Ch. 9
A recently identified organism produces methane (CH4) when provided with glucose in the absence of oxygen. This means the organism is
capable of anaerobic catabolism and uses carbon dioxide in place of oxygen as its terminal electron acceptor.
ATP synthase is the protein complex that
captures the potential energy of the proton gradient in the intermembrane space as the chemical energy in phosphate bonds of ATP.
When NADH is the electron donor to the respiratory chain, 2.5 ATP are formed, but when FADH2 is the electron donor, only 1.5 ATP are formed. This difference occurs because
complex I accepts electrons from NADH but not FADH2, resulting in an extra step that allows a larger proton gradient to form.
NAD+ helps harvest energy from glyceraldehyde 3-phosphate by functioning as a(n)
electron acceptor.
Oxidative phosphorylation has two major components: ______________ and _______________
electron transport; chemiosmosis
Fermentation is a process that occurs
in muscle tissue when there is an insufficient supply of oxygen.
The difference between oxidation and reduction is that
oxidation reduces the number of electrons, while reduction increases the number of electrons.
Choose the phrase that correctly completes this sentence: Oxidative phosphorylation is a process - in which ATP is formed as a result of the transfer of electrons to H2O.that requires a membrane that is permeable to protons. - that occurs in the cytoplasm in eukaryotes and in the plasma membrane in prokaryotes. - that involves the respiratory chain and ATP synthases. - that does not require the presence of ADP and Pi.
that involves the respiratory chain and ATP synthases.
Refer to the figure. Carbon-13 is a non-radioactive isotope of carbon that is safe for humans to ingest. This isotope can be identified and quantified using an analytical instrument called a mass spectrometer. The figure shows results of such an analysis of the fate of 13C-labeled alanine given orally to human volunteers just before they began intensive and prolonged exercise. From the results shown, it can be concluded that the majority of alanine ingested just before exercise is
used as an energy source.
How many reaction steps are involved in the citric acid cycle?
Eight
The cell harvests a very large amount of free energy from glucose in the form of ATP. Which statement can be used as part of an explanation about how the cell accomplishes this harvesting process with high efficiency (i.e., with very little loss in energy as heat)?
Electron transport uses a series of several proteins, each of which functions to capture a portion of the total energy of the electrons entering the chain.
Fermentation is an important process that allows organisms growing in anaerobic environments to harvest energy from glucose. Which statement about fermentation explains one other reason why fermentation is important to anaerobic organisms?
Fermentation provides a means for the cycling of NADH back to NAD+ so that glycolysis can continue.
In eukaryotes, the proton-motive force allows protons to move passively through ATP synthase in which direction?
From the mitochondrial inner membrane space to the mitochondrial matrix
What is an example of anabolic interconversion?
Gluconeogenesis
Which sequence of metabolic paths could a carbon atom take to go from a molecule of glucose to a molecule of DNA?
Glycolysis → pyruvate oxidation → citric acid cycle → amino acid biosynthesis → purine biosynthesis
A biochemist discovers several new microorganisms in a sample taken from the bottom of a deep lake in Antarctica. In characterizing one of these organisms, she finds that it cannot survive in an aerobic environment and produces lactic acid as a waste product. What is also likely true about this organism?
It lacks genes for citric acid cycle enzymes.
Refer to the figure. Some of the chemical energy present in pyruvate is harvested during an oxidation-reduction process taking place in the multistep reaction shown in the figure. Pyruvate → Acetly CoA In which molecule is this harvested chemical energy stored?
NADH
What is the net free energy captured by 32 moles of ATP?
234 kcal
The reaction equation that represents the chemical change resulting from glycolysis followed by alcoholic fermentation is C6H12O6 → 2 C2H6O + 2 CO2 + _______ ATP; the reaction equation that represents the chemical change resulting from glycolysis followed by cellular respiration is C6H12O6 + 6 O2 → 6 CO2 + _______ ATP + 6 _______.
2; 32; H2O
Some poisons are compounds that interfere with metabolic pathways. Which poison would interfere with the citric acid cycle but not affect glycolysis?
A compound that inhibits pyruvate dehydrogenase
The carbon-containing molecule that enters glycolysis differs from the one that enters the citric acid cycle. How do the numbers of carbon atoms per molecule compare in these two cases?
A six-carbon molecule enters glycolysis, while a two-carbon molecule enters the citric acid cycle.
Refer to the figure. A student made this diagram as a study guide for learning the steps involved in the aerobic catabolism of glucose. One step could be added to better illustrate these steps. Which step should be added?
A step to show that pyruvate is oxidized to acetyl CoA, the compound that enters the citric acid cycle
Which reaction is not an example of an oxidation-reduction reaction?
ADP + Pi → ATP + H2O
The compound 2,4-dinitrophenol (DNP) is a lipid soluble compound that has been used as a weight loss agent. It functions this way by causing the inner mitochondrial membrane to become leaky with respect to protons. Which result might be expected if cells treated with DNP were examined in detail?
ATP production would be slower in these cells than in untreated cells.
A microbiologist is characterizing a newly discovered microorganism that requires an anaerobic environment to live and uses either lactic acid or alcoholic fermentation in its energy metabolism. Which would be a way to determine the type of fermentation the microorganism uses?
Analyze whether two molecules of carbon dioxide are released for every one molecule of glucose fermented.
Which list places the molecules, from left to right, from most oxidized to least oxidized?
CO2 > CHOOH > CH3OH > CH4
What is the cellular location of glycolysis in eukaryotes?
Cytoplasm
You are practicing 200-meter sprints, running them back-to-back. You are hoping to improve your time with each repetition, but instead find that your running time is longer with each repetition. Discouraged, you go home and rest. The next day, you run a 200-meter sprint and have your fastest time yet. What is a logical explanation for these results?
During rest, lactate dehydrogenase was able to reduce the lactic acid levels in your muscles by using O2 to catalyze the oxidation of lactic acid back to pyruvate.
In an experiment, the F1 portion of the ATP synthase was attached to a glass slide, and fluorescently labeled microfilaments were attached to its central peptide. The rotation of the ATP synthase was observed when ATP was added. Because there was no proton gradient to drive the molecular motor in the direction of ATP synthesis, ATP was hydrolyzed to ADP and Pi, and this energy caused the motor to spin. When ATP plus oligomycin was added to the slide, the rotation continued even though oligomycin can inhibit ATP hydrolysis in mitochondrial inner membrane vesicles containing ATP synthase (F1-F0). Based on your knowledge of ATP synthase, which hypothesis is supported by these observations?
Oligomycin binds the ATP synthase (F1-F0) only when it is attached to the membrane.
Malate dehydrogenase is responsible for catalyzing which reaction?
Oxidation of malate to oxaloacetate
Five statements about energy metabolism in cells are given. Which statement can be used to explain the importance of the process shown in the figure?
Oxidation of molecules from glucose is coupled to reduction of oxygen, which allows for controlled release of energy in a form that the cell can use.
Which statement regarding glycolysis is true? - Pyruvate is not formed. - Oxygen is not required. - NADH is not formed. - Glucose is not catabolized. - ATP is not formed.
Oxygen is not required.
Refer to the figure showing the reaction that links glycolysis to the citric acid cycle. Pyruvate → Acetly CoA Which statement correctly describes the chemical changes depicted in this reaction?
Pyruvate is decarboxylated and oxidized to acetyl CoA, and NAD+ is reduced to NADH.
How many enzymatic steps are involved in glycolysis in animals?
Ten
Energy production occurs in different locations in prokaryotic and eukaryotic cells. Which statement is true for eukaryotes? - The respiratory chain enzymes are found at the plasma membrane. - The conversion of pyruvate to lactate occurs in the mitochondria. - The citric acid cycle enzymes are found in the cytoplasm. - The conversion of glucose to pyruvate occurs in the mitochondria. - The conversion of pyruvate to CO2 and H2O occurs in the mitochondria.
The conversion of pyruvate to CO2 and H2O occurs in the mitochondria.
If the regeneration of NAD+ were inhibited during lactic acid fermentation, which of the following would likely occur?
The rate of lactic acid production would decrease.
Refer to the figure showing an experiment using thylakoids from chloroplasts. If an experiment based on the one illustrated in the figure were carried out, which thylakoids would produce the most ATP?
Thylakoids preincubated in a pH 4 solution and then moved to a pH 7.5 solution containing ADP and Pi
Refer to the figure. A biochemist inoculated a test tube containing liquid medium with a few bacterial cells of a single species. A concentration gradient of oxygen was present in the tube, with very low levels of oxygen at the bottom of the tube and increasingly higher concentrations toward the top of the tube. The highest levels of oxygen were at the top of the liquid medium. Glucose was present in equal concentrations throughout the tube. The particular bacterial species used to inoculate the tube is able to grow either aerobically or anaerobically. Which tube would most likely represent the growth pattern of bacteria under these conditions, and why?
Tube Z, because cells grow fastest when they harvest the greatest available energy from glucose.
Catabolic interconversion is a metabolic pathway in which
a large molecule is broken down into its constituent molecules and releases energy.