Practice Questions Flashcards
What is the general name of the enzymes that catalyse the transamination reactions?
Transaminase or amino trasnferase
Why are transamination reactions important?
- Involved in both synthesis and catabolism of amino acids
- Route for the redistribution of amino acid nitrogen
- First step in catabolism of most amino acids once they have reached the liver
What is the relationship between the reaction catalysed by glutamate dehydrogenase and the urea cycle?
Glutamate dehydrogenase releases the amino group from glutamate. The free NH4+ can then enter the urea cycle
In which tissue does the urea cycle occur?
Liver
Why is the function of the urea cycle important?
The urea cycle converts toxic not very water soluble ammonium ions to less toxic and more water soluble urea which can be readily removed from the body
What are the enzymes that catalyse the three irreversible steps in glycolysis?
Heoxkinase
Phosphofructokinase-1
Pyruvate kinase
What is the substrate and product of hexokinase?
Glucose -> Glucose-6-phosphate
What regulates hexokinase? Does it inhibit or stimulate?
Glucose (stimulates)
What is the substrate and product of phosphofructokinase-1?
Fructose-6-phosphate -> Fructose 1,6, bisphosphate
What regulates phosphofructokinase-1? Does it inhibit or stimulate?
Fructose-6-P (stimulates) ATP (inhibits) AMP (stimulates) ADP (stimulates) Citrate (inhibits)
What is the substrate and product of pyruvate kinase?
Phophoenol pyruvate -> pyruvate
What regulates pyruvate kinase? Does it inhibit or stimulate?
ATP (inhibits)
Acetyl CoA (inhibit)
Glucagon (inhibit)
True or False:
Glycogen synthase is active in the dephosphorylated form
True
True or False:
Insulin results in the phosphorylation of glycogen synthase
False
True or False:
Glycogen synthase kinase is responsible for the activation of glycogen synthase
False
True or False:
Glucose-6-phosphate is an allosteric activator of glycogen synthase
True
Describe the impact of a deficiency of the enzyme adenosine deaminase including the molecular changes that occur
loss of ADA activity results in:
• increased dATP levels (1 mark)
• dATP is a feed back inhibitor of ribonucleotide reductase therefore high dATP reduces synthesis of other dNTP’s (1 mark)
• reduced dNTP pool effects T and B cell proliferation (1 mark)
(0.5 each – max of 1 1 mark )
• susceptibility to infectious diseases
• total inability to mount an immune response
• T and B lymphocytes are affected
b. What is the general name of the enzymes that catalyse the transamination reactions?
Transaminase or amino transferase (either accepted)
c. Why are transamination reactions important?
- involved in both synthesis & catabolism of amino acids
- Route for the redistribution of amino acid nitrogen
- 1st step in catabolism of most amino acids once they have reached the liver
d. What is the relationship between the reaction catalysed by glutamate dehydrogenase and the urea cycle?
Glutamate dehydrogenase releases the amino group from glutamate. The free NH4+ can then enter the urea cycle
e. In which tissue does the urea cycle occur?
Liver
f. Why is the function of the urea cycle important?
The urea cycle converts toxic not very water soluble ammonium ions to less toxic and more water soluble urea which can be readily removed from the body
Explain the differences in carbohydrate metabolism between a person with normal metabolism and a person with untreated Type 1 Diabetes immediately after a meal.
- Instead of glucose being taken up by the liver after a meal and either used in glycolysis or stored as glycogen ….
- Glucose is released from the liver (from either glycogen stores or synthesised by gluconeogenesis) into the blood stream.
Explain the differences in lipid metabolism between a person with normal metabolism and a person with untreated Type 1 Diabetes immediately after a meal.
- Instead of fatty acids being taken up by adipocytes and stored as triacylglycerols after a meal..
- stored triacyl glycerols are broken down to fatty acids and glycerol both of which are released into the blood stream.
