Recall from previous lectures that lipids can be membrane associated like:
1) Phospholipids and 2) Glycolipids
OR stored as TAG droplets in adipose tissue
Glycolipid’s
structure:
sphingosine
backbone, FA,
TAG: have and a sugar
a glycerol molecule (one)
backbone monosaccharide
with 3 fatty or more
acids (FA) oligosaccharide
Phospholipids compose the majority of membrane lipids, classified into:
A) glycerophospholipids: **main phospholipids
Structure: a glycerol backbone, FA on carbon no.1 & no.2, phosphate group on carbon no.3 +
head group (usually an alcohol) attached to the phosphate.
B) sphingolipids have a sphingosine backbone, FA on C2, PO4 on C1 + Choline
this structural molecule is known as sphingomyelin the only existing phosphosphingolipid.
Side note: (not mentioned in the lecture)
Remember that phospholipids are amphipathic, and u can conclude that from
their structure:
hydrophobic tail→ fatty acids hydrophilic head→ phosphate + alcohol
Glycerophospholipids metabolism & degradation is the main topic of C1: FA
this lecture
Glycerol
C2: FA
Classification of Glycerophospholipids:
• Phosphatidic acids: the basic glycerophospholipid, the precursor to all
glycerophospholipids. phosphatidic acid
the Head group attached to the phosphate in phosphatidic acid is -H structure
-different head groups can attach to the phosphate group in phosphatidic acid as the following
composing different type of glycerophospholipids:
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, phosphatidic acid PA(base) + head group → different glycerophospholipids
Glycerophospholipids Head group (alcohol)
Phosphatidylethanolamine (PE) Ethanolamine
2 carbons (ethanol) + amino group
Phosphatidylcholine PC (lecithin) Choline
2 carbons + quaternary amine
Phosphatidylserine (PS) Serine
2 carbons + amino group + carboxyl
group
Phosphatidylglycerol (PG) Glycerol
Phosphatidylinositol (PI) Myo-Inositol 4,5-bisphosphate
Specifically, phosphatidyl inositol 4,5- Inositol + 2 phosphates
a sugar molecule + 2P
bisphosphate
Other Glycerophospholipids:
• Cardiolipin (Complex structure) • Plasmalogens (ether phospholipids)
Head: Phosphatidyl glycerol
Synthesis
• Location: smooth ER
(except for ether lipids—discussed in page 9)
• synthesis of phospholipids requires activation by attaching CDP
→Activation is attachment of a group that gives a molecule high energy, for example
glucose-6P is an activated molecule because it has a phosphate group attached to it, same
concept applies to UDP-glucose that’s involved in glycogen metabolism.
• High energy molecules have specificity in their activation in biosynthetic reactions:
carbs→ activated by attachment to UDP-
Proteins→ activated by attachment to GDP-
lipids→activated by attachment to CDP-
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1) Phospholipids and 2) Glycolipids
OR stored as TAG droplets in adipose tissue
Glycolipid’s
structure:
sphingosine
backbone, FA,
TAG: have and a sugar
a glycerol molecule (one)
backbone monosaccharide
with 3 fatty or more
acids (FA) oligosaccharide
Phospholipids compose the majority of membrane lipids, classified into:
A) glycerophospholipids: **main phospholipids
Structure: a glycerol backbone, FA on carbon no.1 & no.2, phosphate group on carbon no.3 +
head group (usually an alcohol) attached to the phosphate.
B) sphingolipids have a sphingosine backbone, FA on C2, PO4 on C1 + Choline
this structural molecule is known as sphingomyelin the only existing phosphosphingolipid.
Side note: (not mentioned in the lecture)
Remember that phospholipids are amphipathic, and u can conclude that from
their structure:
hydrophobic tail→ fatty acids hydrophilic head→ phosphate + alcohol
Glycerophospholipids metabolism & degradation is the main topic of C1: FA
this lecture
Glycerol
C2: FA
Classification of Glycerophospholipids:
• Phosphatidic acids: the basic glycerophospholipid, the precursor to all
glycerophospholipids. phosphatidic acid
the Head group attached to the phosphate in phosphatidic acid is -H structure
-different head groups can attach to the phosphate group in phosphatidic acid as the following
composing different type of glycerophospholipids:
2|Page
, phosphatidic acid PA(base) + head group → different glycerophospholipids
Glycerophospholipids Head group (alcohol)
Phosphatidylethanolamine (PE) Ethanolamine
2 carbons (ethanol) + amino group
Phosphatidylcholine PC (lecithin) Choline
2 carbons + quaternary amine
Phosphatidylserine (PS) Serine
2 carbons + amino group + carboxyl
group
Phosphatidylglycerol (PG) Glycerol
Phosphatidylinositol (PI) Myo-Inositol 4,5-bisphosphate
Specifically, phosphatidyl inositol 4,5- Inositol + 2 phosphates
a sugar molecule + 2P
bisphosphate
Other Glycerophospholipids:
• Cardiolipin (Complex structure) • Plasmalogens (ether phospholipids)
Head: Phosphatidyl glycerol
Synthesis
• Location: smooth ER
(except for ether lipids—discussed in page 9)
• synthesis of phospholipids requires activation by attaching CDP
→Activation is attachment of a group that gives a molecule high energy, for example
glucose-6P is an activated molecule because it has a phosphate group attached to it, same
concept applies to UDP-glucose that’s involved in glycogen metabolism.
• High energy molecules have specificity in their activation in biosynthetic reactions:
carbs→ activated by attachment to UDP-
Proteins→ activated by attachment to GDP-
lipids→activated by attachment to CDP-
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