Fatty acid catabolism Flashcards
____% of dietary lipids are _____________, a hydrophobic, neutral molecule made from reaction of OH group of glycerol and COO- group of fatty acids.
90
Describe fatty acid structure
Fatty acids are made up of a long hydrophobic hydrocarbon chain (highly reduced) and a carboxylic acid polar group.
Sources of Fat available for oxidation: (3)
- Dietary fat
Function of fats: (3)
-Stored fat acts as major energy source when there is no carbohydrate available,
He does not have any fat storage, thus he faces the following problems: (3)
- Looks sick: bad complexion or look
saturated vs unsaturated fats: (indicate difference and how they appear at room temp)
Saturated –> as many hydrogens as possible, no double bonds, no kinks,
What is a trans-fat?
Trans-saturated fatty acid is trans double bond instead of cis, which makes it similar to saturated structure, doesn’t have the kinks anymore
Cholesterol plays an important role in what?
Transport and metabolism of lipids.
Describe cholesterol structure
four carbon rings, one OH group, one alkyl chain
Importance of Bile acids or salts
Tri-acylglycerols (fat) molecules are highly hydrophobic. After ingestion they are present in the form of oil droplets. In order to get digested and absorbed, they need to be emulsified (partially solubilized.
What makes bile salts amphipathic?
carbon rings, but also has a sulfate group to emulsify the fats
Bile Acids:
These are amphiphathic (with polar and non-polar structures) detergent like molecules synthesized in liver. They help solubilize or emulsify the triglycerides (fat) in the small intestine.
Pancreatic Lipases:
These are pancreatic enzymes that catalyze the hydrolysis of fat to release fatty acids and glycerol in intestine.
Bile acid and Fatty acid binding proteins:
They facilitate absorption of lipids in intestine.
Intestinal Fatty acid binding proteins (I-FABP):
these proteins are present inside the intestinal cells, they bind to fatty acids and protect cells from the detergent like behavior of fatty acids.
Chylomicrons:
These are lipoprotein granules containing specific lipoproteins, dietary cholesterol, phospholipids and triacylglycerol. These transport granules transport cholesterol and lipids from intestine to adipose tissues and liver via blood.
Lipoprotein lipase:
These enzymes are present in the capillaries of the peripheral tissues. They digest triglycerides into Fatty acid and glycerol.
Why are detergents damaging to the body?
Detergents damages body because it destroys membrane and solubilizes cells
Briefly describe the pathway taken by fats in the body
So, fats are broken down into glycerol and fatty acids. In intestinal cells, they are reformed into fats, and are bound to a carrier (chylomicrons) to bring fat to adipose tissue and liver via blood.
Provide the pathway of digestion, absorption, transport and tissue intake of fatty acids and lipids: (assuming uptake occurs)
Stomach we generally only digest protein, fats more in small intestines
If __________ aren’t present, this adipocyte fat can be converted to fatty acids and brought into blood stream.
micelles
Carrier of lipids from intestine to tissue and liver
chylomicrons
Describe the structure of chylomicron:
triacylglyerols and cholesterols bound to apolipoproteins (b-48, c-III, and C-II), which are hydrophilic structures that allow for movement in blood
Chylomicrons transport cholesterol and lipids from intestine to adipose tissues and liver via blood. true or false?
TRUE
Very low density lipoproteins (VLDL):
are synthesized in liver and transport endogenous triacylglycerol and cholesterol from liver to adipose and muscle tissue. Capilary lipoprotein lipases degrade VLDL and fatty acid and glycerol are delivered to adipocytes or muscle.
Describe what happens to VLDL:
After giving up their triacylglycerols, the VLDL remnants appear in the blood as Intermediate density lipoproteins (IDL) and then as low density lipoproteins (LDL).
Describe the implications of HDL vs VLDL
HDL is the good cholesterol
Blood plasma is found to be brown and cloudy. Why?
chylomicrons after a meal or high vldl levels if you have excess fat and are not exercising
What is the cycle we see in lipid transport in human blood system?
Chylomicrons brings fats to capillaries, where lipoprotein lipases create free fatty acids to bring to different tissues (mammary, muscle, adipose)
If you are not exercising and fat tissue is already loaded, chylomicron will not be good salesman and VLDL will not be converted to LDL, IDL and HDL. True or false?
TRUE
It would be nice to have HDL to get capillaries cleaned up of lipids and brought back to liver. true or false?
TRUE
What are the 3 kinds of lipases we see?
pancreatic lipase, capillary/tissue (lipoprotein lipase), adipocyte (triacylglycerol lipase)
Provide the pathway for utilization of stored fat and describe what needs to happen to the fat to make it useable.
- Low blood glucose and energy need trigger the secretion of epinephrine and glucagon hormones
Catabolism of glycerol after lipase reaction:
After the triacylglycerol (fat) is digested by lipase, it releases fatty acids, and glycerol.
So what are the 3 types of reactions in glycerol catabolism?
phosphorylation, oxidation, isomerization
What must happen to fatty acid before oxidation? Why?
activation by fatty acyl CoA synthase (thiokinase) to form fatty acyl coA
Describe FA activation reaction
Same enzyme does both steps (thiokinase)
There are different isoforms of Fatty acyl CoA synthase specific for different kind of FAs. True or false?
TRUE
Describe the transport of fatty acyl CoA into mitochondria
FA cannot go into mitochondria
Cytosolic and mitochondrial CoA pools have different functions; for ___________ and ___________ reaction respectively.
biosynthetic
Why is it called beta-oxidation?
Name beta comes from the fact that the beta carbon is what gets oxidized to become C1 after acetyl CoA formation from C1 and alpha carbon.
So _____ electrons are carried into the ETC, making ATP
24
The first enzyme of B-oxidation
Fatty Acyl CoA dehydrogenase
true or false?
TRUE
The b-Oxidation of fatty acyl-CoA: (4 steps)
1.FAD is used by acyl-CoA dehydrogenase to make a double bond between the alpha and beta carbons on palmitoyl-CoA, makes fadh2 and trans delta-2 enoyl coa
Fatty acyl -CoA dehydrogenase is linked to electron transport chain via what?
Electron transferring flavoprotein (ETF) and ETF-Q oxidoreductase
Thus there will be production of ____ FADH2, ____ NADH molecules during the b-oxidation cycles.
7
From 8 acetyl-CoA there will be generation of what in CAC?
8 GTPs, 8 FADH2, 24 NADH and 16 CO2
provide the amount of NADH and FADH2 produce in full oxidation of 16C fatty acid
16 co2
Read through slide 7 calculations of energy and water generation
okay
Fat catabolism supports life during hibernation by providing ____________ and ____________
energy
Describe oxidation of unsaturated fatty acids:
All the steps are same except, and additional enzyme called enoyl-CoA isomerase is required to convert the cis-double bond to trans double bond that can be recognized by enoyl-CoA hydratase.
Describe what happens when more than one bond is unsaturated:
When more than one bonds are unsaturated, then one more additional enzyme is used to saturate the second double bond using NADPH.
What about odd-chain fatty acids?
In case of odd-chain fatty acyl-CoA, a three carbon unit , the propionyl-CoA is left at the last cycle of b-oxidation.
Why does pandey say it is bad to eat a lot of fat?
When we eat a lot, peroxisome starts catabolizing fatty acids because there is so much. This has an adverse effect on us.
How does peroxisomal beta oxidation occur?
Very long chain diffuses into peroxisomes and are catabolized into medium chain fatty acids, then go back to mitochondria for complete oxidation
What is the difference between peroxisomal beta-oxidation and mitochondrial?
There is one difference between peroxisomal beta-oxidation.
Describe omega oxidation
Sometimes the beta-oxidation decides to start on the end. The omega end.
Name the ketone bodies:
Acetoacetate, β-hydroxybutyrate, acetone
Why make ketone bodies?
They are hydrophilic, able to travel in blood
Describe the problem with ketone bodies and the subsequent reactions as a result
Problem: acetoacetate is very acidic, so we must convert some of it to acetone and b-hydroxybutyrate
Ketone body formation regenerates free CoA which are required for b-oxidation.
okay
True or false?
TRUE
In untreated diabetes, the concentration of ketone bodies (two of which are acids) in blood increases so much that it decreases the pH of blood. This condition is called “___________” which can lead to coma or death.
acidosis
High concentration of ketone bodies in blood and urine is referred as “__________”. Due to high concentration of acetoacetate, which is converted to acetone, the breath and urine of the untreated diabetic patients smells like acetone.
ketosis
