Download Answers to Mastering Concepts Questions

Answers to Mastering Concepts Questions
Chapter 34
34.1
1. It is partly true that you are what you eat because some of the molecules in your food become
incorporated into your body’s cells and tissues.
2. When an animal eats, food undergoes ingestion, digestion, absorption, and elimination.
3. Herbivores eat only plants. Carnivores eat other animals. Detritivores eat decomposing organic
matter. Omnivores eat a broad variety of foods.
4. Animals obtain nutrients in the following different ways:
- bulk feeders swallow entire meals;
- fluid feeders drink their meals;
- substrate feeders live within their food and eat it from the inside;
- deposit feeders strain partly decayed organic matter from sediments;
- filter feeders strain their food from water.
34.2
1. Digestive enzymes break large food molecules into chemical units that are small enough to be
absorbed across a cell membrane.
2. Intracellular digestion happens in food vacuoles of individual cells. Extracellular digestion
happens in body cavities.
3. One limitation of an incomplete digestive system is that the mouth is used for ingestion and
expelling wastes. This arrangement minimizes the potential for specialization. In addition, wastes
from one meal must be expelled before the animal can eat again.
4. A cow is a ruminant herbivore. Its digestive system includes a four-chambered stomach. Its
first chamber is a rumen where plant matter is fermented. The cow’s digestive system also
includes a long small intestine, large cecum where plant matter is fermented, and a relatively long
large intestine. A chipmunk is a nonruminant herbivore with relatively long intestines and a fairly
large cecum. A wolf is a carnivore. Its digestive system has short intestines and a small cecum.
34.3
1. Peristalsis is the wave of muscular action of the digestive tube that moves food along its
length. Sphincters open either voluntarily or by peristalsis to allow food in or out of the digestive
tube and its organs.
2. The teeth, tongue, and salivary glands are mouth structures that participate in digestion. In the
throat, the esophagus and epiglottis take part in digestion.
3. Mechanical digestion of food in the stomach mixes chewed food with stomach acids, gastric
juices, and pepsin. Chemical digestion of proteins (by pepsin) begins in the stomach.
4. The small intestine maximizes surface area because the inner surface of the small intestine is
folded into finger-like villi that absorb digested food. In addition, the surface of each villus has
hundreds of microvilli that also greatly increase the surface area for absorption.
5. The products of digestion of carbohydrates are monosaccharides. Proteins are digested to
amino acids. Fats are digested to produce fatty acids and monoglycerides. Nucleic acids are
digested to produce nitrogenous bases, sugars, and phosphates.
6. As food passes through the large intestine, water, salts, and minerals are absorbed from
chyme. Cellulose, bacteria, and intestinal cells collect in the rectum as feces. When the rectum is
full, receptor cells trigger a reflex that eliminates feces through the anus.
7. The pancreas secretes sodium bicarbonate that raises the pH of chyme so that pancreatic
enzymes in pancreatic juice can digest small polypeptides, small polysaccharides, nucleic acids,
and emulsified fats. Bile, produced by the liver and stored in and released from the gallbladder,
emulsifies fats, making them better targets for lipases to digest to fatty acids and monoglycerides.
34.4
1. Food labels contain nutritional information about the macro- and micronutrients in a food and
its calorie content.
2. Essential nutrients include carbohydrates, proteins, and fats (the macronutrients), as well as
minerals such as calcium and potassium. Vitamins also are essential in the human diet.
3. Indigestible fiber provides bulk and eases movement of food in the digestive tract. Fiber also
reduces blood cholesterol and helps to regulate blood sugar.
4. Scientists measure the calorie content of food by burning it in a bomb calorimeter and
measuring how much the food raises the temperature of the water that surrounds the device.
5. Body mass index is a measure that divides a person’s weight in kilograms by his or her height
in squared meters.
6. After day 1 without food, sugar and glycogen reserves are gone, and the body begins breaking
down stored fat and muscle protein. At day 3, hunger eases as the body depletes fat reserves.
After this, metabolism slows, blood pressure drops, pulse slows and chill sets in. Still later, skin
becomes dry and hair falls out. Antibodies are dismantled, and the body has no protection from
infection. Mouth sores, anemia, and irregular heartbeat ensue. Bones begin to degenerate.
Finally, the person becomes emaciated, blind, and deaf.
7. Obesity is caused by a person eating more Calories than he or she uses. A diet high in sugar
and fat and an inactive lifestyle lead to obesity, as do genes. Obesity is related to type II diabetes,
high blood pressure, atherosclerosis, congestive heart failure, acid reflux disease, urinary
incontinence, low back pain, stroke, sleep disorders, and cancers of the colon, breast, and uterus.