9 - digestive system II

Question 1

what is involved protein digestion? (3)

Answer 1

1. stomach acid
2. proteinases
3. peptidases

Question 2

what is involved in starch/carbohydrate digestion? (1)

Answer 2

amylase

Question 3

what is involved in neutral fat digestion (2)

Answer 3

1. lipases
2. bile salts

Question 4

salivary gland secretions (3)

Answer 4

1. serous acini - enzymes (amylase, lipase)
2. mucous acini - mucus
3. duct cells - water and HCO3-

Question 5

secretions from the stomach (2)

Answer 5

1. stomach acid (HCL)
2. proteases

Question 6

what produce stomach acid?

Answer 6

parietal cells

Question 7

properties of stomach acid (HCL) (2)

Answer 7

1. very acidic and can denature proteins
2. kills bacteria that may be attached to food

Question 8

How is HCL (stomach acid) generated in the stomach (4)

Answer 8

1. protons transported into gastric gland by K+/H+ ATPase transporter
2. Cl- ions transported by HCO3-/Cl- exchange transporter
3. CL- moves from inside parietal cell to lumen of stomach by anion leak channel following chemical gradient
4. H+ and Cl- combine in lumen of stomach to generate HCL

Question 9

where is pepsinogen produced

Answer 9

chief cells

Question 10

zymogen

Answer 10

proenzymes - enzyme in inactive form (requires activation to become functional)

Question 11

pepsinogen

Answer 11

proenzyme produced by chief cell

Question 12

pepsinogen activation

Answer 12

activated to pepsin by HCL

Question 13

pepsin

Answer 13

digests proteins, active at low pH, 2-3.8, inactive at 3.9

Question 14

what is produced by chief cells (2)

Answer 14

1. pepsinogen
2. stomach lipases

Question 15

what pH are pepsin and lipases active at?

Answer 15

gastric enzymes - most active at low pH (2-3.8)

Question 16

what is the drawback of stomach acid?

Answer 16

very acidic and can denature proteins of stomach lining

Question 17

what are the 2 ways stomach lining is protected from stomach acid? (2)

Answer 17

1. thick layer of mucus on stomach lining makes physical barrier to prevent damage
2. mucous surface cells and mucous neck cells secrete HCO3- into stomach lumen (neutralises acid)

Question 18

role of bile salts

Answer 18

digest neutral fats/fatty acids

Question 19

where are bile salts produced?

Answer 19

gall bladder

Question 20

what secrete pancreatic juice? (digestive enzymes)

Answer 20

pancreatic acinar cells

Question 21

where do digestive enzymes go from the pancreatic acinar cells?

Answer 21

channeled via exocrine duct leading to the digestive tract

Question 22

acinus

Answer 22

arrangement of acinar cells

Question 23

pancreatic hormone secretion

Answer 23

islet cells of langerhans secrete hormones that enter the blood

Question 24

pancreatic juice (3)

Answer 24

1. proenzymes (trypsinogen)
2. enzymes
3. other secretions (HCO3-)

Question 25

process of pancreatic zymogens being activated in the small intestine (3) (trypsinogen)

Answer 25

1. most pancreatic digestive enzymes secreted into lumen of small intestine of small intestine in inactive form (zymogen) 2. activated in a cascade inside small intestine 3. trypsinogen activated by intestinal enteropeptidases to generate trypsin that in turn activates other pancreatic enzymes

Question 26

role of bile

Answer 26

emulsifies lipids for lipid digestion and absorption in the small intestine

Question 27

hepatic secretion of bile and storage in gallbladder (4)

Answer 27

1. hepatocytes produce bile acids in liver 2. bile acids transported into bile ducts 3. water and bicarbonate added by duct epithelial cells 4. bile acids stored and channeled in gall bladder

Question 28

role of gall bladder (4)

Answer 28

1. storage of bile acids 2. bile acids concentrated up to 15 times 3. can form bile acid crystals (gallstones) 4. max vol of 60ml bile acid stored

Question 29

how is fat absorbed in the digestive system? (5)

Answer 29

1. bile salts form liver coat fat droplets 2. pancreatic lipase and colipase break down fats into monoglycerides and fatty acids stored in micelles 3. monoglycerides and fatty acids move out of micelles, enter cells by diffusion 4. absorbed fats combine with cholesterol and proteins in intestinal cells to form chylomicrons 5. chylomicrons removed by lymphatic system (lacteals) or join CVS via inferior vena cava

Question 30

lacteals (2)

Answer 30

1. lymphatic capillaries within villi 2. absorbs fats (enters as chylomicrons)

Question 31

2 gastric hormones (2)

Answer 31

1. peptide hormone gastrin 2. peptide hormone somatostatin

Question 32

peptide hormone gastrin (3)

Answer 32

1. produced by G cells 2. released in response to antrum (chamber) distension 3. gastrin stimulates gastric acid secretion

Question 33

peptide hormone somatostatin (2)

Answer 33

1. produced by D cells 2. somatostatin inhibits gastric acid (HCL) secretion

Question 34

pancreatic juice role in zymogen activation? (6)

Answer 34

1. duodenum receives chyme, secretes gastric hormones (secretin and cholecystokinin) 2. hormones stimulate production of pancreatic juice 3. HCO3- in pancreatic juice decreases acidity of chyme to pH 5 4. enteropeptidase secreted in brush border of duodenum and jejunum 5. enteropeptidases activate proenzymes from pancreas (such as trypsinogen into trypsin) 6. trypsin activates 4 proenzymes (zymogen)