Question

Biochemistry Tutorial: Membrane Lipids

Answer 1

\({\bf{Five~Types~of~Membrane~Lipids:}}\)
- glycerophospholipids: glycerol head group + two fatty acids + phosphate + alcohol
- galactolipids: glycerol head group + two fatty acids + mono/disaccharide
- archaeal tetraether lipids: two long chains + glycerol at both ends
- sphingolipids: fatty acid + sphingosine
- sterols: four hydrocarbon rings

Answer 2

\({\bf{Glycerophospholipid:}}\)

- Fatty Acids (just going to call them FAs for now) are ester linked to glycerol
- phosphate is linked to glycerol thru phosphodiester linkage
- head group contains polar alcohol (represented by X in the diagram above)
- prochial b/c of phosphate group
- named phosphatidyl+polar head group, ex phosphatidylcholine
- polar group may be neutral, pos. charged or neg. charged

- special case, one of the FAs may be ether linked instead of ester linked
> unsaturated (DB between C1 and C2): plasmalogen
> saturated: alkyl ether lipid



in the diagram above the left box shows an ester linkage and the right box shows an ether linkage

Answer 3

\({\bf{Galactolipid:}}\)


- 1 or 2 galactose residues w/ glycosydic linkage to diacylglycerol (here, diacylglycerol means glycerol w/ 2 acyl chains)
- located in membranes of plants, esp. chloroplasts
- if glucose is sulfonated, then called sulfolipid

Answer 4

\({\bf{Archaeal~Lipids:}}\)



- longer than the chains found in eukaryotes/bacteria
- ether bonds are more stable at low pH and high temp.
- polar group can be glycerol + either phosphate or sugar
- formally known as glycerol dialkyl glycerol tetraethers (GDGTs)

Answer 5

\({\bf{Sphingolipids:}}\)

- polar head group + sphingosine (or sphingosine derivative) + fatty acid
- ***no glycerol***
- sphingosine is amino alcohol
- fatty acid amide linked to the NH2 --> result is ceramide[/b]

Three Subclasses: sphingomyelins, neutral glycolipids, gangliosides
- sphingomyelins: have the head groups phosphocholine or phosphoethanolamine
(called sphingomyelin because it's prevalent in myelin)
- neutral glycolipids: head group sugar linked -OH of ceramade at C1
(no phosphate, no charge)
- gangliosides: head group oligosaccharide and sialic acid residue at termini

Answer 6

\({\bf{Misc:}}\)
- sphingolipids are often recognition sites on cell surfaces
- glycerophospholipids have hydrolyzable bonds that are hydrolyzed by the hydrolytic enzymes in lysosomes

Answer 7

\({\bf{Sterol:}}\)


- 4 fused rings; one ring is 5-carbon and the other is 6-carbon
- major example: cholesterol, has polar OH head group at C3, nonpolar body (called the steroid nucleus) + fatty acid
- contained in membranes
- precursors for other products

Answer 8

Source material is section 10.2 of Principles of Biochemistry 7th edition by Nelson, David L., and Cox, Michael M.

Answer 9

side note I would really appreciate if people just left me alone, I'm not here to chat >_>