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