digestive systems (my lab and mastering)
Many people have a tendency to gorge on rich, fatty foods. How could such a preference have evolved?
In ancestral hunter-gatherer communities, individuals with a tendency to gorge on such foods when available would have had a selective advantage.
Which of the following is true?
In the US and the UK, ultra-processed foods tend to be less expensive than non-processed foods.
Consider the interior surface of the human stomach and its secretions, shown in the figure. Why doesn't gastric juice, composed of hydrochloric acid and a protease called pepsin, digest the cells that line the stomach?
The stomach lining secretes mucus, a mixture of glycoproteins, cells, salts, and water. Read about digestion in the stomach
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. Glands are structures that secrete hormones into the interstitial fluid or secrete other substances onto body surfaces or into body cavities. The pits in the stomach wall function as glands by secreting gastric juice into the main chamber of the stomach.
Choose the correct statement from the list below.
Proteins that are consumed in the diet are absorbed as individual amino acids following digestion. The building blocks of proteins are amino acids.
To survive, all animals must _____.
balance consumption of food with use and storage of nutrients Energy input as food is required for growth, survival, and reproduction in all animals.
You are the manager of a grocery store. Which of the following have you most likely observed in the last 10 years?
declining sales of oil and sugar
True or False? The liver is a component of the alimentary canal.
false False. The alimentary canal is the tube through which food passes, beginning at the mouth and ending at the anus. The liver is an accessory organ of digestion and not part of the actual canal through which food passes.
After surgical removal of the gallbladder, a person might need to limit his or her dietary intake of
fat
With ingested foods, the first opportunity for enzymatic digestion occurs in the __________.
mouth Saliva contains salivary amylase, a digestive enzyme that hydrolyzes starch and glycogen.
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 From the oral cavity, food moves to the pharynx, then on to the stomach via the esophagus, then the small intestine, and finally the large intestine.
In which digestive system organ does nearly all nutrient absorption occur?
small intestine
In which organ does almost all enzymatic digestion of food occur?
small intestine
Which of the following people is likely to have the most elevated rates of the hormone PYY?
a person who eats mostly from Nova Group 1 foods
Animals obtain the energy they need for growth by
breaking down organic molecules. If you had trouble with this question, review the following material: When enzymes in an animal's body break down complex organic molecules, some of those molecules' stored potential energy is captured; the rest is dissipated as heat that is lost to the environment. Often, the captured energy is stored in the form of ATP and is then used in synthesizing cell components, including macromolecules.
Your friend follows the Nova system. You decide to give her a cake for her birthday. Which of the following would be best for you to do?
buy the ingredients separately and make it from scratch
Other countries follow Brazil and change their dietary guidelines. What would prompt this?
the increasing rate of obesity
Can you match the following terms about nutrient absorption and processing to their descriptions?
1. During the process of digestion, large food molecules are broken down into small components that can be absorbed into cells that form the lining of the _small intestine_. 2. Circular folds, villi, and microvilli--tiny projections from the surfaces of cells--increase the _surface area_ for absorption. 3. After moving into cells of the intestinal lining, fatty acids and glycerol are recombined into fats, coated with proteins, and transported into _lymphatic vessels_, which eventually empty into large veins. 4. Sugars and amino acids pass from the intestinal epithelium and into _blood capillaries_. 5. The liver removes excess _glucose_ from the blood and stores it as glycogen. 6. The liver also converts nutrients to other essential substances, such as _plasma proteins_, cholesterol, and fats.
Choose the correct statement from the list below.
Carbohydrate digestion begins in the mouth with salivary amylase. Carbohydrate digestion begins with the action of salivary amylase in the mouth
Select the correct statement about essential nutrients.
Essential nutrients must be obtained from diet. This is the definition of essential nutrients.
Which process is not required for an animal to obtain energy from food?
Excretion Excretion of wastes is NOT required for an animal to obtain energy from food.
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 One advantage of having a tube-like digestive tract is that digestive processes with different requirements (for example, an acidic or basic environment) can be separated within the tract.
Choose the correct statement from the list below.
Free fatty acid absorption occurs in the small intestine. Fat digestion is not complete until pancreatic lipases finalize fat digestion 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. H+ is actively transported from parietal cells into the lumen, while Cl- diffuses from parietal cells into the lumen.
What is one function of mucus in the lumen of the stomach?
It protects the epithelium from being digested by gastric juice. A layer of mucus lines the lumen of the stomach, protecting the epithelium from being digested by the substances in gastric juice, especially pepsin.
Which of the following is an example of positive feedback in the lumen of the stomach?
Pepsin digests molecules of pepsinogen, producing more pepsin. Pepsin digests molecules of pepsinogen, producing more pepsin. This is an example of positive feedback because the product of the digestion reaction, pepsin, catalyzes further digestion, producing more pepsin, and so on.
Which structure is not part of the alimentary canal?
Salivary glands. The salivary glands are not part of the alimentary canal but contribute digestive enzymes to break down food in the mouth.
Thinking about the high oxygen demand of active endotherms, how does the concept of descent with modification explain this "imperfect" anatomy of some amniotes?
The high oxygen demands of active endotherms require _nearly continuous breathing_. During mammalian evolution, the connection between the _nasal cavity_ and the esophagus was relocated far back in the throat. This adaptation solved one problem (the need to _breathe while chewing_) but not another (the need to _keep air and food in separate paths_).
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. The pH in the test tube (7.4) was too high to promote enzymatic activity by pepsin, which has an optimal pH close to 2. Therefore, the proteins were not digested.
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 The ruminants are foregut fermenters, with mutualistic microbes residing in chambers or sections of the stomach.
