biochemistry 3 Flashcards
what is gluconeogenesis
- creation of new glucose
where does gluconeogenesis occur
- mainly in liver and Kinsey cortex
when does gluconeogenesis occur
- starvation and prolonged exercise
what is the point of no return in carbohydrate biochemistry
phosphonolpyruvate —>pyruvate
what regulates gluconeogenesis
- pyruvate carboxylase
- phosphoenolpyruvate carboxylkinase
- fructose-1,6-bisphosphatase
- glucose- 6- phosphatase
where is glucose-6-phosphate found
liver and ER
where is pyruvate carboxylase found
mitochondria
where is phosphoneolpyruvate carboxylkinase
cytosol
what are the precursors of gluconeogenesis
- lactate - skeletal muscles
- amino acids - skeletal muscles or food
- glycerol - adipose tissue
when is gluconeogenesis activated
- low energy stores
- low carbohydrate intake
what causes a fructose-1,6-bisphosphate deficiency and what does it cause
- autosmal reccesive disorder
- mutation in FBP1
- reduce gluconeogenesis leads to hypoglycaemia
what does gierke disease cause - type 1- glycogen storage disease
- decreased glucose-6-phosphate in liver or low endoplasmic reticulum uptake
- increased liver glycolysis –> increased blood lactate and pyruvate
what are the symptoms of type 1 - glycogen disgorge disease - gierke disease
- hyperglycaemia between meals
- enlargement of liver
- no raise in blood glucose with epinephrine and glucagon
- increases fat metabolism
what ethanol metabolism 1
Ethanol —> acetaldehyde by alcohol dehydrogenase
acetaldehyde –> acetate by aldehyde dehydrogenase
- both produce NADH
how does increased NADH decrease gluconeogenesis
1) lactic acid build up
2) amino acids converted to pyruvate
3) glycerol converted to glyceraldehyde-3-phosphate
4) oxaloacetate converted to malate
- causes lactic acidosis, fatty liver, hyperglycaemia
how does fatty liver develop
- from glyceraldehyde-3-phosphate –> lipids
how does alcoholic hepatitis occur
liver cells die resulting in inflammation
how does cirrhosis occur
- scar tissue forms
- not able to convert ammonia into urea
- rise in blood ammonia
- neural toxicity
what causes alcoholic flush
- dominant causing allele
- higher protein degradation
- acetaldehyde build up
- overactive ADH
what are the naturally occurring glycosidic links
1,2
1,4 - linear
1,6 - branched
what is the structure importance of glycogen
- glycogen spheres
- large amount of glucose
- short glucose chains - soluble
- less water interacting
glucose-6-phosphate to glucose-1-phosphate
phosphoglucomutase
what converts glucose-1-phosphate to UDP-glucose
- UDP glucose pyrophohorylase
- UPT –>PPI
what are the stages of glycogenesis
- starts with glycogenin
- transfer of glucose from UDP-glucose
- autocatalysis - 6-7 units
- glycogen synthase recruited and further elongation
- branching induced by branching enzyme from 1,4 to 1,6
what is ethanol metabolism 2
ethanol –> acetaldehyde by MEOS - microsomal ethanol-oxidising system
what are the stages of glycogenolysis
1) glycogen phosphorylase breaks down q,4 bonds and glucose-1-phosphate released
2) debranching enzymes - 1,6 residues hydrolysed tp glucose and truncate branch to 1,4 chain
3) phosphoglucomutase - isomerism glucose-1-phosphate to glucose-6-phosphate
what does glycogen synthase do
- promotes glycogen synthesis
- covalent modification pf insulin ang glucagon
- glucagon signalling –> phosphorylated - inactive
- insulin signalling –> dephosphorylated - active
what does glycogen phosphorylase do
- promotes glycogen degradation
- allosteric control of muscle and liver - glucose, ATP and glucose-6-phosphate inhibited and AMP activated
- covalent modification of insulin and glucagon
glucagon - active
insulin - inactive
what causes type 2 glycogen storage disease (Pompe disease) and what are the symptoms
- mutation of alpha 1,4 glucosidase - lysosomal enzyme
- enlargement of the liver and proximal muscle weakness causing cardiorespiratory failure and death before 2
what causes type 3 glycogen storage disease (cori disease ) and what are they symptoms
- mutation of amyloid-1,6-glucosidase
- hyperglycaemia, enlargement of liver, no rain in blood glucose with epinephrine and glucagon
- increase fat metabolism
what causes type 5 glycogen storage disease (McArdle disease) and what are the symptoms
- mutation in muscle glycogen phosphorylase activity making it absent
- increased creatine phosphate breakdown
- short exercise causes fatigue, muscle pain and cramps
