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nutr 3210 > lipids > Flashcards

lipids Flashcards

1
Q

what are lipids?

A
  • soluble in organic solvents
  • wide variety of structures and functions
  • source of energy
  • cell and organelle membranes
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2
Q

what are saturated vs unsaturated fatty acids?

A
  • saturated have the max # of H atoms and only have single bonds
  • unsaturated are missing H atoms and have double bonds with cis or trans config
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3
Q

what is the delta system vs omega system?

A
  • delta: numbering starts from carboxyl end
  • omega: numbering starts from methyl end
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4
Q

what is the delta system nomenclature?

A

carbons:double bonds △^position of double bonds

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5
Q

what is the omega system nomenclature?

A

carbons:double bonds ⍵/n-location of first double bond

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6
Q

what are the essential fatty acids and why are they essential?

A
  • linoleic acid (n-6) and alpha linolenic acid (n-3)
  • humans lack enzymes that insert double bonds beyond the delta 9 position
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7
Q

what are signs of linoleic and alpha linolenic acid deficiency?

A
  • n-6: dermatitis, reduced growth, reduced reproductive maturity
  • n-3: low IQ, low visual acuity
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8
Q

what are the enzymes used in EFA desaturation and elongation?

A
  • desaturase: insert double bonds
  • elongase: adds more carbons
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9
Q

what does linoleic acid convert to and how?

A
  • arachidonic acid
  • desaturation then elongation then desaturation
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10
Q

what does alpha linolenic acid convert to and how?

A
  • eicosapentaenoic acid
  • desaturation, elongation, desaturation
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11
Q

which part of EFA desat and elong is not efficient?

A

conversion of alpha linolenic acid to eicosanoid (less than 8%)

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12
Q

what are eicosanoids?

A
  • derived from FAs
  • hormone like, function locally
  • promote inflammation
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13
Q

what are triglycerides?

A
  • dietary and storage lipids
  • glycerol that has been esterified with 3 fatty acids
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14
Q

what are phospholipids?

A
  • more polar than TAGs
  • in membrane, intracellular signalling
  • hydrophilic head
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15
Q

what are sterols?

A
  • free or esterified with FA
  • in membranes
  • precursor for hormones
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16
Q

what is significant about cholesterol structure?

A
  • most common sterol
  • two different forms
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17
Q

where are lipids digested and by what?

A
  • mouth, stomach, liver, gallbladder, small intestine
  • lipase and bile acids
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18
Q

what are mixed micelles?

A
  • spherical complexes containing lipid digestion products and bile acids
  • access spaces between microvilli in intestine
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19
Q

what is enterohepatic circulation?

A
  1. cholesterol makes bile salts
    1. bile salts stored in the gallbladder
    2. released into small intestine to help emulsify dietary lipids
      a. creates mixed micelles
    3. bile acids are reabsorbed back into the liver
      5% lost in feces
20
Q

how do soluble fibres affect enterohepatic circulation?

A
  • reduce efficiency
  • hold onto bile acids which are lost in feces
21
Q

what are the brush border enzymes involved in lipid absorption?

A
  • pancreatic lipase
  • cholesterol esterase
  • phospholipase
22
Q

how does lipid absorption work?

A

lipids are partially broken down by brush border enzymes and enter across the membrane via lipid transporters, then are remade inside the cell as chylomicrons that enter the lymphatic system via lacteal to bypass the liver and target different tissues

23
Q

what are chylomicrons/chylomicron remnants?

A
  • high lipid and low protein
  • contain apob-48, apoc, apoe
  • increase in circulation after a meal
24
Q

what are VLDLs?

A
  • very low density lipoproteins
  • high lipid, low protein
  • apob-100, apoc, apoe
25
Q

what is lipoprotein lipase?

A
  • enzyme on the surface of endothelial cells lining small blood vessels and capillaries
  • activated by apoc in chylomicrons
  • hydrolizes the TAG in chylomicrons which produces CRs
  • CRs are then removed from circulation through apoe mediated interactions with a receptor in the liver
  • induced by insulin
26
Q

what are LDLs?

A
  • low density lipoprotein
  • bad cholesterol
  • apob-100, apoc, apoe
27
Q

what are HDLs?

A
  • high density lipoproteins
  • low lipid, high protein
  • apoa family
28
Q

what happens to a chylomicron in the intestine?

A

hydrolyzed by LPL to become CR

29
Q

what happens to VLDLs ?

A
  • hydrolized by LPL to produce LDL
  • TAG gets store or used for energy
  • LDL gets taken up by the liver via LDL receptors which recognize apoe and apob100 on the LDL
30
Q

what is the main transporter of newly synthesized hepatic TAGs?

A

VLDL

31
Q

what do apolipoproteins do?

A

allow receptor recognition

32
Q

what are the fates of HDLs?

A
  • picks up cholesterol accumulating in the body and becomes mature with lots of cholesterol
  • lecithin cholesterol acyltransferase (LCAT) esterifies cholesterol to FAs to make chol. esters
  • chol. ester gets transferred to VLDLs or LDLs via CETP
    OR
  • HDL carried back to liver where cholesterol/chol. ester are removed by SRB1s
33
Q

what is SR-B1?

A

scavenger receptor class B1 which is an HDL receptor in the liver

34
Q

what is CETP?

A

cholesterol ester transfer protein that transfers cholesterol ester from HDL to VLDL or LDL

35
Q

what are the fates of cholesterol?

A
  1. converted into bile acids to replenish bile acid pool
  2. secreted with bile and eliminated from body
  3. packaged into VLDL and sent around the body
36
Q

what are higher HDL levels correlated with?

A

more cholesterol returning to the liver

37
Q

how are new fatty acids made for the fatty acid pool?

A

via de novo lipogenesis

38
Q

what are lipids transferred to?

A

they travel from the portal vein to the hepatic vein, enter as VLDL

39
Q

what is the difference betweeh chylomicrons and CRs?

A

adipose tissue gets chylomicrons directly while CRs go to the liver

40
Q

where do lipids fit into metabolic pathways?

A
  • gluconeogenesis: glycerol backbone is glucogenic
  • krebs cycle: fat oxidation via acetyl coa
41
Q

what do lipases do?

A

hydrolyze ester linkages (lipolysis) which releases FAs from triglycerides

42
Q

what is HSL?

A
  • hormone sensitive lipase
  • cleaves a FA from the glycerol backbone
  • inhibited by insulin
43
Q

what is the result of the complete breakdown of a TAG molecule?

A

1 glycerol and 3 FAs

44
Q

where does glycerol end up?

A

glycolysis or gluconeogenesis

45
Q

what is produced by each round of beta oxidation?

A

1 NADH and 1 FADH2

nutr 3210 (5 decks)

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