Lipids, Ketone Bodies And B Oxidation Flashcards
How many classes of lipids are there?
3
What are the 3 classes of lipids?
-Fatty acid derivatives
-Hydroxyl-methyl-glutamic acid derivatives (HMG acid derivatives)
-Fat soluble vitamins
Give 2 examples of fatty acid derivatives and what there function is:
Fatty acids - Fuel molecules
Triacylglycerols - Fuel storage and insulation
Give 2 examples of Hydroxyl-methyl-glutamic (HMG) acid derivatives
Ketone bodies - Water soluble fuel molecules
Cholesterol - steroid hormone synthesis and regulate membrane fluidity
Cholesterol esters- cholesterol storage
What are the 4 lipid soluble vitamins?
A,D,E and K
What is the difference in energy stores between a healthy individual and an obese individual?
Glycogen and muscle protein energy stores remain the same
Triacylglycerols are a lot higher in Obese individual
How are TAGs stored?
They are hydrophobic so are stored in an anhydrous form in adipose tissue
What is esterification?
When fatty acids are added to glycerol to form a Triacylglycerol
What is the opposite of esterification?
Lipolysis
What needs to happen to TAG that has been obtained from the diet so it can be metabolised to release energy?
Needs to be broken down into Fatty acids and glycerol
What breaks down dietary lipids into fatty acids and glycerol and where does this take place?
Pancreatic lipases
Extracellularly in the small intestine (GI tract)
What happens to the fatty acids once they have been taken up by the cells in the GI tract?
Converted back into TAGs and packaged into lipoprotein particles
What is the name of the lipoprotein particle which transports dietary TAG from the small intestines to adipose tissue?
Chylomicrons
How do Chylomicrons containing TAG get carried to adipose tissue?
Through the lymphatic system
What is the name given to the milky looking lymph fluid containing lots of Chylomicrons containing TAG?
Chyle
How are fatty acids transported in the blood once they are required?
Attached to albumin
Albumin-fatty acid complex
Fatty acids undergo Beta Oxidation to release energy, generally what are the 3 key steps to fatty acid metabolism to release energy?
Activation
Transport
Beta oxidation
Where does Fatty acid activation take place?
Outside the mitochondria
How is a fatty acid activated?
Gets Linked to CoA
Where do activated fatty acids get transported to?
Through the inner mitochondrial membrane into the mitochondria
What transports activated fatty acids (fatty acyl CoA) into the mitochondria?
The Carnitine shuttle
What enzyme catalyses the formation of activated fatty acids?
Fatty acyl CoA synthase
What is an activated fatty acid actually called?
Fatty acyl CoA
What occurs in Beta oxidation?
The fatty acyl CoA (activated fatty acid) has a 2 carbons removed evey cycle and forms NADH and FADH2
Generally, what is B Oxidation of an activated fatty acid producing and why is this useful?
Acetyl CoA
Reducing power (NADH and FADH2)
Acetyl CoA can enter into the Krebs cycle and the reducing powe (NADH and FADH2) can be used in oxidative phosphorylation
Where can B oxidation of fatty acids not take place and why?
Brain- Fatty acids can’t cross blood brain barrier
RBC-Don’t have mitochondria
Why does B oxidation of fatty acids need oxygen to take place?
Needed to regenerate NAD+ and FAD in oxidative phosphorylation
What is the rate of FA oxidation regulated by?
AMP
Insulin
Where is glycerol transported to to be metabolised?
Liver
What happens to glycerol in the liver?
It is phosphorylated into Glycerol phosphate
What key enzyme Phosphorylates glycerol into glycerol phosphate in the liver?
Glycerol kinase
What are the 2 fates of glycerol phosphate?
Converted into Triacylglycerols for storage
Or converted into other intermediates so it can enter glycolysis
What is glycerol phosphate converted into if it’s destined for glycolysis?
Dihydroxyacetone-P DHAP
What is DHAP (Dihydroxyacetone-P) converted into so it is actually in Glycolysis?
Glyceraldehyde 3-P
Describe how glycerol enters into glycolysis to be metabolised to release energy
Glycerol converted to glycerol phosphate by glycerol kinase in liver
Glycerol phosphate converted into Dihydroxyacetone-P (DHAP)
Dihydroxyacetone converted into Glyceraldehyde 3-P
Glyceraldehyde 3-P is a metabolite in glycolysis
Where are ketone bodies produced?
In the liver
What are ketone bodies produced from?
Acetyl CoA
When are ketone bodies produced?
When Acetyl CoA is in excess:
-uncontrolled lipolysis or when lipolysis is high
-during fasting and starvation (fatty acids released from adipose tissue to be used as energy source)
How are ketone bodies formed from acetyl CoA?
Step 1
Acetyl CoA converted into HMG CoA by HMG-CoA synthase enzyme
How are ketone bodies produced from acetyl CoA?
Step 2
HMG CoA lyase converts HMG-CoA into the ketone body acetoacetate
From here acetoacetate can be converted into 2 other ketone bodies
What are the 3 ketone bodies?
Acetoacetate
Acetone
B-hydroxybutyrate
What hormones regulate the synthesis of Ketone bodies?
Insulin and glucagon
What occurs when the insulin:glucagon ratio is high in relation to ketone body synthesis?
Enzyme HMG CoA REDUCTASE is activated and HMG CoA Lyase is inhibited so less ketone bodies made
What happens when HMG CoA REDUCTASE is activated?
Cholesterol is synthesised
What drug can decrease cholesterol levels and how does it do this?
Statins
They inhibit the enzyme HMG CoA REDUCTASE so HMG CoA can’t be converted into cholesterol
What happens when the insulin:glucagon ratio is low in relation to ketone body synthesis?
HMG CoA REDUCTASE inhibited
HMG CoA lyases stimulated
Ketone bodies synthesised
So what does it mean when insulin is high?
What does it mean when glucagon is high?
In terms of cholesterol and ketone production:
High insulin = fed, cholesterol is synthesised
High glucagon = starving, ketone bodies synthesised
What is the benefit of producing ketone bodies?
Helps spare glucose in early starvation
Why are ketone bodies dangerous?
They build up in the blood in Type 1 diabetes and cause diabetic ketoacidosis which is very dangerous
