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Biochem 462
Third Exam
4/18/2003
Multiple choice - there is only one right answer to each problem in this section (40%)
1)
What is the product of Complex I that is the substrate of Complex III in the
mitochondrion?
a) Oxidized ubiquinone
b) Reduced ubiquinone (Dihydroubiquinone)
c) NADH
d) NAD+
2)
Complex II of the oxidative phosphorylation electron transfer chain has another
name. What is it?
a) Cytochrome c oxidase
b) Alphaketoglutarate dehydrogenase
c) Succinate dehydrogenase
d) Pyruvate carboxylase
3)
About how many protons are pumped into the intermembrane space of the
mitochondrion for every oxygen molecule (O2) consumed during oxidation of NADH
during oxidative phophorylation (notice this is a whole oxygen molecule we are
talking about here)?
a) 6
b) 10
c) 12
d) 20
4)
Photosystem I in the linear photosynthetic electron transport chain uses light to drive
which reaction?
a) Transfer of electrons from plastocyanin to NADP+
b) Transfer of electrons from NADPH to plastocyanin
c) Transfer of electrons from plastoquinone to water
d) Transfer of electrons from water to plastoquinone
5)
What is the ultimate electron donor in linear photosynthetic electron transfer?
a) NADPH
b) Plastoquinone
c) water
d) oxygen
6)
The cytochrome b6/cytochrome f complex (sometimes called the cytochrome b/f
complex) is similar in function and structure to which complex in the mitochondrial
electron transport chain?
a) Complex I
b) Complex II
c) Complex III
d) Complex IV
7)
Fixation of carbon dioxide during photosynthesis involves which reaction?
a) Addition of CO2 to pyruvate to form oxaloacetate and then PEP which undergoes
gluconeogenesis to form glucose.
b) Addition of CO2 to acetyl Co-enzyme A to form pyruvate which then undergoes
gluconeogenesis to form glucose.
c) Addition of CO2 to ribulose 1,5 bis phosphate to form two molecules of 3
phosphoglycerate.
d) Addition of CO2 to ribose 5 phosphate to form three molecules of acetly Coenzyme A.
8)
The compound carbonylphosphate is important in the mechanism of which reaction?
a) The glucose 6-phosphatase reaction which converts Glucose-6-P to Glucose
b) The fructose 1,6-bisphosphatase reaction converting Fructose 1,6-bisP to
Fructose-6-P
c) The PEP carboxykinase reaction converting Oxaloacetate to PEP
d) The pyruvate carboxylase reaction converting Pyruvate to Oxaloacetate
9)
One substrate of glycogen synthase (the enzyme that synthesizes glycogen) is
a) glucose
b) glucose-6-phosphate
c) UDP-glucose
d) ATP-glucose
10)
The relative levels of glycogen synthesis and degradation are tightly controlled. One
of the main ways this control is performed is through:
a) Changes in membrane potentials in the mitochondrion which then control the two
main enzymes.
b) Changes in the phosphorylation levels of the two main enzymes.
c) Changes in NADH levels which then control the two main enzymes.
d) Changes in Acetyl CoA and fatty acid CoA levels which then control the two
main enzymes.
11)
Before beta oxidation of a fatty acid can occur, what reaction must take place to
activate the fatty acid?
a) Generation of a phosphate ester of the fatty acid.
b) Decarboxylation of the carboxylic acid group on the fatty acid.
c) Reduction of the carboxylic acid group of the fatty acid to an aldehyde.
d) Generation of the Co-enzyme A thiol ester of the fatty acid.
Short Answer (45%)
12)
Write a chemically balanced equation for the reaction mediated by Complex I
in the mitochondrion. You do not need to include the protons pumped across
the membrane in this equation, but you do need to include any protons
involved in the chemical reactions themselves that are needed to balance the
equation.
13)
During mitochondrial electron transfer, there are two mobile carriers that
allow for transfer of electrons between complexes. a) what are these carriers?
b) which one is soluble in the membrane and which one is soluble in the
aqueous solution?
14)
During linear photosynthesis: a) How many photons must be absorbed for
each oxygen molecule (O2) released? b) How many NADPH molecules are
formed for each oxygen molecule (O2) released?
15)
Write down the structure of the 3-phosphoglycerate produced by the
carboxylation reaction of carbon fixation catalyzed by ribulose bisphosphate
carboxylase. If this reaction was performed in the presence of carbon dioxide
containing an isotopically labeled carbon atom, which one of the atoms of 3phosphoglycerate would end up being labeled or partially labeled (circle it)?
16)
When we breath in oxygen it is used in metabolism. Does this oxygen leave
the body as carbon dioxide, water or both? You must justify your answer for
credit.
17)
Let’s suppose you discover that in a metabolic pathway there is the conversion
of an ketose to an aldose (see below). Show the likely intermediate that
would be formed in going from one to the other (hint: consider the pentose
phosphate pathway).
H C=O
|
H C—OH
|
H C—OH
|
R
H2C—OH
|
C=O
|
H C—OH
|
R
Broader Understanding (15%)
18)
I want you to determine the number of oxygen molecules (O2, not ½ O2)
required for the complete oxidation of one 16 carbon fatty acid. Please do this
in three steps (you need to explain your reasoning for full credit). If you
cannot do one step, make an assumption and do the next one.
a) Determine the number of FADH2, NADH and acetyl CoA molecules generated by
beta oxidation of the fatty acid (explain briefly).
b) Determine the number of additional NADH and FADH2 molecules generated when
the acetyl CoA molecules generated by beta oxidation pass in part (a) through the
TCA cycle (explain briefly).
c) Determine the number of oxygen molecules (O2 not ½ O2) that are required to oxidize
(via oxidative phosphorylation) all of the NADH and FADH2 molecules formed by
beta-oxidation and the TCA cycle in parts (a) and (b) above (explain briefly).