BCH 4053 PRE-TEST 4 GROUP NAME _____________________
July 24, 1996
This test is take-home and open book, and it is
intended that all members of the group contribute to
completing it. Only one copy is to be submitted by
the group, and all members who participated should
sign their names below. Test is due by 1:30 pm on
Monday, July 29.
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Points
(8) 1. Identify by name of the enzyme the reaction(s) of glycolysis which:
(a) are isomerases
(b) consume ATP as a substrate coenzyme
(c) produce ATP as a substrate coenzyme
(d) interconvert an aldose and a ketose
(9) 2. For the following enzymes of glycolysis, give the structure of the
non-coenzyme reactants and products, the name (or abbreviation) of
coenzyme substrates or products, and indicate whether the reaction is
normally near equilibrium or metabolically irreversible.
(a) phosphofructokinase-1
(b) glyceraldehyde-3-phosphate dehydrogenase
(c) enolase
(12) 3. Parts of the glycolytic pathway can mediate the catabolism of other
substances. For example, hydrolysis of triglycerides in adipose
tissue produces not only free fatty acids, but glycerol. The
glycerol cannot be re-activated in adipose tissue, but can be taken
up from the blood by liver, and there converted to pyruvate. The
initial reactions of its metabolism in liver are the following:
glycerol + ATP ----> L-à-glycerol phosphate + ADP
L-à-glycerol phosphate + NAD+ ----> dihydroxyacetone + NADH
phosphate
(a) Give the overall pathway by which glycerol is converted to
pyruvate, showing the structures of the carbon-compound
intermediates. (Substrate coenzymes may be abbreviated).
(b) Starting with [sn 1-14C] glycerol, circle the radioactive carbon
of each intermediate, showing which carbon of pyruvate will
become labeled.
(c) Give the overall stoichiometry of the reaction, showing the
total production of ATP and NADH.
(3) 4. A deficiency of the enzyme hexokinase in red cells affects the
binding of oxygen to hemoglobin. Explain why, and predict whether
oxygen dissociation (i.e. P50) would be higher (looser binding) or
lower (tighter binding).
(12) 5. Phosphorylase is an allosteric protein, existing in an R (active) and
a T (inactive) conformation. The T/R ratio is affected by several
allosteric "effectors", which activate or inhibit enzyme activity.
For each of the following compounds, indicate whether it primarily
affects the phosphorylated or non-phosphorylated form of the enzyme,
whether it shifts the T/R ratio toward the T form or the R form, and
whether the effect is an activation or inhibition of enzyme activity.
Phosphorylated or Activation or
Effector Non-phosphorylated T or R Inhibition
ATP ______________ ____ ___________
AMP ______________ ____ ___________
Glucose ______________ ____ ___________
Glucose-6- ______________ ____ ___________
phosphate
(6) 6. Draw structures of oxaloacetate to show the labeling pattern it would
have from incorporation of 14C from [2-14C]acetyl-CoA after
(a) one turn of the TCA cycle.
(b) two turns of the TCA cycle.
(c) three turns of the TCA cycle.
(8) 7. Give the structure of the products formed when sedoheptulose-7-
phosphate reacts with glyceraldehyde-3-phosphate in the presence of:
(a) transaldolase (b) transketolase
(20) 8. As an exercise in tracing radioactive labels, use the enzymes of the
pentose phosphate pathway, as well as any enzymes you may need from
the glycolytic pathway, to show how radioactivity from [2-14C]-
glucose (i.e., glucose labeled with carbon-14 in position 2) can be
converted to 14CO2. Show the structures of the intermediates of your
pathway, circling or starring the radioactive atoms in each
structure, and give the name of the enzyme catalyzing each step.
(22) 9. In your first set of metabolic pathways, you have encountered many
enzymes. Following is an alphabetical list of many of them:
(1) aconitase
(2) aldolase
(3) citrate synthase
(4) enolase
(5) fructose-1,6-bisphosphatase
(6) fructose-2,6-bisphosphatase
(7) fumarase
(8) galactose-1-phosphate
uridylyltransferase
(9) gluconolactonase
(10) glucose-6-phosphatase
(11) glucose-6-phosphate isomerase
(12) glucose-6-phosphate
dehydrogenase
(13) glyceraldehyde-3-phosphate
dehydrogenase
(14) glycogen phosphorylase
(15) glycogen synthetase
(16) hexokinase
(17) isocitrate dehydrogenase (NAD+
requiring)
(18) isocitrate dehydrogenase (NADP+
requiring)
(19) à-ketoglutarate dehydrogenase
complex
(20) malate dehydrogenase
(21) malic enzyme
(22) phosphoenolpyruvate
carboxykinase
(23) phosphofructokinase-1
(24) phosphofructokinase-2
(25) phosphoglucomutase
(26) 6-phosphogluconate
dehydrogenase
(27) phosphoglycerate mutase
(28) phosphoglycerate kinase
(29) pyruvate carboxylase
(30) pyruvate dehydrogenase complex
(31) pyruvate kinase
(32) ribulose-5-phosphate isomerase
(33) ribulose-5-phosphate epimerase
(34) succinate dehydrogenase complex
(35) succinyl-CoA synthetase
(36) transaldolase
(37) transketolase
(38) triose phosphate isomerase
(39) UDP-glucose pyrophosphorylase
(40) UDP-glucose 4'-epimerase
Choose enzymes from the list that are described by the following
statements, and place the number or numbers of the enzyme in the blank to
the left of the statement. In many cases, more than one enzyme will
apply. Given in parenthesis after the statement is a target number of
enzymes for you to identify, though there may be more than that target
number on the list.
(a) __________________ CO2 is a substrate or a product. (four enzymes)
(b) __________________ ATP is a substrate or a product. (four enzymes)
(c) __________________ GTP is a substrate or a product. (two enzymes)
(d) __________________ Coenzyme A is a substrate or a product. (three
enzymes)
(e) __________________ NADH is a substrate or a product. (three enzymes)
(f) __________________ NADPH is a substrate or a product. (three enzymes)
(g) __________________ Thiamine pyrophosphate is a prosthetic group. (three
enzymes)