Lipid Synthesis And Degredation Flashcards
What is the definition of a lipid?
Macromolecules soluble in non-polar solvents
Give some examples of lipids
Fatty acids Glycolipids Glycerolphospholipids Sphingolipids Triglycerides Cholesterol
When are fats synthesised and stored?
When our calorific intake exceeds the immediate needs of the body
How does the energy content of fat per gram compare to carbs and protein?
1g fat= 37kj
1g protein = 17kj
1g carbs = 16kj
What percentage of the energy from the British diet is fat?
40%
How much did obesity rise in adults from 1993->2014?
14.9%->25.6%
What BMI is classified as obese?
30Kg/M^2
What are fats most often made from?
Dietary carbs
What is the preferred energy source for cardiac muscle?
Fats
What is the preferred energy source for the brain?
Glucose
Where and how are fats stored?
In adipose tissue as triglycerides
Give the features of fatty acids
Chains of methyl groups
Terminal carboxylic acid
Double bonds (if present) are usually in cis conformation
No double bonds in less than position nine
What happens to the citrate when the amount of ATP is high and the need for glucose is low?
Citrate is transported out of the mitochondria
What happens to the citrate when its outside the mitochondria?
Converted back to acetyl coA and then synthesised into fatty acids
What happens to the fatty acids once made?
They will either stay in the liver or transported into the bloodstream
Where is cholesterol transported to?
Non-hepatic tissue
What does fatty acid synthesis require?
Acetyl coA
NADPH
ATP
What does the citrate-malate antiPorter do?
Transfer of the acetyl coA to the cytosol
What are the starting and ending molecules in the citrate-maleate antiPorter?
Acetyl coA- oxaloacetate
How is the NADPH provided for the citrate- malate antiPorter?
By the pentose phosphate pathway
What is the first step in fatty acid synthesis activated by?
Citrate
What is the first step in fatty acid synthesis inhibited by?
Palmatic acid
What does the first step in fatty acid synthesis require?
The vitamin biotin
What is fatty acid synthase responsible for?
Fatty acid synthesis
What are the intermediates in fatty acid synthase covalently linked to?
6 acyl carrier protein
What does fatty acid synthase enable?
The efficient and rapid movement of the growing fatty acid chain to be passed from one active site to the next
What are the three steps in fatty acid degradation
Mobilisation (adipocytes)
Activation (liver cytosol)
Degradation (liver mitochondria)
What hormones stimulate the mobilisation of fatty acids?
Glucagon
Adrenaline
What are fatty acids activated by in the liver cytoplasm
Acyl CoA synthase
What does fatty acid coA react with to from fatty acyl carnitine?
The alcohol carnitine
Where is the long chain FA activated?
On the outer mitochondrial membrane
What can carnitine deficiency cause?
Muscle weakness or death
What is fatty acid transport inhibited by?
Malonyl coA
What is the result of fatty acid/ beta oxidation?
FADH2, NADH and acetyl coA
Where does fatty acid/ beta oxidation occur?
In the liver mitochondria
What are the sequence of steps in fatty acid/ beta oxidation?
Oxidation
Hydration
Oxidation
Thiolysis
In non-hepatic tissue how many ATPs does complete oxidation of palmitate yield?
106
Why does ketogenesis happen?
Fasting, uncontrolled diabetes, prolonged exercise
What happens in ketogenesis?
Stimulates fatty acid breakdown producing acetyl coA
Where does the metabolism shift towards in ketogenesis?
Maintain blood glucose
What does the loss of oxaloacetic acid do?
Limits energy production from acetyl coA
What is excess acetyl coA used for?
To form ketone bodies
What are ketone bodies made up of?
Acetoacetate, 3 betahydroxybutyrate and acetone
Where are ketone bodies used?
Cardiac muscle and renal cortex and by the brain (only during starvation)
What does the breakdown of triglycerides give?
Acetyl coA and glycerol
What is glycerol used for in the liver?
The synthesis of glucose by gluconeogenesis
What is glycerol used for in the muscle?
In glycolysis and oxidative phosphorylation to produce ATP
What does insulin increase?
Glycolysis in the liver
Fatty acid synthesis in the liver
Triglyceride in adipose tissue
What does insulin decrease?
Beta oxidation
What do glucagon and adrenaline increase?
Triglyceride mobilisation
