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.
Which hormone class does aldosterone belong to?
Steroid
Which hormone class does Growth hormone belong to?
Peptide
Which hormone class does thyroid hormones belong to?
Amine
Which hormone class does testosterone belong to?
Steroid
Which hormone class does cortisol belong to?
Steroid
Which hormone class does insulin belong to?
Peptide
Receptor tyrosine kinases have a characteristic sequence of events upon activation. What TWO major events occur after the binding of a ligand to a monomeric target receptor tyrosine kinase?
Receptor dimerisation
Autophosphorylation
Transcription factors are _____-binding proteins. For example, a Hox protein has a conserved 60 amino acid domain called the __________.
DNA; homeodomain
A ___________ transformation occurs when one body part develops as a different body part, such as legs instead of antennae in the fly.
Homeotic
In mammals, there are four sets of Hox genes, derived by ancestral duplication. Related genes in the series (Hoxa13, Hoxb13, Hoxc13 and Hoxd13, for example) are called _________.
Paralogues
Describe three types of genetic modifications that convert a proto-oncogene into an oncogene
1
An activating mutation in a DNA coding sequence (deletion or point mutation) – hyperactive protein made in normal amounts
Gene Amplification – normal protein greatly overproduced
Chromosomal translocation – hyperactive fusion protein produced or nearby regulatory sequence causes normal protein to be greatly overproduced
What is an example of a proto-oncogene that is converted into an oncogene by point mutation?
Ras
What is an example of a proto-oncogene that is converted into an oncogene by gene amplification?
EGFR2 (HER2)
or
MYC
What is an example of a proto-oncogene that is converted into an oncogene by chromosomal translocation?
BCR-ABL
