Energy Production: Carbs 3+4 Flashcards
What is the entry point into TCA cycle, what regulates it?
Acetyl CoA is the entry point and pyruvate dehydrogenase is a key site of regulation of entry
Activation/inhibition of PDH
Activated by: pyruvate, CoA, NAD+, ADP, insulin. Inhibited by: acetyl-CoA, NADH, ATP, citrate.
Why doesn’t TCA cycle function without O2?
As the cycle is tightly coupled to the electrons transport train, and O2 is the terminal electron acceptor in this.
Where does electron transport occur?
Across the inner membrane of the mitochondria.
Describe uncoupling of oxidative phosphorylation.
Uncouplers increase the permeability of the mitochondrial inner membrane to protons. This dissipates the proton gradient, reducing the pmf. Therefore, no drive for ATP synthesis.
Describe inhibition of oxidative phosphorylation.
Inhibitors block electron transport, e.g. cyanide, this prevents acceptance of electrons by O2.
Where can brown adipose tissue be found?
In newborn infants (to maintain heat), in hibernating animals (to generate heat to maintain temp).
What are the fat soluble vitamins?
A, D, E, K
Key examples of fatty acid derivatives.
Fatty acids- fuel molecules, Triacylglycerols- fuel storage and mobilisation, Phospholipids- components of membranes and plasma lipoproteins.
In what form are triacylglycerols stored?
They are hydrophobic so they are stored in an anhydrous form in adipose tissue.
How are triacylglycerols stored?
Fatty acids are converted back to triacylglycerols in the GI tract and are packaged into a lipoprotein particle called chylomicrons. Theses are released into circulation via lymphatics and carried to adipose tissue where they are stored as triacylglycerols.
How are fatty acids activated and where does it occur?
Occurs outside the mitochondria, in the cytoplasm. Fatty acids are activated by linking coenzyme A by the action of fatty acyl CoA synthase.
How is fatty acyl-CoA transported?
Transported across the mitochondrial membrane via the carnitine shuttle. This is regulated (AMP, insulin), so control the rate of fatty acid oxidation.
Where do we get ketone bodies from?
The liver constantly generates ketone bodies (synthesised by liver mitochondria) from acetyl CoA, production is much higher during fasting.
Describe ‘fed state’
When the insulin/glucagon ratio is high, Lyase is inhibited + Reductase is activated -> cholesterol synthesis.
Describe ‘starvation state’
When the insulin/glucagon ratio is low, Lyase is activated and Reductase is inhibited -> ketone body synthesis
