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Fall '04
Hackert/Kitto
CH395G
EXAM 3
Name _____________________
UT_ID _____________________
SHOW WORK FOR ALL COMPUTATIONAL PROBLEMS OR NO CREDIT!
1 cal = 4.184 J; R = 8.314 J/mole K = 1.99 cal/mole K; Avagadros number = 6 x 1023
Faraday’s constant = 23.1 Kcal/molV = 96.5 KJ/molV; Assume T=25 C in all problems, unless
stated otherwise.
1. -keto acids are of considerable biochemical utility. Write the structural formulas for
oxaloacetate, pyridoxal-5’-P, and -ketoglutarate. Identify the amino acids that arise from the two
acids by simple transamination in the bottom of the appropriate box.
(6)
Oxaloacetate
Pyridoxal-5’-Phosphate
-Ketoglutarate
AA __________
AA ___________
(4) In the schematic below of the citric acid cycle, fill in the boxes labeled “A”,”C”,”H” and “J”.
(4) Which is the main regulatory step (number) step in the pathway? ______________________.
This enzyme’s name is _____________________: It is inhibited by _____________________.
Which numbered step(s) in the pathway is(are) effectively irreversible? __________________
2. Triacylglycerols have the highest energy content of any of the major nutrients.
(a) If 15% of the body mass of a 70 kg adult consists of triacylglycerols, calculate the total
available fuel reserve, in both kilojoules and kilocalories, in the form of triacylglycerols.
(2)
(b) If the basal energy requirement is approximately 8,400 kJ/day (2,000 kcal/day), how long
could this person survive if the oxidation of fatty acids stored as triacylglycerols were used
as the only source of energy?
(2)
(c) What would be the corresponding weight loss in pounds per day under such starvation
conditions (1 lb = 0.454 kg)?
(2)
(3) If an activated 17-carbon fatty acid goes through just -oxidation, what are the products?
17-C fatty acyl-CoA 
___ acetyl-CoA + ___ FADH2 + ___ NADH + ___ _____________
(3) What is the general role of the ketone bodies?
Name two of the ketone bodies. ____________________ ______________________
Name two conditions that can cause ketosis:
___________________________
___________________________
3. (4) In a mammalian electron transport system, electrons are donated from ________ to
complex I; the enzyme that binds and oxidizes the cofactor is called ____________________
_________________. The electrons pass through complex I and reduce a lipid soluble mobile
carrier called ____________________, which in turn carries ____(#) electrons to complex
_______. Electrons then pass through this complex and reduce a soluble protein carrier called
________________; this reduction requires ____(#) electrons per molecule. The reduced carrier
shuttles electrons to another complex where the electrons pass to the ultimate receptor,
_________________.
(4) Given that the redox potential for O2 is +0.82 V, and that of NAD+ is -0.32 V, how much
energy, in KJ/mol, is released when 2 electrons from NADH are passed to atomic oxygen? Show
work.
(2) Cyanide and dinitrophenol are both inhibitors that decrease the production of ATP. Describe
the differences in the effects of these inhibitors on mitochondrial function.
(2) When the F1 portion of the ATP synthetase complex is removed from the mitochondrial
membrane and studied in solution, does it function as an ATP synthetase? If not, why?
4. (2) Photosynthesis is arguably the most important metabolic pathway, since essentially all our
food and fiber is made by the process. Photosynthetic “light reactions” harvest solar power and
generate high energy chemicals like ATP and NADPH. Name two of the general types of
photosynthetic pigments used to harvest light.
_________________________
_________________________
(2) Why are so many pigments needed?
(3) Sketch the “Z”-scheme of plant photosynthesis illustrating the flow of electrons and
protons. Include in your sketch the following: Water / P700 / P680 / Ferredoxin / NADPH
/ Plastoquinone / Cyt b6f / and Plastocyanin.
(4) In higher plants, photosynthesis moves electrons from the donor molecule
__________________ to the acceptor molecule _________________. This process
corresponds to a Gibbs Free Energy change of about +438 kJ/mol. Given the formula E =
1.2 x 105 (KJ/mol)/nm, estimate the minimum number of photons of green light ( = 560
nm) required, in theory, to supply the energy to move these four electrons? ________.
(2) How many photons are used by nature to accomplish this process? ___________
(2) The compound that condenses with CO2 in the first reaction of carbon dioxide fixation is:
________________________________________________
5. The amine groups from a wide range of amino acids are transferred to -ketoglutarate to form
which amino acid? _________________
(4)
This reaction involves the participation of which vitamin-derived cofactor? ______________
Name the two immediate precursors that furnish the nitrogens incorporated into urea.
________________________ & _____________________________
Name the three common materials synthesized for purposes of disposing of excess nitrogen.
Give an example of an organism that uses each mechanism?
1)
-(3)
2)
-3)
--
(2) Urea synthesis in mammals takes place primarily in the ________________ (organ).
(4) Once amine groups are removed, the carbon skeletons of amino acids can be catabolized much
like carbohydrates. The most common amino acid is alanine; if it is transaminated, what
product remains? __________________. How much energy, in integral ATP units, can be
gained by oxidizing this product all the way to carbon dioxide and water?
______________. (SHOW WORK and STATE ASSUMPTIONS)
(3) Matching:
___ biotin
___ pyridoxal phosphate
___ UTP
___ THF
___ FAD
___ Acyl carrier protein
a) methylene group transfers
b) succinate dehydrogenase
c) CO2 transfers
d) fatty acid synthesis
e) transaminations
f) glycogen and sugar biosynthesis
6. Below are summaries of two clinical case studies: For each case select an enzyme from List A
that is defective and designate the appropriate treatment from the List B. Then answer the
question(s) raised in each case study.
List A - Defective Enzymes
(a) Muscle phosphofructokinase-1
(b) Phosphomannose isomerase
(c) Galactose 1-phosphate uridylyltransferase
(d) Liver glycogen phosphorylase
(e) Triose kinase
(f) Lactase of intestinal epithelial cells
(g) Maltase of intestinal epithelial cells
List B - Treatments
1. Frequent regular feedings
2. Fat-free diet
3. Low-lactose diet
4. Large doses of niacin (the precursor of NAD+ )
Case A – Defective Enzyme = _____________; Treatment = _______________
The patient develops vomiting and diarrhea shortly after milk ingestion. A lactose tolerance test is
administered. The patient ingests a standard amount of lactose, and the glucose and galactose
concentrations in blood plasma are measured at intervals. In lactose-tolerant individuals the levels
increase to a maximum in about 1 h, then decline. Explain why. In this case the patient’s blood
glucose and galactose levels do not increase during the test. Explain why.
(4)
Case B - Defective Enzyme = _____________; Treatment = _______________
The patient is lethargic and her liver is enlarged. A liver biopsy shows large amounts of
excess glycogen. She also has lower than normal blood glucose. Why does this patient have low
blood glucose?
(4)