bio ch 7&8
Of the metabolic pathways listed below, which is the only pathway found in all organisms?
Ancient prokaryotes probably used glycolysis to make ATP long before oxygen was present in Earth's atmosphere. Glycolysis is the most widespread metabolic pathway.
The enzyme rubisco plays a critical role in carbon fixation in which of the following types of plants?
C3 plants only
Which of the following statements is an accurate comparison of C3 and C4 plants
C4 plants can continue to fix CO2 even at relatively low CO2 concentrations and high oxygen concentrations, whereas C3 plants cannot.
Which part of the catabolism of glucose by cellular respiration requires molecular oxygen (O2) and produces CO2?
CO2 is produced in the citric acid cycle, and O2 is taken up in electron transport.
Which of the following statements correctly summarizes a redox reaction that occurs in photosynthesis?
CO2 is reduced to form glucose.
After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of __________.
NADH -cycle produces 3 NADH per turn of the cycle
Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?
Electrons are 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 molecules donates electrons directly to the electron transport chain at the highest energy level?
NADH
In preparing pyruvate to enter the citric acid cycle, which step occurs?
Pyruvate is oxidized and decarboxylated, and the removed electrons are used to reduce an NAD+ to an NADH.
If plants are grown with H2O containing a radioactive isotope of oxygen (18O), subsequent analysis will show that 18O first appears in which of the following molecules produced by the plants?
O2
Photorespiration occurs when rubisco combines RuBP with which of the following molecules?
O2
Why is glycolysis described as having an energy investment phase and an energy payoff phase?
early steps consume energy from ATP, and later steps store an increased amount of energy in ATP and NADH.
Under anaerobic conditions, what carbon sources can be metabolized by yeast cells to produce ATP from ADP?
glucose
Which catabolic processes may have been used by cells on ancient Earth before free oxygen became available?
glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation, using an electron acceptor other than oxygen
The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Halobacterium has a photosynthetic membrane that appears purple. Its photosynthetic action spectrum is the inverse of the action spectrum for green plants. (That is, the Halobacterium action spectrum has a peak where the green plant action spectrum has a trough.) What wavelengths of light do the Halobacterium photosynthetic pigments absorb?
green & yellow
Which process is the one in which glucose is oxidized to generate two molecules of pyruvate, and in which ATP and NADH are produced?
gylcolysis
The function of cellular respiration is to _____
harvest usable energy from glucose
Which of the following indicates a primary path by which electrons travel downhill energetically during aerobic respiration?
glucose →→ NADH →→ electron transport chain →→ oxygen
In the overall process of glycolysis and cellular respiration, __________ is oxidized and __________ is reduced
glucose... oxygen
Which is a correct description of the events of cellular respiration and the sequence of events in cellular respiration?
oxidation of glucose to pyruvate; oxidation of pyruvate; oxidation of acetyl-coA; oxidative phosphorylation
Which of the following metabolic pathways occur(s) in mitochondria?
oxidation of pyruvate to acetyl CoA and the citric acid cycle
Most of the ATP produced in cellular respiration comes from which of the following processes?
oxidative phosphorylation
Which of the following metabolic pathways requires a proton gradient?
oxidative phosphorylation
Which of the following metabolic processes produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis)
Photophosphorylation in photosynthesis is most similar to which of the following processes associated with cellular respiration?
oxidative phosphorylation in mitochondria
During the reaction C6H12O6 + 6 O2 → 6 CO2 + 6 H2O, which compound is reduced as a result of the reaction?
oxygen
Where do the reactions of the citric acid cycle occur in eukaryotic cells?
the matrix of the mitochondrion
Which of the following describes the result of transferring an electron from a less electronegative atom to a more electronegative atom?
the more electronegative atom is reduced, and energy is released
Where are electron transport chains that are responsible for ATP production located in plant cells?
in the thylakoid and inner mitochondrial membranes
C4 plants occur more commonly in desert conditions because __________.
-They can fix carbon at the lower CO2 concentrations that develop when the stomata are fully or partially closed. -To conserve water during hot, dry conditions, the stomata are fully or partially closed, preventing CO2 from reaching high concentrations.
Which is the source of the energy that produces the chemiosmotic gradient in mitochondria?
-electrons moving down the electron transport chain
Which represent the major (but not the only) energy accomplishment of the citric acid cycle?
-formation of NADH and FADH2 -each turn of the cycle releases carbon dioxide, forms one ATP by oxidative phosphorylation, and passes electrons to 3 NAD+ and one FAD
Most of the electrons removed from glucose by cellular respiration are used for which process?
-reducing NAD+ to NADH in glycolysis and the citric acid cycle -producing a proton gradient for ATP synthesis in the mitochondria
If a compound that allows protons to freely diffuse across membranes is added to cells that are actively metabolizing glucose via cellular respiration, which following process would stop?
-the chemiosmotic synthesis of ATP would stop in the mitochondria -substrate-level phosphorylation could continue
Approximately what percentage of the ATP formed by the electron transport chain is produced by substrate-level phosphorylation?
0%
In the citric acid cycle, how many ATP molecules can be made through substrate-level phosphorylation?
1
Assuming glucose is the only energy source for a cell, what fraction of the carbon dioxide produced by aerobic respiration is generated by the oxidation of pyruvate to acetyl CoA?
1/3
Approximately what percentage of the ATP formed by the reactions of glycolysis is produced by substrate-level phosphorylation?
100%
How many carbon atoms from one molecule of pyruvate enter the citric acid cycle?
2
Assuming glucose is the only energy source for a cell, what fraction of the carbon dioxide produced by aerobic respiration is generated by the reactions of the citric acid cycle?
2/3
Catabolism of each molecule of glucose in glycolysis is associated with a net consumption of which of the following other molecules?
2 NAD+ and 2 ADP
Which of the following correctly lists all of the energy-containing molecules produced by the catabolism of one molecule of glucose in glycolysis?
2 NADH, 2 pyruvate, and 2 ATP
For each mole of glucose (C6H12O6) completely oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle?
4
In the complete oxidation of a molecule of glucose (C6H12O6) in aerobic cellular respiration, how many molecules of ATP are produced by substrate-level phosphorylation?
4
Cellular respiration in plant cell mitochondria consumes approximately what proportion of the organic molecules produced by photosynthesis?
50%
For each molecule of glucose that is catabolized in glycolysis and the citric acid cycle, how many NADH molecules are produced?
8
fermentation
A catabolic process that makes a limited amount of ATP from glucose (or other organic molecules) without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.
ATP synthase,
A complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP. ATP synthases are found in the inner mitochondrial membranes of eukaryotic cells and in the plasma membranes of prokaryotes.
Which substance is/are involved in oxidative phosphorylation?
ADP is converted to ATP _____, and oxygen functions as the terminal electron acceptor in ______
Brown fat cells produce a protein called thermogenin in their mitochondrial inner membrane. Thermogenin is an ion channel that facilitates diffusion of protons across the membrane. What will occur in the brown fat cells when thermogenin is present in their inner mitochondrial membranes?
ATP synthesis will decrease, and heat generation will increase
Yeast cells grown anaerobically can obtain energy by fermentation, which results in the production of
ATP, CO2, and ethanol.
Which best describes the electron transport chain?
Electrons are passed from one carrier to another, releasing a little energy at each step. -NADH and FADH2deliver electrons from the breakdown products of glycolysis and the citric acid cycle to the electron transport chain, which passes these electrons from one molecule to another, releasing a small amount of energy at each step.
Which of the following statements correctly describes a reaction associated with photosystem II?
Electrons released from the P680 chlorophyll are replaced by electrons derived from water.
Which of the following molecules donates electrons directly to the electron transport chain at the lowest energy level?
FADH2 -NADH does too, but FADH2 is lower in energy
A young dog has never had much energy. A veterinarian discovers that the dog's mitochondria can use only fatty acids and amino acids for cellular respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of the dog's condition?
His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.
Muscle tissues make lactate from pyruvate to do what?
Human muscle cells make ATP by lactic acid fermentation when oxygen is scarce. This allows them to regenerate NAD+ so that glycolysis can continue.
Sports physiologists at an Olympic training center wanted to monitor athletes to determine at what point their muscles were functioning anaerobically. They could have done this by checking for a buildup of which compound?
In humans, muscle cells switch to lactate fermentation after becoming anaerobic.
Upon completion of glycolysis, what is the fate of the majority of the potential energy contained in the original glucose molecule?
It is retained in two pyruvate molecules.
A man interested in losing weight and increasing his fitness followed a strict diet and exercise regimen for three months. Body fat analysis indicated that the man had lost 7 kg (about 15 pounds) of fat by following this exercise and diet program. What is the most likely form by which the fat left his body?
It was released as CO2 and H2O.
If muscle cells in the human body consume O2 faster than it can be supplied, what is likely to result?
Muscle cells would not be able to produce enough ATP to meet demands, oxidative phosphorylation would stop, and muscle cells would consume glucose at an increased rate.
Some photosynthetic bacteria (e.g., purple sulfur bacteria) have only photosystem I, whereas others (e.g., cyanobacteria) have both photosystem I and photosystem II. No photosynthetic bacteria have only photosystem II. Which of the following might be a possible explanation for this observation?
Photosynthesis with only photosystem I is more ancestral.
Which statement is the best explanation of what happens to the temperature and carbon dioxide concentration during a one-hour class period in a classroom of 300 students if the heating and air conditioning is turned off and all doors are kept closed?
Temperature and the level of carbon dioxide rise as heat and carbon dioxide are by-products of cellular respiration.
In glycolysis in the absence of oxygen, cells need a way to regenerate which compound?
The NAD+ needs to be regenerated, which is why ethanol or lactate is formed.
A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights, which are set to cycle between 12 hours of light and 12 hours of dark. The dissolved oxygen concentrations in both flasks are monitored. Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask.
The concentration of dissolved oxygen in the flask with algae will be higher in the light but lower in the dark.
Which of the following statements is not true of most cellular redox reactions?
The electron acceptor is reduced, acting as a reducing agent.
substrate-level phosphorylation
The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.
Why is the citric acid cycle called a cycle?
The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle.
The pH of the inner thylakoid space has been measured, as have the pH of the stroma and of the cytosol of a particular plant cell. Which of the following relationships would you expect to find when the cell is examined in the light?
The pH within the thylakoid is lower than that of the stroma.
oxidative phosphorylation
The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration.
In glycolysis, there is no production of carbon dioxide as a product of the pathway. Which is the best explanation for this?
The products of glycolysis contain the same total number of carbon atoms as in the starting material.
Which one of the following statements about the redox reactions of the electron transport chain is correct?
The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane.
Carotenoids are found in several foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?
They absorb and dissipate excess light energy that might otherwise react with oxygen to form harmful oxidative molecules.
Why are C4 plants able to photosynthesize with no apparent photorespiration?
They do not use rubisco to fix CO2.
How would you predict that doubling the atmospheric CO2 concentration would affect C3 plants?
They will experience increased rates of photosynthesis and growth.
Which of the following statements correctly describes how ATP is involved in the oxidation of one molecule of glucose in glycolysis?
Two molecules of ATP are used, and four molecules of ATP are produced
In the complete reactions of aerobic respiration, the energy for most of the ATP produced is provided by
a proton gradient across a membrane
In the presence of oxygen, the pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, (2) is oxidized to form a two-carbon compound, which (3) is covalently bound to coenzyme A. These three steps result in the formation of
acetyl CoA, NADH, H+, and CO
When protein molecules are used as fuel for cellular respiration, __________ are produced as waste.
amino groups
During aerobic respiration, molecular oxygen (O2) is used for which of the following purposes?
at the end of the electron transport chain to accept electrons and form H2O
Which of the following metabolic pathways produce(s) reduced soluble electron carriers?
both the light reactions of photosynthesis and the citric acid cycle
Use the figure and the compounds labeled A, B, C, D, and E to answer the following question. Which molecule in the Calvin cycle also serves as the substrate for the first step in the energy payoff phase of glycolysis?
c
Which of the following metabolic processes consume(s) CO2?
calvin cycle only
During intense exercise, as human muscle cells switch from respiration to fermentation, the cells will increase their catabolism of which of the following energy-containing molecules?
carbohydrates only
In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and after a few minutes radioactive oxygen atoms showed up in __________.
carbon dioxide
Which of the following reactions reduce(s) oxygen to form water?
cellular respieration only.
The Calvin cycle in a culture of algae grown in the light utilizes approximately 30,000 molecules of ATP but only 20,000 molecules of NADPH per hour. What is the source of the extra ATP utilized?
cyclic electron flow
Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step __________.
enables the cell to recycle the reduced NADH to oxidized NAD+
Chemiosmosis in chloroplasts involves which of the following processes?
establishment of a proton gradient across the thylakoid membrane
How many molecules of ATP are gained by substrate-level phosphorylation from the complete breakdown of a single molecule of glucose in the presence of oxygen?
four. -net gain of 2 ATP from glycolysis & one per each molecule of acetyl CoA oxidized in the citric acid cycle for a total of 4 per glucose
In mitochondria, the electron transport chain pumps protons from the matrix into the intermembrane space. In what direction are protons pumped by the electron transport chain in chloroplasts?
from the stroma to the thylakoid space
In chemiosmosis in mitochondria, protons flow from the intermembrane space into the matrix. In what direction do protons flow during chemiosmosis in chloroplasts?
from the thylakoid space to into the stroma
During respiration in eukaryotic cells, the electron transport chain is located in or on the __________.
inner membrane of the mitochondrion
An organism is discovered that thrives in both the presence and absence of oxygen. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight. This organism
is a facultative anaerobe.
As a result of an oxidation-reduction reaction, how is the oxidizing agent changed?
it gains electrons and gains potential energy
Which of the following statements is true for a molecule that is phosphorylated?
it has increased chemical potential energy that may be used to do cellular work
Each ATP molecule contains about 1% of the amount of chemical energy available from the complete oxidation of a single glucose molecule. Cellular respiration produces about 32 ATP from one glucose molecule. What happens to the rest of the energy in glucose?
it is converted to heat
In an oxidation-reduction reaction, how is the reducing agent changed?
it loses electrons and loses potential energy
Why does photorespiration decrease the efficiency of photosynthesis?
it reduces the amount of sugar produced
A molecule becomes more oxidized when it
loses an electron
Which organelles or organisms are capable of synthesizing ATP using energy from chemiosmosis?
mitochondria, chloroplasts, and bacteria that generate proton gradients across their plasma membranes
Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
mitochondrial intermembrane space
The oxygen atoms used to form water in the complete reactions of cellular respiration are derived from which of the following molecules?
molecular oxygen O2
How would you predict that blocking the oxidation of pyruvate would affect the levels of oxaloacetate and citrate in the citric acid cycle
oxaloacetate will accumulate, and citrate will decrease
The NADPH required for the Calvin cycle is produced by which of the following metabolic reactions?
reactions initiated in photosystem I
What is the source of the energy used to generate the proton gradient across the inner mitochondrial membrane?
redox reactions in the electron transport chain
During alcohol fermentation in yeast, NAD+ is regenerated from NADH by which of the following processes?
reduction of acetaldehyde to ethanol
An early step in the process of carbon fixation combines three molecules of CO2 with three molecules of RuBP to produce three 6-carbon molecules, which are immediately converted to six 3-carbon molecules. These six molecules are phosphorylated and reduced to produce glyceraldehyde 3-phosphate (G3P). What additional events occur to complete the Calvin cycle?
release of one G3P to make sugars and regeneration of RuBP
When plants produce excess carbohydrates, the extra sugar is generally stored in which of the following forms?
starch
Which of the following processes is responsible for the ATP made during fermentation?
substrate level phosphorylation
Which chemical process generates the ATP produced in glycolysis?
substrate-level phosphorylation
Which chemical process generates the ATP produced in the citric acid cycle?
substrate-level phosphorylation
In most plants the carbohydrates produced by photosynthesis are transported out of the leaves to the rest of the plant as which of the following molecules?
sucrose
Most of the NADH that delivers electrons to the electron transport chain comes from which process?
the citric acid cycle
Where do the reactions of glycolysis occur in a eukaryotic cell?
the cytosol
Which of the following situations results from the transfer of an electron to a more electronegative atom?
the electron loses potential energy
If plants are grown in the light with CO2 containing a radioactive isotope of oxygen (18O), subsequent analysis will show that 18O incorporated in organic molecules first appears in
the stroma
Where are ATP synthase complexes located in a plant cell?
thylakoid membranes and inner mitochondrial membranes
What is the primary function of the Calvin cycle?
to produce simple sugars from carbon dioxide.
Theodor W. Engelmann illuminated a filament of algae with light that passed through a prism, thus exposing different segments of algae to different wavelengths of light. He added aerobic bacteria and then noted in which areas the bacteria congregated. He found that the largest groups were found in the areas illuminated by the red and blue light. This experiment helped to determine the relationship between which of the following parameters?
wavelengths of light and the rate of photosynthesis
Carbon skeletons for amino acid biosynthesis are supplied by intermediates of the citric acid cycle (see the figure). Which intermediate would you predict may directly supply the carbon skeleton for synthesis of a five-carbon amino acid?
α-ketoglutarate
