Changes to metabolism Flashcards
Alanine to pyruvate.
Alanine loses its amino group by transamination to form pyruvate catalysed by alanine aminotransferase.
Aparagine to oxaloacetate.
asparagine is hydrolysed by asparaginase, liberating ammonia and aspartate. Aspartate loses its amino group by transamination via the enzyme asparatate aminotranferase to form oxaloacetate.
Glutamine to a-ketoglutarate.
glutamine is converted to glutamate and ammonia by the enzyme glutaminase (2). glutamate is converted to a-ketoglutarate by oxidative deamination by glutamate dehydrogenase (1).
Causes of starvation.
Inability to obtain food, desire to Lose weight, clinical situations such as; trauma, burns, injury to face, tumour.
During starvation, blood levels of what fall?
amino acids, glucose, and triacylglycerols.
During starvation, explain what happens to blood insulin & glucagon levels.
Blood insulin levels are very low & and glucagon level are very high.
During starvation, Both insulin and glucagon factors trigger a period of catabolism characterised by the degradation of;
glycogen to glucose.
triacylglycerol to fatty acids and glycerol.
protein to amino acids.
During starvation, the results result in an interchange of substrates between…
liver, adipose tissue, skeletal muscle, brain
During starvation, what 2 factors determine the fate of the substrates?
1) the need to conserve glucose for those cells & tissues that need it i.e. red blood cells, brain.
2) The need to mobilise fatty acids from adipose tissue & ketone bodies from liver to supply energy to all other tissues, & for these other tissues to adapt to the non-glucose substrates.
In all situations, the flow of intermediates through biochemical pathways is controlled by 4 mechanisms, what are they?
Availability of substrates.
Allosteric activation/inhibition of enzymes.
Covalent modification of enzymes.
Reciprocal induction or repression of enzyme synthesis.
What happens to the liver during starvation?
Glycogen breakdown, then gluconeogenesis to maintain blood glucose levels & sustain energy provision for the brain & other glucose requiring tissues e.g. red blood cells.
What unique ability does the liver have during starvation?
Can synthesise glucose and becomes increasingly active as glycogen stores begin to deplete.
Where are carbons skeletons derived from?
Glycerol, lactate, amino acids.
What is the main source of energy for liver during starvation?
Oxidation of fatty acids derived from adipose tissue.
In starvation, insulin levels are low therefore, glucose isn’t used for what type of synthesis?
Fattu acid synthesis.
