Lecture 6 - Lipid Catabolism Flashcards
What does the breakdown of lipids produce?
Acetyl CoA and potential energy that can be used in the ETC or other reactions that produce NADH
How are fatty acids converted to acetyl CoA?
Beta-oxidation
How are fatty acids converted to NADH and FADH2?
Beta-oxidation
Are fatty acids amphipathic or aliphatic?
Both
What type of fatty acids are the least soluble in water?
Long chain saturated fatty acids
Are fatty acids typically found in free form?
No, they are often found in complex lipids
What are the most common monocarboxylic acids?
C12 - C24
What are the most common unsaturated fatty acids?
C18 and C20
What usually occurs when more than one double bond are found in one fatty acid?
The double bonds are separate by a methylene group
In most naturally occurring unsaturated fatty acids, the double bonds are in the ____ configuration
Cis
What do fatty acids consist of?
- Carboxyl group
- Hydrocarbon chain
Acetic acid
2 carbons
Capric acid
10 carbons
Lauric acid
12 carbons
Palmitic acid
16 carbons
Stearic acid
18 carbons
Arachidic acid
20 carbons
Palmitoleic acid
16 carbons, double bond at C9
Oleic acid
18 carbons, double bond at C9
Linoleic acid
18 carbons, double bonds at C9 and C12
Gamma-linoleic acid
18 carbons, double bonds at C6, C9, and C12
Alpha-linoleic acid
18 carbons, double bonds at C9, C12, and C15
What does an omega sign mean with respect to fatty acids?
Whatever number is next to the omega is the last double bonded carbon when counting from the end of the chain
What are the 2 main types of lipids?
1) Storage (neutral)
2) Membrane (polar)
What are the simplest lipids constructed from fatty acids?
Neutral triacylglycerol
What is another name for triacylglycerols?
Triglycerides
What are triacylglycerols made of?
3 fatty acyl units (one on each end and one in the middle)
What are the most common membrane lipids?
Glycerophospholipids
What is the first step of lipid catabolism?
Bile salts emulsify dietary fats in the small intestine, forming mixed micelles
What is the second step of lipid catabolism?
Intestinal lipases degrade triacylglycerols
What is the third step of lipid catabolism?
Fatty acids and other breakdown products are taken up by the intestinal mucosa and converted into triacylglycerols
What is the fourth step of lipid catabolism?
Triacylglycerols are incorporated, with cholesterol and apolipoproteins, into chylomicrons
What is the fifth step of lipid catabolism?
Chylomicrons move through the lymphatic system and bloodstream to tissues
What is the sixth step of lipid catabolism?
Lipoprotein lipase converts triacylglycerols to fatty acids and glycerol
What is the seventh step of lipid catabolism?
Fatty acids enter cells
What is the eighth step of lipid catabolism?
Fatty acids are oxidized as fuel or re-esterified for storage
Which type of fatty acids are the main source of energy for animals?
Long chain fatty acids
What are 3 sources of fatty acids?
1) Diet
2) Cell storage
3) Synthesis
Which enzymes convert triglycerides and phospholipids to fatty acids?
Lipases
Where are lipases produced?
In the pancreas
What is the main function of lipases?
Breakdown triglycerides into glycerol and fatty acids
Ingested triglycerides are water ______
Insoluble
What happens to ingested triglycerides in the intestines?
- They are emulsified by bile salts (detergents)
- Lipases break them down to fatty acids and glycerol which are taken up by intestinal mucosa
What happens to triglycerides stored in adipose tissue?
Broken down by lipases, which are triggered by hormonal signals (epinephrine and glucagon)
Which enzyme converts glycerol to glycerol phosphate?
Glycerol kinase
Which enzyme converts glycerol phosphate to dihydroxyacetone phosphate?
Glycerol 3-phosphate dehydrogenase
What is the head group of phosphatidic acid?
-H
What is the head group of phosphatidylethanolamine?
-CH2-CH2-NH3+
What is the head group of phosphatidylcholine?
-CH2-CH2-N+(CH3)3
What is the head group of phosphatidylserine?
-CH2-CH(COO-)-NH3+
What is the head group of phosphatidylglycerol?
-CH2-CH(OH)-CH2-OH
What is the net charge of phosphatidic acid?
-1
What is the net charge of phosphatidylethanolamine?
0
What is the net charge of phosphatidylcholine?
0
What is the net charge of phosphatidylserine?
-1
What is the net charge of phosphatidylglycerol?
-1
Phospholipases are important for _____
Intracellular signals
What is a lysophospholipid?
A phospholipid from which one of the fatty acyl chains has been removed
What does phospholipase C act on and what does it produce?
- Phosphatidyl inositol-4,5 bisphosphate
- Diacylglycerol and inositol-1,4,5 triphosphate which are intracellular second messengers
What does phospholipase A2 release?
Arachidonic acid
