Mastering Bio: Chapter 10
_____ splits water into 1/2 O2, H+, and e- .
A
Chlorophyll can be found in _____.
A & C
For each intermediate compound in the Calvin cycle, identify the number of molecules of that intermediate and the total number of carbon atoms contained in those molecules.
A: 3 molecules, 3 carbons B: 6 molecules, 18 carbons C: 6 molecules, 18 carbons D: 5 molecules, 15 carbons E: 3 molecules, 15 carbons F: 3 molecules, 15 carbons
_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.
B
Energized electrons from ____ are used to reduce NADP+.
C
What is the basic role of CO2 in photosynthesis?
CO2 is fixed or incorporated into organic molecules.
The electrons derived from this oxidation reaction in the Calvin cycle are used to reduce _______ to _______
CO2 to G3P
Some photosynthetic organisms contain chloroplasts that lack photosystem II, yet are able to survive. Which of the following approaches would be the best way to detect the lack of photosystem II in these organisms?
Determine whether they produce O2 in the light.
what is the correct order of electron flow in the light reactions of photosynthesis?
H2O → P680 chlorophyll a pair → PS II primary electron acceptor → Pq → cytochrome complex → Pc → P700 chlorophyll a pair → PS I primary electron acceptor → Fd → NADPH
According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?
Proton gradient
most accurate statement describing the basic function of the light reactions of photosynthesis.
The basic function of the light reactions of photosynthesis is the conversion of solar energy to chemical energy.
Which best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?
The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.
What is the relationship between the wavelength of light and the quantity of energy per photon?
They are inversely related.
How many electrons at a time are passed between the pigment molecules in the light-harvesting complexes?
0
Approximately what wavelength of light is best absorbed by chlorophyll a, the pigment that participates directly in the light reactions?
435nm
Which wavelength of light is best absorbed by chlorophyll b?
455nm
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
6
Which of these equations best summarizes photosynthesis?
6 CO2 + 6 H2O → C6H12O6 + 6 O2
If photosynthesizing green algae are provided with CO2 containing heavy oxygen (18O), which of the following molecules produced by the algae (refer to the accompanying figure) will fail to contain 18O in later biochemical analyses?
ADP
What are the products of linear electron flow during the light reactions of photosynthesis?
ATP and NADPH
Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5 . The solution is then adjusted to pH 8 . What can be concluded from these experimental conditions?
ATP will not be produced because there is no ADP and inorganic phosphate in the solution.
Which of the following statements correctly describes a distinction between autotrophs and heterotrophs?
Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.
Which of these phosphorylates ADP to make ATP?
E
Why is it correct to say that the linear electron flow of the light reactions directly captures energy in NADPH but only indirectly captures energy in ATP?
Electrons are directly transferred to NADP+ to form NADPH, but electron flow is used to generate a proton gradient for ATP synthesis. Electrons are not directly transferred to ATP.
True or false? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain.
False
molecule that is the main product of the Calvin cycle.
G3P
n the light reactions, light energy is used to oxidize ______ to _______
H2O to O2
What sequence represents the flow of electrons during photosynthesis?
H2O → NADPH → Calvin cycle
Can you deduce the logical link between light of different wavelengths and the distribution of bacteria that Engelmann observed?
In this experiment, Engelmann was able to determine which wavelengths (colors) of light are most effective at driving photosynthesis. First, Engelmann used a prism to disperse white light from the sun into the colors (wavelengths) of the visible spectrum. Then, using a microscope, he illuminated a filament of green algae with the visible spectrum. The photosynthetic pigments in the alga absorbed some of the wavelengths of light, using the absorbed energy to drive the reactions of photosynthesis, including oxygen production. Engelmann used his recently discovered aerotactic bacteria to determine which wavelengths of light caused the alga to photosynthesize most. Because the aerotactic bacteria were attracted to areas of highest oxygen concentration, they congregated around the regions of the alga that photosynthesized the most. He then counted the bacteria associated with each region of the alga illuminated by the various colors of light. Engelmann found that some wavelengths of light attracted more bacteria, suggesting that these wavelengths drive more photosynthesis than others.
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.
P680+ is said to be the strongest biological oxidizing agent. Given its function, why is this necessary?
It obtains electrons from the oxygen atom in a water molecule, so it must have a stronger attraction for electrons than oxygen has.
Which molecule is the final electron acceptor for electrons from photosystem I?
NADP+
The electrons derived from this oxidation reaction in the light reactions are used to reduce ______ to _______
NADP+ to NADPH
After 3-PGA is phosphorylated, it is reduced by _____.
NADPH
The reducing power for Calvin cycle reactions is provided by which of the following molecules?
NADPH
Which molecule is the primary product of photosystem I?
NADPH
3. The Calvin cycle oxidizes the light-reactions product ______ to _______.
NADPH to NADP+
If the Calvin cycle slows down, what will happen to the rate of O2 production in PS II, and why?
O2 production will slow down because less NADP+ will be regenerated in the Calvin cycle.
Can you tell from these absorption spectra whether red light is effective in driving photosynthesis?
One cannot tell from this graph, but because chlorophyll a does absorb red light, we can predict that it would be effective in driving photosynthesis.
In autumn, chlorophyll is degraded in the leaves of deciduous trees. Why do the leaves change color to shades of yellow, orange, or red?
Other pigments such as carotenoids are still present in the leaves.
Which term describes ATP production resulting from the capture of light energy by chlorophyll?
Photophosphorylation
Under what conditions do photosynthesis and cellular respiration occur in most plants?
Photosynthesis occurs only in the light, and cellular respiration occurs in both the dark and the light.
Why are plants classified as producers?
Plants are classified as producers because they fix inorganic carbon into organic molecules.
Which particle can pass through the ATP synthase channel?
Protons
_____ has a longer wavelength than _____.
Red ... green
Carbon fixation involves the addition of carbon dioxide to _____.
RuBP
Which molecule is regenerated in the regeneration phase of the Calvin cycle? Without regeneration of this molecule, the Calvin cycle would stop.
RuBP
To identify the molecule that accepts CO2, Calvin and Benson manipulated the carbon-fixation cycle by either cutting off CO2 or cutting off light from cultures of photosynthetic algae. They then measured the concentrations of various metabolites immediately following the manipulation. How would these experiments help identify the CO2 acceptor?
The CO2 acceptor concentration would increase when the CO2 is cut off, but decrease when the light is cut off.
What assumptions did Engelmann make in order to conclude that red and violet-blue light were more effective than green light in driving photosynthesis?
The distribution of chloroplasts within each algal cell was approximately the same.
When a pigment molecule in a light-harvesting complex absorbs a photon of light, what happens to its excited-state electron?
The electron falls back to its ground state, while passing its excited-state energy to an electron in a nearby pigment molecule.
If only chlorophyll a were involved in the light reactions, would blue light (wavelength about 490 nm) be effective in driving photosynthesis?
The graph indicates that chlorophyll a absorbs very little blue light, so we can predict that blue light would not be effective.
What is the importance of the light-independent reactions in terms of carbon flow in the biosphere?
The light-independent reactions turn CO2, a gas, into usable carbon in the form of sugars.
Which of the following events are associated with chemiosmosis in chloroplasts?
The pH of the thylakoid space increases and ATP is synthesized.
The rate of O2 production by the light reactions varies with the intensity of light because light is required as the energy source for O2 formation. Thus, lower light levels generally mean a lower rate of O2 production. In addition, lower light levels also affect the rate of CO2 uptake by the Calvin cycle. This is because the Calvin cycle needs the ATP and NADPH produced by the light reactions. In this way, the Calvin cycle depends on the light reactions. But is the inverse true as well? Do the light reactions depend on the Calvin cycle? Suppose that the concentration of CO2 available for the Calvin cycle decreased by 50% (because the stomata closed to conserve water). Which statement correctly describes how O2 production would be affected?
The rate of O2 production would decrease because the rate of ADP and NADP+ production by the Calvin cycle would decrease.
An action spectrum plots the rate of photosynthesis at various wavelengths of visible light, and it shows that blue light with a wavelength of about 490 nm is effective in driving photosynthesis. Based on this information and the absorption spectra shown at left, what role may chlorophyll b and carotenoids play in photosynthesis?
These pigments are able to absorb more wavelengths of light (and thus more energy) than chlorophyll a alone can absorb. As part of light-harvesting complexes in photosystems, they broaden the range of light that can be used in the light reactions.
What is the function of the pigment molecules in a light-harvesting complex in the thylakoid membranes?
They absorb and transfer light energy to the reaction-center chlorophyll.
You obtain the pigments called carotenoids in your diet when you eat carrots. Why do carotenoids appear yellow and orange?
They absorb blue/green light and reflect yellow and red wavelengths of light.
What is the biological significance of the light-independent reactions of photosynthesis?
They convert carbon dioxide to sugar.
Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. What related function do they have in plants?
They protect against oxidative damage from excessive light energy.
Why are the reaction centers of photosystems composed of several structurally different pigments?
This arrangement enables the plant to absorb light energy of a variety of wavelengths.
A spaceship is designed to support animal life for a multiyear voyage to the outer planets of the solar system. Plants will be grown to provide oxygen and to recycle carbon dioxide. Since the spaceship will be too far from the sun for photosynthesis, an artificial light source will be needed. What wavelengths of light should be used to maximize plant growth with a minimum of energy expenditure?
a mixture of blue and red light
phases of Calvin cycle
carbon fixation, reduction, and regeneration of RuBP.
P700 to Fd (ferredoxin)
energy input required
P680 to Pq (plastoquinone)
energy light required
thylakoid space
f
True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.
false
Halobacterium has a photosynthetic membrane that appears purple. Its photosynthetic action spectrum is the inverse of the action spectrum for green plants (see figure). 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 and yellow
In which of the following organisms did the process of photosynthesis most likely originate?
in prokaryotes
dentify those that are the inputs and outputs of the Calvin cycle.
input: CO2, NADPH, ATP output: G3P, ADP, NAD+ not input or output: O2, Light, Glucose
identify those that are the inputs and outputs of the light reactions.
input: Light,Water,NAD+, ADP output: O2, ATP, NADPH not input or output: Glucose, CO2, G3P.
Which set of reactions uses H2O and produces O2?
light dependent reactions
Carbon dioxide is split to form oxygen gas and carbon compounds in which of the following metabolic pathways?
neither photosynthesis nor respiration
Fd to NADP+
no energy input required
Pq to P700+
no energy input required
water to p680+
no energy input required
photosystem II (PS II)
oxidation of water reduction of electron transport chain between the two photosystems
The mechanism of photophosphorylation is most similar to which of the following processes?
oxidative phosphorylation in cellular respiration
Which process produces oxygen?
photosynthesis
In photosynthetic cells, synthesis of ATP by chemiosmosis occurs during ________.
photosynthesis and respiration
photosystem I (PS I) only
reduction of NADP+ oxidation of electron transport chain between the two photosystems
both PS II and PS I
reduction of primary electron acceptor light absorption
Which of the following processes is most directly driven by light energy?
removal of electrons from chlorophyll molecules
The oxygen released by photosynthesis is produced by which of the following processes?
splitting water molecules
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
In a plant, which of the following reactions produce molecular oxygen (O2)?
the light reactions alone
Where are ATP synthase complexes located in plant cells?
thylakoid membrane and inner mitochondrial membrane
True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.
true
The light reactions of photosynthesis use _____ and produce _____.
water ... NADPH
For every molecule of O2 that is released by photosystem II, ____ H2O molecules are needed, which together pass ____ electrons to the PS II reaction-center complex.
2, 4
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
3
stroma
3
What wavelength of light in the figure is most effective in driving photosynthesis?
420nm