Lipolysis Flashcards
What hormones stimulate lipolysis?
Epinephrine, norepinephrine, glucagon, ACTH, and cortisol
What hormones inhibit lipolysis?
Insulin
The primary control of lipases is through what substance?
Hormones
Hormone sensitive lipase is strongly inhibited by what?
Insulin
What lipase is significantly elevated in type 2 diabetes?
Adipocyte triglyceride lipase
The skeletal muscle protein content of this lipase is significantly reduced in type 2 diabetes.
Hormone sensitive lipase
This secondary messenger stimulates lipolysis in fat cells.
Cyclic AMP
What are the steps of fatty acid degradation?
- Enters the muscle
- Fatty acid is activated by being converted into acyl CoA
- Fatty acid enters the mitochondria
- Fatty acid is oxidized in the mitochondria (oxidation, hydration, oxidation, and thiolysis)
How do fatty acids enter the cell to be degraded?
- Albumin binding protein
- Plasma membrane fatty acid binding protein
- Fatty acid translocase and fatty acid transport protein
Any fatty acid entering the muscle to be oxidized, must be ____ by a protein.
Chaperoned
What protein chaperones fatty acids into muscle?
Cytoplasmic fatty acid binding protein (FABPc)
How is a fatty acid “activated”?
By attaching coenzyme A to the fatty acid to create acyl CoA
What enzyme “activates” fatty acids?
Acyl CoA synthetase
Where does the “activation” of fatty acids take place?
Outer mitochondrial membrane
Hydrolysis of this substance is common in biosynthesis and makes the activation of fatty acids irreversible.
Pyrophosphate by pyrophosphatase
What is responsible for the transport of long chain fatty acids into the mitochondria?
Carnitine Palmitoyltransferase Complex (consists of CPT I, acylcarnitine translocase, and CPT II)
For entering the mitochondria what is considered the rate limiting step?
CPT I
What inhibits fatty acid entrance into the mitochondria? What is the optimum pH for entrance into the mitochondria?
- It is reversibly inhibited by Malonyl-CoA
- Neutral pH is optimum
This term refers to the four steps that occur prior to having fat enter the aerobic system.
Beta Oxidation
What are the four steps of beta oxidation?
- Oxidation
- Hydration
- Oxidation
- Thiolysis
-OHOT
During beta oxidation, what occurs in the first step of oxidation?
Acyl CoA is converted into trans-Δ^2-enoyl CoA by acyl CoA dehydrogenase
During beta oxidation, what occurs in the second step of hydration?
Trans-Δ^2-enoyl CoA is converted into L-3-hydroxyacyl CoA by enoyl CoA hydratase
During beta oxidation, what occurs in the third step of oxidation?
3-hydroxyacyl CoA is converted into 3-Ketoacyl CoA by L-3-hydroxyacyl CoA dehydrogenase
During beta oxidation, what occurs in the fourth step of thiolysis?
3-ketoacyl CoA is converted into Acyl CoA (minus “2”) and acetyl CoA by beta-ketothiolase
What are the similarities of beta oxidation to the Kreb’s cycle?
- Oxidation produces a double bond and FADH2 via dehydrogenase
- The addition of water adds a hydroxyl group and removes a double bond
- Oxidation turns the hydroxyl group into a carbonyl group via dehydrogenase
What additional enzymes are required for unsaturated fatty acid degradation?
Reductase and isomerase
Polyunsaturated fatty acids require only one or two extra enzymes depending on the number of double bonds. Which enzymes are needed for odd numbered? Even numbered?
Odd: isomerase
Even: reductase and isomerase
Each round of beta oxidation releases what?
A two carbon molecule (acetyl CoA)
What are key enzymes of fat burning?
- Lipases (Hormone Sensitive Lipase)
- Acyl CoA synthetase
- Acyl CoA dehydrogenase
What are the inhibitors of fat burning?
- Insulin
- High energy charge (ATP)
- NADH and FADH2
What are the stimulators of fat burning?
- Glucagon
- Low energy charge (ADP or AMP)
- NAD+ and FAD
