ATP.
10. Both are caused by acid creating pain in the stomach. The ulcer is caused by a bacterium which eats away at the lining of the stomach wall. Heartburn is caused by a weak cardiac sphincter, where acid gets into the esophagus.
11. Peristalsis
12. 1-3.5 (created by HCl). It becomes neutral in the S.I. because of the bicarbonate base that is secreted by the pancreas into the S.I. (Long story: the presence of acid in the S.I. triggers the cells there to make the hormone secretin which enters the blood stream, eventually reaching the pancreas to stimulate cells there to secret bicarbonate and other pancreatic juices).
13. Carbs à monosaccharides (glucose most important)
Fats à fatty acids and glycerol
Protein à polypeptides, then amino acids finally
14. Villi increase the surface area of the intestines. Greater area of absorption of nutrients
15. Large intestine; further break down material that we do not have enzymes for (even though this is past the area of major absorption). Also synthesize vitamin K for us which can be absorbed with the water that is absorbed in the LI
16. Lipids. No g.b. means less efficient usage of bile which aids (physically) in the breakdown of fats.
17. Constipation. Even though we can’t digest fiber (a carb), it is useful as a mass moving through out bodies. To aid peristalsis, large undigested masses will stimulate the stretch receptors in our passageways to increase peristalsis – help everything to move along – not staying too long in our L.I.
18. Insulin
19. mouth (chew), stomach (churn, acid shape change), liver/g.b. (b/c bile is a separator).
20. Mouth (carbs), Stomach (proteins), S.I. (carbs, proteins, lipids). Also, realize that the pancreas would be too because it secretes enzymes.
21. Small intestine (nutrients), large intestine (water)
22. Liver. Stored in gall bladder. The gall bladder has a little duct (tube) that joins with the pancreatic duct to become the common bile duct which enters the small intestine
23. stomach banding : less churning = less physical digestion (bigger chunks can’t be broken down as efficiently by enzymes as smaller chunks of food). Less time and area for pepsin to chemically digest proteins. Stomach and small intestine: in addition to above, less area for chemical digestion of all 3 nutrients in s.i. AND less area for actual absorption into body!
24. Kills bacteria that are the target BUT ALSO, kills good bacteria in our gut that make vitamins
25. small intestine
26. Of the ones we studied, pancreas
27. amylase (mouth), (pancreas/s.i.)
28. enzymes: lipase, pancreatic amylase, trypsin(ogen)
29. that we talked about: carbs (this is an evolutionary advantage – we need this the most)
30. chyme
31. hydrolysis
32. through the villi walls of the small intestine into the blood stream (ultimately these capillaries will merge and all nutrients will go to the liver for “sorting”
33. Once food is in the bloodstream (or at least crossed the cells of the sm.int. wall)
34. insulin à a cell receptor that allows glucose to enter the cells of the body.
Secretin à stimulated by the acidic chyme, it stimulates the pancreas to release pancreatic juices
Gastrin à stimulated by the presence of food in the stomach, it stimulates the cells of the stomach to secrete their gastric juices.
(NOT trypsin(ogen) or pepsin(ogen).