Mastering Bio- Chapter 8
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
True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.
False
Select the correct molecule that is the main product of the Calvin cycle.
G3P
Which of the following sequences correctly represents the flow of electrons during photosynthesis
H2O → NADPH → Calvin cycle
Which of the following 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
In the light reactions, light energy is used to oxidize ___________ to ___________
H2O, O2; In the light reactions, light energy is used to remove electrons from (oxidize) water, producing O2 gas.
Through the process of photosynthesis, plants are extremely efficient in turning solar energy into energy they can use. Why is attempting to match nature's efficiency in harvesting and storing solar energy beneficial to us?
Harvesting and storing solar energy, a renewable energy source, can reduce CO2 in the atmosphere since the water-splitting stage of photosynthesis requires CO2.
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.
Energized electrons from ____ are used to reduce NADP+.
PS1
_____ splits water into 1/2 O2, H+, and e- .
PS2
Which term describes ATP production resulting from the capture of light energy by chlorophyll?
Photophosphorylation
Which process produces oxygen
Photosynthesis
____ has a longer wavelength than _____.
Red ... green Red has a longer wavelength than green.
Reddish-pink color of these algae is due to presence of 1 pigments, which absorb blue light, while reflecting 2 light. Those pigments protect the chloroplast from intense 3 light and also 4 radiation, as well as absorbing 5 , which provides the alga with liquid water as the snow melts around it.
Reddish-pink color of these algae is due to presence of carotenoid pigments, which absorb blue light, while reflecting red light. Those pigments protect the chloroplast from intense blue light and also ultraviolet radiation, as well as absorbing heat, which provides the alga with liquid water as the snow melts around it.
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
Select the correct statement about the Calvin cycle.
The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of RuBP.
Select the 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.
C4 plants differ from C3 and CAM plants in that C4 plants _____.
transfer fixed carbon dioxide to cells in which the Calvin cycle occurs
In the electromagnetic spectrum, the type of radiation that we call visible light occurs between _____.
ultraviolet radiation and infrared radiation
The light reactions of photosynthesis use _____ and produce _____.
water, NADPH
Chlorophyll can be found in _____.
A and C
The light reactions of photosynthesis supply the Calvin cycle with
ATP and NADPH
Which of these phosphorylates ADP to make ATP?
ATP synthase
Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5 . The solution is then adjusted to pH 8 . Which of the following conclusions can be drawn from these experimental conditions?
ATP will not be produced because there is no ADP and inorganic phosphate in the solution.
Photosystem 1 only
oxidation of water reduction of electron transport chain between the two photosystems
In mechanism, photophosphorylation is most similar to
oxidative phosphorylation in cellular respiration
Photosynthesis is a redox reaction. H2O is _____ during the light reactions and CO2 is _____ during the Calvin cycle.
oxidized...reduced
Which of the following is(are) produced by the light reactions of photosynthesis?
oxygen, ATP, and NADPH
In C3 plants the conservation of water promotes
photorespiration
According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?
proton gradient
Which of the following particles can pass through the ATP synthase channel?
protons
Photosystem I (PS I) only
reduction of NADP+ oxidation of electron transport chain between the two photosystems
Which of the following does NOT occur during the Calvin cycle?
release of oxygen
Where does the Calvin cycle occur?
stroma
The ultimate source of energy to support most life on Earth is _____.
sunlight
Inputs and outputs of the light reactions
- input: light, water, NADP+, ADP - output: O2, ATP, NADPH - not input or output: glucose, CO2,G3P
Why are plants classified as producers? -Plants are classified as producers because they are at the bottom of the food chain. -Plants are classified as producers because they produce oxygen. -Plants are classified as producers because they fix inorganic carbon into organic molecules.
-Plants are classified as producers because they fix inorganic carbon into organic molecules.
How many electrons at a time are passed between the pigment molecules in the light-harvesting complexes?
0
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
2
Approximately what wavelength of light is best absorbed by chlorophyll a, the pigment that participates directly in the light reactions?
435
Which wavelength of light is best absorbed by chlorophyll b
455
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
Identify the chloroplast.
A
The electrons derived from this oxidation reaction in the Calvin cycle are used to reduce __ to __.
CO2, G3P;The electrons released by the oxidation of NADPH are used to reduce three molecules of CO2 to sugar (G3P), which then exits the Calvin cycle.
In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells.
CYTOPLASM
Identify a thylakoid.
D (coin looking objects)
Identify the stroma
E (space between thylakoid and membrane)
How is photosynthesis similar in C4 plants and CAM plants?
In both cases, rubisco is not used to fix carbon initially.
The overall function of the Calvin cycle is __________
MAKING sugar
After 3-PGA is phosphorylated, it is reduced by _____.
NADH
Which of the following molecules is the primary product of photosystem I?
NADH
The electrons derived from this oxidation reaction in the light reactions are used to reduce __ to __.
NADP+, NADPH; These electrons are ultimately used to reduce NADP+ to NADPH.
Which of the following products of the light reactions of photosynthesis is used during the Calvin cycle?
NADPH
The Calvin cycle oxidizes the light reactions product __ to __.
NADPH, NADP+;In the Calvin cycle, NADPH is oxidized back to NADP+ (which returns to the light reactions).
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.
Which of the following statements 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 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.
Engelmann counted the number of bacteria that were attracted to the algal filament associated with each color of light. As shown in the image below, most of the bacteria were attracted to the regions of the alga illuminated by red or violet-blue light. This distribution of bacteria shows that red and violet-blue wavelengths are most effective in driving photosynthesis. By measuring oxygen production with aerotactic bacteria, Engelmann described an action spectrum for photosynthesis. The action spectrum (indicated by the black line plot in the image above) shows the relative effectiveness of each color of light in driving photosynthesis. What assumptions did Engelmann make in order to conclude that red and violet-blue light were more effective than green light in driving photosynthesis? Select the two that apply.
The number of bacteria clustered at each wavelength (color) was approximately proportional to the amount of oxygen being produced by that portion of the alga.The distribution of chloroplasts within each algal cell was approximately the same.
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? (Assume that the light intensity does not change.)
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.
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.
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
What is the biological significance of the light-independent reactions of photosynthesis?
They convert carbon dioxide to sugar.
Plants are photoautotrophs. What does this mean?
They use light energy to drive the synthesis of organic molecules from inorganic materials.
True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.
True
What is the result of the splitting of a water molecule during the light reactions of photosynthesis
`
For every molecule of O2 that is released by photosystem II, a H2O molecules are needed, which together pass b electrons to the PS II reaction-center complex.
a. 2 b.4
The photosynthetic membranes are found in the _____ in plant cells. a) mitochondria b) chloroplasts c) nucleus d) Golgi apparatus e) endoplasmic reticulum
b
What is the basic role of CO2 in photosynthesis? a) CO2 is taken in by plants as a form of inverse respiration, in which carbon dioxide is "breathed in" and oxygen is "breathed out." b) CO2 is fixed or incorporated into organic molecules. c) CO2 is a source of electrons in the formation of organic molecules.
b
Which of the following statements is a correct distinction between autotrophs and heterotrophs? a. only heterotrophs require oxygen b. autotrophs, but not heterotrophs, can nourish themselves with CO2 and other nutrients that are inorganic c. only heterotrophs have mitochondria d. cellular respiration is unique to heterotrophs
b
Inputs and outputs of the Calvin cycle
input: ATP, NADPH, and CO2 output: ADP, NADP+, G3P
both PS II and PS I
light absorption reduction of primary electron acceptor
Which set of reactions uses H2O and produces O2?
light dependent reactions
_________ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.
electron transport chain
When light strikes chlorophyll molecules of PS II, they lose electrons, which are ultimately replaced by _____.
electrons released by splitting water
