Lipid Metabolism Flashcards
The digestion of lipids is dependent on what?
The length of fatty acids in the TAG.
You encounter a patient who has low levels of bile production. How will their ability to eat fatty foods be altered?
They will have a decreased tolerance to fatty foods since there is not enough bile to emulsify the fat.
You encounter a patient who has a deficiency in the gut hormone cholecystokinin. Do you expect the patient to have a high or low tolerance for fatty foods?
Low tolerance; cholecystokinin is what allows for the release of bile, which subsequently emulsifies fats.
What is the purpose of emulsification?
To increase the surface area of fats for digestion.
How will the activity of pancreatic lipase be affected if short chain fatty acids are present versus long chain fatty acids?
The activity will remain unchanged. Pancreatic lipase can digest fatty acids of any length.
Pancreatic lipase is important for the regulation of pH in the small intestine. What does pancreatic lipase release in order to increase pH?
bicarbonate.
What is the function of esterase, and what organ produces it?
To remove fatty acids from cholestrol esters; the pancreas.
How are dietary lipids absorbed?
By intestinal epithelial cells.
They subsequently enter the blood and are transported into the liver.
Long chain fatty acids are in what conformation when they are emulsified?
micelles.
After fatty acids are reabsorbed, how does their structure change?
They are condensed to form TAGs.
What are chylomicrons?
Vessels that TAGs are packaged into after they have been re-synthesized in the intestinal cells.
Any time a fatty acid enters a reaction, it needs to be ____
Primed; this is done by a CoA molecule.
Once triacylglycerides have been re-formed after absorption and packaged into chylomicrons, where do they travel?
To the lymph system and the blood.
How do chylomicrons become mature?
They accept proteins from HDL within lymph and blood.
What is the function of ApoCII?
To digest chylomicrons.
They are present on capillary endothelial cells in muscle and adipose tissue.
What is the function of ApoE?
It allows for endocytosis of vesicles in the liver.
True or false: chylomicrons can pass through the plasma membrane.
False
You are studying a mouse that has a deficiency in the enzyme lipoproteinlipase. How does this affect the transport of chylomicrons?
The transport is not affected, but the chylomicrons will be unable to release fatty acids into adipocytes.
What are the 3 necessary steps to use fatty acids as fuel?
mobilization, activation and degradation.
What occurs in fatty acid mobilization?
TAGs in adipose tissue are broken to FA and glycerol, released and transported to energy-requiring tissue.
What occurs during fatty acid activation?
Fatty acids must be activated and transported into mitochondria.
What occurs during degradation?
Stepwise breakdown of FA into acetyla CoA which is then processed in TCA cycle.
During fasting and exercise, what activates the mobilization of fatty acids from adipocytes?
glucagon and epinephrine.
What is the function of perilipin?
It guards the fats as they are being mobilized.
In the mobilization of fatty acids from adipocytes, how are perilipin and HS lipase inactivated?
via phosphorylation
What is triacylglycerol broken down into during lipolysis?
glycerol and fatty acids.
The glycerol from lipolysis can be used for what two processes in the liver?
pyruvate and glucose
Fatty acids from lipolysis can be used in what cycle?
TCA
Where is glycerol kinae ONLY found?
The liver.
What is glycerol eventually broken down into in the liver?
Glyceraldehyde-3-phosphate.
Where does fatty acid activation occur?
In the cytosol.
What is the function of the carnitine shuttle?
It carries long-chain fatty acly CoAs across the mitochondrial membranes.
Where does beta oxidation primarily occur?
in the mitochondrial matrix.
What is the role of carnitine?
It makes acyl carnitine from acetyl CoA and carnitine.
Where are all of the enzymes of beta oxidation found?
In the mitochondrial matrix.
What is the first step of fatty acid oxidation?
The conversion of acyl CoA to trans=enoyl CoA.
This is done via acyl CoA dehydrogenase.
What is the second step of fatty acid oxidation?
The conversion of trans-enoyl CoA to hydroxyacyl CoA. This is done via enoyl CoA hydrase.
What is the third step in beta oxidation?
The conversion of hydroxyacyl oA to ktoacyl CoA. This is done via hydroxy Acyl CoA dehydrogenase.
What is the final step in beta oxidation?
Conversion of 3-ketoacyl CoA to acyl CoA and acetyl CoA.
How many molecules of ATP does each acetyl CoA molecule make?
10
What enzyme degrades fatty acids with odd-numbered double bonds?
isomerase.
What enzymes degrade fatty acids with even numbers of double bonds?
reductase and isomerase.
They are converted from propionyl CoA to succinyl CoA, which then enters TCA.
What enzyme degrades monounsaturated fatty acids?
enoyl CoA isomerase
The acetyl CoA produced from the degradation of fatty acids combines with oxaloacetate to form what molecule?
Citrate.
In fasting or diabetes, what does acetyl CoA become?
Ketone bodies (acetoacetate, acetone, hydroxybutryate).
Acetoacetate can be converted into what molecule?
Acetyl CoA.
You encounter a diabetic patient who is in a diabetic coma. A blood test reveals that they have a decreased blood pH. This is a result of the presence of what molecule?
ketone bodies.
When you drink milk (composed of short and medium fatty acid chains), where will it be digested, and what enzymes are responsible for this?
Lingual (tongue) and gastric (stomach) lipases.
