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Chapter 21

Mastering Biology
Which of the following statements regarding animals is false?
Animals that extract food particles suspended in the surrounding water are called fluid feeders.
Digestion is the
breaking down of food into molecules small enough for the body to absorb.
During which of the following stages of food processing is undigested material removed from the digestive tract?
When digested, proteins are broken down into _____.
amino acids
When digested, fats are broken down into _____.
both glycerol and fatty acids
When digested, fats are broken down into _____.
Your small intestine can absorb ____ without their being further digested.
Which of these enzymes begins the breakdown of starch?
Starch can be broken down into the disaccharide known as _____.
Protein digestion begins in the _____.
What is the main component of gastric juice?
_____ is secreted by the _____ and acts to emulsify _____ in the _____.
Bile ... liver ... fats ... small intestine
What acid is responsible for stomach acidity?
hydrochloric acid
Which of the following organisms has a gastrovascular cavity?
An animal digestive tract that consists of two openings (a mouth and anus) is called
the alimentary canal.
An alimentary canal is best defined as
a tube-shaped compartment for the transport, digestion, and absorption of food.
The main function of an earthworm's gizzard is to
grind food
Most mechanical processing of food occurs in the _____.
oral cavity and stomach
Which lists the major segments of the alimentary canal in the correct order?
oral cavity, esophagus, stomach, small intestine, large intestine
Several important enzymes and other secretions aid in digestion as food moves down the alimentary canal, as follows: •in the oral cavity, salivary amylase helps break down _____;
•in the stomach, pepsin helps break down _____;
•and in the small intestine, bile helps break down _____.
starches; proteins; fats and oils
Absorption of food monomers occurs primarily in the _____.
small intestine
Chyme enters the small intestine from the stomach. At this point, _____.
mechanical digestion is essentially complete, but the other processes are ongoing or have not yet begun
Which of the following correctly lists the order of the parts of the human digestive system, from first to last contact with food matter?
oral cavity, pharynx, esophagus, stomach, small intestine, large intestine
Smooth muscle propels food through the alimentary canal by a process called
Regulation of the passage of food from the stomach is accomplished by
Digestion begins in the
oral cavity
The digestion of carbohydrates begins in the mouth. What is the name given to the starch-digesting enzyme secreted by salivary glands?
Human saliva performs all of the following functions except
hydrolyzing proteins.
The tongue does all of the following except
secrete saliva.
The structure of the esophagus fits its function in that
it has smooth muscle for peristalsis.
The Heimlich maneuver is performed to forcibly
elevate the diaphragm.
The mucous-producing cells that line the stomach
lubricate and protect the stomach lining.
Which of the following mechanisms helps prevent the gastric juice from destroying the stomach lining?
generation through mitosis of new cells to replace the stomach lining
The stomach mixes food with secretions of the stomach wall to form
The function of the sphincter between the stomach and small intestine is to
periodically release chyme into the small intestine in squirts.
Heartburn is usually caused by the
reflux of chyme from the stomach into the lower esophagus.
When the wall of the stomach cannot protect the organ from the effects of digestion, the result is
a gastric ulcer.
Most gastric ulcers are caused by
In the digestive system, most nutrient absorption occurs in the
small intestine.
Epithelial cells lining the intestine have surface projections that increase nutrient absorption. These projections are called
What is the main digestive function of the pancreas?
to produce digestive enzymes and an alkaline solution
Which of the following is important in the digestion of lipids?
bile salts
Which of the following is important in the digestion of lipids?
Which of the following nutrients is digested only after it reaches the small intestine?
Nutrients absorbed by the intestines move directly to the liver, which
converts excess glucose to glycogen.
Absorption of water is a major function of the
Which of the following statements regarding animal digestive systems is false?
Meat is more difficult to digest than vegetable matter because of its protein content.
Interestingly, most herbivorous animals do not have the ability to digest the cellulose in plants. However, in the absence of this ability, they have evolved a mechanism that allows them to survive despite eating only plant matter, namely
digestion by symbiotic microorganisms.
Which of the following digestive system structures is greatly expanded in size in koalas, resulting in a very large surface area for prokaryotes to digest plant material?
All animals must obtain ________ from outside sources.
fuel to power body activities
which amino acid is found in corn but not in beans?
Organisms suffering from malnutrition may have a diet deficient in
one or more essential nutrients.
A material that must be ingested in preassembled form because the animal cannot synthesize it is
an essential nutrient.
Essential fatty acids, which are required in the human diet, are
those fatty acids that humans are unable to synthesize.
The essential amino acids
must be obtained from the food we eat.
Which of the following vitamins is fat-soluble and consequently, can be stored in body fat?