Lipids 3 Flashcards
Where does fatty acid synthesis occur?
Adipose tissue
Liver
Lactating mammary gland
What is the de novo synthesis of fatty acids?
It involves the use of acetyl CoA from excess protein, fat and carbohydrate and it uses ATP and NADPH. It occurs in the cytosol.
How does acetyl CoA get from the mitochondria to the cytosol?
In citrate shuttles. It combines with oxaloacetate to produce citrate which crossed the membrane then can be broken down again. It occurs when the citrate concentration in the mitochondria is high and only the acetyl part can cross.
What does the enzyme acetyl CoA carboxylase do?
It helps synthesise malonyl CoA which activates Carbon dioxide.
It can be activated by citrate as that tells it there is enough glucose to make fatty acids. It’s deactivated by palmitoyl CoA as that tells it there’s is enough. It is also activated by insulin and deactivated by glucagon and epinephrine. Insulin removed a phosphate group to activate it and glucagon adds a phosphate group to deactivate it.
What are three steps in the synthesis of fatty acids that is reverse of degradation of fatty acids?
Reduction then dehydration then reduction again. The elongation cycle is repeated six more times (after original before three steps) using malonyl CoA to produce palmityl ACP. A thioesterase then cleaves the palmityl CoA from the ACP.
What is ACP?
The intermediates in fatty acid synthesis are covalently linked to the acyl carrier protein.
What enzyme synthesises most of the reactions?
The multifunctional fatty acid synthase
Where do the NADPH from the palmitate synthesis come from?
6 from the pentose phosphate pathway.
8 from the malic enzyme reaction that converts malware to pyruvate.
Where are any further modifications or elongations of palmitate taken place?
The mitochondria and ER.
What are eicosanoids?
They’re derived from 20 Carbon unsaturated fatty acids and are synthesised throughout the body. They are derived from omega 3 or 6 fatty acids and are precursors to prostaglandins, thrombaxanes and leukotrienes. They have control over inflammation or immunity and as messengers in the CNS. They have a short half life.
What is cholesterol?
It is a component of cell membranes and a precursor to other substances such as sterol Hormones , vitamin D and bile acids. It is made in the liver.
Describe some eicosanoid analogues
Montelukast and Zafirlukast are leukotriene antagonists and are used for asthma treatment as they inhibit the leukotrienes which cause vasoconstriction.
Carboprost induces labour as it is a prostaglandin analogue.
