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BIOC192 2022 > lecture 24 - fat absorption & transport > Flashcards

lecture 24 - fat absorption & transport Flashcards

1
Q

What are the 2 key molecules associated with fat metabolism?

A

triacylglycerol, cholesterol ester

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2
Q

What solubilises fat in the GI tract?

A

Bile salts

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3
Q

What are bile salts synthesised from, and where?

A

Cholesterol, in the liver

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4
Q

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

A

CCK - cholecystokinin

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5
Q

What are the 2 purposes of micelle formation?

A

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

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6
Q

What are the components of bile?

A

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

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7
Q

What are the 3 key hormones that regulate digestion?

A

Gastrin, Secretin, Cholecystokinin

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8
Q

What is the source of gastrin?

A

Stomach

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9
Q

What is the source of secretin?

A

Duodenum

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10
Q

What is the source of cholecystokinin?

A

duodenum

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11
Q

What is the major stimulus for the production of gastrin?

A

Protein containing food in the stomach

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12
Q

What is the major stimulus for the production of secretin?

A

HCl in duodenum - due to entry of acidic chyme

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13
Q

What is the major stimulus for the production of cholecystokinin?

A

Fats and amino acids in the duodenum

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14
Q

What is the action of gastrin?

A

Stimulates the secretion of gastric juices

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15
Q

What is the action of secretin?

A

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

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16
Q

What is the action of cholecystokinin?

A

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

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17
Q

How are triacylglycerols hydrolysed in micelles?

A

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

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18
Q

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

A

Pancreatic lipase

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19
Q

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

A

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

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20
Q

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

A

Excess of fat and fat-soluble vitamins in the faeces

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21
Q

What is Xenical/Orlistat?

A

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

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22
Q

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

A

Xenical/Orlistat

23
Q

what is the function of lipoproteins?

A

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

24
Q

What are the 5 key components of general lipoprotein structure?

A

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

25
Q

What are the 3 functions of apoproteins in lipoproteins?

A

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

26
Q

What apoprotein is used for structure in lipoprotein assembly?

A

apoB

27
Q

What apoproteins are used as ligands for cell surface receptors?

A

apoE, apoB

28
Q

What apoprotein is used as an enzyme cofactor?

A

apoCII (for lipoprotein lipase)

29
Q

What apoprotein acts as a cofactor for lipoprotein lipase>

A

apoCII

30
Q

What are the 4 main classes of lipoprotein?

A

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

31
Q

What type of lipoprotein has the lowest density?

A

Chylomicrons

32
Q

What type of lipoprotein has the highest proportion of protein?

A

High density lipoprotein (HDL)

33
Q

What type of lipoprotein has the highest TAG proportion?

A

Chylomicron

34
Q

What type of lipoprotein has the highest proportion of cholesterol?

A

low density lipoprotein (LDL)

35
Q

What type of lipoprotein has the highest proportion of phospholipids?

A

High density lipoprotein (HDL)

36
Q

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

A

4

37
Q

What are the 2 major lipid transport pathways?

A

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

38
Q

Dietary fat is involved in which lipid transport pathway?

A

Exogenous chylomicron pathway

39
Q

How are chylomicrons assembled?

A

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

40
Q

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

A

Via the lymphatic system

41
Q

Where is lipoprotein lipase found?

A

On the endothelial surface (inner surface) of capillaries

42
Q

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

A

In heart, skeletal muscle and adipose tissue

43
Q

What are the products of TAG hydrolysis by lipoprotein lipase?

A

fatty acids and 2-monoacylglycerol

44
Q

What is the fucntion of hormone sensitive lipase?

A

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

45
Q

What activates lipoprotein lipase?

A

apoCII (apoprotein)

46
Q

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

A

Elevated levels of chylomicrons and plasma triacylglycerol

47
Q

What is the disease caused by a defect to apoCII?

A

Familial apoCII deficiency

48
Q

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

A

Familial hypercholesterolaemia (FH)

49
Q

What is the ‘bad’ cholesterol?

A

LDL

50
Q

What is the ‘good’ cholesterol?

A

HDL

51
Q

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

A

Increase 2 or 3 fold of LDL

52
Q

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

A

Dominant - heterozygotes affected

53
Q

What is familial hypercholesterolemia treated with?

A

Statins - which lower LDL and increase HDL

54
Q

What are xanthomas?

A

Fatty growths under the skin

BIOC192 2022 (37 decks)

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