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Fundamentals of Nutrition > Lipid digestion & Metabolism > Flashcards

Lipid digestion & Metabolism Flashcards

1
Q

What is esterification?

A

fatty acids joined with glycerol to form an ester.

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2
Q

What types of fatty acids are they? what makes them distinct?

A
  1. Saturated –> have NO double bonds
  2. Monounsaturated–> have 1 double bond
  3. Polyunsaturated–> have 2 or more double bonds
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3
Q

give an example of saturated, monounsaturated and polyunsaturated fatty acids.

A
  1. Stearic acid = saturated fatty a
  2. oleic acid = monosaturated
  3. Linoleic acid =polyunsaturated
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4
Q

what types of polyunsaturated fatty acids are there?

A

Cis (same side + folding of the molecule into a U shape) or Trans (opposite sides + linear shape)

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5
Q

What are the classes of lipids?

A
  • sterols & steroids
  • phospholipids
  • glycolipids
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6
Q

What are sterols made of? give an example of one.

A

sterols are monohydroxy alcohol of steroidal structures ex: cholesterol

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7
Q

what are sterols & steroids precursors for?

A
  • bile acids
  • sex hormones
  • cholecaliferol
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8
Q

what are the qualities of cholesteryl esters?

A

they have a lower solubility in water than cholesterol and are more hydrophobic

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9
Q

What is the main lipid constituent of the cell membrane?

A

Phospholipids

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10
Q

what are two types of phospholipids?

A
  1. glycerophosphatides
  2. sphingophosphatides
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11
Q

what do glycerophosphatides contain?

A

glycerophosphatides contain phosphoric acid and they form derivatives with other compounds in the form of phosphatidyl alcohols (ex: lecithin)

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12
Q

what is the most common sphingolipid?

A

sphingomyelins

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13
Q

How are sphingomyelins important in the nervous system?

A

they form the myelin sheath which protects neurons

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14
Q

what do glycolipids contain?

A

they contain carbohydrate component & spingosine moiety

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15
Q

what are the main glycolipids?

A

cerebrosides & gangliosides

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16
Q

what is the function of glycolipids? where are they found?

A

the main function of glycolipids is structural.

  • Cerebrosides: found in white matter of brain
  • Gangliosides: provide the carbohydrate determinants of the human blood group
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17
Q

what are the biological roles for lipids?

A
  • source of energy
  • structural components of membranes (both cellular and subcellular)
  • lubricants for body surfaces (sebaceous glands)
  • signaling molecules (extra and intra cellular)
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18
Q

digestion of lipids starts in the ________ by the action of _________.

A

MOUTH by the action of Lingual lipase

**STOMACH **by the action of Gastric lipase

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19
Q

which one is gastric lipase more effective at hydrolyzing triglycerides? medium chain fatty acids or long chain fatty acids?

A

Medium chain fatty acids

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20
Q

Do gastric lipase hydrolyze cholesteryl esters or phospholipids?

A

NO

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21
Q

Gastric motility is ______ by the presence of fat.

A

gastric motility is INHIBITED by the presence of fat (high satiety value).

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22
Q

what does the pancreas secrete to neutralize chyme entering the small intestine?

A

Bicarbonates (HCO3)

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23
Q

where does emulsification with bile salts occur?

A

Small intestine

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24
Q

most of triglyceride digestion is done by _________ in the _________

A

Pancreatic lipase in the duodenum

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25
Q

what is the end products of triglyceride break down by pancreatic lipase?

A

Monoglycerides and free fatty acids

26
Q

Pancreatic lipase is ____ effective with a bile salt-lipid mixture

A

MORE

27
Q

what is required for the activation of pancreatic lipase?

A

a cofactor called colipase

28
Q

what enzyme is found in the mouth that digests lipids? what lipids does it digest? what are the end products?

A

Lingual lipase digests triacylglycerols into di-acylglycerol and fatty acids

29
Q

what is the end product of digestion of phospholipids?

A

free fatty acids & lysophosphatidylcholine

30
Q

what enzyme(s) digest phospholipids?

A

Phospholipase A2 and phospholipase B

31
Q

what enzyme hydrolyzes cholesterol ester? what is it hydrolyzed to ?

A

cholesterol esterase.

Hydrolyzed to free cholesterol and fatty acids (in the small intestine)

32
Q

what are the end products of lipid digestion?

A
  • free fatty acids -monoacylglycerol - lysophosphatidylcholine -cholesterol
33
Q

what is the main purpose of bile salt micelles?

A

to make lipids more soluble in water phase overlying enterocytes (more lipid molecules can be delivered to the brush border membrane by bile salt micelles)

34
Q

how do monoglycerides and fatty acids enter the enterocyte?

A

by diffusion

35
Q

what are the two mechanisms for uptake of lipid digestion products?

A
  1. Passive diffusion 2. Carrier-mediated transport (Ex: FATP4)
36
Q

when are carrier mediated transport needed to uptake lipids?

A

when fatty acid concentrations are low

37
Q

water soluble digested lipids (ex: glycerol) are effectively taken up by what method?

A

diffusion

38
Q

how does degree of unsaturation affect absorption of lipids?

A

As unsaturation increases, absorption efficiency increases.

39
Q

where in the enterocytes is triacylglycerol resynthesized?

A

in the endoplasmic reticulum

40
Q

triacylglycerols are packaged into _____ in the _______.

A

triacylglycerols are packaged into lipoproteins in the golgi.

41
Q

where does re-esterification of digested lipids occur?

A

at the cytosolic surface of the ER inside the intestinal mucosal cells

42
Q

what are the two pathways for re-esterification of digested lipids?

A
  1. monoacylglycerol pathway (normal conditions most use this pathway) 2. glycerol-3-phosphate pathway
43
Q

Chylomicrons are a type of ______?

A

Lipoprotein

44
Q

What are apoproteins?

A

Triacylglycerol lipid droplets and cholesteryl esters surrounded by the polar phospholipids and proteins

45
Q

what are the three types of lipoproteins in the small intestine?

A
  1. chylomicrons 2. VLDL 3. HDL
46
Q

which lipoproteins are secreted after a fat rich meal?

A

Chylomicrons

47
Q

which lipoproteins are secreted during fasting?

A

VLDL

48
Q

what are some major apoproteins associated with chylomicrons?

A
  • A-I -Apo A-IV -Apo B-48
49
Q

what is needed for the addition of triglyceride to chylomicron?

A

it requires microsomal triglycerol transfer protein (MTP)

50
Q

where does the final step of chylomicron formation occur? (addition of CHO)

A

in the golgi

51
Q

why are lipids re-esterified?

A

to maintain low intercellular concentrations of digested lipids

52
Q

what is the function of Apoproteins?

A

signaling & attracts digestive enzyme

53
Q

what enzyme is involved in esterification of cholesterol ?

A

acyl CoA cholesterol acyltransferase

54
Q

where do chylomicrons move to after leaving the intestinal cells?

A

into the lymphatic capillaries (vessels) by exocytosis and then enter the venous plasma via the left thoracic lymph duct

55
Q

what enzyme is involved in the hydrolysis of triglycerides from chylomicrons? where does this occur?

A

lipoprotein lipases in the muscles & adipose tissues

56
Q

in the liver (hepatocytes) triglycerides are assembled in the form of _______.

A

VLDL

57
Q

LPL (lipoprotein lipase) in cardiac muscles has ______ affinity than that in adipose tissue.

A

Higher

58
Q

during fasting what concentrations are there of VLDL and chylomicrons?

A

during fasting, chylomicrons are almost absent, and VLDL concentration (hepatic) is low

59
Q

during fasting, lipoprotein lipase concentration in the ______ tissue is down regulated while that of _______ is maintained.

A

adipose= down regulated

cardiac muscles = maintained

60
Q

what is used by the muscles for energy during fasting?

A

triglycerides (VLDL)

61
Q

After a meal, (fed state) where are triglycerides (as chylomicrons) stored?

A

they are stored in the adipose tissue

Fundamentals of Nutrition (14 decks)

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