MasteringBiology Ch 41

Which of the following hypothetical situations might result in a blood sugar level that is too high? -A diabetic accidentally injects too much insulin. -An individual has an autoimmune disorder that destroys the beta cells of the pancreas. -An individual's insulin receptors are defective.

-An individual has an autoimmune disorder that destroys the beta cells of the pancreas; If a person's beta cells were damaged, then insulin could not be produced and the person's blood glucose level would remain too high. AND -An individual's insulin receptors are defective; If a person had defective insulin receptors, then insulin would not stimulate cells to take up glucose and the person's blood glucose level would remain too high.

What are the stages of food processing in the order they occur?

1. Ingestion 2. Digestion 3. Absorption 4. Elimination

When digested, proteins are broken down into _____. -glycerol only -fatty acids only -monosaccharides -amino acids -both glycerol and fatty acids

Amino acids.

Proteins that are consumed in the diet are absorbed as individual ___________ following digestion.

Amino acids; these are the building blocks of proteins

Monosaccharides __________, and polysaccharides __________.

Are single monomer units; are made of many monosaccharides chained together

To survive, all animals must _____. See Concept 41.1 (Page 897). -digest plant material -balance consumption of food with use and storage of nutrients -hibernate -have a complete digestive system -ingest nutrients from the environment every day of their lives

Balance consumption of food with use and storage of nutrients; Energy input as food is required for growth, survival, and reproduction in all animals.

_____ is secreted by the _____ and acts to emulsify _____ in the _____. -Trypsin ... pancreas ... fats ... small intestine -Nucleases ... pancreas ... nucleic acids ... stomach -Bile ... liver ... fats ... small intestine -Amylase ... salivary glands ... starch ... stomach -Lipase ... small intestine ... fats ... small intestine

Bile, liver, fats, small intestine

When digested, fats are broken down into _____. -glycerol only -fatty acids only -monosaccharides -amino acids -both glycerol and fatty acids

Both glycerol and fatty acids.

Animals obtain the energy they need for growth by -synthesizing macromolecules. -recycling heat from the environment. -breaking down organic molecules. -using ATP in food.

Breaking down organic molecules.

The "essential nutrients" for proper human nutrition include _____. See Concept 41.1 (Page 897).

Calcium, sodium, potassium, and other minerals.

Different types of food are eaten by various groups of animals, but it is usually true that _____. See Concept 41.4 (Page 909) -cellulose digestion in ruminant mammals occurs before the ingested foods reach the small intestine -the teeth of herbivores tend to be sharper than the teeth of carnivores -animals typically produce enzymes that hydrolyze cellulose -the intestines of carnivores tend to be longer than the intestines of herbivores of similar overall body size -many carnivorous vertebrates house large populations of symbiotic bacteria and protists in special fermentation chambers in their stomachs

Cellulose digestion in ruminant mammals occurs before the ingested foods reach the small intestine; The ruminants are "front-end" fermenters, with mutualistic microbes residing in chambers or sections of the stomach.

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 presence of fatty acids and amino acids in the stomach contents triggers the small intestine to secrete CCK. CCK then stimulates the gall bladder to release bile and the pancreas to secrete pancreatic enzymes.

Which process is not required for an animal to obtain energy from food? -Excretion -Ingestion -Secretion -Digestion

Excretion.

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.

True or False? The liver is a component of the alimentary canal.

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.

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.

_________ 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 childbearing age should consume the recommended amount of this vitamin.

Folic Acid

Your small intestine can absorb ____ without its being further digested. -fat -protein -starch -nucleic acid -fructose

Fructose; Fructose is a monosaccharide, and monosaccharides can be absorbed without having to be broken down into smaller units.

How do hydrogen ions (H+) and chloride ions (Cl-) get into the lumen of the stomach? -Both H+ and Cl- diffuse from parietal cells into the lumen. -Parietal cells actively transport both H+ and Cl- into the lumen. -H+ is actively transported from parietal cells into the lumen, while Cl- diffuses from parietal cells into the lumen. -Parietal cells actively transport hydrochloric acid (HCl) into the lumen, and HCl then dissociates into H+ and Cl-.

H+ is actively transported from parietal cells into the lumen, while Cl- diffuses from parietal cells into the lumen.

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. -Fatty foods are very rich in calories and consuming them is an efficient way to gain weight. -Most people find fatty foods tasty and satisfying.

In ancestral hunter-gatherer communities, individuals with a tendency to gorge on such foods when available would have had a selective advantage.

How do glucagon and insulin differ?

Insulin causes some cells to take up glucose, whereas glucagon causes some cells to secrete glucose; Insulin and glucagon are said to be antagonistic hormones--the effects of one oppose the effects of the other. The release of insulin stimulates nearly all cells in the body to take up glucose. Conversely, glucagon release stimulates liver cells to break down glycogen stores and return glucose to the blood.

What is one function of mucus in the lumen of the stomach? -It protects the epithelium from being digested by gastric juice. -It prevents H+ secreted by parietal cells from entering the lumen. -It neutralizes HCl in the lumen. -It prevents pepsinogen from digesting proteins inside chief cells.

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 organs is incorrectly paired with its function? -pancreas-enzyme production -oral cavity-starch digestion -stomach-protein digestion -small intestine-nutrient absorption -large intestine-bile production

Large intestine-bile production

Which of the following is hydrophobic and therefore insoluble in water? -ribonucleotide -nucleotide -phospholipid -lipid

Lipid; Lipids, which are nonpolar, are described as hydrophobic (from the Greek phobos, fearing) because they seem to repel water. An example from the kitchen is vegetable oil, which, as you know, does not mix stably with water-based substances such as vinegar. In contrast, phospholipids, nucleotides, and ribonucleotides are all polar and are soluble in water.

Bile is produced by the _____ and stored by the _____ until it is secreted into the small intestine.

Liver, gall bladder; Bile is continuously produced by the liver and is stored in the gall bladder until CCK triggers its release.

Starch can be broken down into the disaccharide known as _____.

Maltose

For ingested foods, the first opportunity for enzymatic digestion occurs in the _____. See Concept 41.3 (Page 903)

Mouth; Saliva contains salivary amylase, a digestive enzyme that hydrolyzes starch and glycogen.

Which of the following is not a major activity of the stomach? -enzyme secretion -mucus secretion -nutrient absorption -HCl secretion -mechanical digestion

Nutrient absorption

The gastrovascular cavity differs from the alimentary canal in that only the gastrovascular cavity _____. See Concept 41.2 (Page 902).

Only has a single opening.

Proteins consist of amino acids linked to _____.

Other amino acids; Proteins are a macromolecule constructed from amino acids linked in unbranched polymers. The bond between amino acids is called a peptide bond, so a polymer of amino acids is called a polypeptide. Sugars, phosphates, and fatty acids are components of other macromolecules.

Secretin stimulates the _____ to secrete _____.

Pancreas, bicarbonate; the acidity of the stomach contents triggers the small intestine to secrete secretin, which in turn stimulates the pancreas to secrete bicarbonate to neutralize this acidity.

Which of the following is an example of positive feedback in the lumen of the stomach? -Pepsin works best in the acidic environment produced by hydrochloric acid. -Pepsin digests molecules of pepsinogen, producing more pepsin. -Chief cells secrete pepsinogen, which is a precursor to pepsin. -Hydrochloric acid converts pepsinogen to 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.

The mammalian trachea and esophagus both connect to the _______.

Pharynx.

Starch is a type of _____. -disaccharide -nucleotide -polysaccharide -fatty acid -monosaccharide

Polysaccharide; Starch is a carbohydrate composed of many monomers (many monosaccharide units).

Carbohydrate digestion begins in the mouth with ___________.

Salivary amylase

Which structure is not part of the alimentary canal? -Salivary glands. -Stomach. -Mouth. -Esophagus.

Salivary glands; The salivary glands are not part of the alimentary canal but contribute digestive enzymes to break down food in the mouth.

The acidity of the stomach contents triggers the small intestine to secrete a hormone known as _____.

Secretin; The acidity of the stomach contents triggers the small intestine to secrete secretin; secretin then stimulates the pancreas to secrete bicarbonate to neutralize this acidity.

Free fatty acid absorption occurs in the ____________.

Small intestine; Fat digestion is not complete until pancreatic lipases finalize fat digestion in the small intestine.

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 temperature was too low. -Pepsin must be converted to its active form, pepsinogen, which digests proteins. -Pepsin doesn't digest animal proteins. -The pH was too high.

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.

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.

Sort the vitamins according to whether they are water-soluble or fat-soluble.

The water-soluble vitamins act as cofactors in enzymes. They can diffuse from enzyme to enzyme and are only needed in small amounts. The fat-soluble vitamins do not act as coenzymes in enzymes, but they are important in many processes in the body, such as vision, bone formation, oxidative protection, and blood clotting.

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. -They secrete a mixture of gastric juice and partially digested food into the small intestine. -They secrete the hormone pepsinogen into the blood. -They secrete food into the main chamber of the stomach.

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.

In the experiment on mental agility after tasting (but not swallowing) sweet liquids, the reporter got the highest score after tasting glucose. According to the reporter, what does the boost in mood and brainpower from tasting glucose illustrate?

This boost ensures that we will continue to seek foods high in glucose.

Among humans, increased interest in food intake normally occurs _____. See Concept 41.5 (Page 915).

Via chemical signals released when the stomach is empty; A shrunken, empty stomach releases ghrelin, a protein hormone that sharply increases appetite.

__________ 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

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

Cholecystokinin (CCK) stimulates the _____ to secrete _____.

pancreas, pancreatic enzymes; the presence of fatty acids and amino acids in the stomach contents triggers the small intestine to secrete CCK. CCK then stimulates the pancreas to secrete enzymes that play a role in the digestion of these nutrients.

Choose the correct anatomical sequence that presents the order in which food in the digestive system passes through. See Concept 41.3 (Page 903). -esophagus → pharynx → stomach → small intestine -pharynx → small intestine → large intestine → stomach -pharynx → esophagus → stomach → small intestine → large intestine -esophagus → stomach → pharynx → small intestine -pharynx → stomach → esophagus → small intestine

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.

The lower esophageal sphincter surrounds the upper opening into the stomach. If this sphincter failed to properly constrict, there might be a problem with _____. See Concept 41.3 (Page 905)

regurgitation of acidic stomach contents into the esophagus, commonly called "heartburn"; The lower esophageal sphincter "guards" the junction between the esophagus and stomach. In infants, the muscles are weak and regurgitation is quite common.