chapter 41 homework
Compare the relative abundance of Actinobacteria in the microbiome of a healthy adult's intestinal tract to that of a healthy adult's stomach. Which statement best represents the relative abundance of Actinobacteria in each?
Actinobacteria are abundant in the stomach, but rare in the intestinal tract of healthy adults.
Which statement best represents the bacterial community composition of a healthy adult's stomach?
Actinobacteria are the most abundant bacteria in the stomach of healthy adults, followed by Firmicutes, and roughly equal amounts of Bacteroidetes and Proteobacteria.
If you place a small piece of a cracker on your tongue, what would you expect to happen?
Salivary amylase degrades the starch from the cracker into maltose.
Which structure is not part of the alimentary canal?
Salivary glands.
What benefit is gained by intestinal bacteria living in a mutualistic relationship with an animal?
The bacteria are provided with a regular source of nutrients.
Mechanical digestion, the process of breaking down large chunks of food into smaller pieces, is important because smaller pieces of food ________.
have more surface area for chemical digestion than do larger pieces of food
To survive, all animals must _____.
balance consumption of food with use and storage of nutrients
When digested, fats are broken down into _____.
both glycerol and fatty acids
Animals obtain the energy they need for growth by
breaking down organic molecules
The presence of fatty acids and amino acids in the chyme from the stomach triggers the small intestine to secrete a hormone known as _____.
cholecystokinin, or CCK
The bile salts _____.
emulsify fats in the duodenum
After surgical removal of an infected gallbladder, a person must be especially careful to restrict dietary intake of _____.
fat
The ____________________ are not involved as coenzymes. But they are still essential in our diet, and they are involved in important processes such as vision, bone formation, protection from oxidation, and blood clotting.
fat-soluble vitamins
After surgical removal of an infected gallbladder, a person must be especially careful to restrict dietary intake of
fat.
Animals that migrate great distances would obtain the greatest energetic benefit of storing chemical energy as _____.
fats
A fat molecule also includes one, two, or three _____________ molecules.
fatty acid
__________________ is a vitamin that is used in reactions that transfer single-carbon units. The vitamin also helps reduce the risk of birth defects such as spina bifida and cleft lip. Women of child-bearing age should consume the recommended amount of this vitamin.
folic acid
Your small intestine can absorb ____ without their being further digested.
fructoses
A fat molecule is composed of two types of smaller molecules, including only one molecule of _______________.
glycerol
The gastrovascular cavity differs from the alimentary canal in that only the gastrovascular cavity _____.
has only a single opening
Cattle are able to survive on a diet consisting almost entirely of plant material because cattle _____.
have cellulose-digesting, symbiotic microorganisms in chambers of their stomachs
A fasting animal whose energy needs exceed those provided in its diet will draw on its stored resources in which order?
liver glycogen, then muscle glycogen, then fat
Drag each statement into the appropriate bin depending on whether the event occurs in the lumen of the small intestine, in a small intestine epithelial cell, or in a lacteal.
lumen of small intestine: -Lipase breaks triglycerides down into monoglycerides and fatty acids. epithelial cell: -Monoglycerides and fatty acids are reassembled to form triglycerides. -Triglycerides are coated with phospholipids, cholesterol, and proteins to form chylomicrons. -Chylomicrons leave this structure by exocytosis. lacteal: -Chylomicrons are transported in this structure to veins. -This structure contains lymph.
Starch can be broken down into the disaccharide known as _____.
maltose
A fat molecule with only one fatty acid is called a ______________.
monoglyceride
The absorption of fats differs from that of carbohydrates in that _____.
most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood
For ingested foods, the first opportunity for enzymatic digestion occurs in the _____.
mouth
If you were to jog 1 km a few hours after lunch, which stored fuel would you probably tap?
muscle and liver glycogen
Which of the following is not a major activity of the stomach?
nutrient absorption
Proteins consist of amino acids linked to
other amino acids
Secretin stimulates the _____ to secrete _____.
pancreas ... bicarbonate
Cholecystokinin (CCK) stimulates the _____ to secrete _____.
pancreas ... pancreatic enzymes
Over-the-counter medications for acid reflux or heartburn block the production of stomach acid. Which of the following cells are directly affected by this medication?
parietal cells
Choose the correct anatomical sequence that presents the order in which food in the digestive system passes through.
pharynx → esophagus → stomach → small intestine → large intestine
The mammalian trachea and esophagus both connect to the
pharynx.
Starch is a type of _____.
polysaccharide
The digestion of ________ begins in the stomach.
protein
The lower esophageal sphincter surrounds the upper opening into the stomach. If this sphincter failed to properly constrict, there might be a problem with _____.
regurgitation of acidic stomach contents into the esophagus, commonly called "heartburn"
The acidity of the stomach contents triggers the small intestine to secrete a hormone known as _____.
secretin
Which of the following organs is correctly paired with its function?
small intestine: polysaccharide digestion
Protein digestion begins in the _____.
stomach
When the digestion and absorption of organic carbohydrates results in more energy-rich molecules than are immediately required by an animal, the excess is _____.
stored as glycogen in the liver and muscles
Among mammals, it is generally true that _____.
the epiglottis prevents swallowed food from entering the trachea
Among humans, increased interest in food intake normally occurs _____.
via chemical signals released when the stomach is empty
Examine the digestive system structures in the figure. Most of the digestion of fats occurs in structure(s) ________.
4
Examine the digestive system structures in the figure. The highest rate of nutrient absorption occurs at location ________.
4
Examine the digestive system structures in the figure. The agents that help emulsify fats are produced in location ________.
9
When used appropriately, antibiotic treatment can effectively reduce bacteria populations and help fight infections. However, antibiotic treatments can have unintended effects. What is one concern when using antibiotics?
Antibiotics may also kill the beneficial bacteria of the microbiome, thereby disrupting digestive health.
_____ is secreted by the _____ and acts to emulsify _____ in the _____.
Bile ... liver ... fats ... small intestine
Choose the correct statement from the list below.
Carbohydrate digestion begins in the mouth with salivary amylase.
Which process is not required for an animal to obtain energy from food?
Excretion.
True or False? The liver is a component of the alimentary canal.
False.
True or false? One advantage of having a tube-like digestive tract is that digestion of all compounds can take place simultaneously down the tract.
False.
Locate the pie chart showing the microbiome of a healthy adult's intestinal tract. Which statement best represents the bacterial community composition of a healthy adult's intestinal tract?
Firmicutes are the most abundant bacteria in the intestinal tract of healthy adults, followed by Bacteroidetes and a small amount of Actinobacteria and Proteobacteria.
Choose the correct statement from the list below.
Free fatty acid absorption occurs in the small intestine.
How do hydrogen ions (H+) and chloride ions (Cl-) get into the lumen of the stomach?
H+ is actively transported from parietal cells into the lumen, while Cl- diffuses from parietal cells into the lumen.
Pepsinogen is converted to its active form in the stomach by ________.
HCl
What is one function of mucus in the lumen of the stomach?
It protects the epithelium from being digested by gastric juice.
Animals cannot produce enzymes to digest cellulose, yet many termite species consume cellulose from plant material as a main part of their diet. How do termites access the nutrients contained in cellulose?
Mutualistic bacteria in the hindgut of the termite digest the cellulose into sugars.
If you put the following events in the order they occur in the human digestive system, the third event in the series would be:
Pepsin activates pepsinogen.
Which of the following is an example of positive feedback in the lumen of the stomach?
Pepsin digests molecules of pepsinogen, producing more pepsin.
Choose the correct statement from the list below.
Proteins that are consumed in the diet are absorbed as individual amino acids following digestion.
A researcher added a mixture of animal proteins to a physiological buffer solution (pH 7.4) in a test tube incubated at 37°C. The researcher then added purified pepsin to the mixture, but even after several hours, the proteins were not digested. Which of the following would explain this result?
The pH was too high.
Why do the cells of the digestive system secrete proteolytic enzymes, such as pepsin, in their inactive forms?
These proteolytic enzymes, in active form, would digest the very tissues that synthesize them
What is the importance of the mucus that are released by salivary glands?
They are glycoproteins that make food slippery enough to slide easily through the esophagus.
The epithelium that lines the stomach has many deep infoldings, or pits. In what way do these pits function as glands?
They secrete gastric juice into the main chamber of the stomach.
Stomach cells are moderately well adapted to the acidity and protein-digesting activities in the stomach by having _____.
a thick, mucous secretion and active mitosis of epithelial cells
The large surface area in the gut directly facilitates _____.
absorption
The process by which digested dietary substances cross cell membranes to be used by the body is known as ________.
absorption
Fat digestion yields fatty acids and glycerol, whereas protein digestion yields amino acids. Both digestive processes __________.
add a water molecule to break bonds
When digested, proteins are broken down into _____.
amino acids
Which of these enzymes begins the breakdown of starch?
amylase
Birth defects of the neural tube in humans _____.
are reduced from about 6% without folic acid supplements in the periconception interval to about 1% when the supplements were taken
The "essential nutrients" for proper human nutrition include _____.
calcium, sodium, potassium, and other minerals
Different types of food are eaten by various groups of animals, but it is usually true that _____.
cellulose digestion in ruminant mammals occurs before the ingested foods reach the small intestine
Nutrient-rich blood from the intestine is carried through the ________ to the liver.
hepatic portal vein
A fatty acid includes a carboxyl group (-COOH) at one end as well as a long _____________________.
hydrocarbon chain
What acid is responsible for stomach acidity?
hydrochloric acid
The hydrocarbon chains found in fats store a lot of energy. They also make fats __________________, or insoluble in water.
hydrophobic
Choose the list that presents the four stages of food processing in the order in which they naturally occur.
ingestion → digestion → absorption → elimination
Upon activation by stomach acidity, the secretions of the parietal cells _____.
initiate the chemical digestion of protein in the stomach
In a healthy person, after a carbohydrate-rich meal, the production of ________ will increase, causing the uptake of ________ from the blood into liver cells.
insulin; glucose
Which of the following organs is incorrectly paired with its function?
large intestine-bile production
Which of the following is hydrophobic and therefore insoluble in water?
lipid
Bile is produced by the _____ and stored by the _____ until it is secreted into the small intestine.
liver ... gall bladder
If you were to jog one kilometer a few hours after lunch, which stored fuel would you probably tap?
liver glycogen and muscle glycogen
The function of chylomicrons is to ________.
transport lipids from the intestine to other organs
A fat molecule with three fatty acids is called a triacylglycerol, or a _______________.
triglyeride
__________________ is absorbed from some foods like carrots in the form of carotene. The vitamin accumulates in the rods and cones of the eyes and plays a role in vision.
vitamin a
________________ is involved in the formation of hydroxyproline and hydroxylysine, which are important amino acids and part of the collagen that forms the connective tissues. Lack of this vitamin causes scurvy, which can be prevented with citrus and other fruits.
vitamin c
What is the main component of gastric juice?
water
Sort the vitamins according to whether they are water soluble or fat soluble. Sort the items into the appropriate bin.
water soluble: vitamin c, vitamin b1 fat soluble: vitamin k, vitamin e, vitamin d
The __________________ act as coenzymes in the body. They do not stay bonded to only one enzyme, but are used over and over again by different enzymes.
water-soluble vitamins
