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Biochemistry MBS > Intro to lipids > Flashcards

Intro to lipids Flashcards

1
Q

lipids

A
  • hydrophobic organic molecules that can be extracted from cells by non-polar solvents
  • associated with each other, excluding water
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2
Q

2 classes of lipids

A
  • fatty acids

- isoprenoids

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3
Q

fatty acids

A
  • amphipathic, micelle forming, soaps
  • energy storage (fat dep to cushion organs and insulate)
  • membranes (electrical insulation) including phospholipids and sphingolipids
  • signals
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4
Q

isoprenoids

A
  • bile acids/ salts
  • membranes
  • signals
  • cofactors
  • fat soluble vitamins
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5
Q

fatty acid nomenclature

A
  • carboxyl carbon = 1
  • FA symbol: # before colon = total length of chain
  • at neutral pH, FA’s are charged and act as soaps
  • # after colon = number of double bonds
  • superscript is the double bond start point, it then reaches to the subsequent carbon
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6
Q

stearic acid

A

18: 0

- zero after colon representation full saturation

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7
Q

palmitic acid

A

16:0

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8
Q

alpha, beta, and omega

A
  • alpha = first C after the carboxyl
  • beta = second C after the carboxyl
  • omega = last C of the chain
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9
Q

omega number

A

number of carbons from the terminal methyl to the nearest double bond

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10
Q

linoleic acid

A
  • 18:2
  • 9,12
  • omega 6
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11
Q

arachidonic acid

A
  • 20:4
  • 5,8,11,14
  • omega 6
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12
Q

linoleic and linolenic deficiency

A
  • these are essential FA’s
  • symptoms: scaly dermatitis, alopecia (hair loss), thrombocytopenia (low platelet count), and cognitive development in children
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13
Q

triacylglycerols (TAGs)

A
  • dietary and storage fats
  • effectively formed by dehydration reactions between 3 FA’s and glycerol
  • fully hydrophobic
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14
Q

TAG nomenclature

A
  • change the FA suffix from “-ic acid” to “-oyl”

- list by position before glycerol

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15
Q

what determines the physical properties of FA containing compounds

A
  • melting point
  • this is what will determine if they are solids or liquids at RT
  • determines if membranes formed from FA containing compounds are fluid or semi crystalline
  • MP increases with length
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16
Q

effects of tran saturation

A
  • allows the FA’s to pack more closely together

- natural foods have cis double bonds

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17
Q

leptin

A
  • released by adipose tissue
  • suppresses food intake by altering the hormones released by the hypothalamus
  • leptin KO’s are extremely obese
18
Q

ghrelin

A

hunger hormone

19
Q

percentage of fat in the typical US diet

A
  • 35-40% of caloric intake

- triglycerides are the major source

20
Q

bile acids made from cholesterol in the liver are…

A
  • converted to bile salts

- conjugated with glycine or taurine

21
Q

gall stones

A

-imbalance of cholesterol, bile salt and phospholipid secretion

22
Q

pancreatic lipases can not access hydrophobic fat droplets until

A
  • emulsification happens
  • gall bladder relases bile salts and phospholipids which get cleaved by pancreativ lipases
  • these amphipathic molecules surround the TAG droplet and eventualy peristalsis makes them smaller
  • these droplets with surrounding bile salts are called micelles
23
Q

micelles form at

A

-critical micelle concentrationconcentration

24
Q

hydrolysis of TAGs by pancreatic lipases

A
  • TAG to diacylglycerol to monoacylglycerol
  • full hydrolysis is not necessary, since the two hidroxyl groups on 2-MAG make is sufficiently soluble in water
  • pancreatic lipase doesnt recognize olestra (FAs in ester linkages to hydroxyl groups on sucrose
25
Q

pancreatitis

A
  • deep recurrent moderate to severe abdominal, back, or epigastric pain exacerbated y alcohol
  • nausea and vomiting
  • steatorrhea in chronic cases
  • elevated serum kipases and serum amylase
  • 300,000 cases a year, 20,000 die
26
Q

steatorrhea

A
  • lipid digestion disorders other than pancreatitis can cause this
  • can be due to probelms with emulsification (biliary obstruction), lipolysis (pancreatic disease), or absorption by intestinal epithelia (celiac)
  • causes intestinal discomfort, loss of essential FAs and fat soluble vitamins
27
Q

micelles facilitate absorption

A
  • free FAs and 2-MAG at CMC are passively absorbed by intestinal epithelia
  • this reduces their concentration to below the CMC, and micelles break down to restore the CMC
28
Q

bile salt recylcing

A

95% done through enterohepatic circulation

29
Q

how to get FA’s out of the epithelial cell

A
  • resynthesize the TAG without CoA

- with CoA, the FA can not leave the epithelial cell

30
Q

absorbing cholesterol esters

A
  • hydrolysis of cholesterol esters to allow absorption

- resynthesis of CEs to drive absorption and prepare for transport

31
Q

peristalsis in lipid metabolism

A

-turns TAG droplets into micelles

32
Q

Critical micelle concentration

A

FA’s can solubilize up until a threshold concentraiton

  • above this concentration, they must form micelles in the gut
  • as free fatty acids are removed from the gut via absorption, FA’s will break away from the micelle to maintain equilibrium
33
Q

hydrolysis of TAGs by pancreatic lipase

A
  • removes two FAs from TAG resulting in two free FA’s and 2-monoacyl glycerol
  • full hydrolysis is not necessary as the two hydroxyl groups on 2-MAG make it sufficiently water woluble
  • pancreatic lipase does no recognize olestra (FA’s in ester linkages to hydroxyl groups on sucrose)
34
Q

biliary obstruction

A
  • dietary fat (TAG) can not be emulsified
  • leads to steatorrhea
  • bile salts can not be realeased through the bile duct from the gall bladder
35
Q

pancreatic disease

A
  • emulsified TAG’s can not be lipolysed

- problem with the release of pancreatic lipase

36
Q

celiac disease

A
  • low intestinal surface area

- inhibits lipolysed lipids (FA’s) from being absorbed into the intestinal epithelium

37
Q

chylomicron formation

A
  • FA’s, 2MAG, and cholesterol are inside the intestinal epithelium, they are re converted back into TAG’s and CE’s in between the bilayer of the ER using TAG synthase and ACAT
  • Once in TAG and CE form,, they bud into the ER lumen and ApoB48 is addedto the membrane, creating a nascent chylomicron
38
Q

MTP

A
  • loads chylomicrons with lipid and TG

- the chylomicron is then sent to the golgi for manufacturing and secretion

39
Q

chylomicron release

A
  • nascent chylomicrons are transported from the ER to the golgi
  • vesicles from the golgi fuse with the cell mem, releasing nascent chylomicrons into lymphatic system through lacteals
  • ApoC2 and E are transferred from HDL, forming a mature chylomircon in the lymph
  • chylomicrons then enter the blood through the thoracic duct
40
Q

lacteal

A

lymphatic capillary that absorbs dietary fats in the villi of the small intestine

41
Q

ApoC2

A

activates lipoprotein lipase on blood vessel inner surface (adipose and other tissue)

42
Q

ApoE and ApoB48

A

bind LDL receptor related protein (LRP) and allow chylomicron remnants to be internalized by the liver

Biochemistry MBS (36 decks)

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