What are the four general types of membrane lipids?
Phospholipids, glycolipids, archaeal tetraether lipids, and sterols.
Describe the molecular components/bonds of: Glycerophospholipids (also called phosphoglycerides)
Its backbone is glycerol; it contains 2 fatty acids, ester linked at C1, C2 1 phosphate head group + alcohol at C3 via phosphodiester bond
In a glycerophospholipids/phosphoglycerides, the phosphate group bears a ____ (negative/positive/neutral) charge at neutral pH.
What is a plasmalogen?
A type of glycerophospholipid with an ether-linked chain and double bond between C1 and C2.
Describe the molecular components/bonds of: Glycolipids (also called sulfolipids)
Its backbone is glycerol; it contains 2 fatty acids, ester linked at C1, C2 1 mono/di-saccharide head group at C3 via glycosidic linkage
What is the most abundant membrane lipid in the biosphere?
Galactolipids; they are a type of glycolipid abundant in thylakoid membranes. They make up 70%-80% of the total membrane lipid content of vascular plants.
Describe the linkages within membrane lipids within some archaea living within ecological extremes. In other words, how are their membranes so resistant to high temperature or low pH?
They have their fatty acid chains linked via ETHER bond instead of ester bond; ether groups are much more resilient against hydrolysis at these ecological extremes.
Describe the molecular components/bonds of: Sphingolipids
Sphingolipids are a subtype of both glycerophospholipids AND glycolipids. Its backbone is sphingosine; it contains 1 long nonpolar chain (part of sphingosine) 1 (nonpolar) fatty acid chain 1 polar head group; Head group is either a phosphate or sugar. (attached via phosphodiester bond or glycosidic linkage)
Describe what makes a sphingolipid a ceramide.
When the fatty acid is attached to the sphingosine's C2 via amide linkage.
What are the functions of ceramides?
Regulation of protein kinases, cell division, differentiation, migration, and apoptosis.
What are the three subclasses of sphingolipids? What do all of them have in common, and where do they differ?
Sphingomyelins, glycosphingolipids, and gangliosides. Common: All derivatives of ceramides. Differ: Head groups
Describe sphingomyelins. Out of the four general types of membrane lipids, which does this fall under?
Sphingomyelins are sphingolipids, specifically ceramides, whose head groups are phosphocholine or phosphoethanolamine.
Sphingomyelins are phospholipids.
Describe glycosphingolipids Out of the four general types of membrane lipids, which does this fall under?
Glycosphingolipids are sphingolipids whose head groups are one or more saccharides connected directly to the C1-OH of the ceramide.
Glycosphingolipids are glycolipids because their head groups are sugars
What are the two subtypes of glycosphingolipids called? What differentiates them?
Cerebrosides: One sugar head group. Globosides: Two or more sugar head groups.
Describe gangliosides. Out of the four general types of membrane lipids, which does this fall under?
Gangliosides are sphingolipids whose head groups are comprised of oligosaccharides with N-acetylneuraminic acid (Neu5Ac) at the ends.
What distinguishes gangliosides from globosides?
Gangliosides, due to their Neu5Ac end groups, are negatively charged at neutral pH. Globosides are uncharged at neutral pH.
What enzymes within the lysosome degrade glycerophospholipids?
Phospholipase A removes one fatty acid, degrading the glycerophospholipid into what is called a lysophospholipid.
Then, a lysophospolipase cleaves the remaining fatty acid
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Describe the molecular components/bonds of: Sterols
Sterols are characterized by the steroid nucleus, made up of four fused rings.
All sterols in eukaryotes are made from isoprene subunits. Side groups are as follow: Fatty acid chains attached at C17 Polar head group attached at C3
What are other functions of lipids, aside from structure and storage?
Signaling, acting as cofactors, becoming pigments.
What is PIP2? What is its function?
Phosphatidylinositol 4,5 bisphosphate Its function is to serve as a reservoir of signaling molecules. Upon cleavage by phospholipase C, it yields signaling molecules.
What signal molecules does PIP2 release upon hydrolysis?
prostaglandins, thromboxanes, leukotrienes, and lipoxins
Describe the characteristic molecular components of prostaglandins. What are their functions?
Prostaglandins are characterized by their 5-membered ring.
Their functions include:uterus contraction during menstruation and labor, blood flow to specific organs, the wake-sleep cycle, regulating responsiveness of certain tissues to hormones, elevation of body temperature causation of inflammation and pain.
Describe the characteristic molecular components of thromboxanes. What are their functions? (hint: what are they produced by?)
Thromboxanes are characterized by their 6-membered ring containing an ether. Produced by thrombocytes (blood platelets)
Their functions include: formation of blood clots and reduction of blood flow to the site of a clot.
Describe the characteristic molecular components of leukotrienes. What are their functions?
Leukotrienes are characterized by their linear chain with 3 conjugated double bonds.
Their functions include: contraction of smooth muscle (leukotrienes are the cause for asthmatic attacks)
Describe the characteristic molecular components of lipoxins. What are their functions?