Biology 12: Digestion Review Story

Biology 12: Digestion Review Story 1

Review Questions: 1. Define digestion. Why is this process important? 2. List the 4 functions of the digestive system. 3. How does saliva contribute to the formation of a bolus? 4. What prevents food form entering the nasal chamber and the trachea during swallowing of food? 5. The opening to the larynx is called the glottis , which is covered when the trachea moves up by the epiglottis . 6. What is responsible for heartburn and how is it normally prevented from occurring? 7. List the functions of the stomach. What is chyme? 8. What is the function of the gastric glands in the stomach? 9. What is an ulcer an why does it form? 10. List 4 functions of the small intestine. What molecule from the pancreas neutralizes the acidity of chyme? 11. Describe the structure of villi and microvilli in the small intestine. 12. How are the small nutrient molecules absorbed across the wall of each villus? What do they enter? 13. What is the function of the large intestine? How does its size compare with the small intestine? 14. Which organ of the large intestine may play a role in immunity and if inflamed leads to appendicitis? 15. Over 99% of the colon bacteria are E.coli (obligate anaerobes) , bacteria that die in the presence of oxygen. 16. Describe the effects of bacteria in the large intestine. What does a high chloriform count in swimming water mean? 17. Why will food poisoning and nerve stimulation cause diarrhea? 18. How does mil of magnesia and mineral oil work to overcome constipation? 19. What is the exocrine function of the pancreas? How does its products get to the duodenum? 20. Name the 2 hormones secreted from the duodenal wall that signal the pancreas and the gallbladder to release their products. 21. What are the components of bile? Give their function. What organ produces bile? Where is it stored? 22. Explain why the liver is said to act as the gatekeeper to the blood. 23. Define deamination. What happens to those amino groups in the liver? How is urea excreted? 24. List the 6 (7?) functions of the liver. 25. Name the enzyme found in the stomach. What is it formed from? What does it act upon? What products will it form?

Questions:

1. Name the Pancreatic enzyme that in the duodenum will: a. digest starch: amylase It forms the product maltose

b. digest Protein: trypsin It forms the product peptides c. digest fat droplets: lipase It forms the product fatty acids + glycerol

Biology 12: Digestion Review Story 2

d. The end products of fat digestion reform in the epithelial cells and are attached to phospholipids , cholesterol ¸ and

protein to form a temporary fat carrier molecule called a chylomicron . These carrier molecules are then dumped into the lacteal (part of the lymphatic system system) and will enter the blood-stream with the rest of the lymph at the left

subclavian vein. They will be picked up eventually by the liver which will convert them to a lipoprotein

The “bad” lipoproteins are called low density lipoproteins (LDL )

And the “good” lipoproteins are called High Density lipoproteins (HDL ).

When your body has too much energy, or saturated fat, the liver tends to put fats into the

LDL’s . When the body needs the energy from the fat, the liver tends to send it to the cells in HDL’s . LDL’s are associated with

atherosclerosis (clogging of the arteries).

2. The 2 enzymes produced by the epithelial cells to complete the digestion of peptides and maltose are peptidases and maltase

The end products that are formed from these degradations are amino acids

and glucose .

3. Lactose intolerance is due to inability to digest milk - usually a lack of lactase

. The consequence of drinking milk for these individuals is

the sugar lactose is used by the bacteria in the gut as a food source - they

produce flatulus- causes cramping, irritation, diarrhea, etc

4. The stomach is directly connected to the esphagus above and the duodenum below. Biology 12: Digestion Review Story 3

5. The major food digested in the stomach is Protein , which is hydrolyzed by the enzyme Pepsin .

6. Among its chemical aspects, every digestive enzyme has a preferred pH and temp.

7. Before fats are digested by the enzyme lipase , they are first emulsified by bile .

8. Pancreatic juices enter the small intestine by way of the pancreatic duct

duct and contain enzymes for the digestion of every type of food.

9. The liver first receives the products of digestion by means of the hepatic portal

vein; any excess glucose is stored as glycogen (in the liver)

10. The secretion of digestive juices is controlled in general by gastrin, CCK

and secretin . (page 208 in text)

11. Surface area in the small intestine is increased greatly by the presence of

folds and villi and microvilli .

12. Complete the following table:

Hormone Where Cause of Affects What Affected Organ

Produced Release Organ? Releases a. gastrin Stomach Meal high in Stomach HCl and

protein pepsinogen b. secretin Cells of Acid in Pancreas and Bile, Pancreatic

duodenal wall duodenum liver juices Biology 12: Digestion Review Story 4

c. CCK Cells of Part. digested Pancreas and Bile, pancreatic

duodenal wall fat or protein liver juices

13. List 6 functions of the Liver

detoxifies blood

**** stores iron and fat soluble vitamins (I missed this one in the notes)

makes blood proteins makes lipoproteins

maintains blood glucose levels

produces urea from breaking down amino acids

converts Hb from RBCs into billirubin and biliverdin

produces bile

14. Vitamins are often portions of coenzymes , necessary for cellular metabolism. a. In which part of the digestive tract are nutrient molecules absorbed? S.intestines

b. The absorbed nutrient molecules enter what vein associated with the intestine?

Hepatic portal vein c. In which part of the digestive tract does pancreatic juice enter? duodenum

d. In which part of the digestive tract does bile enter? duodenum

e. What parts of the digestive tract do not actually contain food and might be called accessory organs of digestion? Salivary glands, pancreas, liver, gallbladder

Biology 12: Digestion Review Story 5 f. What parts of the digestive tract do not have ducts entering them and do not secrete digestive juices? Esophagus, large intestine, rectum, anus

Digestion of Carbohydrate (starch)

Starch digestion begins in the mouth . Here the ducts empty from the salivary glands. The salivary juice contains the enzyme amylase and this enzyme breaks down starch to the disaccharide maltose . Starch is also acted on in the

duodenum . Here, a duct empties from the pancreas

Pancreatic juice contains the enzyme amylase

which breaks down starch to the disaccharide maltose

. Starch digestion is complete when this disaccharide is broken down to

glucose , a monosaccharide, which can be absorbed by intestinal villi. The enzyme that converts maltose to glucose is called maltase

and this enzyme is secreted by epithelial cells of the intestinal villus.

17. Digestion of Protein (meat)

Protein digestion begins in the stomach . The gastric

Glands line the wall of the stomach. They secrete the enzyme pepsinogen (pepsin)

which breaks down protein to peptides . Another enzyme called trypsin is secreted by the pancreas

and this enzyme acts on protein in the duodenum , also breaking down protein to peptides . Protein digestion is Biology 12: Digestion Review Story 6 complete when peptides are broken down to amino acids , molecules small enough to be absorbed by the villi. This is achieved by the enzyme

peptidase that is produced in the epithelial cells of the intestinal villus.

18. Digestion of fat (butter)

Fat is first emulsified by bile , a substance made by the liver and stored in the gall bladder . The contents of the latter enter the small intestine by way of the bile duct. After the fat has been emulsified, it is broken down by the enzyme lipase which is found in pancreatic juice, which enters the small intestine by way of the pancreatic duct. Fats are broken into glycerol and fatty acids, molecules small enough to be absorbed by intestinal villi. After resynthesis, fats enter the

lacteal , which are part of the lymphatic system.

19. Path of food. a. Food consists of the large organic molecules proteins and

carbohydrates and lipids and

nucleic acids . In the mouth, the only type of food digested is starch . The mouth has a neutral pH.

The food passes down the long tube called the esophagus . A rhythmic contraction called peristalsis pushes the food along. After passing through a sphincter, (circular muscle), the food enters the stomach Biology 12: Digestion Review Story 7

where the primary food acted on is protein . The food, now called chyme, passes through another sphincter into the duodenum

Two ducts enter this organ: they are the pancreatic duct from the

pancreas and the bile duct from the gall bladder . Bile contains an emulsifier

which divides fat up into fat droplets. Pancreatic juice contains enzymes that act on

lipids , protein , and carbohydrates

Lining the walls of the intestine are epithelial cells with microvilli

on the apical surface of each cell. The epithelial cells produce enzymes that finish digestion by converting maltose to glucose and

peptides to amino acids. Thus the small nutrient molecules that are absorbed by the villi are

Amino acids , glucose , nucleotide ,and

Fatty acids and glycerol . Fat products enter the lacteal

and the other molecules enter the hepatic portal vein.

This vein takes the nutrients to the liver ,an organ of homeostasis. For example, this organ stores glucose as glycogen and always keeps the blood glucose level constant. This organ can also remove amino groups from amino acids and convert the amino groups to

urea a nitrogenous waste product. Biology 12: Digestion Review Story 8

20. Digestive Enzyme Activity. For each combination of substances below, decide whether digestion will or will not occur at the maximum rate. Give an explanation if digestion will NOT occur maximally.

a. trypsin, NaHCO3, egg white, warm gently

maximal rate

b. salivary amylase, water, egg white, warm gently

no reaction - wrong substrate! (amylase works on starch!) c. Pepsin, HCl, egg white, freeze

no reaction - enzyme will not work when temperatures drop that low!

d. pancreatic amylase, HCl, starch, heat to boiling

no reaction - boiling denatures the enzyme (+ the pH is wrong!)

e. lipase, NaHCO3, fats, warm gently

maximum rate f. maltase, HCl, maltose, warm gently

will work, but not very well. Wrong pH g. peptidases, fat, HCl, warm gently

no reaction - wrong substrate, + wrong pH Biology 12: Digestion Review Story 9 h. pepsin, HCl, egg white, warm gently

maximum rate i. trypsin, starch, water, warm gently

no reaction - wrong substrate j. HCl, egg white, water, warm gently

no reaction - no enzyme!

Questions:

1. Name the Pancreatic enzyme that in the duodenum will: a. digest starch: It forms the product b. digest Protein: It forms the product c. digest fat droplets: It forms the product ______d. The end products of fat digestion in the epithelial cells to form a temporary fat carrier molecule called a . These carrier molecules are then dumped into the (part of the ______) and will enter the blood-stream with the rest of the lymph at the left

vein.

2. The 2 enzymes produced by the epithelial cells to complete the digestion of peptides and maltose are and

The end products that are formed from these degradations are and .

3. Lactose intolerance is due to . The consequence of drinking milk for these individuals is Biology 12: Digestion Review Story 10

4. The stomach is directly connected to the above and the

below.

5. The major food digested in the stomach is , which is hydrolyzed by the enzyme .

6. Among its chemical aspects, every digestive enzyme has a preferred _____&_____.

7. Before fats are digested by the enzyme , they are first emulsified by .

8. Pancreatic juices enter the small intestine by way of the duct and contain for the digestion of every type of food.

9. The liver first receives the products of digestion by means of the vein; any excess glucose is stored as

10. Surface area in the small intestine is increased greatly by the presence of

and and __ .

11. List 6 functions of the Liver

______

14. Biology 12: Digestion Review Story 11 a. In which part of the digestive tract are nutrient molecules absorbed? b. The absorbed nutrient molecules enter what vein associated with the intestine?

c. In which part of the digestive tract does pancreatic juice enter? d. In which part of the digestive tract does bile enter? e. What parts of the digestive tract do not actually contain food and might be called accessory organs of digestion?

f. What parts of the digestive tract do not have ducts entering them and do not secrete digestive juices? ______

Digestion of Carbohydrate (starch)

Starch digestion begins in the . Here the ducts empty from the glands. The salivary juice contains the enzyme

______and this enzyme breaks down starch to the disaccharide . Starch is also acted on in the

. Here, a duct empties from the Pancreatic juice contains the enzyme which breaks down starch to the disaccharide . Starch digestion is complete when this disaccharide is broken down to , a monosaccharide, which can be absorbed by intestinal villi. The enzyme that converts maltose to glucose is called Biology 12: Digestion Review Story 12

and this enzyme is secreted by

cells of the intestinal villus.

17. Digestion of Protein (meat)

Protein digestion begins in the . The ______glands line the wall of the stomach. They secrete the enzyme which breaks down protein to . Another enzyme called

is secreted by the and this enzyme acts on protein in the , also breaking down protein to .

Protein digestion is complete when peptides are broken down to

, molecules small enough to be absorbed by the villi. This is achieved by the enzyme that is produced in the epithelial cells of the intestinal villus.

18. Digestion of fat (butter)

Fat is first emulsified by , a substance made by the liver and stored in the . The contents of the latter enter the small intestine by way of the duct. After the fat has been emulsified, it is broken down by the enzyme which is found in pancreatic juice, which enters the small intestine by way of the pancreatic duct. Fats are broken into

and fatty acids, molecules small enough to be absorbed by intestinal villi. After resynthesis, fats enter the which are part of the lymphatic system.

19. Path of food. Biology 12: Digestion Review Story 13 a. Food consists of the large organic molecules and

and and

. In the mouth, the only type of food digested is

. The mouth has a pH. The food passes down the long tube called the . A rhythmic contraction called pushes the food along. After passing through a sphincter,

(circular muscle), the food enters the where the primary food acted on is

. The food, now called chyme, passes through another sphincter into the .

Two ducts enter this organ: they are the duct from the

and the duct from the

. Bile contains an which divides fat up into fat droplets. Pancreatic juice contains enzymes that act on

, , and ______

Lining the walls of the intestine are with on the apical surface of each cell. The epithelial cells produce enzymes that finish digestion by converting to glucose and to amino acids. Thus the small nutrient molecules that are absorbed by the villi are

, , ,and

. Fat products enter the and the other molecules enter the portal vein. Biology 12: Digestion Review Story 14

This vein takes the nutrients to the ,an organ of homeostasis. For example, this organ stores glucose as and always keeps the blood glucose level constant. This organ can also remove amino groups from

and convert the amino groups to

a nitrogenous waste product.

a. trypsin, NaHCO3, egg white, warm gently

b. salivary amylase, water, egg white, warm gently

______c. Pepsin, HCl, egg white, freeze

d. pancreatic amylase, HCl, starch, heat to boiling

Biology 12: Digestion Review Story 15

e. lipase, NaHCO3, fats, warm gently

f. maltase, HCl, maltose, warm gently

g. peptidases, fat, HCl, warm gently

h. pepsin, HCl, egg white, warm gently

i. trypsin, starch, water, warm gently

j. HCl, egg white, water, warm gently