BIO 334 FINAL EXAM QUESTIONS AND
ACCURATE ANSWERS
How does the mitochondrial electron transport chain progressively contribute to aging
and disease in humans? - ANSWER - ROS are harmful byproducts of the mito's ETC (Up
to 4% of O2 are consumed by mito are lost to ROS)
- Aging occurs because of worn out/ "leaky" mitos that steadily increase ROS
production (damaging the mito and nuclear DNA coupled with decreased capacity for
ROS detoxification)
How was metabolic engineering used to prove that the alternative oxidase (AOX) helps
plants to survive nutritional phosphate deprivation? - ANSWER - During Pi starvation
plants use alternative pathway of ETC, AOX helps limit the production of ROS during
during this bypass pathway. Metabolic engineering showed transgenic plants lacking
AOX had increased levels of harmful ROS during stress
How do mitochondria relocate to ATP-consuming areas of eukaryotic cells? - ANSWER
Using the Cytoskeleton of the cell
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
(a) The rate of O2 consumption was greatly elevated when 5 mM pyruvate was added to
all 3 mitochondrial preparations. Why? - ANSWER - ADP and Pi are substrates for ATP
synthase. PMF is depleted. ATC can continue to pump protons out and consumes O2 in
the process
- Increased ADP will drive that reaction forward to make more ATP, need ADP and Pi to
make ATP.
- This will use the ETC (ATP synthase), which consumes O2
,- Because pyruvate is added, it can then be metabolized for oxidative phosphorylation
- Pyruvate is needed as a source of high energy electrons
- Complete oxidation to Co2 in mito generates live NADH and some FADH
- Supplies electrons to ETC
- Can then be passed to oxygen.
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
(b) One minute after adding pyruvate, 5 mM potassium cyanide (KCN) was added to
each mitochondrial prep. After KCN addition O2 consumption by mammalian muscle
and brown fat mitochondria became completely undetectable, whereas the rate of O2
consumption by snail muscle mitochondria was reduced by about 60%.Why did O2
consumption by mammalian muscle or brown fat mitochondria stop when KCN was
added? (note: your answer should include name of specific location(s - ANSWER - O2
consumption stopped because in the ETC electrons are transferred from NADH and
FADH2 to complex V(4) which binds to oxygen
- However, CN irreversibly bonds to complex V (4) , thus blocks electrons transfer to
oxygen. Therefore, oxygen cannot be reduced and thus preventing respiration.
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
,(c) Why was O2 consumption by snail (mollusk) mitochondria only partially inhibited
when KCN was added? - ANSWER - Molluscs have the AOX that bypass complex V so
they remain unaffected by cyanide, allowing electron transfer to oxygen and allowing
respiration
- this is called 'cyanide resistant respiration', some flux still travels through the
traditional pathway which is why oxygen consumption is partially reduced
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
(d) In another experiment, mitochondria from mammalian muscle and brown fat tissue
were separately placed into aerated solutions containing 5 mM pyruvate, and
maintained at physiological pH and temperature. Respiratory O2 consumption by
mitochondria from mammalian muscle was totally dependent upon the subsequent
addition of both 1 mM ADP and 1 mM Pi (e.g. only in the presence of pyruvate). Why? -
ANSWER - ADP + Pi are substrates of ETC → in their presence, ETC will be able to pump
protons easily and O2 will be able to be consumed by ETC (ATP synthase can function
and deplete PMF)
- In muscle mitochondria, the proton gradient generated by the ETC is exclusively used
for ATP production via ATP synthase
- This requires ADP and Pi as its substrates.
- Therefore, a muscle cell prep containing pyruvate will only consume O2 in the
presence of the substrates necessary to produce ATP pyruvate will not be oxidized/
COX will not reduce O2 unless ADP and Pi are present.
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
(e) However, a significant rate of O2 consumption was observed with mitochondria from
, mammalian brown fat tissue in the absence of any added ADP or Pi. Why? - ANSWER -
While brown fat uses thermogen to dissipate PMF without using ATP synthase, the PMF
is still being created by mitochondrial enzymes.
- This process requires oxygen to be the final electron acceptor in order to shuttle H+
into the intermembrane space to create the PMF
20. (a) What type of proteins create 'proton motive force' during mito-respiration in
mammalian brown fat tissue?
(b) What is the major physiological function of 'brown fat' in mammals?
(c) Describe 1 specific developmental or environmental situation when a mammal would
need to use 'brown fat'. - ANSWER (a) Thermogenin
(b) Thermoregulation.
(c) When hibernating.
What is the overall (net) reaction for 'classical' glycolysis (fill in the blanks) - ANSWER
Glucose + __2 ADP__ + _2NAD+__ + ___2 Pi_ → 2(pyruvate) + __2 ATP__ + __2 NADH__
What physiological situation would cause the cyclic-AMP concentration of mammalian
hepatocytes (liver cells) to increase? - ANSWER Starvation- Glucagon binding to
hepatocyte receptors activating intracellular adenylyl cyclase
Some biochemists believe that limited aerobic (O2 dependent) respiration may have
evolved with life's origins, long before the evolution of cyanobacteria capable of
'oxygenic photosynthesis'.
(a) What is the name of the 'ROS detoxifying' enzyme that produces O2? (1 mark)
ACCURATE ANSWERS
How does the mitochondrial electron transport chain progressively contribute to aging
and disease in humans? - ANSWER - ROS are harmful byproducts of the mito's ETC (Up
to 4% of O2 are consumed by mito are lost to ROS)
- Aging occurs because of worn out/ "leaky" mitos that steadily increase ROS
production (damaging the mito and nuclear DNA coupled with decreased capacity for
ROS detoxification)
How was metabolic engineering used to prove that the alternative oxidase (AOX) helps
plants to survive nutritional phosphate deprivation? - ANSWER - During Pi starvation
plants use alternative pathway of ETC, AOX helps limit the production of ROS during
during this bypass pathway. Metabolic engineering showed transgenic plants lacking
AOX had increased levels of harmful ROS during stress
How do mitochondria relocate to ATP-consuming areas of eukaryotic cells? - ANSWER
Using the Cytoskeleton of the cell
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
(a) The rate of O2 consumption was greatly elevated when 5 mM pyruvate was added to
all 3 mitochondrial preparations. Why? - ANSWER - ADP and Pi are substrates for ATP
synthase. PMF is depleted. ATC can continue to pump protons out and consumes O2 in
the process
- Increased ADP will drive that reaction forward to make more ATP, need ADP and Pi to
make ATP.
- This will use the ETC (ATP synthase), which consumes O2
,- Because pyruvate is added, it can then be metabolized for oxidative phosphorylation
- Pyruvate is needed as a source of high energy electrons
- Complete oxidation to Co2 in mito generates live NADH and some FADH
- Supplies electrons to ETC
- Can then be passed to oxygen.
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
(b) One minute after adding pyruvate, 5 mM potassium cyanide (KCN) was added to
each mitochondrial prep. After KCN addition O2 consumption by mammalian muscle
and brown fat mitochondria became completely undetectable, whereas the rate of O2
consumption by snail muscle mitochondria was reduced by about 60%.Why did O2
consumption by mammalian muscle or brown fat mitochondria stop when KCN was
added? (note: your answer should include name of specific location(s - ANSWER - O2
consumption stopped because in the ETC electrons are transferred from NADH and
FADH2 to complex V(4) which binds to oxygen
- However, CN irreversibly bonds to complex V (4) , thus blocks electrons transfer to
oxygen. Therefore, oxygen cannot be reduced and thus preventing respiration.
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
,(c) Why was O2 consumption by snail (mollusk) mitochondria only partially inhibited
when KCN was added? - ANSWER - Molluscs have the AOX that bypass complex V so
they remain unaffected by cyanide, allowing electron transfer to oxygen and allowing
respiration
- this is called 'cyanide resistant respiration', some flux still travels through the
traditional pathway which is why oxygen consumption is partially reduced
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
(d) In another experiment, mitochondria from mammalian muscle and brown fat tissue
were separately placed into aerated solutions containing 5 mM pyruvate, and
maintained at physiological pH and temperature. Respiratory O2 consumption by
mitochondria from mammalian muscle was totally dependent upon the subsequent
addition of both 1 mM ADP and 1 mM Pi (e.g. only in the presence of pyruvate). Why? -
ANSWER - ADP + Pi are substrates of ETC → in their presence, ETC will be able to pump
protons easily and O2 will be able to be consumed by ETC (ATP synthase can function
and deplete PMF)
- In muscle mitochondria, the proton gradient generated by the ETC is exclusively used
for ATP production via ATP synthase
- This requires ADP and Pi as its substrates.
- Therefore, a muscle cell prep containing pyruvate will only consume O2 in the
presence of the substrates necessary to produce ATP pyruvate will not be oxidized/
COX will not reduce O2 unless ADP and Pi are present.
19. A biochemist used an oxygen (O2) electrode to study the rate of O2 consumption by
purified, functional mitochondria isolated from: (i) mammalian skeletal muscle tissue, (ii)
mammalian 'brown fat' tissue, and (iii) muscle tissue of a marine invertebrate mollusk
(snail). Each mitochondria prep was separately placed into an aerated (oxygenated)
solution containing 2 mM ADP and 2 mM inorganic phosphate (Pi), and maintained at
physiological pH and temperature.
(e) However, a significant rate of O2 consumption was observed with mitochondria from
, mammalian brown fat tissue in the absence of any added ADP or Pi. Why? - ANSWER -
While brown fat uses thermogen to dissipate PMF without using ATP synthase, the PMF
is still being created by mitochondrial enzymes.
- This process requires oxygen to be the final electron acceptor in order to shuttle H+
into the intermembrane space to create the PMF
20. (a) What type of proteins create 'proton motive force' during mito-respiration in
mammalian brown fat tissue?
(b) What is the major physiological function of 'brown fat' in mammals?
(c) Describe 1 specific developmental or environmental situation when a mammal would
need to use 'brown fat'. - ANSWER (a) Thermogenin
(b) Thermoregulation.
(c) When hibernating.
What is the overall (net) reaction for 'classical' glycolysis (fill in the blanks) - ANSWER
Glucose + __2 ADP__ + _2NAD+__ + ___2 Pi_ → 2(pyruvate) + __2 ATP__ + __2 NADH__
What physiological situation would cause the cyclic-AMP concentration of mammalian
hepatocytes (liver cells) to increase? - ANSWER Starvation- Glucagon binding to
hepatocyte receptors activating intracellular adenylyl cyclase
Some biochemists believe that limited aerobic (O2 dependent) respiration may have
evolved with life's origins, long before the evolution of cyanobacteria capable of
'oxygenic photosynthesis'.
(a) What is the name of the 'ROS detoxifying' enzyme that produces O2? (1 mark)
