Chapter 23 Test 6

5. The digestive juice product containing enzymes capable of digesting all four major foodstuff categories is (a) pancreatic, (b) gastric, (c) salivary, (d) biliary.

A

Q3. Where do kidneys get the vitamin D that they activate? (Hint: vitamin D is the "sunshine vitamin.")

A steroid is converted in successive chemical steps by enzymes in the skin, liver, and kidney.

36. What is the result of stimulation of stretch receptors in the rectal walls?

Answer: Activation of stretch receptors in the rectal walls initiates the defecation reflex.

30. What common advantage do circular folds, villi, and microvilli provide to the digestive process?

Answer: All of these modifications increase the surface area of the small intestine.

31. What are brush border enzymes?

Answer: Brush border enzymes are enzymes associated with the microvilli of the enterocytes of the small intestine mucosa.

13. The final product of carbohydrate digestion is __________. polysaccharides disaccharides glycogen monosaccharides starch

Answer: Monosaccharides

26. What is the functional difference between pancreatic acini and islets?

Answer: Pancreatic acini produce the exocrine products of the pancreas (digestive enzymes and bicarbonate-rich juice). The islets produce pancreatic hormones, most importantly insulin and glucagon.

6. The main propulsive force that occurs in the majority of the alimentary canal is called __________. peristalsis swallowing segmentation defecation ingestion

Answer: Peristalsis

23. Pepsin enzymatically digests __________. nucleic acids protein fat carbohydrate

Answer: Protein

14. Before the blood carrying the products of protein digestion reaches the heart, it first passes through capillary networks in (a) the spleen, (b) the lungs, (c) the liver, (d) the brain.

Answer:Before blood carrying the products of protein digestion reaches the heart, it first passes through capillary networks in (c) the liver. (p. 902)

25. Explain why fatty stools result from the absence of bile or pancreatic juice.

Answer:The absence of bile (which causes fat emulsification) and/or pancreatic juice (which contains essentially the only important source of lipase) causes fat absorption to be so slow as to allow most of the fat to remain unabsorbed and be passed into the large intestine. (p. 897)

2. Does bile catalyze chemical reactions of lipids? A. Yes - it breaks fat into smaller fat molecules. B. No - it breaks up fat physically, but there is no chemical reaction. C. No - bile only acts on proteins, not lipids.

B

Q4. How does pancreatic bicarbonate help with this danger?

Bicarbonate, as a base, accepts free H+, taking it out of solution.

Q1. Which one of these is secondary active transport? Why is it also known as cotransport?

Bottom right: secondary active transport/cotransport. Uses ATP indirectly. One substance goes down its gradient while another goes against its gradient. Called "cotransport" because two substances are always transported together.

5. The gallbladder (a) produces bile, (b) is attached to the pancreas, (c) stores and concentrates bile, (d) produces secretin.

C

5. Which of the following is not characteristic of the colon? (a) It is divided into ascending, transverse, and descending portions; (b) it contains abundant bacteria, some of which synthesize certain vitamins; (c) it is the main absorptive site; (d) it absorbs much of the water and salts remaining in the wastes.

C

Q2. Where are the sensors/integrators that determine that calcium absorption needs to be increased?

Chemosensors in the parathyroid gland.

3. Which substances get from the intestinal lumen into the blood via facilitated diffusion and/or secondary active transport? A. amino acids B. calcium ions C. monosaccharides D. all of the above E. none of the above

D

Q2. The main function(s) of mucus in the digestive tract include a) protecting the cells of the body from acid and microbes b) providing lubrication to enhance movement of the contents of the digestive tract c) physically breaking up lipids into smaller chunks to increase enzymes' access to them d) both A and B e) all of the above

D

Q4. Which of the following is/are secreted by the pancreas? a) HCO3- b) glucagon c) many digestive enzymes d) all of these

D

Q2. What is the difference between digestion and absorption?

Digestion entails chemical breakdown, whereas absorption is the movement of those newly created pieces out of the GI tract, into epithelial cells and then the blood.

Q1. In what ways is chemical digestion of carbohydrates similar to digestion of proteins but different from digestion of lipids?

Digestion of both carbohydrates and proteins begins upstream of the small intestine (in the mouth and stomach, respectively) but mostly occurs in the small intestine lumen (with enzymes supplied by the pancreas) and the brush border (with enzymes supplied by the epithelial cells there). Both undergo digestion from polymers (starch and polypeptides) to smaller pieces (disaccharides and peptides) in the lumen and then monomers (monosaccharides and amino acids) in the brush border. Lipids are not polymers and do not undergo the same 2-stage process in the small intestine.

Q1. Where does most macronutrient absorption occur, according to this figure?

In the small intestine.

Q1. Why is HCl (hydrochloric acid) helpful in digestion?

Kills most bacteria, denatures proteins so enzymes can break them down more easily.

Q8. Imagine that, instead of being released into the duodenum, trypsin is released into the stomach. Predict whether trypsin would be more active, less active, or equally active in the stomach than it is in the small intestine. Explain your answer.

Less active, due to the low stomach pH not being optimal for this enzyme.

(6) What chemical reaction is catalyzed by the enzyme lipase?

Lipase breaks down triglycerides, usually into monoglycerides plus two free fatty acids.

Q2. What is the enzyme that catalyzes the reaction shown here? Where is it made, and where does it do its job?

Lipase; mostly produced by pancreas and found in small intestine (also some lingual and gastric).

Q1. Where do bile salts come from?

Made by liver, stored in gallbladder. (Bile gets from liver and gallbladder to intestine via the bile duct.)

Q1. Are chemical or mechanical stimuli more likely to prompt smooth muscle contractions? Why?

Mechanical stimuli - if there's food present, let's move it along. It doesn't necessarily matter what the chemical composition is like.

Q2. Which substances do NOT need the help of proteins to get into epithelial cells? Why don't they need this help?

Monoglycerides and fatty acids, because they are lipophilic and can diffuse straight through the cell membrane. Sugars and amino acids do need transporters to help them across because they're hydrophilic.

Q2. Would a gastric bypass (RNY) surgery patient be more likely to have an iron deficiency or a vitamin K deficiency?

More likely to have an iron deficiency, since iron is only absorbed in the duodenum and jejunum (most of which is removed by the surgery), but vitamin K is absorbed all along the tract.

Q3. How were the proteases involved in clotting kept under control?

Most proteases remained in an inactive form until being temporarily activated (often via another protease). The same idea applies here....

(2) List the organs that ingested substances go through, from mouth to anus.

Mouth, esophagus, stomach, small intestine, large intestine (includes rectum and anus).

Q2. Are bile salts enzymes?

No, but they physically break up the lipid blobs so that lipase has better access to more of them (more surface area to attack).

Q2. Why are proteases potentially dangerous?

Proteases could also cleave your own proteins, which you need!

(3) Where along this "alimentary canal" is the single biggest site of chemical digestion?

Small intestine (especially duodenum)

(4) Where along this "alimentary canal" is the single biggest site of nutrient absorption into the blood?

Small intestine.

Q1. What are the main stimuli here?

Stimulus: pressure in rectum felt by stretch receptors (mechanoreceptors) when food arrives.

Q3. The figure shows transport of Na+ and the amino acid glutamine (abbreviated Gln) through a cell membrane into the cytoplasm (bottom of figure). This can be considered a form of active transport even though this protein does not itself use ATP. Why?

The Na+/K+ pump (not pictured here) used ATP to establish the Na+ gradient, which this transporter can then take advantage of, letting Na+ flow down its gradient to offset the transfer of Gln against its gradient. Since ATP is used indirectly by this transporter, this can be considered secondary active transport.

Q2. What is the "brush border"?

The brush border is the microvilli of intestinal epithelial cells, where additional enzymes further break down carbs and protein fragments prior to absorption.

(5) How does the exocrine pancreas contribute to digestion, respectively?

The exocrine pancreas produces numerous enzymes that help digest carbohydrates, lipids, and proteins. The liver produces bile salts, which physically break up lipids into smaller pieces that can more easily be broken down by the enzyme lipase.

Q1. Is micronutrient absorption similar to macronutrient absorption, location-wise?

The two are somewhat similar, but not identical. Most reabsorption of both micronutrients (vitamins and minerals) and macronutrients (breakdown products of carbs, lipids, and proteins) occurs in the duodenum and jejunum, but the ileum is a major absorber of vitamin B12, and the large intestine is important for the substances listed there in the figure

Q1. Why is a triglyceride called a TRIglyceride?

There are 3 fatty acids attached to the glycerol backbone.

Q3. How do tight junctions help with the acid danger?

Tight junctions prevent acid from leaking into underlying connective tissue and wreaking havoc.

Q1. Does vitamin D act more like a steroid or a non-steroid hormone?How so?

Vitamin D and its receptor are going to the nucleus, binding to DNA, and affecting gene expression, which is what steroid hormones generally do. Indeed, vitamin D is made from a steroid precursor. Though the final structure lacks the steroid signature of 4 interlocking rings, it is still quite hydrophobic and thus passes through cell membranes rather easily.

Q1. Why are proteases helpful in digestion?

Why are proteases necessary? Break down proteins in food. Scary, though, too, because....

13. The __________ is the first segment of the small intestine. ileum duodenum colon jejunum

Answer: duodenum

15. Bile is stored and concentrated in the __________. gallbladder liver stomach pancreas

Answer: gallbladder

17. Emulsification of which organic molecules would be most affected if the liver were severely damaged? nucleic acids proteins lipids carbohydrates

Answer: lipids

14. Digestion of carbohydrates and proteins by brush border enzymes occurs within the __________ of the small intestine. villi circular folds goblet cells microvilli

Answer: microvilli

4. Why would oral antibiotics possibly lead to a digestive tract infection? A. Oral antibiotics kill off many existing residents of the digestive tract, giving pathogens more "space" to invade. B. Oral antibiotics raise the stomach pH so it no longer kills most bacteria. C. Oral antibiotics strip away the layer of mucus that normally protects the epithelium. D. Oral antibiotics suppress your vomiting reflex, so you're less likely to get rid of pathogens that way.

A

5. The sphincter between the stomach and duodenum is (a) the pyloric sphincter, (b) the gastroesophageal sphincter, (c) the hepatopancreatic sphincter, (d) the ileocecal valve.

A

5. What is the fate of the digestive enzymes that you secrete into your digestive tract? A. They will be digested too, and the amino acids will be reabsorbed. B. They will be spared because the immune system recognizes them as "self." C. They will be spared because they don't contain any of the amino acids at which they cleave the proteins in your food. D. They will apparate back to the pancreas to wait for the next meal.

A

Q9. As shown in the figure, your body breaks down complex macromolecules into much smaller components, then uses the components to build macromolecules. Your little brother notices you studying this figure and says that it seems pointless to break down large molecules and then use the components to build more large molecules. Give your brother 3 general reasons why the body does this.

A) Most fundamentally, we can't efficiently absorb really large molecules across cell membranes, so we must break them into smaller, more absorbable pieces. (B) Even if we could absorb intact proteins etc., we wouldn't want to because the specific macromolecules we're making are different from the ones we ate. We need the raw materials to make our own proteins in our own proportions. (C) Not all of the large molecules we eat are reassembled into new large molecules; many (carbohydrates and lipids) are simply broken down to release chemical energy used to power various other cellular processes.

28. Which of the following is a function of the gallbladder? storing and concentrating bile secreting pancreatic juice metabolizing carbohydrate converting pepsinogen to pepsin

Answer: storing and concentrating bile

Q1. Where in the small intestine are these 4 enzymes (amylase, lipase, pepsin, trypsin)found? What is the source of each?

Amylase comes from pancreas to digest in small intestine lumen. Maltase, sucrase, and lactase are in the brush border of the small intestine and produced by those epithelial cells lining the intestine.

28.What stimulates CCK release and what are its effects on the digestive process?

Answer: CCK is secreted in response to the entry into the duodenum of chyme rich in protein and fat. It causes the pancreatic acini to secrete digestive enzymes, stimulates the gallbladder to contract, and relaxes the hepatopancreatic sphincter.

32. Distension of the stomach and duodenal walls have different effects on stomach secretory activity. What are these effects?

Answer: Distension of stomach walls enhances stomach secretory activity. Distension of the walls of the small intestine reduces stomach secretory activity (to give the small intestine time to carry out its digestive and absorptive activities).

1.In order to prevent self-digestion of the pancreas, activation of pancreatic proteases occurs in the __________. gallbladder duodenum liver stomach pancreas

Answer: Duodenum

20. How are the respiratory passages blocked during swallowing?

Answer: During swallowing the larynx rises and the epiglottis covers its lumen so that foodstuffs are diverted into the esophagus posteriorly.

8. Which regulatory chemical stimulates gastric gland activity and motility? vasoactive peptide CCK histamine secretin gastrin

Answer: Gastrin

11. Jerry has been given a drug that inhibits parasympathetic stimulation of his digestive tract. Should he "eat hearty" or temporarily refrain from eating, and why?

Answer: He should temporarily refrain from eating because the parasympathetic nervous system stimulates digestive activities.

5. __________ circulation collects nutrient-rich blood from the GI tract and delivers it to the liver. Cardiac Hepatic portal Aortic Peritoneal right answer feedback:

Answer: Hepatic portal

16. Which of the following is NOT a characteristic of the liver? It has three lobes. It stores glucose as glycogen. It is highly regenerative. It has a role in detoxifying the blood.

Answer: It has 3 lobes

41. WHAT IF? Suppose you had a patient that was unable to make bile salts. What digestive processes would be affected and what might be some of the consequences?

Answer: Lack of bile salts would dramatically decrease both digestion and absorption of fats and fat-soluble vitamins. Without bile salts, you would expect the patient to have fatty stools. The patient might exhibit signs of weight loss and malnutrition. (In children this would be seen as lack of growth and failure to thrive.) The patient may also exhibit signs of deficiency of fat-soluble vitamins (see Table 24.2).

5. What are the main organic molecules digested in the stomach? nucleic acids proteins salts carbohydrates lipids

Answer: Proteins

9.When sensors in the GI tract are stimulated, they trigger reflexes. What types of digestive activity may be put into motion via those reflexes?

Answer: Reflexes associated with the GI tract promote muscle contraction and secretion of digestive juices or hormones.

2. The major site for nutrient absorption is the __________. mouth stomach small intestine large intestine

Answer: Small Intestine

19. What is the functional significance of the epithelial change seen at the esophagus-stomach junction?

Answer: The esophagus is merely a chute for food passage and is subjected to a good deal of abrasion, which a stratified squamous epithelium can withstand. The stomach mucosa is a secretory mucosa served well by a simple columnar epithelium.

3. Which digestive system activity actually moves nutrients from the outside to the inside of the body?

Answer: The process of absorption moves nutrients into the body.

10. The term "gut brain" does not really mean there is a brain in the digestive system. What does it refer to?

Answer: The term "gut brain" refers to the enteric nervous system, the web of neurons closely associated with the digestive organs.

18. Most digestion occurs in the small intestine. True False

Answer: True

11. What would be the effect of stripping the small intestines of their villi? A duodenal ulcer would develop. decreased surface area for absorption The large intestine would take over as the primary absorptive site. Salivary amylase secretion would increase.

Answer: decreased surface area for absorption

19.Lara was on a diet but she could not eat less and kept claiming her stomach had a mind of its own. She was joking, but indeed, there is a "gut brain" called the enteric nervous system. Is it part of the parasympathetic and sympathetic nervous system? Explain.

Answer:The digestive system does contain local nerve plexuses known as the local (enteric) nervous system. This is composed of nerve plexuses in the wall of the alimentary canal that extend the entire length of the GI tract, and is the major nerve supply supplying the GI tract. The enteric system does link to the CNS, however, by afferent visceral fibers and autonomic branches. (p. 874)

14. The products of protein digestion enter the bloodstream largely through cells lining (a) the stomach, (b) the small intestine, (c) the large intestine, (d) the bile duct.

Answer:The products of protein digestion enter the bloodstream largely through cells lining (b) the small intestine. (p. 915)

14. The protein molecule must be digested before it can be transported to and utilized by the cells because (a) protein is only useful directly, (b) protein has a low pH, (c) proteins in the circulating blood produce an adverse osmotic pressure, (d) the protein is too large to be readily absorbed.

Answer:The protein molecule must be digested before it can be transported to and utilized by the cells because (d) the protein is too large to be readily absorbed. (p. 915)

14. The protein molecule will be digested by enzymes made by (a) the mouth, stomach, and colon, (b) the stomach, liver, and small intestine, (c) the small intestine, mouth, and liver, (d) the pancreas, stomach, and small intestine.

Answer:The protein molecule will be digested by enzymes made by (d) the pancreas, stomach, and small intestine. (p. 915)

Q6. Fecal transplants are an experimental therapy in which "good" bacteria are transferred from one person 1 to person 2 via poop. Why might fecal transplants be most helpful to person 2 after he/she has been using antibiotics?

Antibiotics can kill a lot of the "good" bacteria that normally inhibit the GI tract and thus prevent "bad" bacteria from establishing a base there. Repopulating the GI tract with "good" bacteria might thus reduce the chances of bad bacteria invading successfully.

5. The parasympathetic nervous system influences digestion by (a) relaxing smooth muscle, (b) stimulating peristalsis and secretory activity, (c) constricting sphincters, (d) none of these.

B

5. The site of production of cholecystokinin is (a) the stomach, (b) the small intestine, (c) the pancreas, (d) the large intestine.

B

Q7. Once digestive proteases are made by ribosomes, they generally A. are fully active right away B. are inactive until cleaved by another protease C. are inactive until receiving cofactors from the person's next meal D. digest themselves before they can find other proteins

B

7. Bicarbonate that is made in the pancreas... A. lowers the pH in the duodenum B. lowers the pH in the stomach C. raises the pH in the duodenum D. raises the pH in the stomach E. none of the above (what happens in the pancreas stays in the pancreas)

C

Q1. What is the difference between chewing/churning/segmentation and digestion?

Chewing is part of the PHYSICAL (not chemical) breakdown of food. Example: take a hunk of fat and chop it into smaller hunks of fat, which does not alter it chemically. Digestion is the CHEMICAL changes (breaking of individual MOLECULES into smaller molecules - e.g., protein gets chopped into pieces), catalyzed by enzymes.

Q2. What are the main motor responses?

Contraction of rectum, relaxation of internal anal sphincter. Separately, a voluntary decision is made to relax the external anal sphincter (left-most red arrows).

Q5. You start to eat a spaghetti dinner. Which of these will your pancreas secrete FIRST? A. amylase B. bicarbonate C. insulin D. a and b (at about the same time) E. b and c (at about the same time)

D

Q4. Based on calcium's chemical structure, what are its options for getting through cell membranes? How many of those are shown in the next slide?

Everything but simple diffusion. (It's too hydrophilic for that.)

Q10. Be able to compare and contrast the enzymes amylase, lipase, pepsin, and trypsin based on their substrates, products, where they're made, where they act, etc. Example A: Which of these enzymes is/are most active at near-neutral pH? Example B: Which of these enzymes is/are aided by bile salts?

Example A: all except pepsin. Example B: lipase.

Q2. Why is HCl potentially dangerous?

HCl acidity could denature OTHER proteins - not just the ones that were ingested.

Q1. Which cells are the exocrine cells, and which are endocrine? What is produced by each?

The endocrine cells are the little islands (islets) surrounding a blood vessel. Endocrine cells produce insulin (beta cells) and glucagon (alpha cells). Exocrine cells produce digestive enzymes (for carbs, lipids, and proteins) and also bicarbonate (HCO3-).

Q1. Review: why is calcium important in the body?

We have previously discussed its role in neurons (promoting neurotransmitter release at the axon terminal) and muscles (skeletal: triggering muscle contractions upon release from SR; cardiac: voltage-gated calcium channels also play a role in action potentials).

Q1. Based on the number of enzymes present, where does MOST digestion take place: mouth, esophagus, stomach, or small intestine?

Where is digestion occurring? Some in mouth, some in stomach, but MOSTLY in small intestine.

22What protects us? (from digestive dangers)

a. Stomach acid kills most microbes. b. Presence of "good" microbes makes it harder for bad ones to gain a foothold. c. Mucus keeps most bacteria away from epithelium. d. Epithelium is difficult to penetrate (tight junctions, etc.). e. Lymphoid tissues in the submucosa provide immune defense. f. When all else fails, vomit!