lecture 12 - proteins in the small intestine

Question 1

If digestive enzymes were synthesised in their active form what would happen?

Answer 1

• they woild digest the very cells that make them which is why inactive precursors become activated

Question 2

Where are cholecystokinin receptors located and what dp they respond with?

Answer 2

pancreas - additional enzyme delivery
galbladder - contracts to deliver bile
sphincter of oddi - relaxes to facilitate delivery of the enzymes and bile salts

Question 3

What happens when there is an increase in intestinal fatty acids and proteins?

Answer 3

1. ) small intestine increases CCK secretion
2. ) Plasma CCK increases
3. ) pancreases secretes more enzymes
4. ) increase of flow of enzymes into the small itnestine
5. ) increase in digestion of fats and proteins

Question 4

what are the proteases and peptidases that are produced by the pancreas?

Answer 4

proteases - trypsin and chymotrypsin
peptidases - carboxypolypeptidases

-trypsin inhibitor is secretee by pancreas to block action called kazal

Question 5

what do the pancreatic proteases do?

Answer 5

• digest proteins to peptides

- trypsin activates other proteases peptidases

Question 6

what do the pancreatic peptidases do?

Answer 6

• digest polypeptides to small peptides and amino acids

- carboxy terminal amino acid

Question 7

what are the brush border proteases and peptidases?

Answer 7

proteases - enterokinase

peptidases - aminopolypeptidases

Question 8

what does enterokinase do?

Answer 8

activates trypsin

Question 9

what does aminopolypeptidase do?

Answer 9

• digest polypeptides to small peptides and amino acids

- amino terminal

Question 10

how are free amino acids, mono, di and tri peptides absorbed into the epithelium?

Answer 10

by active transport, facilitated diffusion and mainly in crypts

Question 11

some small peptides are carried across the eptihelium by ….

Answer 11

transcytosis

Question 12

proteins are broken down to peptide fragments in the stomach by …. and in the small intestine by …. and ….. the major …. secreted by the pancreas

Answer 12

• pepsin
• trypsin
• chymotrypsin
• proteases

Question 13

peptide fragments are further broken down to free amino acids by…. from the pancreas and ….. located on the luminal membranes of the small intestine epithelial cells

Answer 13

• carboxypeptidase

- aminopeptidase

Question 14

how do free amino acids enter the epthelial cells ?

Answer 14

by secondary active transport coupled to Na+

Question 15

how are short chains of 2 to 3 amino acids absorbed ?

Answer 15

secondary active transport coupled to hydrogen ion gradient

Question 16

…. stimulates the galbaldder which responds by contracting and delivering more ….. to the ….. through the ….. which relaxes in response to …..

Answer 16

• CCK
• bile
• duodenum
• sphincter of oddi
• CCK

Question 17

what is bile secreted by?

Answer 17

hepatocytes

Question 18

bile is rich in …. and contains ….

Answer 18

• cholestrol

- bile salts, lecithin (phospholipid), bile pigments, water

Question 19

what are some bile salts?

Answer 19

-bile acids: cholestrol and amino acids

Question 20

what are some bile pigments?

Answer 20

• bilirubin

- biliverdin

Question 21

Where is bile stored?

Answer 21

• in the gallbladder

Question 22

What is the max capacity of the gall baldder?

Answer 22

60 ml

Question 23

how can bile be concentrated?

Answer 23

by the absorption of fluid and electrolytes by epithelium of gall bladder

Question 24

how is the release of bile triggered?

Answer 24

-CCK and AcH: relaxes the sphincter of oddi

Question 25

what are gall stones and what are they caused by?

Answer 25

-they are crystals of cholestrol and they are caused by high fat diets

Question 26

What is the digestive function of bile?

Answer 26

Emulsification:

• mechanical processes break up fat droplets
• lipase digests fats in the presence of colipase which is a cofactor needed for lipase to penetrate bile salts

Question 27

what is the absorptive function of bile?

Answer 27

micelle formation:

• complexes with a sterol necleus that ferry fats through the brush border to allow absorption into epithelial cells
• bile salts reabsorbed in the ileum (94%)
• re secreted

Question 28

what does the non polar and polar surfaces of a bile salt help in?

Answer 28

non polar - emulsify fats

polar - water solubility

Question 29

emulsified fat globules are small enough that ….. gain access to degrade …. to …… and ….. which enter absorptive cells by …… or …. to form loosely held micelles which readily break them down

Answer 29

• lipase enzymes
• triglycerides to monoglycerides
• simple diffusion or aggregate

Question 30

steps of fat to distrubution and processing?

Answer 30

1. ) big droplet of fat
2. ) small droplets of fat
3. ) micelles
4. ) fatty acids and monoglycerides
5. ) chylomicron assembly
6. ) distribution and processing

Question 31

…. vitamins are absorbed like other ……

Answer 31

• fat soluble

- lipids

Question 32

…. vitamins are absorbed by ….. or ….. except for vitamin …. which must first bind to a transport protein known as …

Answer 32

• water soluble
• diffusion or mediated transport
• B12
• intrinsic factor