Quiz 9 & 10
Which portion of the pathway shown in the figure below contains a phosphorylation reaction in which ATP is the phosphate source?
A
During the chemiosmosis phase of oxidative phosphorylation, potential energy stored during the electron transport phase is converted to energy stored in the form of:
ATP
What are the products of linear photophosphorylation?
ATP and NADPH
Which of the following are products of the light reactions of photosynthesis that are subsequently utilized in the Calvin cycle?
ATP and NADPH
Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
ATP and NADPH
The light reactions of photosynthesis supply the Calvin cycle with
ATP and NADPH.
Besides CO2 and H2O, to produce sugars through the reactions of the Calvin cycle cells also require
ATP as an energy source to "drive" the otherwise endergonic reaction and NADPH as a reducing agent.
Brown fat cells produce a protein called thermogenin in their mitochondrial inner membrane. Thermogenin is a channel for facilitated transport of protons across the membrane. What will occur in the brown fat cells when they produce thermogenin?
ATP synthesis will decrease, and heat generation will increase.
The oxygen consumed during cellular respiration is involved directly in which process or event?
Accepting electrons at the end of the electron transport chain
Why is less ATP produced by anaerobic respiration than by aerobic respiration?
Anaerobic respiration uses a final electron acceptor that is less electronegative than O2, which is used as the final electron acceptor in aerobic respiration.
Synthesis of ATP by the chemiosmotic mechanism occurs during
Both photosynthesis and respiration
Which step in in the figure shown below is a redox reaction?
C
In the reaction shown below CH4 + 2 O2 → CO2 + energy + 2 H2O
CH4 is oxidized and O2 is reduced
The "building blocks" for the production of sugar molecules that occurs during photosynthesis are
CO2 and H2O
A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide. If the power fails and the lights go dark, what will happen to CO2 levels?
CO2 will rise as a result of both animal and plant respiration.
During cellular respiration, what is the direction of energy flow?
Chemical bonds in food - to NADH - to a proton gradient - to chemical bonds in ATP
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 events listed below occurs in the light reactions of photosynthesis?
Energy from light is absorbed and funneled to a reaction-center chlorophyll a molecule.
When electrons move closer to a more electronegative atom, what happens?
Energy is released and the more electronegative atom is reduced
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the
H+ concentration across the membrane holding ATP synthase.
Which of the following sequences correctly represents the flow of electrons during photosynthesis?
H2O → NADPH → Calvin cycle
In the thylakoid membranes, what is the main role of the pigment molecules in the light-harvesting complexes?
Harvest photons and transfer light energy to the reaction-center chlorophyll
Why is glycolysis described as having an investment phase and a payoff phase?
It first uses two stored ATP and then forms four ATP, for a net increase of two ATP.
In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?
It increases the surface for oxidative phosphorylation
You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave her body?
It was released as CO2 and H2O.
The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mol and the free energy for the reduction of NAD+ to NADH is +53 kcal/mol. What is the main reason that 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.
In addition to ATP, what are the end products of glycolysis?
NADH and pyruvate
Which of the following shows the molecules in the order of least to most electronegative?
NADH, e- transport chain, O2
During photosynthesis, the carbon in CO2 is reduced, helping to form sugar molecules. Which of the following statements about this process is TRUE?
NADPH donates electrons to CO2
During photosynthesis, the carbon in CO2 is reduced, helping to form sugar molecules. Which of the following statements about this process is TRUE?
NADPH is the reducing agent for CO2
In the reaction shown below Na and Cl → Na+ and Cl-
Na is the reducing agent and Cl is the oxidizing agent
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 statements best describes the relationship between photosynthesis and respiration?
Photosynthesis stores energy in complex organic molecules, whereas respiration releases it.
Which of the following statements about proton gradients is FALSE?
Proton gradients cannot be used to do work
In prokaryotes, the respiratory electron transport chain is located
The correct answer is: in the plasma membrane.
When a pigment molecule in a light-harvesting complex absorbs the energy from a photon of light, an electron in the pigment molecule becomes "excited". What does this mean?
The electron has achieved a higher-energy state, meaning that it is located further from the nucleus.
Which of the following is an important difference between aerobic and anaerobic respiration
The electron transport chain used in aerobic respiration uses O2 as the final electron acceptor whereas the electron transport chain used in anaerobic respiration uses something other than O2 as the final electron acceptor.
Which statement describes the functioning of photosystem II?
The electron vacancies in P680+ are filled by electrons derived from water.
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.
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, inorganic phosphate, and NADP+ to the light reactions.
A mutation in yeast makes it unable to convert pyruvate to ethanol. How will this mutation affect these yeast cells?
The mutant yeast will be unable to grow anaerobically.
When electrons flow along the electron transport chain in mitochondria, which of the following changes occurs?
The pH of the matrix increases.
Which of the following statements about the light reactions of photosynthesis is FALSE?
Upon absorbing the energy from a photon of light, pigment molecules in the light-harvesting complex may transfer an excited electron to a special chlorophyll a molecule in the reaction-center complex
If your muscles used alcohol fermentation instead of lactic acid fermentation, which of the following might occur?
You might become drunk during an intense workout.
In the process known as "substrate-level phosphorylation",
a phosphate group is transferred from a substrate molecule to ADP
During photosynthesis, energy from light is first captured by
a pigment molecule in a light harvesting complex
In cellular respiration, the energy for most ATP synthesis is supplied by
a proton gradient across a membrane.
Pyruvate is transported into mitochondria by
a symporter that transports pyruvate up its concentration gradient while transporting protons down their electrochemical gradient.
The primary role of oxygen in cellular respiration is to
act as an acceptor for electrons and hydrogen, forming water.
The movement of protons that occurs during transfer of electrons through the electron transport chain is an example of
active transport
The transport of pyruvate into mitochondria depends on the proton-motive force across the inner mitochondrial membrane. How does pyruvate enter the mitochondrion?
active transport
When comparing electronegativities,
all of these answers are correct
Which of the following metabolic processes include glycolysis?
all of these answers are correct
When an electron moves from
all of these statements are true
High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of
allosteric regulation.
Most of the energy released during cellular respiration ends up:
being lost as heat
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
An important difference between oxidative phosphorylation and photophosphorylation is
both "b" and "c" are correct
Plants photosynthesize only in the light. Plants respire
both in light and dark.
During the metabolic processes of cell respiration and photosynthesis, the complexes that are components of the electron transport chain
both oxidize and reduce during electron transport
Generation of proton gradients across membranes occurs during
both photosynthesis and respiration.
When skeletal muscle cells continue to do work under conditions of insufficient oxygen (e.g. anaerobic exercise), they become fatigued and painful. This is now known to be caused by
buildup of lactate.
Inside an active mitochondrion, most electrons follow which pathway?
citric acid cycle → NADH → electron transport chain → oxygen
Where does glycolysis take place in eukaryotic cells?
cytosol
The reactions of the Calvin cycle are
endergonic, and thus require a source of free energy to occur
In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + inorganic phosphate to ATP?
energy released from movement of protons through ATP synthase, down the electrochemical gradient
What does the chemiosmotic process in chloroplasts involve?
establishment of a proton gradient across the thylakoid membrane
The transfer of electrons from the primary electron acceptor of photosystem II to the P700+ chlorophyll a molecules of photosystem I is
exergonic as the P700+ chlorophyll a molecule is more electronegative than the primary electron acceptor
During aerobic respiration, electrons travel downhill in which sequence?
food to NADH to electron transport chain to oxygen
During the light reactions of photosynthesis, electrons are transferred
from special chlorophyll a molecules to primary electron acceptors
Which metabolic pathway is common to both cellular respiration and fermentation?
glycolysis
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
glycolysis
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
glycolysis
Which of the following occurs in the cytosol of a eukaryotic cell?
glycolysis and fermentation
A molecule that is phosphorylated
has an increased chemical potential energy; it is primed to do cellular work.
Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur?
in all cells all the time
The reactions of the Calvin cycle can take place
in either the dark or the light
Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount of ATP in a cell would be expected to
inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle.
Where is ATP synthase located in the mitochondrion?
inner membrane
An enzyme, ribulose bisphosphate carboxylase oxygenase, or "Rubisco", attaches CO2 to a 5-carbon long sugar to form a 6-carbon long molecule, which
is unstable and splits to form two 3-carbon long molecules
During the process of photosynthesis,
less than 100% of the energy captured from sunlight is transformed into potential energy in the form of a hydrogen ion gradient and then into potential energy in the form of covalent bonds
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction
loses electrons and loses energy
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
mitochondrial intermembrane space
During cellular respiration, acetyl CoA accumulates in which location?
mitochondrial matrix
During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?
molecular oxygen (O2)
In a plant leaf, the reactions that produce NADH (NADH, not NADPH) occur in
neither the light reactions nor the Calvin cycle.
The process known as "substrate-level phosphorylation"
occurs during both glycolysis and the citric acid cycle.
It is possible to prepare vesicles from portions of the inner mitochondrial membrane. Which one of the following processes could still be carried on by this isolated inner membrane?
oxidative phosphorylation
Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis)
In mechanism, photophosphorylation is most similar to
oxidative phosphorylation in cellular respiration.
When comparing oxidative phosphorylation with photophosphorylation, you should notice that
oxidative phosphorylation uses up NADH whereas photophosphorylation generates NADPH
One function of both alcohol fermentation and lactic acid fermentation is to
oxidize NADH to NAD+.
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule become
oxidized.
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
oxygen.
The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during
photosynthesis nor respiration.
During the light reactions of photosynthesis, energy from light is used to
produce ATP and NADPH
In mitochondria, exergonic redox reactions
provide the energy that establishes the proton gradient.
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD+
pyruvate
Which of the following are directly associated with photosystem I?
receiving electrons from the thylakoid membrane electron transport chain
To sustain high rates of glycolysis under anaerobic conditions, cells require
regeneration of NAD+
Which of the following does not occur during the Calvin cycle?
release of oxygen
Which process is most directly driven by light energy?
removal of electrons from chlorophyll molecules
The energy from an excited electron can be passed from one pigment molecule to another via a process known as
resonance energy transfer
Chemiosmosis
serves to generate ATP in both photosynthesis and respiration, but NADPH is produced by chemiosmosis during photosynthesis whereas NADH is used up by chemiosmosis during respiration
An electron loses potential energy when it
shifts to a more electronegative atom.
As electrons are being transported down the electron transport chain from photosystem II to photosystem I
some of the energy that is released is used to generate a proton gradient
When oxygen is released as a result of photosynthesis, it is a direct by-product of
splitting water molecules.
Where do the enzymatic reactions of the Calvin cycle take place?
stroma of the chloroplast
Where does the Calvin cycle (i.e.the dark reactions of photosynthesis) take place?
stroma of the chloroplast
The ATP made during fermentation is generated by which of the following?
substrate-level phosphorylation
The ATP made during glycolysis is generated by
substrate-level phosphorylation.
What is the primary function of the Calvin cycle?
synthesize simple sugars from carbon dioxide
Reactions that require CO2 take place in
the Calvin cycle alone.
Which pathways generate reduced electron carriers?
the citric acid cycle and glycolysis
When an electron moves from one molecule to another molecule that is more electronegative
the electron loses potential energy
During the light reactions of photosynthesis
the initial source of electrons is H2O and the final electron acceptor is NADP+
In mitochondria, during chemiosmosis protons move from the intermembrane space to the matrix, whereas in chloroplasts, during chemiosmosis protons move from
the inter-thylakoid space to the stroma.
The reactions that produce molecular oxygen (O2) take place in
the light reactions alone.
The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is
the proton-motive force across the inner mitochondrial membrane.
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
In photosynthesis, "resonance energy transfer" refers to
the transfer of energy from an excited electron in one pigment molecule to an electron in a different pigment molecule
What percentage of living organisms are dependent, directly or indirectly, on food molecules produced via photosynthesis?
the vast majority
In a plant cell, where are the ATP synthase complexes located?
thylakoid membrane and inner mitochondrial membrane
The purpose of fermentation reactions is
to regenerate NAD+ so glycolysis can continue
In vertebrate animals, brown fat tissue's color is due to abundant blood vessels and capillaries. White fat tissue, on the other hand, is specialized for fat storage and contains relatively few blood vessels or capillaries. Brown fat cells have a specialized protein that dissipates the proton-motive force across the mitochondrial membranes. Which of the following might be the function of the brown fat tissue?
to regulate temperature by converting most of the energy from NADH oxidation to heat
The transfer of an electron from a P680 chlorophyll a molecule to the primary electron acceptor of photosystem II
will only occur if the P680 molecule has an electron that is sufficiently excited (i.e. of sufficiently high energy)
