BSC2010 Exam 2
Which of the following is the most correct interpretation of the figure? A cycle with ATP at the top and ADP plus P subscript 1 at the bottom, with arrows pointing clockwise. Energy from catabolism enters with an arrow pointing toward ATP; after ATP another arrow labeled Energy for cellular work exits the diagram.
ATP is a molecule that acts as an intermediary to store energy for cellular work.
In glycolysis, what starts the process of glucose oxidation?
ATP. Some ATP energy is used to start the process of glucose oxidation.
Active and passive transport of solutes across a membrane typically differ in which of the following ways?
Active transport is usually against the concentration gradient of the solute, whereas passive transport is always down the concentration gradient of the solute. Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy. Active transport always requires the use of transport proteins, but passive transport can sometimes be accomplished without a protein
If glucose is the sole energy source, what fraction of the carbon dioxide exhaled by animals is generated only by the reactions involved in oxidation of pyruvate to acetyl CoA?
1/3
In glycolysis there is a net gain of _____ ATP.
2 It takes 2 ATP to produce 4 ATP.
How many NADH are produced by glycolysis? How many NADH are produced by glycolysis?
2 Two NADH molecules are produced by glycolysis.
What wavelength of light in the figure is most effective in driving photosynthesis?
420 nm
Which of the following statements is not true of most cellular redox reactions?
A hydrogen atom is transferred to the atom that loses an electron. A hydrogen atom (proton, or H+) is often transferred to the atom that gains an electron.
Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?
Anion and cation. Each atom will carry a charge from the transfer of electrons.
Net redox reaction in acetyl CoA formation and the citric acid cycle pyruvate is oxidized to (a) CO2 NAD+ is reduced to (b) NADH (c) FAD is reduced to (d)FADH2
As in glycolysis, the electrons removed from carbon-containing intermediates during acetyl CoA formation and the citric acid cycle are passed to the electron carrier NAD+, reducing it to NADH. The citric acid cycle also uses a second electron carrier, FAD (flavin adenine dinucleotide), the oxidized form, and FADH2, the reduced form.
Which domains of life are classified as prokaryotes?
Bacteria and Archaea
How would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATP synthesis in glycolysis or the citric acid cycle.)
Both electron transport and ATP synthesis would stop. Oxygen plays an essential role in cellular respiration because it is the final electron acceptor for the entire process. Without O2, mitochondria are unable to oxidize the NADH and FADH2 produced in the first three steps of cellular respiration, and thus cannot make any ATP via oxidative phosphorylation. In addition, without O2 the mitochondria cannot oxidize the NADH and FADH2 back to NAD+ and FAD, which are needed as inputs to the first three stages of cellular respiration.
Which of the summary statements below describes the results of the following reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C6H12O6 is oxidized and O2 is reduced.
During osmosis, water diffuses across a selectively permeable membrane from the region of higher______ concentration and lower______ concentration to the side with lower______ concentration and higher______ concentration.
During osmosis, water diffuses across a selectively permeable membrane from the region of higher (free water) concentration and lower (solute) concentration to the side with lower (free water) concentration and higher (solute) concentration.
Which term describes the degree to which an element attracts electrons?
Electronegativity. Electronegativity is the tendency of an atom to attract electrons toward itself.
In general, enzymes are what kinds of molecules?
Enzymes are proteins.
Enzymes work by _____.
Enzymes work by reducing the energy of activation.
Which of the following is a major difference between prokaryotic cells and eukaryotic cells?
Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not.
Which of these is NOT a product of glycolysis?
FADH2 FADH2 is a product of the citric acid cycle.
NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2 to water in the final step of electron transport. However, the amount of ATP made by electrons from an NADH molecule is greater than the amount made by electrons from an FADH2 molecule. Which statement best explains why more ATP is made per molecule of NADH than per molecule of FADH2?
Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor. Electrons derived from the oxidation of FADH2 enter the electron transport chain at Complex II, farther down the chain than electrons from NADH (which enter at Complex I). This results in fewer H+ ions being pumped across the membrane for FADH2 compared to NADH, as this diagram shows. Thus, more ATP can be produced per NADH than FADH2.
Cellular locations of the four stages of cellular respiration: Glycolysis Acetyl CoA Citric acid cycle Oxidative phosphorylation
Glycolysis - Cytosol Acetyl CoA - Mitochondrial matrix Citric acid cycle - Mitochondrial matrix Oxidative phosphorylation - inner mitochondrial membrane Cellular respiration begins with glycolysis in the cytosol. Pyruvate, the product of glycolysis, then enters the mitochondrial matrix, crossing both the outer and inner membranes. Both acetyl CoA formation and the citric acid cycle take place in the matrix. The NADH and FADH2 produced during the first three stages release their electrons to the electron transport chain of oxidative phosphorylation at the inner mitochondrial membrane. The inner membrane provides the barrier that creates an H+ gradient during electron transport, which is used for ATP synthesis.
Which of the following sequences correctly represents the flow of electrons during photosynthesis?
H2O → NADPH → Calvin cycle
Gaseous hydrogen burns in the presence of oxygen to form water: 2H2 + O2 → 2H2 O + energy Which molecule is oxidized and what kind of bond is formed?
Hydrogen, polar. Hydrogen loses electrons to oxygen, which is more electronegative and thus pulls the electrons closer to itself in the water molecule.
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
Hydrolysis: involves breaking bonds with the addition of water.
Acetyl CoA Formation
In acetyl CoA formation, pyruvate (a product of glycolysis) is oxidized to acetyl CoA, with the reduction of NAD+ to NADH and the release of one molecule of CO2. Net Input: NAD⁺, coenzyme A, pyruvate Net Output: NADH, acetyl CoA, CO₂ not input or output: O₂, ADP, glucose and ATP
Oxidative Phosphorylation
In oxidative phosphorylation, the NADH and FADH2 produced by the first three stages of cellular respiration are oxidized in the electron transport chain, reducing O2 to water and recycling NAD+ and FAD back to the first three stages of cellular respiration. The electron transport reactions supply the energy to drive most of a cell's ATP production. Net Input: NADH, ADP, O₂ Net Output: NAD⁺, ATP, and Water Not Input or Output: Pyruvate, Glucose, Acetyl CoA, Coenzyme A and CO₂.
Citric Acid Cycle
In the citric acid cycle, the two carbons from the acetyl group of acetyl CoA are oxidized to two molecules of CO2, while several molecules of NAD+ are reduced to NADH and one molecule of FAD is reduced to FADH2. In addition, one molecule of ATP is produced. Net Input: Acetyl CoA, NAD⁺, ADP Net Output: Coenzyme A, CO₂, NADH, ATP Not Input or Output: Pyruvate, Glucose, O₂
What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?
Ionic. The complete transfer of an electron from lithium to fluorine results in a stable compound in which both atoms have full outermost shells.
Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane?
It exhibits specificity for a particular type of molecule.
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
It is lost to the environment.
What happens to the free energy released as electrons are passed from photosystem II to photosystem I through a series of electron carriers?
It is used to establish and maintain a proton gradient.
Which of the following describes the process of glycolysis?
It represents the first stage in the chemical oxidation of glucose by a cell. Catabolism of glucose begins with glycolysis.
Which of the following statements best describes the primary role played by oxygen in cellular respiration?
It serves as the final acceptor for electrons from the electron transport chain.
______ is the compound that functions as the electron acceptor in glycolysis.
NAD+
Which of the following statements about NAD+ is true?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is stored in the form of which of the following molecules?
NADH
The reduced form of the electron acceptor in glycolysis is______.
NADH. In the net reaction for glycolysis, glucose (the electron donor) is oxidized to pyruvate. The electrons removed from glucose are transferred to the electron acceptor, NAD+, creating NADH.
Which molecule is the final electron acceptor for electrons from photosystem I?
NADP+
The reducing power for Calvin cycle reactions is provided by which of the following molecules?
NADPH
Which of the following products of the light reactions of photosynthesis is consumed during the Calvin cycle?
NADPH. During the Calvin cycle electrons stored in NADPH are used to reduce carbon.
the net inputs and net outputs of glycolysis.
Net Input: ADP, NAD⁺, Glucose Net Output: ATP, NADH and Pyruvate, not input or output: O₂, CO₂, coenzyme A and acetyl CoA In glycolysis, the six-carbon sugar glucose is converted to two molecules of pyruvate (three carbons each), with the net production of 2 ATP and 2 NADH per glucose molecule. There is no O2 uptake or CO2 release in glycolysis.
Which of the following statements is true of the bonds in a water molecule?
Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero. The oxygen and hydrogen atoms in water have partial charges, but the molecule has a net charge of zero.
What molecule is indicated by the letter D? Cellular Respiration Diagram: the final electron acceptor.
Oxygen. Oxygen is the final electron acceptor of cellular respiration.
The figure illustrates the energy states associated with the reaction A + B ↔ C + D. Which of the following in the figure would be the same in either an enzyme-catalyzed or a noncatalyzed reaction?
The Ea after the dips on the top
Which of the following is true when comparing an uncatalyzed reaction to the same reaction with a catalyst?
The catalyzed reaction will have the same ∆G.
What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water?
The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.
he binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation? See Concept 8.4 ( page 157)
The compound is a competitive inhibitor. A competitive inhibitor slows down the enzyme by competing with the substrate for binding at the active site. Increasing substrate concentrations will reduce the effectiveness of a competitive inhibitor.
The figure illustrates the energy states associated with the reaction A + B ↔ C + D. Which of the following represents the activation energy required for the non-enzyme-catalyzed reaction in the figure?
The entire Ea for that slope
Which of the following statements about the combustion of glucose with oxygen to form water and carbon dioxide (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is correct? See Concept 8.2 ( page 147)
The entropy of the products is greater than the entropy of the reactants. A large molecule (glucose) has been converted into several smaller molecules (water and carbon dioxide); thus, the products have more disorder (greater entropy) than the reactants.
If the pores in the selectively permeable membrane became larger, but still not large enough to let the sugar pass through, what would happen during osmosis in the U-shaped tube compared to what is shown in the figure?
The final water levels would be the same as shown in the figure, but the solutions would reach near equal concentrations faster. The relative concentrations of solutes and free water on either side of the membrane determines the amount of osmosis, but the size of the pores determines how fast osmosis occurs.
Five dialysis bags, constructed of a type of membrane that is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed), and the percent change in mass of each bag was graphed. Which line in the graph represents the bag with the highest initial concentration of sucrose?
The line that has the highest increase in mass
Five dialysis bags, constructed of a type of membrane that is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed), and the percent change in mass of each bag was graphed. Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?
The line that is increasing at 50 minutes
Five dialysis bags, constructed of a type of membrane that is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed), and the percent change in mass of each bag was graphed. Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?
The line that's mass change stays at zero over time
What happens when electrons are passed from one atom to a more electronegative atom?
The more electronegative atom is reduced, and energy is released.
Which of the following statements is true for all exergonic reactions?
The reaction proceeds with a net release of free energy.
Which of the following statements is true for a system at chemical equilibrium?
The system can do no work.
Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?
The two sides of a cell membrane face different environments and carry out different functions.
If more sugar were added to the solution on the left side of the tube, what would happen to the water level on the right side of the tube?
The water level would go down. If more solute were added on the left side, it would draw more water to cluster around the solute molecules, lowering the free water on the left compared to the right side. That would cause osmosis of water toward the left side, lowering the water level on the right side.
When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane?
There is random movement of substances into and out of the cell.
Which of the following statements describes a common characteristic of catabolic pathways?
They are exergonic and provide energy that can be used to produce ATP from ADP and (P)i.
Which of the following statements about anabolic pathways is true?
They consume energy to build up polymers from monomers.
Carbon atoms in acetyl CoA formation and the citric acid cycle
This diagram of the citric acid cycle shows the carbon skeletons of each intermediate. The net result of this complex series of reactions is the complete oxidation of the two carbon atoms in the acetyl group of acetyl CoA to two molecules of CO2.
Which of these is ATP?
Three phosphate groups Ribose Adenine
In facilitated diffusion, what is the role of the transport protein?
Transport proteins provide a hydrophilic route for the solute to cross the membrane. This is the most general description of facilitated diffusion by membrane transport proteins.
Which of the following statements about the conditions shown in the U-shaped tube are true?
Water is tightly clustered around the hydrophilic solute molecules on both sides of the membrane. There is less free water in the right arm of the tube than in the left arm of the tube. Water molecules will cluster around hydrophilic solute molecules (shown as green dots), leaving less water "free" in the solution. There is more solute in the right arm of the tube, so there is less free water on that side.
The force driving simple diffusion is ________, while the energy source for active transport is ________.
a concentration gradient; ATP hydrolysis
Which of the following is an example of potential rather than kinetic energy?
a molecule of glucose
Which of the following structures would decrease the electrochemical gradient across a membrane?
a potassium channel
Which of these is exhibiting kinetic energy?
a space station orbiting Earth. Kinetic energy is energy of motion.
A series of enzymes catalyze the reactions in the metabolic pathway X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. What is substance X?
a substrate
The oxygen consumed during cellular respiration is directly involved in which of the following processes or events?
accepting electrons at the end of the electron transport chain
What is the name of the thermodynamic barrier that must be overcome before products are formed in a spontaneous reaction?
activation energy
If the concentration of phosphate in the cytosol is 2.0 mM and the concentration of phosphate in the surrounding fluid is 0.1 mM, how could the cell increase the concentration of phosphate in the cytosol?
active transport. For the cell to accumulate phosphate, it must move calcium against the concentration gradient. This process requires energy.
For a protein to be an integral membrane protein, it would have to be _____.
amphipathic, with at least one hydrophobic region
A series of enzymes catalyze the reactions in the metabolic pathway X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. With respect to the enzyme that converts X to Y, substance A functions as ________.
an allosteric inhibitor
Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes?
aquaporins
How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction?
by binding to an allosteric site, thus changing the shape of the active site of the enzyme
An animal cell lacking carbohydrates on the external surface of its plasma membrane would likely be impaired in which function?
cell-cell recognition
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
cellular respiration. This is the name given to the process by which the body converts food energy to energy stored in ATP.
A decrease in entropy is associated with which type of reaction?
dehydration
"Conservation of energy" refers to the fact that _____.
energy cannot be created or destroyed but can be converted from one form to another.
What is the correct label for "A"? The figure shows the graph of the potential energy of the reactants and products in the reaction. The potential energy of the reactants is higher than the potential energy of products. For initiation of this reaction, it is necessary to add definite amount of energy. This amount is labeled A.
energy of activation. The energy of activation must be overcome in order for a reaction to proceed.
In chemiosmosis, 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, down their electrochemical gradient
The figure illustrates the energy states associated with the reaction A + B ↔ C + D. Which of the following terms best describes the forward reaction in the figure?
exergonic, G < 0
In glycolysis, the carbon-containing compound that functions as the electron donor is ______.
glucose
Which of the following sequences describes the path by which electrons travel downhill energetically in aerobic respiration?
glucose → NADH → electron transport chain → oxygen
Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?
glycolysis and fermentation
What process occurs in Box A? Glucose->>>Pyruvate
glycolysis. Glycolysis occurs in the cytosol.
Identify Structure A. Structure A is composed of both a carbohydrate and a protein.
glycoprotein
Which of these are by-products of cellular respiration?
heat, carbon dioxide, and water
Endocytosis moves materials _____ a cell via _____.
into ... membranous vesicles. The prefix "endo-" means "inward."
An enzyme _____.
is an organic catalyst. Enzymes are proteins that behave as catalysts.
Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water_____.
is hypotonic and the salt solution is hypertonic to the cells of the celery stalks
As a result of its involvement in a reaction, an enzyme _____.
is unchanged Enzymes are not changed as a result of their participation in a reaction.
The overall function of the Calvin cycle is _____.
making sugar. Using the ATP and NADPH made during the light reactions, carbon is reduced in the Calvin cycle and sugar is made.
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
Energy released by the electron transport chain is used to pump H+ ions into which location in eukaryotic cells?
mitochondrial intermembrane space
Which structure is common to plant and animal cells?
mitochondrion
Which of the following membrane activities requires energy from ATP hydrolysis?
movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid.
Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation?
oxidation of NADH to NAD+
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
When a compound donates (loses) electrons, that compound becomes ______. Such a compound is often referred to as an electron donor.
oxidized
Which of the following is a product of the light reactions of photosynthesis?
oxygen, ATP, and NADPH
Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?
peripheral membrane proteins
A white blood cell engulfing a bacterium is an example of _____.
phagocytosis. Phagocytosis occurs when a cell engulfs a large particle.
Identify Structure D.
phospholipid bilayer of membrane. Phospholipids can be recognized by the presence of a head and two tails.
The difference between pinocytosis and receptor-mediated endocytosis is that _____.
pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.
Chemical energy is a form of _____ energy.
potential. Chemical energy is a form of stored energy.
Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called ______.
pyruvate
Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions
pyruvate, ATP, and NADH. ATP is the main product of cellular respiration that contains energy that can be used by other cellular processes. Some ATP is made in glycolysis. In addition, the NADH and pyruvate produced in glycolysis are used in subsequent steps of cellular respiration to make even more ATP.
When a compound accepts (gains) electrons, that compound becomes ______. Such a compound is often referred to as an electron acceptor.
reduced
When the protein gramicidin is integrated into a membrane, an H+ channel forms and the membrane becomes very permeable to protons (H+ ions). If gramicidin is added to an actively respiring muscle cell, how would it affect the rates of electron transport, proton pumping, and ATP synthesis in oxidative phosphorylation? (Assume that gramicidin does not affect the production of NADH and FADH2 during the early stages of cellular respiration.) Sort the labels into the correct bin according to the effect that gramicidin would have on each process.
remains the same: proton pumping rate, electron transport rate, rate of oxygen uptake. decreases or goes to zero: rate of ATP synthesis, size of protein gradient. Gramicidin causes membranes to become very leaky to protons, so that a proton gradient cannot be maintained and ATP synthesis stops. However, the leakiness of the membrane has no effect on the ability of electron transport to pump protons. Thus, the rates of proton pumping, electron transport, and oxygen uptake remain unchanged.
Which of the following are found in plant, animal, and bacterial cells?
ribosomes
What kinds of molecules pass through a cell membrane most easily?
small and hydrophobic
Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane?
small ions
When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by _____.
splitting water. The electrons removed from water are transferred to P680.
What is the function of Structure E? (cholesterol)
stabilization of the phospholipids. Cholesterol helps to stabilize the structure of the plasma membrane.
Where in a plant cell does the Calvin cycle take place?
stroma of the chloroplast
In mitochondria, an electron transport chain pumps protons from the matrix into the intermembrane space, whereas in chloroplasts, an electron transport chain pumps protons from the ________.
stroma to the thylakoid space
What name is given to the reactants in an enzymatically catalyzed reaction?
substrate
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation. A phosphate group is transferred from glyceraldehyde phosphate to ADP.
Which of the following processes would be most directly affected if a thylakoid membrane is punctured so that the interior of the thylakoid is no longer separated from the stroma?
synthesis of ATP
You can recognize the process of pinocytosis when _____.
the cell is engulfing extracellular fluid. Pinocytosis is "cell drinking."
What process occurs within Box B? Cellular Respiration Diagram: circular cycle
the citric acid cycle. The citric acid cycle transfers electrons to NADH and FADH2.
Which of the following events takes place in the electron transport chain?
the harnessing of energy from high-energy electrons derived from glycolysis and the citric acid cycle
Where are ATP synthase complexes located in plant cells?
thylakoid membrane and inner mitochondrial membrane
In mitochondrial electron transport, what is the direct role of O2?
to function as the final electron acceptor in the electron transport chain. The only place that O2 participates in cellular respiration is at the end of the electron transport chain, as the final electron acceptor. Oxygen's high affinity for electrons ensures its success in this role. Its contributions to driving electron transport, forming a proton gradient, and synthesizing ATP are all indirect effects of its role as the terminal electron acceptor.
In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?
two ATP. Four ATP are made, but two ATP are consumed to start the process of glycolysis.
In glycolysis, for each molecule of glucose oxidized to pyruvate, ________.
two molecules of ATP are used, and four molecules of ATP are produced
