lecture 24 - fat absorption & transport

Question 1

What are the 2 key molecules associated with fat metabolism?

Answer 1

triacylglycerol, cholesterol ester

Question 2

What solubilises fat in the GI tract?

Answer 2

Bile salts

Question 3

What are bile salts synthesised from, and where?

Answer 3

Cholesterol, in the liver

Question 4

What hormone triggers the release of bile from the gall bladder?

Answer 4

CCK - cholecystokinin

Question 5

What are the 2 purposes of micelle formation?

Answer 5

Bile salts aid in solubilising fats in an aqueous environment, Decrease size to increase surface area for digestion

Question 6

What are the components of bile?

Answer 6

Water, bile acids, electrolytes, phospholipids, cholesterol, bile pigments

Question 7

What are the 3 key hormones that regulate digestion?

Answer 7

Gastrin, Secretin, Cholecystokinin

Question 8

What is the source of gastrin?

Answer 8

Stomach

Question 9

What is the source of secretin?

Answer 9

Duodenum

Question 10

What is the source of cholecystokinin?

Answer 10

duodenum

Question 11

What is the major stimulus for the production of gastrin?

Answer 11

Protein containing food in the stomach

Question 12

What is the major stimulus for the production of secretin?

Answer 12

HCl in duodenum - due to entry of acidic chyme

Question 13

What is the major stimulus for the production of cholecystokinin?

Answer 13

Fats and amino acids in the duodenum

Question 14

What is the action of gastrin?

Answer 14

Stimulates the secretion of gastric juices

Question 15

What is the action of secretin?

Answer 15

Stimulates the secretion of alkaline bile (HCO3- and pancreatic fluids

Question 16

What is the action of cholecystokinin?

Answer 16

Stimulates the release of pancreatic enzymes and bile from the gall bladder

Question 17

How are triacylglycerols hydrolysed in micelles?

Answer 17

Pancreatic lipase and colipase enzyme system binds to the lipid/aqueous interface of the micelle and performs hydrolysis

Question 18

What enzyme hydrolyses TAGs in micelle form in the small intestine?

Answer 18

Pancreatic lipase

Question 19

On a chemical level, how does pancreatic lipase hydrolyse TAG, and what is the product?

Answer 19

Hydrolyse the bonds with fatty acids at positions 1 and 3 of the glycerol backbone, leaving 2-monoacylglycerol

Question 20

What is the result of fat malabsorption in the GI tract?

Answer 20

Excess of fat and fat-soluble vitamins in the faeces

Question 21

What is Xenical/Orlistat?

Answer 21

A potent inhibitor of pancreatic lipase that prevents TAG breakdown by forming a covalent bond with the lipase active site

Question 22

What is the potent inhibitor of pancreatic lipase that prevents TAG breakdown?

Answer 22

Xenical/Orlistat

Question 23

what is the function of lipoproteins?

Answer 23

Help to solubilise lipids for transport to tissues via the blood, and then provide a delivery system for lipid entry and exit of cells

Question 24

What are the 5 key components of general lipoprotein structure?

Answer 24

Phospholipid capsule, unesterified cholesterol, esterified cholesterol, triglycerides, accessory proteins (apoproteins)

Question 25

What are the 3 functions of apoproteins in lipoproteins?

Answer 25

Structure for assembly, ligands for cell surface receptors, act as enzyme cofactors

Question 26

What apoprotein is used for structure in lipoprotein assembly?

Answer 26

apoB

Question 27

What apoproteins are used as ligands for cell surface receptors?

Answer 27

apoE, apoB

Question 28

What apoprotein is used as an enzyme cofactor?

Answer 28

apoCII (for lipoprotein lipase)

Question 29

What apoprotein acts as a cofactor for lipoprotein lipase>

Answer 29

apoCII

Question 30

What are the 4 main classes of lipoprotein?

Answer 30

Chylomicrons, very low density lipoproteins (VLDL), low density lipoproteins (LDL), high density lipoproteins (HDL)

Question 31

What type of lipoprotein has the lowest density?

Answer 31

Chylomicrons

Question 32

What type of lipoprotein has the highest proportion of protein?

Answer 32

High density lipoprotein (HDL)

Question 33

What type of lipoprotein has the highest TAG proportion?

Answer 33

Chylomicron

Question 34

What type of lipoprotein has the highest proportion of cholesterol?

Answer 34

low density lipoprotein (LDL)

Question 35

What type of lipoprotein has the highest proportion of phospholipids?

Answer 35

High density lipoprotein (HDL)

Question 36

How many lines should be seen on normal blood plasma gel electrophoresis, indicating the different types of lipoprotein present?

Answer 36

4

Question 37

What are the 2 major lipid transport pathways?

Answer 37

Exogenous chylomicron pathway (dietary fat), endogenous VLDL/LDL pathway (endogenously synthesised fat)

Question 38

Dietary fat is involved in which lipid transport pathway?

Answer 38

Exogenous chylomicron pathway

Question 39

How are chylomicrons assembled?

Answer 39

TAGS and other lipids combine with apoB in the endoplasmic reticulum of intestinal epithelial cells to form chylomicrons

Question 40

How do chylomicrons secreted from intestinal epithelial cells enter the blood stream?

Answer 40

Via the lymphatic system

Question 41

Where is lipoprotein lipase found?

Answer 41

On the endothelial surface (inner surface) of capillaries

Question 42

Where does lipoprotein lipase have the highest activity of TAG hydrolysis?

Answer 42

In heart, skeletal muscle and adipose tissue

Question 43

What are the products of TAG hydrolysis by lipoprotein lipase?

Answer 43

fatty acids and 2-monoacylglycerol

Question 44

What is the fucntion of hormone sensitive lipase?

Answer 44

Mobilises TAG stored in adipose tissue by hydrolysing TAG to glycerol and free fatty acids

Question 45

What activates lipoprotein lipase?

Answer 45

apoCII (apoprotein)

Question 46

If there are mutations to apoCII or lipoprotein lipase, what are the consequences?

Answer 46

Elevated levels of chylomicrons and plasma triacylglycerol

Question 47

What is the disease caused by a defect to apoCII?

Answer 47

Familial apoCII deficiency

Question 48

What is the disease caused by defects to apoE and LDL receptors?

Answer 48

Familial hypercholesterolaemia (FH)

Question 49

What is the ‘bad’ cholesterol?

Answer 49

LDL

Question 50

What is the ‘good’ cholesterol?

Answer 50

HDL

Question 51

What is the affect of familial a hypercholesterolemia (FH) on blood cholesterol levels?

Answer 51

Increase 2 or 3 fold of LDL

Question 52

What is the inheritance pattern of familial hypercholesterolemia (FH)?

Answer 52

Dominant - heterozygotes affected

Question 53

What is familial hypercholesterolemia treated with?

Answer 53

Statins - which lower LDL and increase HDL

Question 54

What are xanthomas?

Answer 54

Fatty growths under the skin