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Biochem 3 > Lipids > Flashcards

Lipids Flashcards

1
Q

membrane composition

A

Lipids: phospholipds (sphingolipids (SM), PC, PE, PS, PI), cholesterol, glycolipids
Proteins (specific to membrane type)

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2
Q

Lipid/protein content in different membranes

A
  • variable between different membranes
  • constant for specific membrane

Myelin: 75% lipid, 25% protein
RBC: 40% lipid, 60% protein
IMM: 20% lipid, 80% protein

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3
Q

RBC plasma membrane lipid types

A

40% lipids:
cholesterol 15%
phospholipids 25% (mostly PC and SM since they’re choline lipids)

50% of lipid mass is unsaturated fatty acids

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4
Q

amphipathic

A

has both hydrophobic portion and hydrophilic portion

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5
Q

temperature/fluidity and phospholipid bilayer

A
  • affected by fatty acid chain length and degree of unsaturation
  • longer chain=higher melting temperature
  • more unsaturation=lower melting temperature
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6
Q

Cholesterol in bilayer

A
  • modulates membrane fluidity

- -OH on outside of membrane

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7
Q

Lipid distribution on cytoplasmic vs extracellular layer of bilayer

A
  • asymmetric distribution of lipid types on inside and outside
  • lipids can diffuse along same layer (lateral) or can move from inner to outer or from outer to inner (transverse)
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8
Q

protein flipase

A

can aid in transverse movement of phospholipids from one side of bilayer to the other

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9
Q

RBC plasma membrane inner/outer lipid distribution

A

-inner mostly PS and PE
-Outer mostly PC and SM (choline containing)
More choline on outer surface

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10
Q

Integral/intrinsic proteins

A
  • detergents to isolate
  • hydrophobic
  • structural role
  • pumps/transporters, receptors, enzymes
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11
Q

Peripheral/Extrinsic proteins

A
  • pH, ions to isolate
  • hydrophilic
  • enzymes, cytoskeletal protein
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12
Q

RBC proteins

A
  • isolated after osmotic shock
  • Extrinsic/peripheral proteins: spectrin, ankyrin, actin, band 4.1 and 4.2
  • intrinsic/integral: band 3 (anion transport), glycophorin, G3PD
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13
Q

Glycophorin

A
  • first membrane protein ever sequenced
  • antigen
  • abundant in RBC
  • N terminal 70aa outside cell with sugars
  • 23 apolar aa in transbilayer domain
  • 38aa at c terminus is internal charged domain
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14
Q

Width of bilayer

A

35A
23amino acids
(1.5A is rise/residue of alpha helix, 1.5*23=~35A)

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15
Q

plasma lipoproteins

A
  • complex of lipids and specific proteins (apolipoproteins)
  • used to solubilize fat and transport in blood
  • 4 major types: chylomicrons (CM), very low density (VLDL), low density (LDL), high density (HDL)
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16
Q

FA storage

A
  • FA stored at triglygerides
  • TG broked down into FA and glycerol by lipase
  • FA uptake by cell
  • FA used as energy, stored, restored back to TG, or beta oxidized
17
Q

Cholesterol ester

A
  • for storage/transport of cholesterol

- cholesterol coupled with FA to make cholesterol ester

18
Q

CM composition/location

A
  • 90% TG
  • B, C, E apoprotein classes
  • 2000A big
  • from intestine
  • removed from blood in adipose tissue/liver
19
Q

VLDL composition/location

A
  • 65% TG
  • B, C, E apoprotein classes
  • 600A medium sized
  • from liver
  • removed from blood in adipose tissue
20
Q

LDL composition

A
  • 50% CE
  • B class apoprotein
  • 200A small
  • from VLDL catabolism
  • removed from blood in liver and peripheral cells
21
Q

HDL composition

A
  • 20% CE, 25% PL, 50% protein
  • A class apoprotein
  • 100A very small
  • from liver and removed from blood in liver
22
Q

LDL function

A

cholesterol delivery (bad)

23
Q

HDl function

A

for cholesterol removal from cells and body (good)

24
Q

Lipoprotein lipase (LPL)

A
  • plasma enzyme
  • breaks TG into FA
  • Apo-C is coenzyme
25
Q

Lechithin cholesterol acyl transferase (LCAT)

A
  • plasma enzyme
  • takes FA from phospholipid to make CE
  • Apo A is cofactor in bloodstream
26
Q

Acyl-CoA cholesterol acyl transferase (ACAT)

A

takes acyl-CoA and cholesterol and makes CE

inside liver cells

27
Q

HMG-CoA reductase

A

makes cholesterol, rate limiting step in cholesterol synthesis
regulates body cholesterol

28
Q

Apolipoproteins

A
  • Apo A: LCAT cofactor, ligand for ABC-A1 and SRB1
  • Apo B: ligand for LDL receptor
  • Apo C: LPL cofactor
29
Q

Biological microemulsion

A

droplet of fat (TG/CE) at core, coated with phospholipid monolayer dotted with apolipoproteins for stability and enzymatic function

30
Q

Cholesterol in the liver

A

Cholesterol synthesis (FA–>TG)
some cholesterol –> CE
some cholesterol –> bile (only way to remove from body)

31
Q

Familial hyperchosesterolemia

A

genetic disease resulting in inability of cells to take up cholesterol by LDL and high cholesterol in bloodstream

32
Q

Receptor mediated endocytosis

A
  • LDL receptors cluster causing ‘fatty coat’ on outside of cell
  • clatherin coat formed and makes invagination of plasma membrane
  • vesicle endocytosed, merge with endosome to disocciate receptor/LDL
  • receptors recycled to cell surface
  • Apo B and CE broken down in lysosome to aa and cholesterol/FA respectively
  • cholesterol used for membrane biogenesis, steroid hormones (in adrenal gland), bile acids (in liver) or put in storage as CE (via ACAT) which turns off HMG-coa reductase and stops cholesterol synthesis
33
Q

Reverse cholesterol transport

A

Only method of cholesterol removal

  • ABC-A1 transports cholesterol and PL out of peripheral cell (with Apo A as ligand)
  • LCAT converts cholesterol to CE in nascent HDL
  • mature HDL formed
  • CE selectively taken into liver cell by SRB1 (using apo A as ligand)
  • CE in liver to bile acid synthesis or secreted into bile for removal.

Biochem 3 (5 decks)

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