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BIOC 3300 Study Guide - Midterm Guide: Lipoprotein Lipase, Ldl Receptor, Pancreatic Lipase Family

Biochem & Molecular Biology
Course Code
BIOC 3300
Mc Leod Roger
Study Guide

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1. How are ether phospholipids synthesized (what from, what
is added, etc.)?: Synthesized from 1-acyl-dihydroxyacetone-3-
phosphate by addition of saturated fatty alcohol to 1-position,
releasing fatty acid
2. How are plasmogens formed?: sn-1 alkyl group undergoes
*desaturation* after headgroup attachment and sn-2 position
3. How is phosphatidic acid synthesized from G3P?: acyl chains
are added in two consecutive steps as thioesters from ACP to
generate phosphatidic acid
4. In bacteria, at what level is regulation of phospholipid
biosythesis achieved, and why does this fact make sense in
the context of bacterial usage of FA's?: Regulation at the level
of *fatty acid synthesis*
This makes sense because FA's are not used as energy sources
in bacteria, only membranes
5. *IN BACTERIA*, From CDP-diacylglycerol, what is added to
create cardiolipin and phosphatidylethanolamine?:
Cardiolipin: made from PG3P; hydrolysis of Pi to make
phosphatidylglycerol, then combination of 2x
phosphatidylglycerol to make cardiolipin
phosphatidylethanolamine: sythiesized form
phosphatidylserine, decarboxylation to make
6. *IN BACTERIA*,From CDP-diacylglycerol, what is added to
create phosphatidylserine and PG3P?:
Phosphatidylserine: *serine* is added
PG3P: *G3P* is added
7. *IN EUKARYOTES*, how are headgroups added?: The future
headgroup itself is activated by CTP, then condensed with
8. In what organ is the PE-PC reaction important?: Liver
9. What are glycerphospholipids synthesized from?: 3 carbon
sugar phosphate that is acylated and has a nitrogen base
added to it
10. What are phospholipids' only function in bacteria?:
membrane components
11. What are the 3 fatty acids found in bacteria?: Palmitate
12. What are the 3 glycerophospholipids found in bacteria?:
13. What are the reactions that catalyze headgroup exchange
reactions of phospholipids?:
14. What are the three sources of phosphatidic acid in
eukaryotes?: G3P
Reduction of DHAP by CoA thioester acylation
DAG phosphorylation
15. What are the two strategies for generation of a
phosphodiester linkage?:
Activation of glycerol or activation of head group
16. What are two roles of phospholipids?: Structural
components of membrane bilayers
Biological regulators
17. What cofactor stimulates and allows base-exchange
reactions to occur?: Calcium
18. What donates a methyl group to PE to crete
phosphatidylcholine?: adoMet
19. What is the biological function of PAF?: Stimulates platelet
20. What is the branch point between the synthesis of
Phospholipids and Triacylglycerols?: Phosphatidic acid
Lecture 11 - Phospholipid Metabolism
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21. What is the function of phosphatidylinositol?: Signal molecule (cyclic ring for X group)
22. What is the function of phosphoinositides, what are they synthesized from, and how is the inositol activated for synthsis?:
important second messengers in membrane signalling pathways
Synthesized on demand and degraded rapidly
Generated by phosphorylation of OH groups of inositol
23. What is the most abundant phospholipid, and where is it normally found?: Glycerophospholipid, found as components of
24. What is the most important of the headgroup-exchange reactions?: PE to PS
25. What is the reaction that adds the headgroup to the phospholipid?: activation by CTP (at sn-3 position), releasing PPi (driving the
reaction forward) and CMP
26. What is the role of phospholipases?:
Hydrolytic enzyme that degrades phospholipids
Can remodel phospholipids to replace fatty acids that have been damaged by oxidation
27. What is the structure of a glycerophospholipid?:
Saturated fatty acid
unsaturated fatty acid
Phosphate head group
28. What is the structure of a sphingolipid?: Sphingosine group + -H (ceramide) or -Phosphocholine (sphingomyelin)
29. What is the structure of platelet activating factor (PAF) compared to normal ether phospholipids?: PAF also has an *sn-2 acetyl
30. What pH range do base-exchange reactions take place at?: Alkaline pH
31. What positions are saturated and unsaturated on phosphatidic acid?: *sn-1 position is almost always (90%) saturated*
*sn-2 is usually (90%) unsaturated*
32. Where are headgroup exchange reactions localized in the cell?: within the ER
33. Where does synthesis of phosphatidylinositol occur?: mitochondria

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1. From phosphatidic acid, what enzymes catalyze the creation
of TAG or Glycerophospholipids?:
TAG: *Phosphatidic acid phosphatase (PAP) removes
phosphate group to create diacylglycerol (DAG), then
diacylglycerol acyltransferase (DGAT)* uses fatty acyl-CoA to
add a fatty acid to sn-3 position
Glycerophospholipid: headgroup is attached to the phosphate
2. How can glycerol enter glycolysis in the liver?: Through
*glycerol kinase* to form G3P
3. In de novo biosynthesis of TAG, after G3P is synthesized,
what two steps are required to finally create phosphatidic
Addition of two fatty acid chains to G3P. This is done by the
enzyme *G3P acyltransferase (GPAT), which adds once fatty
acyl chain at a time using ATP (energy from hydrolysis of PPi
drives reaction*). After both chains have been added,
phosphatidic acid is formed
4. In de novo biosynthesis of TAG, what two enzymes catalyze
the synthesis of G3P from DHAP and glycerol, respectively?:
*G3P dehydrogenase* (DHAP -- G3P)
*Glycerol kinase* (Glycerol -- G3P)
5. Once TAG has been hydrolyzed to glycerol by HSL, why can't
it be resynthesized into TAG in adipocytes? Where is
glycerol transported so that it can be resynthesized back
into TAG?: Because adipocytes don't have *glycerol kinase*
glycerol is transported to *liver*
6. What are glucagon and epinepherine's effect on TAG
metabolism in the adipocyte?: Glucagon/epinepherine
promote TAG hydrolysis by binding to a G-protein coupled
receptor, causing a protein kinase cascade which activates
*hormone-sensitive lipase (HSL)*, turning TAG into glycerol
7. What are important sites of TAG metabolism?: enterocytes
8. What are the steps involved in TAG metabolism by
pancreatic lipase?: - lipase and procolipase form complex in
presence of FA and bile salt micelles
- procolipase N- and C- terminal domains are cleaved to expose
lipid-binding domains
- pancreatic lipase then conformationally changes to expose
lipid-binding domain
- complex binds to micelle, catalytic triad reoriented to be
exposed to TAG
- FA is released
9. What composes chylomicrons?: TAG + apolipoprotein
10. What determines the activity of adipose tissue?: hormonal
11. What is a characteristic structural feature of lipases?: *Lid*
that covers active site
12. What is adipose tissue's speciality in terms of TAG
metabolism?: specialized for storage and mobilization of
energy in the form of TAG
13. What is glucagon's effect on TAG metabolism in the *liver*?:
Increases gluconeogenesis
Increases FA oxidation
Increases glucose export
Increases FA incorporation into TAG and secretion as VLDL for
delivery to muscle for use as fuel.
Lecture 12 - Triacylglycerol Metabolism
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