Digestion

Question 1

salivary alpha-amylase

Answer 1

cleaves a(1-4) bonds of starch and glycogen in the mouth.

Inhibited in the acidic stomach lumen

Question 2

Lingual Lipase

Answer 2

Released with siliva in the mouth with lipolytic activity continuing through to the stomach

Hydrolyzes long-chain triglycerides into partial glycerides and free fatty acids.

Act mainly on medium chain fatty acids.

Question 3

7 common pancreatic inactive proteases/proteins that are proteolytically activated by Trypsin

Answer 3

trypsinogen, chymotrypsinogen, proelstase, two procarboxypeptidases, procolipase, prophospholipase A2.

Question 4

Gastrin

Answer 4

leads to release of gastric acid from parietal cells into the lumen of the stomach.

secreted from G cells at the bottom of the gastric gland.

Question 5

First phase of digestion

Answer 5

Digestion in the mouth: Salivary alpha amylase and lingual lipase secreated in saliva to break down starch and fats.

Question 6

Second phase of digestion

Answer 6

Digestion in the stomach: Alpha amylase inactivated, lingual lipase still active. gastric lipase active. pepsinogen activated to pepsin.

Denaturing of DNA/RNA
Degradation of proteins and TAGs

Question 7

Third Phase of Digestion

Answer 7

Intestinal digestion: release of secretin and cholecystokinin (CCK)

Neutrilization of pH in duodenum
secreation of bile salts and pancreatic enzymes (alpha amylase, phospholipase A2, trypsinogen)

trypsin activates enzymes for protein and lipid digestion,

Absorption of proteins, lipids, and sugars in intestinal lumen.

Question 8

Secretin

Answer 8

Released in the presence of high proton concentration

Secretion of water and bicarb from the pancreas.

Inhibits to a certain degree the release of chyme from the stomach which allows time for neutralization of the present chyme

Question 9

Cholecystokinin

Answer 9

activates secretion of bile from the gallbladder
inhibits gastric motility

activates enteropeptidase in duodenum

activates secretion of pancreatic enzymes

Question 10

Bile Salts

Answer 10

Glycine or taurine (formed from cysteine in the liver) are conjugated with bile acids. Conjugated bile acids are often named bile salts

Released by the liver into the bile (95% taken up again via the enterohepatic circulation as Secondary bile acids)

•transport of free cholesterol in bile from the liver to
the duodenum

• emulsification of dietary lipids for digestion by pancreatic enzymes
• uptake of products of lipid digestion into intestinal mucosal cells

Question 11

Pancreatic Lipase

Answer 11

Digestion of dietary triacylglycerols, needs emulsification of lipids performed by conjugated bile salts.

forms 2-monoacylglycerol that is absorbed in the intestinal lumen.

Question 12

colipase

Answer 12

Anchors pancreatic lipase on the lipid droplet

Question 13

Chylomicrons

Answer 13

lipid transport from intestinal cell to lymph/blood circ.  
monolayer lipid membrane filled with: 
TAGs formed inside the cell
fat-soluble Vitamins
Cholesterol esters

Question 14

SGLT

Answer 14

Glucose/glactose transporter into cell lumen

Amino acid transport

Using Na pump

Question 15

Medium Chain Fatty acids in Digestion

Answer 15

released from intestinal mucosal cells directly as free fatty acids into the portal vein and reach the liver.

milk is a good source, allows the rapid uptake into the liver for energy metabolism.

TAGs with medium-chain fatty acids can be degraded by lingual and gastric lipase which do not need bile salts for activity

Question 16

Pepsin

Answer 16

Pepsin acts mainly as endopeptidase, which means that it cleaves proteins from the inside and leads to smaller proteins and peptides

Formed from pepsinogen secreted by cheif cells. pepsinogen is activated to pepsin by acid catalyzed cleavage from HCl or by already active pepsin.

Question 17

Pancreatic alpha-amylase

Answer 17

cleaves dietary polysaccharides to disaccharides in the duodenum

cleaves alpha (1-4) linkages of sugars

Question 18

Enteropeptidase

Answer 18

Synthesized by cells of the duodenum, with the purpose that it is not in contact with zymogens of the pancreas until these zymogens reach the intestines.

Cleaves trypsinogen to trypsin (an irreversible activation by proteolytic cleavage)

Question 19

Phospholipase A2

Answer 19

Cleaves glycerophospholipids and releases the fatty acyl group.

It forms a free fatty acid and a lyso-phospholipid, both molecules have detergent character and can now be used to emulsify dietary lipids.

Question 20

Apo b48

Answer 20

Marks chylomicrons for transport into lymph

Question 21

Trypsin cleavage of proteins

Answer 21

After Arg or Lys residues

long, narrow binding pocket

Question 22

Chymotrypsin cleavage of proteins

Answer 22

After bulky (Met, Leu) and aromatic (Phe, Tyr, Trp) residues

wide, large binding pocket

Question 23

Elastase cleavage of proteins

Answer 23

After Ala, Gly, Ser

Small binding pocket

Question 24

Carboxypeptidase cleavage of proteins

Answer 24

Cleave from carboxyl-end

Ala Leu, Ile, Val, Arg, Lys

Question 25

Cholelithiasis

Answer 25

Gallstones

Often due to a decrease of bile salts and phosphatidylcholine in bile,
or due to increased biliary cholesterol secretion