Week 2 RAS live Lecture 6 Flashcards
1) Why are amino acids important?
1) Include:
a) Proteins
b) Peptides
c) Biosynthesis of nucleotides
d) Biosynthesis of porphyrins
2) What are the general principles of amino acid biosynthesis?
2) Include:
a) Gather intermediates from glycolysis, Krebs (citric acic cycle) cycle or PPP
b) Side chain assembly via a keto acid
c) NH4 group added by transamination
3) What is transamination?
3) The transfer of an amino group especially between keto acids and amino acids
4) How is chirality achieved in amino acid formation?
4) Using pyridoxal phosphate which achieves the L-amino acid conformation by transamination
5) Link between amino acid and Keto acid reactions:
5) The R groups replace each other. Uses the enzyme transaminase (aminotranferase)
a) K = is ~1 therefore fairly reversible
6) What is the biological significance of having k(equilibrium) = 1?
6) Amino acids form a ‘pool’ which can freely interchange the R groups to meet particular demands.
7) When is glutamine used and when is glutamate usually used?
7) Glutamine and glutamate both have different uses and produce different products:
a) Glutamate is usually used in amino acid transamination
b) Glutamine is usually used to donate NH2 in biosynthesis
8) Difference between essential and non-essential amino acids?
8) Non-essential amino acids are the amino acids that can be produced by the organism while essential amino acids cannot be produced therefore need tp be consumed.
9) How are amino acids classified?
9) classified according to their biosynthetic precursor e.g. Oxaloacetate, PEP etc
10) How is serine biosynthesised?
10) Start with 3-phosphoglycerate which comes from glycolysis.
a) NAD is added
b) Then in the transamination state, glutamate is added
c) Finally, water is added
11) What are the enzymes used to initiate the entry of nitrogen in metabolism?
11) Include;
a) Glutamate dehydrogenase
b) Glutamate synthase
c) Glutamine synthetase
12) How does the glutamate dehydrogenase reaction work?
12) Alpha-ketoglutarate + NH3 + NAD(P)H glutamate + NAD(P)
a) In this reaction, there is a Schiff base intermediate which ensures the H ion is added at a specific site.
13) How are glutamine and glutamate linked?
13) Glutamine and glutamate can be linked and recycled together in reaction cycle.
14) There are 2 equivalent models of amination, what are they and how do they work?
14) 2 models:
a) When there’s is high concentrations of [NH3] and it uses NADH
b) When there is low concentration of [NH3] and it used ATP (more expensive)
15) How is glutamine synthetase regulated?
15) It catalyses the reaction from glutamate to glutamine;
a) Has 2 conformations; De-adenylated GS (more active- less sensitive to feedback inhibition), other form is the adenylated GS (less active- more sensitive to feedback inhibition. These 2 conformations are interconverted at adenyal transferase. Which is controlled by uridyl transferase.
b) So if there is a lot of glutamine, thered more adenyal transferase so less glutamine produced.
