Test 170 Notecards Flashcards
What is the term for metabolic pathways that release stored energy by breaking down
complex molecules?
catabolic pathways
The molecule that functions as the reducing agent (electron donor) in a redox or
oxidation-reduction reaction
loses electrons and loses energy
When electrons move closer to a more electronegative atom, what happens?
Energy is released.
The more electronegative atom is reduced.
Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and
water release free energy?
Electrons are being moved from atoms that have a lower affinity for electrons (such as
C) to atoms with a higher affinity for electrons (such as O).
Which of the following statements describes the results of this reaction?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C6H12O6 is oxidized and O2 is reduced
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction
reaction, the molecule becomes
oxidized.
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom
(not a hydrogen ion) the molecule becomes
reduced.
Which of the following statements describes NAD+?
NAD+ is reduced to NADH during both glycolysis and the citric acid cycle.
Where does glycolysis takes place?
cytosol
The ATP made during glycolysis is generated by
substrate-level phosphorylation
The oxygen consumed during cellular respiration is involved directly in which process or
event?
accepting electrons at the end of the electron transport chain
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or
absent?
glycolysis
An electron loses potential energy when it
shifts to a more electronegative atom.
Why are carbohydrates and fats considered high energy foods?
They have a lot of electrons associated with hydrogen
Which step shows a split of one molecule into two smaller molecules?
B
In which step is an inorganic phosphate added to the reactant?
C
In which reaction does an intermediate pathway become oxidized?
C
Which step involves an endergonic reaction?
A
Which step consists of a phosphorylation reaction in which ATP is the phosphate source?
A
Substrate-level phosphorylation accounts for approximately what percentage of the ATP
formed during glycolysis?
100%
During glycolysis, when glucose is catabolized to pyruvate, most of the energy of glucose is
retained in the pyruvate.
In addition to ATP, what are the end products of glycolysis?
NADH and pyruvate
e. Why are only two
molecules of NADH formed during glycolysis when it appears that as many as a dozen
could be formed?
Most of the free energy available from the oxidation of glucose remains in pyruvate,
one of the products of glycolysis
Starting with one molecule of glucose, theʺnetʺproducts of glycolysis are
2 NADH, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O.
In glycolysis, for each molecule of glucose oxidized to pyruvate
2 molecules of ATP are used and 4 molecules of ATP are produced.
A molecule that is phosphorylated
has an increased chemical reactivity; it is primed to do cellular work.
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
Why is glycolysis described as having an investment phase and a payoff phase?
It uses stored ATP and then forms a net increase in ATP.
These three steps result in the formation of
acetyl CoA, NADH, H+, and CO2.
Why is coenzyme A, a sulfur containing molecule derived from a B vitamin, added?
to provide a relatively unstable molecule whose acetyl portion can readily bind to
oxaloacetate
How does pyruvate enter the mitochondrion?
active transport
Which of the following intermediary metabolites enters the citric acid cycle and is formed,
in part, by the removal of a carbon (CO2) from one molecule of pyruvate?
acetyl CoA
During cellular respiration, acetyl CoA accumulates in which location?
mitochondrial matrix
How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one
molecule of pyruvate?
2
Starting with one molecule of isocitrate and ending with fumarate, what is the maximum
number of ATP molecules that could be made through substrate-level phosphorylation?
1
Carbon skeletons for amino acid biosynthesis are supplied by intermediates of the citric
acid cycle. Which intermediate would supply the carbon skeleton for synthesis of a
five-carbon amino acid?
΅a-ketoglutarate
How many molecules of carbon dioxide (CO2) would be produced by five turns of the
citric acid cycle?
10
How many reduced dinucleotides would be produced with four turns of the citric acid
cycle?
4 FADH2 and 12 NADH
Starting with citrate, which of the following combinations of products would result from
three turns of the citric acid cycle?
3 ATP, 6 CO2, 9 NADH, and 3 FADH2
Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?
oxidation of pyruvate to acetyl CoA and the citric acid cycle
For each molecule of glucose that is metabolized by glycolysis and the citric acid cycle,
what is the total number of NADH + FADH2 molecules produced?
12
Of the following, which is the best explanation of his condition?
His mitochondria lack the transport protein that moves pyruvate across the outer
mitochondrial membrane.
Cellular respiration harvests the most chemical energy from which of the following?
chemiosmotic phosphorylation
During aerobic respiration, electrons travel downhill in which sequence?
food → NADH → electron transport chain → oxygen
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
Which of the following describes the sequence of electron carriers in the electron transport
chain, starting with the least electronegative?
FMN, Fe•S, ubiquinone, cytochromes (Cyt)
During aerobic respiration, which of the following directly donates electrons to the electron
transport chain at the lowest energy level?
FADH2
The primary role of oxygen in cellular respiration is to
act as an acceptor for electrons and hydrogen, forming water.
Inside an active mitochondrion, most electrons follow which pathway?
citric acid cycle → NADH → electron transport chain → oxygen
During oxidative phosphorylation, H2O is formed. Where does the oxygen for the
synthesis of the water come from?
molecular oxygen (O2)
In chemiosmotic phosphorylation, what is the most direct source of energy that is used to
convert ADP + Pi to ATP?
energy released from movement of protons through ATP synthase
Energy released by the electron transport chain is used to pump H+ ions into which
location?
mitochondrial intermembrane space
The direct energy source that drives ATP synthesis during respiratory oxidative
phosphorylation is
the difference in H+ concentrations on opposite sides of the inner mitochondrial
membrane
When hydrogen ions are pumped from the mitochondrial matrix across the inner
membrane and into the intermembrane space, the result is the
creation of a proton gradient.
Where is ATP synthase located in the mitochondrion?
inner membrane
Which one of the following processes could still be carried on by this isolated
inner membrane?
oxidative phosphorylation
Each time a molecule of glucose (C6H12O6) is completely oxidized via aerobic respiration,
how many oxygen molecules (O2) are required?
6
Which of the following produces the most ATP when glucose (C6H12O6) is completely
oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis)
Approximately how many molecules of ATP are produced from the complete oxidation of
two molecules of glucose (C6H12O6) in cellular respiration?
76
If each of the 77 dinucleotides
were used, approximately how many ATP molecules could be generated as a result of
oxidative phosphorylation (chemiosmosis)?
1102
Approximately what percentage of the energy of glucose (C6H12O6) is transferred to
storage in ATP as a result of the complete oxidation of glucose to CO2 and water in cellular
respiration?
40%
What is the approximate efficiency of cellular respiration for aʺmutantʺ
organism that produces only 29 moles of ATP for every mole of glucose oxidized, rather
than the usual 36-38 moles of ATP?
30%
What is proton-motive force?
the transmembrane proton concentration gradient
In liver cells, the inner mitochondrial membranes are about 5 X the area of the outer
mitochondrial membranes, and about 17 X that of the cellʹs plasma membrane. What
purpose must this serve?
It increases the surface for oxidative phosphoryation.
After the first disruption, when electron transfer and ATP synthesize still occur, what must
be present?
all of the electron transport proteins as well as ATP synthase
After the second agitation of the membrane vesicles, what must be lost from the
membrane?
ATP synthase, in whole or in part
It should be possible to reconstitute the abilities of the vesicles if which of the following is
added?
intact ATP synthase
The accompanying figure shows the electron transport chain. Which of the following is the
combination of substances that is initially added to the chain?
NADH, FADH2, and electrons
Which of the following most accurately describes what is happening along this chain?
Each electron carrier alternates between being reduced and being oxidized.
The parts of the figure labeled with Roman numerals symbolize what concept?
multimeric groups of proteins in 4 complexes
What happens at the end of the chain?
4 electrons combine with oxygen and protons.
Which of the following couples chemiosmosis to energy storage?
ATP synthase
Which of the following describes ubiquinone?
a small hydrophobic coenzyme
Which of the following normally occurs whether or not oxygen (O2) is present?
glycolysis
Which of the following occurs in the cytosol of a eukaryotic cell?
glycolysis and fermentation
Which metabolic pathway is common to both cellular respiration and fermentation?
glycolysis
The ATP made during fermentation is generated by which of the following?
substrate-level phosphorylation
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
ATP, CO2, and ethanol (ethyl alcohol).
In alcohol fermentation, NAD+ is regenerated from NADH during which of the following?
reduction of acetaldehyde to ethanol (ethyl alcohol)
One function of both alcohol fermentation and lactic acid fermentation is to
oxidize NADH to NAD+
When returned to normal air, the organism does fine. Which of the following best describes the organism?
It is a facultative anaerobe.
Glycolysis is thought to be one of the most ancient of metabolic processes. Which statement
supports this idea?
Glycolysis is the most widespread metabolic pathway.
Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
It is found in the cytosol, does not involve oxygen, and is present in most organisms.
What happens to the lactate in skeletal muscle cells?
It is taken to the liver and converted back to pyruvate.
When muscle cells are oxygen deprived, the heart still pumps. What must the heart cells be able to do?
continue aerobic metabolism when skeletal muscle cannot
When muscle cells undergo anaerobic respiration, they become fatigued and painful. This is now known to be caused by
increase in potassium ions
How did the fat leave her body?
It was released as CO2 and H2O.
Which of the following statements describes a function of phosphofructokinase?
It is an allosteric enzyme.
In the presence of oxygen, an increase in the amount ATP in a cell would be expected to
inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle.
Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur?
in photosynthesizing cells in dark periods and in other tissues all the time
Which of the following might be the function of
the brown fat tissue?
to regulate temperature by converting energy from NADH oxidation to heat
What is the purpose of beta oxidation in respiration?
breakdown of fatty acids
Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?
acetyl CoA
What is the reducing agent in the following reaction?
NADH
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is
the H+ concentration gradient across the inner mitochondrial membrane.
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
glycolysis
In mitochondria, exergonic redox reactions
provide the energy that establishes the proton gradient.
The final electron acceptor of the electron transport chain that functions in aerobic oxidative
phosphorylation is
oxygen.
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
The pH of the matrix increases.
Cells do not catabolize carbon dioxide because
CO2 is already completely oxidized.
Which of the following is a true distinction between fermentation and cellular respiration?
NADH is oxidized by the electron transport chain in respiration only.
Most CO2 from catabolism is released during
the citric acid cycle.
If photosynthesizing green algae are provided with CO2 synthesized with heavy oxygen (18O), later analysis will show that all but one of the following compounds produced by the algae contain the 18O label. That one is
O2.
Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
ATP and NADPH
What are the products of the light reactions that are subsequently used by the Calvin cycle?
ATP and NADPH
Where does the Calvin cycle take place?
stroma of the chloroplast
In any ecosystem, terrestrial or aquatic, what group(s) is (are) always necessary?
autotrophs
In autotrophic bacteria, where are the enzymes located that can carry on organic synthesis?
along the inner surface of the plasma membrane
When oxygen is released as a result of photosynthesis, it is a by-product of which of the following?
) splitting the water molecules
A plant has a unique photosynthetic pigment. The leaves of this plant appear to be reddish yellow. What wavelengths of visible light are being absorbed by this pigment?
blue and violet
What did Engelmann conclude about the congregation of bacteria in the red and blue areas?
Bacteria congregated in these areas because these areas had the most oxygen being
released.
An outcome of this experiment was to help determine
the relationship between wavelengths of light and the oxygen released during
photosynthesis.
If you ran the same experiment without passing light through a prism, what would you predict?
The bacteria would be relatively evenly distributed along the algal filaments.
) Figure 10.1 shows the absorption spectrum for chlorophyll a and the action spectrum for
photosynthesis. Why are they different?
Other pigments absorb light in addition to chlorophyll a.
What wavelength of light in the figure is most effective in driving photosynthesis?
420 mm
Compared with the lines for chlorophyll a in the figure, where would you expect to find the lines to differ for chlorophyll b?
The absorption spectrum line would be lowest for chlorophyll b somewhat to the right
of that for chlorophyll a (500—600).
In the thylakoid membranes, what is the main role of the antenna pigment molecules?
harvest photons and transfer light energy to the reaction-center chlorophyll
The reaction-center chlorophyll of photosystem I is known as P700 because
this pigment is best at absorbing light with a wavelength of 700 nm.
Which of the events listed below occur in the light reactions of photosynthesis?
light is absorbed and funneled to reaction-center chlorophyll a.
Which statement describes the functioning of photosystem II?
The electron vacancies in P680 are filled by electrons derived from water.
Which of the following are directly associated with photosystem I?
receiving electrons from plastocyanin
Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. The best way to detect the lack of photosystem II in these organisms would be
to test for liberation of O2 in the light.
What are the products of linear photophosphorylation?
ATP and NADPH
As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find 30,000 molecules of ATP consumed, but only 20,000 molecules of NADPH. Where did the extra ATP molecules come from?
cyclic electron flow
Assume a thylakoid is somehow punctured so that the interior of the thylakoid is no longer separated from the stroma. This damage will have the most direct effect on which of the following processes?
the synthesis of ATP
What does the chemiosmotic process in chloroplasts involve?
establishment of a proton gradient
Suppose the interior of the thylakoids of isolated chloroplasts were made acidic and then transferred in the dark to a pH-8 solution. What would be likely to happen?
The isolated chloroplasts will make ATP.
In a plant cell, where are the ATP synthase complexes located?
thylakoid membrane and the
inner mitochondrial membrane
In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis translocates protons from
the stroma to the thylakoid space.
Which of the following statements best describes the relationship between photosynthesis and respiration?
Photosynthesis stores energy in complex organic molecules, while respiration releases
it.
Where are the molecules of the electron transport chain found in plant cells?
thylakoid membranes of chloroplasts
Synthesis of ATP by the chemiosmotic mechanism occurs during
both photosynthesis and respiration
Reduction of oxygen which forms water occurs during
respiration
Reduction of NADP+ occurs during
photosynthesis.
The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during
neither photosynthesis nor respiration.
Generation of proton gradients across membranes occurs during
both photosynthesis and respiration.
What is the relationship between wavelength of light and the quantity of energy per photon?
They are inversely related.
In a protein complex for the light reaction (a reaction center), energy is transferred from pigment molecule to pigment molecule, to a special chlorophyll a molecule, and eventually to the primary electron acceptor. Why does this occur?
The molecular environment lets it boost an electron to a higher energy level and also
to transfer the electron to another molecule.
P680+ is said to be the strongest biological oxidizing agent. Why?
This molecule results from the transfer of an electron to the primary electron acceptor
of photosystem II and strongly attracts another electron
Some photosynthetic bacteria (e.g., purple sulfur bacteria) have photosystem I but not II, while others (e.g. cyanobacteria) have both PSI and PSII. Which of the following might this
observation imply?
Photosystem I must be more ancestral.
Cyclic electron flow may be photoprotective (protective to light-induced damage). Which
of the following experiments could provide information on this phenomenon?
using mutated organisms that can grow but that cannot carry out cyclic flow of
electrons and compare their abilities to photosynthesize in different light intensities
Carotenoids are often found in foods that are considered to have antioxidant properties in
human nutrition. What related function do they have in plants?
They dissipate excessive light energy.
In thylakoids, protons travel through ATP synthase from the stroma to the thylakoid space.
Therefore the catalyticʺknobsʺof ATP synthase would be located
on the stroma side of the membrane.
Which of the following statements best represents the relationships between the light reactions and the Calvin cycle?
The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle
returns ADP, Pi, and NADP+ to the light reactions.
Where do the enzymatic reactions of the Calvin cycle take place?
stroma of the chloroplast
What is the primary function of the Calvin cycle?
synthesize simple sugars from carbon dioxide
Produces molecular oxygen (O2)
light reactions alone
Requires ATP
the Calvin cycle alone
Produces NADH
neither the light reactions nor the Calvin cycle
Produces NADPH
light reactions alone
Produces three-carbon sugars
the Calvin cycle alone
Requires CO2
the Calvin cycle alone
Requires glucose
neither the light reactions nor the Calvin cycle
The sugar that results from threeʺturnsʺof the Calvin cycle is glyceraldehyde-3-phosphate
(G3P). Which of the following is a consequence of this?
The formation of starch in plants involves assembling many G3P molecules, with or
without further rearrangements.
In the process of carbon fixation, RuBP attaches a CO2 to produce a 6 carbon molecule, which is then split in two. After phosphorylation and reduction, what more needs to happen in the Calvin cycle?
regeneration of rubisco
If ATP used by this plant is labeled with radioactive phosphorus, in which molecules will the radioactivity be measurable after oneʺturnʺof the cycle?
in B, C, D, and E
) If the carbon atom of the incoming CO2 molecule is labeled with a radioactive isotope of
carbon, where will the radioactivity be measurable after one cycle?
in E only
Which molecule(s) of the Calvin cycle is/are most like molecules found in glycolysis?
C and D only
In metabolic processes of cell respiration and photosynthesis, prosthetic groups such as
heme and iron-sulfur complexes are encountered. What do they do?
both oxidize and reduce during electron transport
The pH of the inner thylakoid space has been measured, as have the pH of the stroma and
of the cytosol of a particular plant cell. Which, if any, relationship would you expect to find?
The pH within the thylakoid is less than that of the stroma
Which of the following statements is true concerning Figure 10.3?
It represents cell processes involved in C4 photosynthesis.
Referring to Figure 10.3, oxygen would inhibit the CO2 fixation reactions in
cell II only.
In which cell would you expect photorespiration?
Cell II
In an experiment studying photosynthesis performed during the day, you provide a plant
with radioactive carbon (14C) dioxide as a metabolic tracer. The 14C is incorporated first
into oxaloacetate. The plant is best characterized as a
C4 plant
Why are C4 plants able to photosynthesize with no apparent photorespiration?
They use PEP carboxylase to initially fix CO2.
CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this
because they
fix CO2 into organic acids during the night.
Photorespiration lowers the efficiency of photosynthesis by preventing the formation of
3-phosphoglycerate molecules
The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?
Each one both minimizes photorespiration and optimizes the Calvin cycle.
If plant gene alterations cause the plants to be deficient in photorespiration, what would most probably occur?
Less ATP would be generated.
