3 - Glycogen and Fat Stores Flashcards
What are the major energy stores in a 70kg man?
What tissues have an absolute requirement for glucose?
- Inner cells of kidney medulla
- Neutrophils
- Red blood cells
- Lens of eye
What happens during hyperglycaemia and especially when it becomes chronic?
- Protein glycation, sugar sticking to proteins causes complications
- Neuropathy, poor microcirculation, Retinopathy ( Type II Diabetes)
How do you measure blood glucose more accurately than just testing blood sugars at a point in time?
- HBA1C blood test
- Measures amount of glycation of Hb, more glycation means hyperglycaemia
What are the signs of hypoglycaemia?
How is glucose stored?
Glycogen granules in the liver and muscles. Glucose release from liver can replenish plasma glucose but in muscles glucose from glycogen can only be used in muscles
Outline the process of glycogenesis.
Outline the process of glycogenolysis.
Never fully degraded as always need a bit of primer
How does glycogenolysis vary between muscles and the liver?
Muscles lack the enzyme glucose-6-phosphatase
What glucose transporters are in the liver and muscles?
- Liver has GLUT2, bidirecitonal
- Muscles have GLUT4, insulin regulated
What are the rate limiting enzymes of glycogenolysis and glycogenesis and what inhibits and activates them?
- Glucagon has no effect on muscles as they have no receptor for it
- AMP allosterically activates muscle phosphorylase but not liver phosphorylase
What are glycogen storage diseases and the consequences of these diseases?
- Error of metabolism due to deficiency or dysfunction of enzymes
1. Tissue damage if xs storage
2. Fasting hypoglycaemia
3. Poor exercise tolerance
4. Abnormal glycogen storage
5. Liver and muscle affected
When and where does gluconeogenesis occur?
- In the liver, (some in kidney cortex), 8-10 hours of fasting as glycogen stores deplete
- Precursors: Lactate, Glycerol, AA (alanine)
- NO NET SYNTHESIS OF GLUCOSE FROM ACETYL COA AS CANNOT BE CONVERTED BACK TO PYRUVATE
What are the key enzymes involved in gluconeogenesis?
1 and 2 are major controls of pathway
How are enzymes in gluconeogenesis regulated and what causes regulation?
- Stress
- Exercise
- Starvation
Where does glucose needed for glycolysis come from at different points in the day?
Food = 2 hours
Glycogenolysis = Up to 8 hours
Gluconeogenesis = 8-10 hours onwards
When is the energy store of TAG used?
Exercise, starvation, stress, pregnancy under hormonal control
What are fats stored as in adipose tissue?
- Cholesterol esters and TAG
- Typicall 0.1mm diameter but expand in size before dividing
How are TAG’s metabolised?
After hormone sensitive lipase, glycerol can go to liver for gluconeogenesis or go to muscles and other tissues for b-oxidation
Outline the process of lipogenesis.
Outline the differences between lipolysis and lipogenesis
Why is it beneficial to have degradative and biosynthetic routes occuring by partially different routes?
- Greater flexibility
- Better control
- Thermodynamically irreversible steps can be by-passed
What are the main anabolic and catabolic enzymes?
Anabolic: Insulin, GH
Catabolic: Adrenaline, Glucagon, Cortisol, Thyroid Hormones
Where does glucose come from over a time scale of 10 hours?
What is the difference between respiratory and metabolic acidosis?
What should the normal bloods look like for a fasting blood test?
What is the oral glucose tolerance test?
- Standard dose of glucose ingested by mouth (1g/kg weight) after 8 hour fast
- Glucose checked at time of administration and then 30 min intervals
- Should increase after 1hr and peak and fall to normal by 2hr
How do galactose and fructose feed into gluconeogenesis?
If a patient has fructose-1,6-bisphosphotase deficiency how can this be managed?
Avoid long periods of starvation
What is Von Gierke’s disease?
- Glucose-6-phosphotase deficiency, cannot mobilise glucose from glycogen
- Will have raised fatty acids after a fast as stress due to hypoglycaemia so adrenaline released for lipolysis
