BIO EXAM 4
Which of theses statements best describes a strong oxidizing agent?
Strong oxidizing agents oxidize other compounds by accepting electrons
In the example above we discussed the signal sequence that targets proteins for the endoplasmic reticulum. Other proteins in the cell, however, may need to be exported to different organelles. Which of these proteins do you think should be exported to the nucleus after its synthesis in the cytoplasm?
TATA binding protein
You join a lab studying a receptor protein thought to facilitate infection of human intestinal cells by a new virus. You are interested in understanding how the receptor was inserted into the plasma membrane of the host cells. The protein has the following general structure across the plasma membrane. Glycosylation is shown by the blue hexagons. You notice that the previous student forgot to label the cytosolic and extracellular sides of the plasma membrane on the diagram. Given the diagram, where are the N and C termini of the protein?
The N terminus is on the cytosolic side and the C terminus is on the extracellular side, since the C terminus is on the same side of the membrane as the glycosylation.
The ethanol in wine and beer is produced from metabolic reactions carried out by the yeast Saccharomyces cerevisiae. Since it is of great commercial value, researchers have studied factors that influence ethanol production. To maximize ethanol yield, which environmental factor should be limiting?
oxygen
In a typical human secretory cell, which of the following membranes has the largest surface area?
rough ER
Inner membrane
separates compartments of different pH
Matrix
site of the TCA cycle
In the absence of oxygen, in cells that cannot carry out fermentation, glycolysis would halt at which step?
the oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate
TCA cycle
mitochondrial matrix
In substrate-level phosphorylation, a phosphate is transferred from an organic compound (the "substrate") to ADP to form ATP. Cells contain many phospho-compounds, some of which could potentially be used for substrate-level phosphorylation. Given the standard free energy of hydrolysis of ATP (-30.6 kJ/mol), which of the following molecules could serve as a phosphate donor for substrate-level phosphorylation? The standard free energy of hydrolysis for each compound is indicated in parentheses. Choose all that apply—there may be more than one correct answer.
1,3-Bisphosphoglycerate (-49.0 kJ/mol) Creatine phosphate (-43.0 kJ/mol)
In this illustration of the structure of ATP synthase, which of the components rotate?
1,5
Glycolysis occurs in a series of 10 steps using 10 different enzymes. Place the following broad events that occur during glycolysis into their correct order.
1. Energy is inveseted by using up some ATP 2. The six-carbon sugar is split into two smaller molecules 3. Energy is captured as ATP and NADH 4. Two molecules of pyruvate are generated
Order these organelles from lowest to highest percentage of total cell volume they occupy in an average cell.
1. Lysosomes 2. Golgi apparatus 3. Endoplasmic reticulum 4. Mitochondria
If 6 molecules of FADH2 are made in the citric acid cycle in a given amount of time, then you would expect _______ NADH to be made during the same time interval (same number of times around the TCA cycle).
18 One FADH2 molecule is generated during each round of the citric acid cycle. If 6 FADH2 have been generated, the citric acid cycle must have completed 6 rounds. There are three NADH molecules produced for each cycle of the citric acid cycle. So, 6 rounds with three NADH molecules per round is 18 total NADH produced.
In which of these molecules is carbon more oxidized?
A
Which arrow points to the direction of proton travel through the ATP synthase?
A
Substrate-level phosphorylation is used to produce ______during glycolysis
ATP
The drug 2,4-dinitrophenol (DNP) makes the mitochondrial inner membrane permeable to H+. The resulting disruption of the proton gradient inhibits the mitochondrial production of ATP.What additional effect would DNP have on the transport of ATP out of the mitochondrial matrix?
ATP export will decrease because its carrier exploits the difference in voltage across the inner membrane.
Suppose the shaft of ATP synthase that is attached to the rotor were truncated (shortened) such that it no longer extended into the F1 ATPase head. What would be the consequence of this mutation?
ATP would not be produced because the conformation of the F1 ATPase head would not be changed.
After the Covid spike protein is synthesized, it is packaged in the membranes of vesicles and secreted from the cell. Given that its secretion is constant and is not induced by specific stimuli, the Covid spike protein therefore is secreted through
Constitutive secretion
Which label points to the site of ATP synthesis in the ATP synthase?
B
Which of these molecules has more high-energy electrons?
B
Which of these molecules is pyruvate?
B
Why do we say that the ETC carries out "oxidative phosphorylation"?
Because each successive component of the electron transport chain oxidizes the previous component
When mRNA from the vaccine enters cell, it is used to produce the viral spike protein. For the immune system to be able to respond to the spike protein, it needs to be exported out of the cell. The viral spike protein will therefore be processed through the
Biosynthetic pathway
Not all fat cells are equivalent. Humans and other animals contain both white fat cells and brown fat cells, named after their color. Because increases in brown fat cells may aid weight loss, researchers are interested in factors that control the ratio of white fat cells and brown fat cells, as detailed in a 2017 article in Obesity Reviews. What is the mechanism for how brown fat cells aid weight loss?
Brown fat cell mitochondria contain an uncoupling protein.
Select all that apply. Which of these components of the ETC pump protons into the intermembrane space? Select all that apply.
Complex I Complex III Complex IV
Which of the following reactions is the final step of a fermentation pathway? Choose all that apply—there may be more than one correct answer.
Electrons are passed from NADH to acetaldehyde (CH3CHO) to produce ethanol (CH3CH2OH). Electrons are passed from NADH to pyruvate to produce lactate.
When ATP and food molecules such as fatty acids are abundant, which will occur?
Enzymes involved in gluconeogenesis will use energy to produce glucose.
Experiments performed by Hans Krebs in the 1930s revealed that the set of reactions that oxidize food molecules and produce CO2 occur in a cycle. In one experiment, Krebs exposed pigeon muscles to malonate, a compound that inhibits succinate dehydrogenase—the enzyme that converts succinate to fumarate, indicated in red in the linear representation of the reactions of the citric acid cycle (below).Which of the following observations, made in malonate-treated muscle, led Krebs to believe that this set of reactions is cyclical?
If fumarate were added, succinate would accumulate.
Electron transport chain
Inner mitochondrial membrane
Which of these molecules is a product of both glycolysis and the TCA cycle in humans?
NADH
This reactions occurs as part of the TCA cycle in humans. Given that in this reaction carbons on the reactant molecule are oxidized, what are the products of this reaction? Select all that apply.
NADH CO2
This reactions occurs as part of glycolysis in humans. Given that in this reaction carbons on the reactant molecule (top) are oxidized, what are the products of this reaction in addition to those shown? Select all that apply.
NADH H+ (a free proton)
In cells, like cardiac muscle cells, that cannot carry out fermentation, which products derived from glycolysis will accumulate under anaerobic conditions?
NADH pyruvate
Antimycin A is a piscicide (fish poison) used to manage fisheries and kill invasive species. Antimycin A blocks the transfer of electrons through the cytochrome b-c1 complex. What components of the electron transport chain are bound to high-energy electrons after treating a mitochondrion with antimycin A?
NADH and the NADH dehydrogenase complex are bound to high-energy electrons while O2 and the cytochrome c oxidase complex are not.
What would be the consequences to NADPH production if the redox potential of pC (plastocyanin) were altered to be more negative than the redox potential of cytochrome b6-f?
NADPH production would halt since pC would no longer accept electrons from the cytochrome b6-f complex, blocking the electron transport chain.
Investigators introduce two proteins into the membrane of artificial lipid vesicles: (1) an ATP synthase isolated from the mitochondria of cow heart muscle, and (2) a light-activated proton pump purified from the prokaryote Halobacterium halobium. The proteins are oriented as shown in the diagram. When ADP and Pi are added to the external medium and the vesicle is exposed to light, would this system produce ATP?
No, because ATP synthase is not oriented correctly.
Which statements below accurately describe an aspect of the citric acid cycle?
Oxaloacetate is regenerated by the end of the citric acid cycle. NADH is generated in steps 3, 4, and 8.
To which organelle should the vaccine mRNA be targeted during its synthesis, given your answers above?
Rough endoplasmic reticulum
Antibiotics should inhibit bacterial cell growth without generating side effects in the human patient, but that is not always the case. Some antibiotics that inhibit bacterial protein synthesis by binding to bacterial ribosomes induce negative side effects in patients. What is the most likely cause of these side effects?
The antibiotics interfere with mitochondrial ribosomes.
For proteins that are bound for synthesis at the RER, the signal peptide is synthesized first. It then binds the signal recognition particle. What happens next?
The the ribsome containing the partially translated protein (just the signal peptide) and the untranslated mRNA downstream of the signal peptide is moved to the RER where its translation is completed
Your friends are on a low-fat, high-carbohydrate diet, which they claim will prevent fat accumulation within their bodies. They eat tons of pasta and bread without worrying about calorie count. What can you correctly say to your friends about their potential to accumulate lipids on their low-fat diet?
They will accumulate fats because cells can convert glycolytic metabolites into lipids.
To explore how yeast cells metabolize glucose, investigators use a DNA microarray to examine the effect the sugar has on the expression of a variety of genes. Cultured yeast cells are supplemented with high concentrations of glucose. mRNAs are extracted from the cells, converted into cDNAs, and labeled with a fluorescent marker. The samples are then hybridized to a DNA microarray that includes probes representing yeast genes.Shown here is a data set representing genes involved in ribosome biogenesis and electron transport. Red indicates that supplementing the growth medium with glucose has increased the expression of the genes, whereas green indicates that the added glucose has decreased gene expression.
Yeast cells exposed to high concentrations of glucose grow by fermentation.
To aid in the purification of your protein, you want the cells to secrete the protein into the culture media. What do you need to add to the protein-coding DNA sequence to enable secretion of the protein from the cell?
an ER signal sequence
ATP synthase is a large molecular machine that converts the energy in an electrochemical gradient into the bond energy stored in ATP. Which of the following events are required for the synthesis of ATP?
conformational changes of the F1 ATPase movement of protons down their gradient through ATP synthase rotation of the rotor in the membrane
fermentation
cytoplasm
glycolysis
cytoplasm
Pyruvate oxidation
mitochondrial matrix
When electron moves closer to the nucleus of an electronegative atom,
energy is released
You are packing for a hiking trip during which you'll be burning a lot of calories with physical activity. You want to pack as efficiently as possible since you need to carry a tent and all your food. You can get the most calories out of 5kg of food if it is in the form of ____________.
fat, The oxidation of a gram of fat releases about twice as much energy (9 calories versus 4 calories) as the oxidation of a gram of glycogen. Fats contain mostly highly reduced C-H bonds, whereas carbohydrates are already partially oxidized.
After an overnight fast, most of the acetyl CoA entering the citric acid cycle is derived from what type of molecule?
fatty acids
Inter-membrane space
has a low pH
The chemistry of many metabolic reactions was deciphered using molecules labeled with radioactive isotopes. If acetyl CoA labeled with radioactive 14C in both carbon positions were fed into the citric acid cycle, where would the radioactivity be after one turn of the cycle?
in oxaloacetate
If acetyl CoA labeled with radioactive 14C in both carbon positions were fed into the citric acid cycle, where would the radioactivity be after two turns of the cycle?
in oxaloacetate and in CO2
Outer membrane
transports a large variety of molecules and ions
