15.7

Question 1

Effect of cholecystokinin:

Answer 1

Peptide hormone from duodenum, released in response to chyme from stomach.
Stimulates gall bladder contraction and digestive enzyme production by the pancreas, and release of insulin from pancreatic islets.

Question 2

There is more bicarbonate/alkali in ___ juices than in ___

Answer 2

Pancreatic juices than in bile

Question 3

Composition of bile:

Answer 3

Mostly water, and bile pigments (mostly bilirubin diglucuronide), bile salts (derivatives of cholesterol)

Question 4

___ contributes to gall stones

Answer 4

Cholesterol!

Question 5

Bile salts are at a limit of level to keep cholesterol in ___

Answer 5

Micelles - so if there is a change in the balance there is a change in solubility and formation of gallstones that are mostly cholesterol!

Question 6

Derivatives of cholesterol i.e. bile acids:

Answer 6

Cholic acid, chenic acid, desoxycholic acid

Modified by glycine or taurine to increase hydrophilicty and detergent ability

Question 7

Detergents are ___

Answer 7

Amphipathic - hydrophilic and hydrophobic groups

Question 8

In cholic acid, not only a side group but a ___ of the 3D structure is hydrophilic

Answer 8

Face

Question 9

Process of fat digestion:

Answer 9

TAGs = fatty acids and glycerol.
Free fatty acids = detergent - so if not stored can cause destruction of membranes, fats, etc -> storage in glycerol.
Bile salts and acids emulsify dietary fats in the SI -> mixed micelles.
Intestinal lipases degrade TAGs to free fatty acids and monoacylglycerols - uptake by intestinal mucosa and conversion back into TAGs

Question 10

Fats are absorbed in the ___ gut and bile salts and cholesterol are reabsorbed in the ___ gut

Answer 10

Upper

Lower

Question 11

Treatment of obesity?

Answer 11

Orlistat/xenical reduces fat absorption by inhibiting lipase activity -> produces artificial steatorrhoea.
Can lead to deficiencies in essential fatty acids and fat soluble vitamins (ADEK)

Question 12

In ___ L of bile per day there can be up to ___ grams of cholesterol out as bile salts.

Answer 12

1L, 30 grams!

But the liver only produces approx 0.8 grams of cholesterol per due - because 0.8 grams is excreted in faeces.

Question 13

How much of bile salts are reabsorbed and recycled in the terminal ileum?

Answer 13

Approx 95%

Gut flora dehydroxylate some bile salts and recycle these too e.g. deoxycholeglycine.

Question 14

Cholestyramine

Answer 14

Sequesters cholesterol -> excretion, but has no effect on HMG-CoA reductase

Question 15

Logicol margarins, plant sterols

Answer 15

Blocks uptake of cholesterol in gut!

Question 16

ACh, secretin AND CCK signal for release of ___ digestive enzymes

Answer 16

Pancreatic!

Question 17

Release of pancreatic enzymes is signalled by enteric nervous system (ACh) and CCK.
Secondary pathway by secretin - mostly in stomach acid secretion, but in pancreas by ___, release of digestive granules

Answer 17

Activation of PLC -> DAG and IP3 -> IP3 releases calcium from stores -> release of digestive granules.

Secretin by cAMP -> release of digestive granules.

Question 18

In the pancreatic DUCT (NOT acini), secretin increases ___ content of pancreatic secretions

Answer 18

Bicarbonate

To neutralise stomach acid in duodenum

Question 19

Process of secretion and activation of pancreatic enzymes:

Answer 19

Intestinal endocrine cell -> releases CCK and secretin.
CCK and secretin -> release of pancreatic digestive enzymes.
CCK -> release of enteropeptidase from gut cells - activates trypsinogen to trypsin.

Question 20

In pancreatitis there is inappropriate activation of ___ in the pancreas

Answer 20

Zymogens

Main causes are alcohol abuse and gall stones