T or F: fatty acids are a major source of energy for all tissue.
False
What is the consequence of fats being more reduced than carbohydrates?
They produce more high energy molecules
In what cellular compartments does oxidation of fatty acids occur?
Mitochondria: ß-oxidation
Peroxisome: alpha and ß-oxidation
Endoplasmic reticulum: omega oxidation
T or F: the stored fats used in fatty acid oxidation are pulled out of chylomicrons to enter the target tissue.
False
- While its true that chylomicrons carry DIETARY fatty acids to tissues, STORED fatty acids are released from fat cells via serum albumin
What is the upper limit for fatty acids that the mitochondria can handle, where does oxidation of larger fatty acids occur?
20 carbons = Arachindonate
- any larger than 20 they go to peroxisomes
What are the essential fatty acids (fatty acids that we can’t synthesize ourselves from others)?
omega 3
omega 6
Why do fat cells have to produce all of their glycerol 3-phosphate from glucose instead of just using glycerol from the environment?
- they lack the Glycerol kinase enzyme
What is another name for the hormone sensitive lipase, what hormones is it sensitive to?
- Triacyglycerol lipase
- glucagon and epinephrine (lipolytic hormones)
What is an antilipolytic hormone?
- Insulin
- works by decreasing adipocyte cAMP
Why do people with type I diabetes have a high risk for ketoacidosis?
- They lack insulin to down regulate Triacylglycerol lipase. With this active fatty acids are constantly being created by TG breakdown, these go into the liver to become ketone bodies.
What are the activated transport intermediates in fatty acid uptake?
FACoA and FAcarnitine
How are fatty acids mobilized by fat tissue?
- Glucagon or Epinephrine binds to GPCR stimulating cAMP cascade
- TAG lipase is phosphorylated and activated
- TAG is converted to diacylglycerol which is broken down further to Fatty acids and Glycerol by other lipases
- Fatty acids are then bound to serum albumin once transported out of adipose tissue
How are fatty acids activated in the cytosol?
Fatty acyl CoA synthase converts fatty acids to the activated Fatty Acyl CoA and pyrophosphate
What is the function of pyrophosphatase?
converts pyrophosphate into 2 organic phosphates
What are the 3 metabolic routes of Fatty acyl CoA?
- Energy (ß-oxidation and ketogenesis)
- Membrane Lipid Formation (phospholipids and sphingolipids)
- Storage (as TAGs)
T or F: short and medium chain fatty acids can cross the inner mitochondrial membrane.
True
What must fatty acyl CoA be converted to to cross the inner mitochondrial membrane and by what?
Fatty acylcarnitine by CPT-I
-CPT-1 replaces CoA with carnitine
What moves fatty acylcarnitine across the inner mitochondrial membrane?
a translocase
What is the carnitine cycle?
- CPT-1 converts FACoA to FA carnitine
- Translocase move FAcarnitine through inner membrane
- Matrix CPT-II converts FA carnitine back to FACoA
- Carnitine is transported back to make another cycle
What the the two main ways beta oxidation is regulated?
- Malonyl CoA
- High ATP (which negatively affects ETC)
What is the major energetic difference between saturated and unsaturated ß-oxidation?
- No FADH2 is produced because acyl CoA dehydrogenase is bypassed
- If doubly unsaturated
- NADPH must be used (energetically costly) - FADH2 producing step is bypassed a second time
How is the problem of odd chain fatty acid oxidation solved?
- Propionyl CoA is left over
- A carbon is added by proponyl CoA carboxylase creating succinyl CoA
- Succinyl CoA can then enter the TCA cycle
What is the difference in first step of long chain fatty acid oxidation and very long chain fatty acid breakdown
- Peroxide instead of FADH2 is produced in VLCFA breakdown because it takes place in the peroxisome
When does omega oxidation of fatty acids occur?
Happens only when medium chain fatty acids build up in individuals
NOTE: This is a sign that ß-oxidation of fatty acids is compromised in an individual
