Lipid Metabolism Flashcards
What are triacylglycerols?
Storage form of fatty acids
Why are glycogen and triacylglycerol similar?
They are both the storage form of their respective macromolecule
How are lipid droplets bound in adipocytes?
Phospholipid monolayers
These structures restrict access to the inside of the triacylglycerol molecule
perilipins
What is triacylglycerol synthesized from?
glycerol and free fatty acids
What is the starting molecule of Glycerol 3 phosphate?
Dihydroxyacetone Phosphate (DHAP)
Glycerol 3 phosphate dehydrogenase
catalyzes the reduction of DHAP to form glycerol 3 phosphate
what is Glycerol 3 phosphate
activated form of glycerol
Importance of triosphosphate isomerase as it relates to lipids
This reaction is reversible and can be utilized to form DHAP and ultinamtely glycerol 3 phosphate from glyceraldehyde 3 phosphate
What is Acyl CoA?
intermediary in converting lipid to carb
Fatty acid + CoA - SH
CoA SH or COASH
Coenzyme A with an attached sulfihydryl group
Acyl CoA Synthetase
Catalyzes formation of Acyl CoA from Fatty acid
Fatty Acid + ATP + CoA SH <> Acyl CoA, AMP, PPi
Glycerol Phosphate AcylTransferase
Catalyzes the reaction joining glycerol 3 phosphate and Acyl CoA to form Phosphatidate
Where is the carbon located on a molecule of phosphatidate?
Carbon 3
Where is the saturated fatty acid located on a molecule of phosphatidate?
Carbon 1
Where is the unsaturated fatty acid located on a molecule of phosphatidate?
Carbon 2
Triacylglycerol Synthase
Catalyzes the conversion of phosphatidate to triacylglycerol
Diacylglycerol
Intermediary in conversion of phosphatidate to triacylglycerol
what is removed in the coversion of phosphatidate into triacylglycerol? What is it replaced with?
Loses Phosphoryl group
gains third acyl group
What is lipolysis
breakdown of triacylglycerol into free fatty acids
where does lipolysis occur?
cytosol
which two enzymes catalyze lipolysis?
Triacylglycerol Lipase
Monoacylglycerol Lipase
Triacylglycerol Lipase
Converts triacylglycerol to monoacylglycerol, uses water to remove carbon 1 and 3. results in 2 monoacylglycerol and two fatty acids
monoacylglycerol lipase
hydrolyzes the ester linkage at position 2 of the glycerol, breaks down monoacylglycerols
Net yield of lipolysis of one triacylglycerol
three fatty acids
one glycerol
What is Beta Oxidation
Preparation of fatty acid molecules so that they can be used for energy (synthesis of Acyl CoA)
Where does Beta Oxidation occur?
Mitochondria
What must happen in order for fatty acids to enter the mitochondria for Beta Oxidation?
Fatty acids must pass both inner and outer membrane
How does fatty acid activation occur?
Conversion to Acyl CoA
How many carbons do Acyl Groups have?
> = 14
How do acyl groups cross the inner mitochondrial membrane?
attaches to carnitine
What is cytosolic fatty acyl CoA converted to in order to cross the mitochondrial inner membrane?
Fatty acyl carnitine
Carnitine Acyl Transferase I
catalyzes the reaction in which carnitine removes the acyl group from Acyl CoA to form Acyl Carnitine.
grants entry to INTERMEMBRANE SPACE ONLY
Translocase (carnitine-acylcarnitine translocase)
Enzyme that helps Acyl carnitine cross the inner mitochondrial membrane
Carnitine Acyl Transferase II
Ezyme responsible for the reverse acyl carnitine reaction, linkes acyl group back to CoA
How many carboons does Acetyl CoA have that are used in Krebs Cycle?
2
How many carbons does pyruvate have that are used in Krebs Cycle?
3
How many carbons does Citrate have?
6
How many carbons are lost in the conversion of Citrate to oxaloacetate?
2
how many acetyl co A are produced during one round of beta oxidation?
1
how many FADH2 are produced during one round of beta oxidation?
1
How many NADH are produced during one round of beta oxidation?
1
Stage 1 of fatty acid oxidation
long chain fatty acid is oxidized to yield 1 acetyl CoA
Stage 2 of fatty acid oxidation
acetyl CoA are oxidized to CO2 via the citric acid cycle
Stage 3 of fatty acid oxidation
Electrons from stage 1 and 2 are passed to O2 via mitochondrial respiratory chain providing energy for ATP synthesis via oxidative phosphorylation
Acyl CoA Dehydrogenase: Process, Substrates, Products
1st step of beta oxidation
process: dehydrogenation
Acyl CoA + FAD > Enoyl CoA + FADH2
Enol CoA Hydratase: Process, Substrates, Products
2nd step of beta oxidation
Hydration
Enoyl CoA + Water > L-3 hydroxyacyl CoA
where does the water come from in the Enol CoA Hydratase reaction of beta oxidation?
End of the electron transport chain
Hydroxy Acyl CoA Dehydrogenase: Process, substrates, products
3rd step of beta oxidation
Dehydrogenation
L-3 hydroxyacyl CoA + NAD+ > 3 ketoacyl CoA +NADH + H+
Thiolase: Process, substrates, products
4th step of beta oxiation
splitting
3 ketoacyl CoA + CoA SH > Acetyl CoA + Acyl CoA (n-2 carbons)
How many total ATP equivalents are produced form one round of Beta Oxidation?
5
1 NADH (3)
1 FADH2 (2)
How many ATP equivalents are formed from one round of beta oxidation including those produced from the acetyl coA used in krebs?
17 total
For each round of beta oxidation how many carbons are removed?
2
How many ATP equivalents are produced from the complete degradation of one molecule of palmitic acid?
129
What is the end product of the breakdown of 1 molecule of acetyl CoA in Krebs?
2 CO2
3 NADH
1 FADH2
1 GTP
Where are the NADH and FADH2 from beta oxidation and krebs utilized?
they are oxidized in the ETC
At rest what macromolecule does the body prefer to use for energy?
fatty acids (during rest and light exercise)
What is the fate of the glycerol molecule formed during lipolysis?
it becomes a source of carbon for gluconeogenesis in the liver (DHAP)
Glycerol Kinase:
phosphorylates glycerol to yield Glycerol 3 phosphate
What is glycerol 3 phosphate converted to and where is it used?
DHAP
glycolysis and gluconeogenesis
When are ketone bodies used?
carbohydrate starvation, high fat diets
Describe the process of ketone body formation
Liver catabolizes fat to acetyl CoA,
Acetyl CoA converted to Ketones
Where are ketone bodies taken up after being released into systemic circulation?
brain, muscle, nerves