Lecture 2 Flashcards
How does fatty acid oxidation begin
with activation; due to ATP
How is fatty acid activated
the formation of a thioester bond between carboxyl group of the FA and the thiol of the CoA-SH
true or false; the resulting CoA ester during fatty acid activation is more soluble
true
What is the enzyme for fatty acid activation
acyl CoA synthetase
What is the role of carnitine in acyl-CoA transfer
acyl group is transferred to carnitine, carried across the inner mitochondrial membrane, then transferred to mitochondrial CoA
true or false; acyl-CoA crosses the outer mitochondrial membrane but not the inner membrane
true
What is the enzyme used for the transfer of acyl group to carnitine
carnitine palmitoyltransferase (CPT-1)
what has CPT-1 have specificity for
acyl groups between 14 and 18 carbons long
where does the breakdown of fatty acids occur
mitochondrial matrix and proceeds by successive removal of 2C as acetyl CoA
What do you call the reaction that each 2C moiety must undergo to be converted to acetyl CoA
B-oxidation
What is B-oxidation
a series of four reactions that cleaves carbon atoms two at a time from the carboxyl end of the fatty acid
What are the 4 central reactions of B oxidation
- ) dehydrogenation across a-B and C-C bond (-H2O)
- ) hydration of the same bond (H2O)
- ) second dehydrogenation yields a B-keto group
- ) attack by CoASH to form a new, shorter FA-CoA and acetyl CoA
What are the saturated FAs with even number chain length
C14, 16, 18 etc
true or false; saturated FAs with even number chain length can be completely oxidized by this route B oxidation
true
true or false; odd numbered carbon FAs can be metabolized via the B oxidation as well but a 3C unit remains
true
what is the 3C unit that remain after B oxidation of an odd numbered fatty acid
propionyl CoA
what is propionyl CoA converted to
methylmalonyl CoA by carbon dioxide fixation; this can also enter the TCA cycle via the coversion to succinyl CoA
What happens to unsaturated fatty acids
FAs containing a double bond require an additional enzyme for degradation
the cis-enoyl group is converted to the trans configuration by an ISOMERASE
true or false; lipid oxidation generates water and CO2
true
Why do ketone bodies form
- surplus acetyl CoA cannot be oxidized by the TCA cycle if cellular levels of oxaloacetate are insufficient to react with; instead acetyl CoA is converted to ketone bodies
What causes low oxaloacetate
diet high in lipids and low carbs
diabetes not well controlled
starvation
what are 2 types of ketone bodies
acetone
B-hydroxybutyrate
acetoacetate
where are ketone bodies formed
in liver mitochondria
what uses ketone bodies
can be used in most tissue and organ including the brain but only after prolonged starvation
- metabolic state called KETOSIS
what is excess carbohydrate stored as
fat
true or false; fat is a compact energy storage form, being highly reduced an anhydrous
true
What are the major producers of fat
liver and fat cells
- mammary glands also have the ability to synthesize fat during milk production
why cant mammals synthesize glucose from fatty acids
because pyruvate dehyrogenase and pyruvate kinase are irreversible
how much energy is in 1 g of fat
9 kcal
how much energy is in 1g of carbs
3.75kcal
how much energy is in 1g of protein
4 kcal
What is the symbol for respiratory quotient
RQ
Expression of RQ
CO2 generated in mol/ O2 consumed in mol
true or false; after digestion is complete the RQ is nearly 1.0
true
- shows that carbs (as liver glycogen) is preferentially oxidized in this state
What is the RQ during starvation
- 71
- fats are preferentially oxidized in the starved state
where is the chain lengthening and introduction of double bond for FA metabolism
ER
