Session 2-Energy Production:Lipids Flashcards
True or false: lipids are generally soluble in water
FALSE - insoluble
Lipids are more reduced than carbs. What are the consequences of this?
Lipids release more energy when oxidised
What are the three classes of lipids?
1) Fatty acid (FA) derivatives
2) Hydroxy-methyl-glutaric (HMG) acid derivatives
3) Vitamins
Which vitamins are lipid molecules?
A, D, E and K
Which fatty acid derivatives do we need to know?
Fatty acids
Triacylglycerols (triglycerides)
What are FA stored as?
Triacylglycerols
Which HMG acid derivative do we need to know?
Ketone bodies (C4)
What are ketone bodies?
Water soluble fuel molecules-alternative substrate when glucose is low, solubilise energy in fat
Which process produces triacylglycerols (TAG)?
Esterification
True or false: triacylglycerols (TAG) are hydrophilic
FALSE - hydrophobic
How are triacylglycerols (TAG) stored within cells?
Lipid droplets
When are TAGs utilised?
Prolonged exercise
‘Starvation’
During pregnancy
How is the storage/mobilisation of TAGs controlled by hormones?
Glucagon mobilises fat
Insulin puts fat into store
What are chylomicrons?
Lipoproteins formed to package FA and allow them to be transported in the blood
Which enzyme catalyses the breakdown of lipids in the small intestine?
Pancreatic lipase
How are FA carried to tissues?
Albumin-FA complex
Complete the sentence:
FA can be saturated, ___________ or _____________
Unsaturated
Amphipathic
Why are some polyunsaturated FA essential?
Because mammals cannot introduce a double bond beyond C9
Where does triacylglycerol metabolism occur?
GI tract, extracellular
Where does FA metabolism occur?
Mitochondria
What activates FA outside the mitochondrion?
Linking to coenzyme A by the action of fatty acyl CoA synthase
How are FA transported across the inner mitochondrial membrane?
Carnitine shuttle
How many carbons are removed with each cycle of FA catabolism?
2
What inhibits the transport of fatty acyl-CoA across the mitochondrial membrane?
Malonyl-CoA
What is another term for FA catabolism?
Beta-oxidation
How many ATP molecules are produced from C6 FA?
41
Why doesn’t FA metabolism occur in the brain?
FA cannot pass through the blood/brain barrier
Why doesn’t FA metabolism occur in RBCs?
No mitochondria
Where is glycerol metabolised?
Liver
What is the main convergence point for catabolic pathways?
Acetyl CoA
Which vitamin does CoA contain?
B5
Which atom links CH3CO group to coenzyme A?
S-atom
True or false: ketone bodies are more hydrophilic than lipid
TRUE
Which three ketone bodies are produced in the body?
1) Acetoacetate
2) Acetone
3) beta-hydroxybutyrate
True or false: acetone is produced by the spontaneous decarboxylation of acetoacetate
TRUE
What is the normal plasma ketone body concentration?
<1mM
What is the plasma ketone body concentration in untreated type 1 diabetes?
> 10mM
What synthesises ketone bodies?
Liver mitochondria
What ensures that acetyl-CoA doesn’t enter the TCA cycle and instead forms ketone bodies?
NADH-high energy signal which inhibits the enzymes in the TCA cycle so acetyl-CoA doesn’t enter the TCA cycle
Complete the sentence:
When the insulin/glucagon ratio is high (ie fed state), _______ is inhibited, _____________ is activated and this leads to the synthesis of cholesterol
Lyase
Reductase
Complete the sentence:
When the insulin/glucagon ratio is low (ie starvation, diabetes), ______ is activated, ___________ is inhibited, leading to the synthesis of ________ _________
Lyase
Reductase
Ketone bodies
What is ketonuria?
Excretion of large amounts of ketone bodies in the urine
What can ketonuria be a test for?
Diabetes
Volatile acetone may be excreted via which organ?
Lungs
