lecture 36 - starvation Flashcards
What is starvation, and how is it distinguished from under nutrition?
The absolute deprivation of food, rather than consuming insufficient food
What is the main hormone regulating metabolism during starvation?
Glucagon
When is glucagon released, and from where?
released from alpha islet cells in the pancreas when blood glucose levels fall
What does glucagon stimulate during starvation?
Once glycogen stores are expended, stimulates the mobilisation (lipolysis) of TAGs from adipose tissue
What is glycogen converted to when stimulated by glucagon?
glucose-1-phosphate then glucose-6-phosphate then glucose (in glycogenolysis)
What is gluconeogenesis?
The generation of new glucose from non-carbohydrate substrates (essential reverse glycolysis)
Where does the majors of gluconeogenesis occur?
In the liver
What are the substrates for gluconeogenesis?
Lactate from skeletal muscle glycogen, alanine from muscle protein and glycerol from adipose tissue TAG.
where is the lactate for gluconeogenesis from?
From anaerobic metabolism of the products of skeletal muscle glycogenolysis
Where is the alanine for gluconeogenesis sourced from?
Muscle protein
Where is the glycerol for gluconeogenesis sourced from?
Adipose tissue TAGs
What key fuel molecule cannot be used as a substrate for gluconeogenesis?
Fatty acids
When are ketone bodies synthesised?
When people are starved
What parts of the body can use ketone bodies for fuel?
The brain and other aerobic tissues
Where are ketone bodies synthesised?
The liver
What are ketone bodies synthesised from?
acetyl-CoA that is generated by beta-oxidation of fatty acids
What is the name of the process that generates ketone bodies?
Ketogenesis
How many carbons do keto acids have, and why?
4 carbons - are essentially two 2 carbon acetyl-CoA units joined together
what are keto acids formed from?
two 2 carbon Acetyl-CoA molecules
Why can keto acids enter the brain?
They are short and water soluble so can cross the blood brain barrier
How do stored TAGs provide the brain with energy during starvation?
Although fatty acids cannot be used by the brain directly, they can be converted to ketone bodies that can be used.
How is lactate produced from the anaerobic metabolism of glucose recycled?
By gluconeogenesis
