Lecture 41: Fatty Acid Synthesis and Obesity Flashcards
What are ways in which people can fight obesity?
Diet and Exercise
Prescription weight loss medication
Bariatric surgery
What is gastric bypass?
It is when the size of the stomach is reduced via surgery. It has 50-70% success in patients five years later.
How do you acquire lipids in adipose tissue?
- ingestion of lipids
2. ingestion of carbohydrates
Triglyceride absorption is _______.
Indirect
Where and what first break down are triglycerides?
Lingual lipase in the oral cavity
Triglycerides are converted which two types of molecules?
- fatty acid
2. beta monoacylglycerol
After the triglycerides are converted to fatty acids and beta monoacylglycerol, where are the compounds converted back to triglycerols?
mucosal cells
What are chylomicrons?
They are a type of plasma lipoprotein.
They are loaded with triglycerides and travel through the lymphatic system.
What enzyme hydrolyzes chylomicrons as they arrive at adipose/ muscle (etc.) tissue?
Lipoprotein lipase (hydrolyzes the triglyceride portion)
Fatty acids made from lipoprotein lipase can be used in which two ways?
- oxidized in muscle for energy
2. stored as (reconverted) triglycerides in adipose tissue
T/F: Fatty acids are used during exercise and when “relaxing”.
False. Fatty acids are used only during rigorous exercise.
Why can patients not eat 8-10 hours before blood testing?
There will be chylomicrons in the blood which make it appear milky. Also, it will cause problems when testing for enzymes.
What is Orlistat?
Orlistat is a drug that is prescribed to patients that have high levels of triglycerides in their blood.
What is a side effect of Orlistat?
Since essential fatty acids (i.e. derived from plants) are triglycerides, Orlistat inhibits the absorption of these essential triglycerides, as well.
What is Lovaza?
It is ethyl esters of omega 3 and omega 6 fatty acids.
What is the difference between Orlistat and Lovaza?
Orlistat inhibits the absorption of triglycerids. EPA/ DHA inhibit the synthesis of triacyl glycerol in the liver. They might also stimulate the activity of lipoprotein lipase and inhibit acyl CoA.
T/F: Olestra is not broken down by pancreatic lipase.
True. It is too big so pancreatic lipase cannot handle it. It causes diarrhea.
How does carbons of acetyl CoA go from the mitochondria to the cytosol?
They need shuttles like citrate translocase which moves citrate from mitochondria to cytosol.
Once citrate is in the cytosol it is cleave by ________ which makes it into acetyl CoA and oxaloacetate.
citrate lyase
What three substrates get together to form fatty acids?
acetyl CoA (glucose)
malonyl CoA
NADPH (hexose monophosphate shunt)
What is the importance of Acetyl CoA Carboxylase (ACC) in fatty acid synthesis?
It is the rate limiting enzyme in fatty acid synthesis. It controls the rate at which fatty acids are synthesized.
In prokaryotes,what are the three different components of ACC?
Biotin carboxyl carrier protein (BCCP) which carries CO2.
Biotin Carboxylase which takes bicarbonate and puts it in BCCP and carboxylates it.
Transcarboxylase (TC) adds acetyl CoA to BCCP-CO2 and makes Malonyl CoA.
What is the difference between prokaryotic versus eukaryotic ACC?
ACC is a multi unit protein in eukaryotes and is found on a single polypeptide chain.
In prokaryotes, there are three distinct proteins.
What is the significance of CO2 in fatty acid synthesis?
Bicarbonate is used to activate acetyl CoA so it is important in activation and removal.
What is the importance of fatty acid synthase?
Fatty Acid Synthase makes fatty acids from acetyl CoA, malonyl CoA and NADPH.
What is the structure of fatty acid synthase and how is it different in prokaryotes versus eukaryotes?
It has 6 different enzyme activites and ACP (acyl carrier protein) in prokaryotes but is one unit in eukaryotes.
Although acyl carrier protein and coenzyme A look alike, what is the difference between the two?
ACP is used for fatty acid synthesis and coenzyme A is used for fatty acid oxidation.
What are acetyl- SACP and malonyl SACP combined to form?
Acetoacetyl SACP
What needs to be done to Acetoacetyl SACP to form beta hydroxybutyrl- SACP?
reduction reaction
After beta hydroxybutyryl is dehydrated what compound is formed?
Crotonyl SACP or Enoyl SACP?
What type of reaction occurs to convert crotonyl SACP/ enoyl SACP to butyryl SACP?
Reduction Reaction
Which compound continues to be added to add two carbons to the fatty acid for every reaction?
Malonyl SACP
Which enzyme cleaves the fatty acid once it reaches 16 Carbons?
thioesterase
What is the role of citrate in the regulation of fatty acid synthesis?
It is used to form polymers (activated form) of ACC. In the presence palmitoyl CoA and malonyl CoA, the polymer is converted back to the inactive form.
The ACC dimer can be inactivated by phosphorylation by AMP protein kinase which is coupled to ______.
high concentration of glucagon in plasma
If citrate is added to ACC and glucose is ingested (increasing insulin and activating protein phosphatase 2) what will be formed?
Highly active ACC polymer
T/F: In eukaryotes, we can put double bonds after the 9-10 carbon.
False. Mammals cannot introduce double bonds beyond C-9.
What are two essential fatty acids?
Linolenate and linoeate
Why is linolenic and linoleic acid so important?
It produces arachidonic acid which is essential for cell membranes.
