23-Lipid synthesis and Lipid formation Flashcards
What are lipoproteins?
Particles that transport lipids
What are lipoproteins made up of?
Triglyceride Phospholipids Cholesterol Cholesterol ester Apolipoproteins
What are the three functions of apolipoproteins?
Interact with lipid component and help solubilize the particles
Enzyme activation or inhibition
Receptor binding
What are triglycerides broken down to during digestion?
Three fatty acids and glycerol
How are fatty acids stored?
Stored in adipose tissue as triglyceride
What fatty acids used for?
Used as a source of energy
Converted to ketone bodies in liver
What is beta oxidation?
Beta carbon atom on the fatty acid is what is being oxidised
What happens during beta oxidation of fatty acids?
4 step cyclic process taking off two carbons each cycle
What does one beta oxidation cycle release?
One molecule of acetyl CoA and reduced nucleotides
What is the net gain of ATP from the complete oxidation of C16?
129 ATPs
What happens if there is excess acetyl- CoA? Where does this occur and what is it known as?
Acetyl CoA can be converted to ketone bodies
Occurs in liver mitochondria
Known as Ketogenesis
What is the role of ketone bodies?
Ketone bodies enter the blood and travel to other tissue where they can be oxidised to provide energy.
Can be converted back to acetoacetyl-CoA and then acetyl-CoA
People with diabetes often have a strong smell on the breath what is this from?
Acetotacetate decarboxylates to acetone
What is lipogenesis?
Fatty acid formation
The process by which acetyl-CoA is converted to fatty acids, and subsequently triglycerides
Where does fatty acid synthesis take place?
Cytosol
What is the first step in fatty acid synthesis catalysed by?
Acetyl-CoA carboxylase
What are the enzymes involved in fatty acid synthesis?
7 enzymes joined by a polypeptide chain called fatty acid synthesis
How is the growing fatty acid chain elongated?
The sequential addition of two carbon units derived from acetyl CoA, and the active donor of this 2 carbon unit is malonyl- CoA
What is the reductant in fatty acid synthesis?
NADPH
When does the elongation of the fatty acid complex stop?
When there is a C16 - palmitate
What are the 3 steps of fatty acid synthesis?
Activation
Elongation
Termination
Where is Acetyl CoA generated?
Mitochondria and cannot cross the inner mitochondrial membrane
How is acetyl- CoA supplied for lipogenesis?
Acetyl- CoA combines with oxaloacetate to produce citrate
What is meant by the term elongation which happens during lipogenesis?
Chain elongation mainly occurs in the ER by ezymes called fatty acid elongases.
2C are added at a time from malonyl-CoA and the reductant is again NADPH
What is meant by desaturation which happens during lipogenesis?
Desaturase enzymes located in the ER membrane introduce specific bonds at specific postitions in the fatty acid chain.
This requires NADP and O2
What is cholesterol?
Biological lipid made up of 27 carbons
What is the rate limiting step during cholesterol synthesis?
HMG-CoA reductase
What happens in the rate limiting step in cholesterol synthesis?
HNG-CoA becomes mevalonate
What happens when cholesterol levels are high?
Result in decreased HMG-CoA reductase transcription- caused reduced cholestrol production
What happens when cholesterol levels are too low?
Increased HMG-CoA reductase transcription - caused increased cholesterol production
What are satins used for?
Inhibit HMG- CoA reductase and reduce cholesterol biosynthesis
