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1. The first stage of digestion is ingestion, when you take a bite of food. That food is broken up during the process of digestion, when large molecules are broken up into smaller components. The small components are more easily taken up into the bloodstream through the process of absorption. Finally, any indigestible material is passed out of the body through elimination.
2. Hydrolysis reactions break up macromolecules (protein, fats, nucleic acids, and large polysaccharides) into monomers.
3. The lining of the small intestine is highly folded, increasing its surface area. The higher the surface area, the faster the rate of nutrient absorption through the intestinal wall into the capillaries. The folds are called villi, each covered with cells with hair-like projections called microvilli.
4.
5. Mechanical digestion (such as chewing up food and bile’s emulsification of fat) is simply breaking up big pieces into little pieces; no covalent bonds are broken and no enzymes are used. Chemical digestion, on the other hand, is driven by enzymatic hydrolysis and covalent bonds are broken.
6.
1. k
2. j
3. e
4. f
5. i
6. g
7. h
8. a
9. c
10. d
11. b
7. The tiger is a carnivore, whose diet consists of mostly meat (and very little cellulose). Since the cecum plays a role in cellulose digestion, the tiger would have a small cecum. The rabbit, on the other hand, is an herbivore with an entirely plant-based diet. In order to help digestion, the rabbit would evolve to have a very large cecum.
8. Interesting poop trivia! About a third of your poop is composed of bacteria, and poop is brown because of pigments produced from the breakdown of red blood cells/hemoglobin/bile/bilirubin (any of these answers work!).
9. c. Starch begins digestion in the mouth (salivary amylase) and continues as it passes through the small intestine (pancreatic amylase).