FINAL - Digestion

Question 1

Outline why food needs to be digested.

Answer 1

• Macromolecules must be broken down into smaller molecules so they are small enough to be absorbed into your bloodstream

Question 2

Explain how starch is digested.

Answer 2

• Hydrolyzed into maltose in the small intestine by amylase produced by the pancreas

Question 3

Explain how proteins are digested.

Answer 3

• Hydrolyzed into peptides in the stomach by pepsin produced by the gastric glands
• Hydrolyzed into amino acids in the small intestine by protease produced by the pancreas

Question 4

Explain how fats are digested.

Answer 4

• Hydrolyzed into glycerol and fatty acids in the small intestine by lipase produced by the pancreas

Question 5

Explain the nervous and hormonal mechanisms that control the secretion, volume, and content of gastric sections.

Answer 5

• Smell/sight of food causes brain to send nerve impulses via vagus nerve to medulla
• glands in stomach secrete gastric juice
• chemo- / stretch receptors in stomach wall detect food
• releases gastrin hormone; stimulates secretion of acid

Question 6

Outline the roles of the stomach.

Answer 6

• Produces acid to break down molecules
• Churns food in mechanical digestion
• Produces protease/pepsin to digest proteins

Question 7

Outline the roles of HCl in the stomach.

Answer 7

• Kills bacteria
• Activates pepsin into pepsinogen for protein digestion
• Maintains low pH of stomach

Question 8

Outline the causes, consequences, and treatment of stomach ulcers.

Answer 8

Cause: Helicobacter pylori infection
Cons: digestion of stomach lining by HCl (stomach ulcers), inflammation
Treatment: PPIs, antacids to decrease acidity

Question 9

Outline the use of PPI’s to reduce stomach acid secretion.

Answer 9

• Acidity achieved by proton pumps
• PPIs bind irreversibly to proton pumps
• Lowers amount of acid produced

Question 10

Describe how the structure of a villus is adapted to its function.

Answer 10

Function: Efficient absorption of nutrients in the small intestine
Epithelial cells - surround each villus (decreases diffusion distance for nutrients into bloodstream)
Rich Capillary Network - large concentration gradient (between blood and the fluid in the small intestine)
allows for rapid absorption of nutrients
Lacteals - Absorb lipids (into lymphatic system – transports fats, drains tissues of excess fluids)
Intestinal crypts - release juices that act as ‘carrier fluids’ for nutrients

Question 11

Describe the method of transport used to absorb the products of starch digestion in the small intestine.

Answer 11

Facilitated diffusion - movement through channel proteins

Question 12

Describe the method of transport used to absorb the products of protein digestion in the small intestine.

Answer 12

Active transport - against concentration gradient using proton pumps

Question 13

Describe the method of transport used to absorb the products of lipid digestion in the small intestine.

Answer 13

Endocytosis - by means of vesicles (lipoprotein particles)

Question 14

Distinguish between exocrine and endocrine glands (with regard to their structure and function)

Answer 14

Exocrine glands - secretes substances through ducts / secretory cells to an epithelial surface (salivary glands, gastric glands)
Endocrine glands - secretes hormones into the bloodstream (liver)

Question 15

Outline the benefits of a diet rich in fiber.

Answer 15

• Prevents constipation
• Decreases hunger so less obesity
• Ensures correct movement of food through intestines
• Decreased risk of colon cancer

Question 16

State which substances are egested by the human body.

Answer 16

BELCH
Bile pigments
Epithelial cells
Lignin
Cellulose
Human microflora

Question 17

Outline the effects of the cholera toxin.

Answer 17

• V. cholerae produces toxin
• Toxin causes ions to be pumped into small intestine
• Drawing water thru osmosis into intestine
• Leading to dehydration, diarrhea, vomiting

Question 18

Explain how the pancreas maintains homeostatic levels of glucose in the blood.

Answer 18

• Homeostasis is the maintenance of a constant internal environment
• Negative feedback controls glucose levels
• Pancreas produces hormones that regulate levels of glucose
• If glucose lvls are high, beta-cells produce insulin
• Insulin causes cells to take up glucose (lowers lvls)
• Liver stores excess glucose as glycogen
• If blood/glucose levels are low, alpha-cells produce glucagon
• Glucagon causes liver two break down glycogen into glucagon (increases lvls)

Question 19

Explain the causes, consequences, and treatment of Type I diabetes.

Answer 19

Cause: Autoimmune reaction, beta cells of pancreas become destroyed
Cons: high blood sugar, glucose in urine
Treat: insulin injections

Question 20

Explain the causes, consequences, and treatment of Type II diabetes.

Answer 20

Cause: obesity, lack of exercise
Cons: desensitized to insulin
Treat: consume complex carbs for gradual release of glucose into blood, eat more high fiber foods to satisfy appetite but not get absorbed, reduce intake of fats to reduce weight.

Question 21

Outline the dual supply of blood to the liver.

Answer 21

• It is blood from hepatic artery and hepatic portal vein
• Blood in hepatic artery provides oxygen to liver
• Hepatic vein carries blood rich in nutrients from intestines
• Allows glucose to be stored and released in response to hormones

Question 22

Explain how the liver regulates nutrient levels in the blood (including nutrients that are stored by the liver).

Answer 22

• Liver stores glucose as glycogen (iron is also stored)
• Releases glucose under influence of insulin or glucagon depending on blood/glucose levels
• Kupffer cells break down red blood cells by phagocytosis
• Hemoglobin slept into heme/globin
• Iron from heme carried to bone marrow
• Excess cholesterol converted to bile salts

Question 23

Explain how the liver breaks down and recycles the components of erythrocytes (red blood cells).

Answer 23

• Erythrocytes rupture after 120 days
• Kupffer cells in sinusoids of the liver
• Kupffer cells ingest erythrocytes
• Hemoglobin split into heme and globin groups
• Heme group broken down into iron and bilirubin
• Irons stored in liver / Bilirubin becomes part of bile

Question 24

Outline the production of bile and the causes and consequences of jaundice.

Answer 24

• Erythrocytes broken down in liver
• Heme group converted to bilirubin
• Bilirubin transferred to bile and eliminated in feces
• Jaundice;
  Caused: by blockage of bile ducts
  Cons: liver does not excrete bilirubin, bilirubin accumulates in the blood