Lecture 33 - Lipid Metabolism II Flashcards
Fatty acid synthesis occurs in the (liver/all cells)
liver
Fatty acid break down occurs in (liver/all) cells
all
Enzymes for FA synthesis are localized in the (cytoplasm/mitochondria)
cytoplasm
Enzymes for FA degradation are localized in the (cytoplasm/mitochondria)
mitochondria
Acetyl-CoA is converted to _________ as the first step of FA synthesis.
A. malonyl-CoA
B. Acetoaceyl-CoA
C. Malonate
D. 3-D-hydroxybutyrate
A. malonyl-CoA
Synthesis of acetyl CoA for FAs occurs when ____ is produced in the mitochondria.
citrate
Citrate is formed in the mitochondria utilizing what two enzymes?
Pyruvate carboxylase (to form oxaloacetate)
PDH (to form acetyl-CoA)
Following citrate formation, it is shuttled to the mitochondria to be broken down into OAA and Acetyl-CoA. What enzyme is used for this breakdown?
A. malic enzyme
B. PDH
C. citrate lyase
D. pyruvate carboxylase
C. citrate lyase
For continued generation of Acetyl-Coa, malate is transformed back into pyruvate via ______, which also produces NADPH
malic enzyme
Addition of CO2 to acetyl-CoA produces ______ via acetyl-CoA carboxylase.
malonyl-CoA
Rate limiting step in FA synthesis
Acetyl-CoA to malonyl-CoA
(+) allosteric regulator of ACC
A. Insulin
B. glucagon
C. High carb diet
D. Citrate
D. citrate (precursor to the citrate-> OAA/Acetyl-CoA reaction)
(-) allosteric regulator of ACC
A. Citrate
B. Long chain FAs
C. Epinephrine
D. High carbohydrate diet
B. Long chain FAs
Control of ACC by dephosphorylation
insulin (high insulin indicates a large carbon pool, forcing dephosphorylation of ACC, producing more FAs)
Phosphorylation of ACC is caused by what compounds?
epinephrine and glucagon (indicate low energy state, no need to take “time” to produce FAs)
In the presence of low blood glucose, epinephrine and glucagon are released. These molecules inhibit acetyl-coa carboxylase, and prevent the formation of fatty acids. The Acetyl-CoA is instead utilized to make what compounds for energy?
Ketone bodies
Malonyl-CoA undergoes addition of two carbon fragments by the enzyme _____ until _____ is formed.
Fatty Acid Synthase Complex;
palmitate (16:0)
The fatty acid synthase complex contains what residue that is important for addition of CO2 to malonyl-CoA?
phosphopantetheine residue (PP)
PP of the acyl carrier protein on one FAS domain is attached to the _____ of the other FAS domain.
cysteinyl sulfhydryl group
The first step of FA synthesis is the _____ step.
A. condensation
B. reduction
C. Dehydration
A. condensation (adding of acetyl-CoA to malonyl-CoA to form acetoacetyl-CoA)
The second step of FA synthesis is the ___ step.
A. condensation
B. reduction
C. Dehydration
B. reduction (formation of ketoalcohol with production of NADP+)
The third step of FA synthesis is the ____ step.
A. condensation
B. reduction
C. Dehydration
C. dehydration (loss of water to form double bond)
The final step in FA synthesis is the ___ step.
A. condensation
B. reduction
C. Dehydration
B. Reduction (FA lengthened by two carbons)
FAS is stimulated by what allosteric effect?
Presence of phosphorylated sugars (indicates large amounts of carbohydrates)
Like ACC, FAS is also stimulated at the genetic level by ______.
high carbohydrate, low fat diets
Desaturation of FAs occurs with what three enzymes?
NADH-Cytochrome B5 reductase
Cytochrome B5
Stearoyl CoA desturase
De Novo synthesis of Triacylglycerols occurs in what two cells types?
Hepatocytes
Adipocytes
Hepatocytes utilize _____ to form G-3-P
A. glycerol
B. glucose
C. glycogen
D. DHAP
A. glycerol
Adipocytes utilize ___ to help form G-3-P in conjuction with hepatocytes.
A. glycerol
B. glucose
C. glycogen
D. DHAP
B. Glucose
Following formation ofo G-3-P, ___ is cleaved to form phosphatidic acid.
2x Acyl-CoA
G-3-P + Acyl-CoA forms ____
Phosphatidic acid
Following the removal of the inorganic phosphate from phosphatidic acid, a ___ is produced.
A. ketone
B. diacylglycerol
C. monoacylglycerol
D. triacylglyercol
B. diacylglycerol
The addition of acyl group to the DAG molecule in TAG synthesis produces _______.
TAG (triacylglycerol)
TAGs are packaged into _____ in the liver.
VLDL
Oxidation of arachidonic acid produces _______.
eicoisanoids
What are the 4 families of eicosanoids?
1) prostaglandins
2) prostaclycins
3) thromboxanes
4) leukotrienes
What two phospholipids are produced by reaction of a CTP-Head group with DAGs?
Phosphatidylcholine
Phosphatidylethanolalmine
What two phospholipids are produced from CDP-DAGs?
Phosphatidylinositol
Cardiollipin
Ethanolamine can be produced by ______ of phosphatidylserine.
decarboxylation
phosphatidyleserine can be formed adding _____ to ehtanolamine.
serine
Phosphatidyletanolamine can be methylated to form _____
phosphatidylcholine
Biosynthesis of cholesterol is regulated primarily by ______.
A. content of cholesterol in the PM
B. dietary intake
C. lysis of cell PMs
B. dietary intake
Approximately __ of cholesterol is produced by the liver daily.
1 gram
Acetyl-CoA is converted to mevalonate by ______.
HMG CoA Reductase (rate limiting step of cholesterol biosynthesis)
Production of the cholesterol ring begins at what intermediate?
A. mevalonate
B. dimethylallyl pyrophosphate
C. lanosterol
D. squalene
D. squalene
HMG CoA reductase forms HMGCoA by combining ____ and _____.
acetoacetyl-CoA
acetyl-CoA
*Similar as the formation of FAs, but utilizing a different enzyme
The major carbon source for fatty acid synthesis is ____.
A. TAGs
B. Cholesterol
C. Amino Acids
D. Dietary carbohydrates
D. Dietary carbohydrates
Which of the following contains the highest TAG content?
a. TAG
b. VLDL
c. LDL
D. HDL
a. TAG
Which of the following contains the largest amount of cholesterol?
a. TAG
b. VLDL
c. LDL
D. HDL
C. LDL
Which of the following contains the largest amount of protein/phospholipids?
a. TAG
b. VLDL
c. LDL
d. HDL
D. HDL
