Fatty Acid Metabolism German 9/27/16 Flashcards
What are three sources to obtain lipids and fatty acids?
- Diet
- Adipose storage
- Synthesis in tissue
What are the four fates of lipids and fatty acids?
- Energy substrates
- Precursors
- Structural elements
- Signaling Molecules
What are dietary lipids processed and transported as?
Chylomicrons
T/F Fatty acids are hydrophobic and stable in water
True
What is the first step in processing dietary lipids?
-Bile salts emulsify fats in the small intestine forming mixed micelles
In the second step of processing dietary lipids what brakes down triacylglycerols?
Intestinal lipases
In the third step of processing and transporting the dietary lipids what takes up the fatty acids and break down products?
Intestinal mucosa
In the third step of processing the dietary lipids are taken up by the intestinal mucosa and converted into what?
Triacylglycerols
What happens in the fourth step of processing dietary lipids?
The Triacylglycerols are incorporated with cholesterol and apolipoproteins into chylomicrons
In the fifth step of processing dietary lipids where do the chylomicrons move?
From the lymphatic system and bloodstream to the tissues
While in the capillary what happens to the triacylglycerols found in the chylomicrons?
Lipoprotein lipase breaks them down to fatty acids and glycerols
What are the three functions of apolipoproteins?
- Lipid binding proteins
- Combine with lipids to form lipoproteins
- Diverse functions
What are the two ways that fatty acids are transported?
- Free Fatty acids
- Lipoproteins
How are free fatty acids transported?
carried by serum albumin
What is a phospholipid, cholesterol, and protein membrane-bound vesicles containing triglycerides?
Lipoproteins
What are the four classes of lipoproteins?
- Chylomicrons
- Very Low Density Lipoprotein (VLDL)
- Low Density Lipoprotein (LDL)
- High Density Lipoprotein (HDL)
Which type of lipoprotein has the highest amount of triacylglycerides in it?
chylomicrons
Which type of lipoproteins has the lowest amount of triacylglycerides in it?
HDL
What are the two major pathways of lipid transport?
- Exogenous
- Endogenous
What type of lipoprotein is responsible for delivering fatty acids to target tissues?
VLDL
What types of lipoproteins are responsible for transporting cholesterol?
- LDL
- HDL
What is responsible for activating lipases?
Apolipoproteins
What type of protein do you find in the exogenous pathway?
Chylomicrons
What pathway do you find LDL, HDL, and VLDL?
Endogenous pathway
T/F
Only 25% of the fatty acids transported are used by the tissues.
True
Where is VLDL, HDL, and LDL synthesized?
Liver
Where are LDL receptors synthesizes?
ER
What is the first step of LDL entering the cell?
The LDL particle binds to the LDL receptor on the membrane
What is the second step of LDL entering the cell?
LDL is internalized in and endosome
What is the third step of LDL entering the cell?
-LDL receptors get recycled
What is the fourth step of LDL entering the cell?
The LDL endosome fuses with a lysosome
What is the fifth step of LDL entering the cell?
The lytic enzymes from the lysosome break down LDL particle
What is the LDL particle broken down into?
- Amino Acids
- Fatty Acids
- Cholesterols (lipid droplet)
When does the triacylglycerol cycle occur?
During starvation
What are triacylglycerols broken down into in the triacylglycerol cycle?
- Glycerol
- Fatty acid
What combines with a fatty acid in the liver to form a triacylgycerol?
Glycerol 3-phosphate
What hormone initiates the release/breakdown of fatty acids?
Glucagon
After glucagon has interacted with its receptor on the adipose tissue what does that eventually activate?
PKA
What does PKA phosphorylate in the lipid droplet that creates an opening along the membrane?
Perilipin
What breaks down the adipose triglycerides? (from triaclyglycerol to diacylglycerol)
ATGL (Adipose Triglyceride Lipase)
What removes the glycerol linker in adipose triglycerides?
MGL (Monoglyceride lipase)
Where does the glycerol that is released when the trigacylglycerides are broken down go for energy creation?
Glycolysis
Where do the fatty acids from the triacylglycerides go for energy?
Form fatty acyl-CoAs used in Beta Oxidation
Where are the fatty acyl-CoAs transported for oxidation?
Mitochondria
What transports the fatty acyl-CoAs into the mitochondria?
Acyl-Carnitine/Carnitine Transporter
What are the three stages that fatty oxidation occurs in?
- B-oxidation
- CAC
- Oxidative Phosphorylation
What do you release per oxidation step in fatty acid B-Oxidation?
- 1 Acetyl CoA
- 1 NADH
- 1 FADH2
How many carbons are reduced from the fatty acid per each step of the B-oxidation?
2 Carbons are removed
What enzyme from B-oxidation feeds directly into the electron transport chain?
Acyl-CoA dehydrogenase
Acetyl-CoA produced from B-oxidation enters two places what are they?
- CAC
- Forms Ketone bodies
T/F Lipids can be a precursor for Amino Acid synthesis
True
What are three important Ketone bodies produced from the Acetyl-CoA?
- Acetoacetate
- Acetone
- d-B-hydroxybutyrate
What are ketones used as an energy source for?
- Heart
- Skeletal muscle
- Kidney
- Brain
Which two ketone bodies are exported as energy for the heart, skeletal muscle, kidney, and the brain?
- Acetoacetate
- D-B-Hydroxybutyrate
T/F Acetone can be converted back to Acetyl CoA
False
It Can NOT
How many carbons does palmitate have?
16
T/F
Excess Acetyl-CoA can form fatty acids
True
What hormone activates acetyl-CoA and Fatty acid synthesis?
Insulin
What is the first step of fatty acid synthesis?
Transport of Acetyl-CoA into the cytoplasm
What is the second step of fatty acid synthesis?
Carboxylation of acetyl-CoA into malonyl-CoA
In the third step of fatty acid synthesis what enzyme combines acetyl-CoA and molonyl-CoA to start an acyl chain?
Fatty acid synthase
In the fourth step of fatty acid synthesis what does fatty acid synthase do?
Adds Malonyl-CoA carbons to create palmitate
Where are fatty acids modified?
In the ER
What are four things that fatty acids can be modified into in the ER?
- Phospholipids
- Sterols
- FA elongation
- FA desaturation
Where does lipid synthesis occur?
Cytoplasmic space
Where is acetyl-CoA produced?
Mitochondrial matrix
How does acetyl-CoA get from the mitochondrial matrix to the cytoplasmic space?
Citrate Shuttle
What enzyme is responsible for carboxylating acetyl-CoA to from malonyl-CoA?
Acetyl-CoA Carboxylase (ACC)
What vitamin is necessary for ACC?
Biotin (vitamin b7)
Why is malonyl-CoA necessary?
For acyl chain initiation and synthesis
How many types of Fatty Acid synthase are there?
two
Which type of fatty acid synthase is found in humans?
FAS I
What is unique about FAS I?
It can only produce 16 carbon saturated fatty acids
What are the two essential fatty acids?
Linoleate
A-Linolenate
What is responsible for shuttling malonyl CoA to FAS?
Acyl Carrier Protein
What is essential for the acyl carrier protein?
Pantothenic acid
What are two ways that NADPH is produced?
- Pentose Phosphate Pathway
- Malic Enzyme
T/F Insulin activates ACC via phosphatase that leads to fatty acid synthesis
True
T/F ACC activity regulates the balance of FA synthesis and oxidation
True
What inhibits the Fatty acyl-CoA from being converted into the fatty-acyl carnitine?
Malonyl-CoA
What is required for FA synthesis to occur?
- 2 NADPH
- 1 Acetyl CoA
- 1 Malonyl CoA
What two molecules help form phosphatidic acid?
- Glucose
- Glycerol
T/F
FA addition to phosphatidic acid forms phospholipids and triglycerides
True
T/F Cholesterol is not formed from acetyl-CoA
False
it is formed from acetyl CoA
T/F Cholesterol is involved in lipoprotein and hormone formation
True
If phosphatidic acid has a phosphate removed what does it become?
Triacylglycerol
If phosphatidic acid has a phosphate group added what does it become?
Phospholipids
What does HDL do?
Brings foam cells back to the liver
What does a low level of HDL allow?
Plaque formation from foam cells