Lipids 2 Flashcards
What process does the body utilise to breakdown fatty acids?
beta oxidation
Where does beta oxidation occur?
mitochondria
What does beta oxidation produce as products?
acetyl-CoA which can enter the citric acid cycle
NADH and FADH2 which are used in terminal respiration
ketone bodies
How are free fatty acids transported in the blood?
in complex with albumin
How are FAs released from TAG in adipocytes?
by hormone sensitive lipase which are triggered by phosphorylation by epinephrine
How does the beta oxidation pathway degrade fatty acids?
2 carbons at a time
What are the 3 stages of beta oxidation?
- activation
- transport
- degradation
Where does the activation stage occur?
the cytosol
What happens in the activation stage?
fatty acid activated to form fatty acyl coA in cytoplasm
What happens in the transport stage of beta oxidation? Basics
transport of fatty acyl coA from cytosol into matrix of the mitochondrion by mechanism of the carnitine shuttle
How is fatty acyl coA transferred from the cytosol to the matrix by the carnation shuttle?
- fatty acylcoA loses the coA and is transferred by the CAT-1 enzyme into the mitochondrion
- in the matrix, the fatty acyl recombines with a CoA
What inhibits the carnitine shuttle?
malonyl coA
What is the significance of the regulatory action of the presence of malonyl CoA?
prevents synthesis and degradation happening at the same time
What is CAT-1 deficiency?
no beta oxidation occurs resulting in hypoglycaemia
How is CAT-1 deficiency hypoglycaemia treated?
IV glucose
What is the therapy for a CAT-1 deficiency?
give medium chain fatty acids that do not require CAT for mitochondrial transport
There are 4 stages to the final stage of beta oxidation. What are they? Degradation
- dehydrogenation to produce FADH2
- Hydration
- Dehydration to produce NADH
- Thiolysis (leaved) to produce acetyl coA
What is produced in each beta oxidation cycle?
one acetyl CoA and a species two carbons shorter than the original (keeps occurring with 2 carbons chopped off each time)
also FADH2 and NADH
How much energy in ATP is produced from beta oxidation of palmitate?
129
only 32ATP produced per molecule of glucose!
What length of fatty acids undergo preliminary beta oxidation in the peroxisome?
> 22 carbons
What is a disadvantage of having to have preliminary beta oxidation?
first step doesn’t produce FADH2 and so less energy efficient
What happens to excess acetyl CoA from beta oxidation?
cannot convert acetyl CoA into glucose
in fasting/starvation is converted to ketone bodies or enters the citric acid cycle to be converted to oxaloactetate which can be used in gluconeogenesis
What does acetyl CoA inhibit and what does it do?
inhibits pyruvate dehydrogenase which is the enzyme responsible for converting pyruvate to Acetyl CoA
What does Acetyl CoA activate and what does it do?
activates pyruvate carboxylase which converts pyruvate to oxaloacetate which can be used in gluconeogenesis
