Photosynthesis and Respiration: Chapter 9 and 10 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?
A and C are correct
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
reduce
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
The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mole and the
free energy for the reduction of NAD+ to NADH is +53 kcal/mole. 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
In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid
cycle. First, however, the pyruvate 1) loses a carbon, which is given off as a molecule of CO2, 2) is
oxidized to form a two-carbon compound called acetate, and 3) is bonded to coenzyme A.
29) 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?
΅-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
A young animal has never had much energy. He is brought to a veterinarian for help and is
sent to the animal hospital for some tests. There they discover his mitochondria can use
only fatty acids and amino acids for respiration, and his cells produce more lactate than
normal. 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
It is possible to prepare vesicles from portions of the inner membrane of the mitochondrial
components. 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
Assume a mitochondrion contains 58 NADH and 19 FADH2. If each of the 77 dinucleotides
were used, approximately how many ATP molecules could be generated as a result of
oxidative phosphorylation (chemiosmosis)?
212
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%
Recall that the complete oxidation of a mole of glucose releases 686 kcal of energy (̇ G =
-686 kcal/mol). The phosphorylation of ADP to form ATP stores approximately 7.3 kcal per
mole of ATP. 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.
Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes.
However, the fragments will resealʺinside out.ʺThese little vesicles that result can still transfer electrons
from NADH to oxygen and synthesize ATP. If the membranes are agitated still further however, the
ability to synthesize ATP is lost.
65) 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+.
An organism is discovered that consumes a considerable amount of sugar, yet does not
gain much weight when denied air. Curiously, the consumption of sugar increases as air is
removed from the organismʹs environment, but the organism seems to thrive even in the
absence of air. 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.
Muscle cells, when an individual is exercising heavily and when the muscle becomes
oxygen deprived, convert pyruvate to lactate. 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
You have a friend who lost 7 kg (about 15 pounds) of fat on aʺlow carbʺdiet. How did the
fat leave her body?
It was released as CO2 and H2O.
Phosphofructokinase is an important control enzyme in the regulation of cellular
respiration. Which of the following statements describes a function of
phosphofructokinase?
It is an allosteric enzyme
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 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
In vertebrate animals, brown fat tissueʹs color is due to abundant mitochondria. White fat
tissue, on the other hand, is specialized for fat storage and contains relatively few
mitochondria. 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 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
