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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.
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
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
Why are carbohydrates and fats considered high energy foods?
They have a lot of electrons associated with hydrogen.
In addition to ATP, what are the end products of glycolysis?
NADH and pyruvate
Starting with one molecule of glucose, the ʺnetʺ products 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.
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
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
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
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
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.
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)
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)
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
Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in cellular respiration?
76
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
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.
Which of the following couples chemiosmosis to energy storage?
ATP synthase
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?
One function of both alcohol fermentation and lactic acid fermentation is to
oxidize NADH to NAD+
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.
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.
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 step shows a split of one molecule into two smaller molecules
Step B
In which step is an inorganic phosphate added to the reactant?
step C
In which reaction does an intermediate pathway become oxidized?
Step C
Which step consists of a phosphorylation reaction in which ATP is the phosphate source?
Step A
