Lecture 5 Flashcards
Topic: cholesterol metabolism.
Used as a paradigm to learn how nutrients regulate gene function.
Endogenous source od cholesterol.
De novo synthesis from acetyl-CoA; it comes from the TCA cycle, so all cells can do this. Anything from the outside is viewed as excess cholesterol that can overwhelm the system.
Exogenous source of cholesterol.
From the diet: animal products.
Endogenous cholesterol pathway.
Acetyl-CoA produces HMG-CoA. HMG-CoA conversion to mevalonic acid by HMG-CoA reductase is the rate limiting step.
Statins.
They inhibit HMG-CoA reductase activity, which shuts down cholesterol biosynthesis.
Site of cholesterol synthesis.
The ER.
Exogenous source of cholesterol.
Meat and animal products.
Digestions.
Enzymes in the saliva break down the food, the stomach hydrolyzes the food, the pancreas sends in more hydrolytic enzymes. result: the food is used to produce ATP.
Excess lipids.
The liver can repackage excess lipids from the intestine and send it back into the blood, where the process repeats, but in the absence of chylomicrons this time.
Storage of excess fat.
Converted into triglycerides and deposited in fat tissue.
Adipocytes.
Specialized for converting excess fatty acids to triacylglycerol and storing it; this type of cell has a propensity to store fat easily, which is why weight loss is a long-term process.
Bile acids.
Made in the liver, act as detergents in the intestine.
Lipases.
Important in the digestion of lipids.
Lipids.
Anything that does not dissolve in water.
Bile acids are made from cholesterol through 4 processes.
Hydroxylation of the sterol, epimerization.
Which is the only organ capable of making bile acids?
The liver.
