Lecture 35 Flashcards
Why are energy stores needed in our body?
ATP is not transfered between tissues, it must be produced in the tissue as needed. It is not an energy store, the fuels that are stored are glycogen and fat. These fuel stores are necessary to provide fuels for oxidisation because of this inability to store ATP.
We also need to maintain a supply of glucose between meals, immediate fuel for increased activity and for long periods when food intake may be inadequate.
How are our foods stored? In order of amount (highest to lowest).
Most fuel in our body is stored as triacylglycerol in adipose tissue (fat), protein is stored mainly in muscle, glycogen (quite important for immediate access) is in the muscle and liver and there is a small amount of glucose and fatty acids circulating.
How is fat storage done?
Fat storage is done by forming triacylglycerols (can be simple, all the same fatty acids or mixed, different fatty acids) by joining free fatty acids and triglycerols, it is stored as fat droplets in adipose tissue (a squishee tissue with some space between) and can be produced from excess fat and carbohydrates from the diet. It is an unlimited storage.
Where do the parts used in synthesising triacylgycerols come from? What is the equation?
Fatty acids come from chylomicrons and VLDL(can’t enter adipose without insulin activated ligase receptors), glycerol backbones come from glucose, the fatty acids are activated by acyl-CoA (done by different enzymes depending on length) and the acyl groups are esterified to glycerol-3-P. These processes are all stimulated by insulin. The equation is R-COOH + CoA-SH becomes R-CO.SCoA via fattyacylCoA synthetase at the cost of ATP to AMP. These can then be attached to the glycerol 3-Phosphate to form the triacyl glycerols which can then be mobilised via hormones like adrenaline into glycerol and fatty acids (then to fatty acid-albumin complexes).
How is mobilisation of triacylglycerols done?
Mobilisation of triacylglycerols is done via hydrolysis, it is catalysed by hormone-sensitive lipase and stimulated via adrenaline (and another hormone).
What is glycogen and how is it synthesised?
Glucose can be stored as glycogen, this is done via 1,4 alpha bonds between the glucose and roughly every 10 glucose an additional alpha 1,6 bond which creates a network. It will end in non reducing ends. Its synthesis occurs mainly in the liver and muscle immediately after a meal (insulin) and requires usage of ATP and UTP, it creates an activated high energy precursor (UDP-glucose), the cleavage of this bond is used by glycogen synthase (and branching enzyme) to snap it on to the growing glycogen.
What is UDP glucose phosphorylase?
UDP glucose phosphorylase is the enzyme which produced UDP-glucose from Glucose-1-phosphate.
How is glycogen mobilisation done?
Mobilisation of glycogen is done via degradation by glycogenolysis, liver glycogen is released as glucose into the blood, muscle glycogen releases fuel for glycolysis within the muscle cell.
What tissues use what fuel?
The brain and red blood cells only use glucose, the heart and liver use mostly fatty acids and muscle uses mostly fatty acids when resting or a mix off fatty acids and glucose in sport.
