Which process produces oxygen? 1. Photosynthesis 2. Cellular Respiration
1. Photosynthesis -Oxygen is a by-product of the photosynthetic process.
Which set of reactions uses H2O and produces O2?
The light-dependent reactions -The light-dependent reactions use H2O and produce O2.
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. -CO2 is unusable until plants have "fixed" this carbon into sugar.
True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.
True -The water molecules are split to replenish electrons in photosystem II, leaving behind protons, which are used to generate a proton gradient for the formation of ATP, and oxygen, which is released as a by-product.
Which of the following molecules is the primary product of photosystem I?
NADPH -The NADPH produced by photosystem I is used to supply energy for the production of sugars during photosynthesis.
What is the biological significance of the light-independent reactions of photosynthesis?
They convert carbon dioxide to sugar. -All organisms use the sugars produced by photosynthesis to generate energy.
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. -Light energy drives the formation of ATP and NADPH during the light-dependent reactions; these energy molecules are then used during the light-independent reactions to form sugars.
Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose?
Regeneration of RuBP -The regeneration of RuBP ensures that the Calvin cycle can proceed indefinitely, since RuBP fixes carbon dioxide into an organic molecule that is used to produce sugar.
Photosynthesis is a redox reaction. This means that H2O is _____ during the light reactions and CO2 is _____ during the Calvin cycle.
Oxidized.... reduced -During the light reactions of photosynthesis, water is oxidized, and during the Calvin cycle, carbon is reduced.
Plants are photoautotrophs. What does this mean?
They use light energy to drive the synthesis of organic molecules from inorganic materials. -Photoautotrophs use light as a source of energy to synthesize organic substances
The ultimate source of energy to support most life on Earth is _____.
Sunlight -For the most part, life on Earth is solar-powered. Plants are photoautotrophs, organisms that use light as a source of energy to synthesize organic substances.
Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
ATP and NADPH
Where does the Calvin cycle take place?
Stroma of the chloroplast
Which term describes ATP production resulting from the capture of light energy by chlorophyll?
Photophosphorylation -The excitation of chlorophyll by light energy initiates a chain of events that leads to ATP production.
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 -The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP.
According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?
Proton gradient -A proton gradient across chloroplast and mitochondrial membranes drives ATP synthesis by the enzyme ATP synthase.
Which of the following particles can pass through the ATP synthase channel?
Protons -The channels formed by ATP synthase are specific for protons.
True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.
False -The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which protons can pass.
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. -This statement is true; although the proton gradient is present, ADP and inorganic phosphate are required to make ATP and were not added to the reaction.
_____ has a longer wavelength than _____.
Red... green -Red has a longer wavelength than green
Which of these phosphorylates ADP to make ATP?
ATP synthase phosphorylates ADP
_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment.
The energy released as electrons are passed along the electron transport chain is used to pump protons into the thylakoid compartment.
_____ splits water into 1/2 O2, H+, and e- .
Photosystem II splits water into 1/2 O2, H+, and e- .
Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+.
Energized electrons from photosystem I are used to reduce NADP+.
Chlorophyll can be found in _____.
The photosystems contain chlorophyll.
the figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. What colors of light are least effective in driving photosynthesis?
In the thylakoid membranes, what is the main role of the pigment molecules in a light-harvesting complex?
transfer light energy to the reaction-center chlorophyll
Which of the following events occurs in the light reactions of photosynthesis?
Light is absorbed and funneled to reaction-center chlorophyll a.
Which of the following is directly associated with photosystem I?
receiving electrons from the thylakoid membrane electron transport chain
In a plant cell, where are ATP synthase complexes located?
thylakoid membrane and inner mitochondrial membranes
Which of the following statements about the relationship between photosynthesis and cellular respiration is true?
Cellular respiration is catabolic and photosynthesis is anabolic.
Where are the molecules of the electron transport chain associated with photophosphorylation located in plant cells?
thylakoid membranes of chloroplasts
The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during
neither photosynthesis nor respiration.
Generation of proton gradients across membranes occurs during
both photosynthesis and cellular respiration.
Carbon fixation involves the addition of carbon dioxide to _____.
RuBP -In the Calvin cycle, carbon dioxide is added to RuBP.
After 3-PGA is phosphorylated, it is reduced by _____.
NADPH -NADPH supplies the electrons that reduce the phosphorylated 3-PGA.
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
6 -Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
Which of the following products of the light reactions of photosynthesis is used during the Calvin cycle?
NADPH -During the Calvin cycle, electrons stored in NADPH are used to reduce carbon.
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.
C4 plants occur more commonly in desert conditions because __________.
they can fix carbon at the lower CO2 concentrations that develop when the stomata are closed -To conserve water during hot, dry conditions, the stomata are fully or partially closed, preventing CO2 from reaching high concentrations.
In the process of carbon fixation, three molecules of RuBP combine with three molecules of CO2 to produce three six-carbon molecules, which are then split to produce 12 molecules of 3-phosphoglycerate. After phosphorylation and reduction produce 12 glyceraldehyde 3-phosphate (G3P), what more needs to happen to complete the Calvin cycle?
release of one G3P to make sugars and regeneration of RuBP
What compound provides the reducing power for the Calvin cycle reactions?
Photorespiration occurs when rubisco combines RuBP with
CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because they
fix CO2 into organic acids during the night when temperatures are cooler.
Compared to C3 plants, C4 plants
can continue to fix CO2 even at relatively low CO2 concentrations and high oxygen concentrations.
In C3 plants the conservation of water promotes _____.
Photorespiration -Conserving water simultaneously reduces the amount of carbon dioxide available to the plant.
In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells.
Cytoplasm -In C4 and CAM plants carbon dioxide fixation occurs in the cytoplasm.
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 C3 and CAM plants carbon dioxide fixation and the Calvin cycle occur in the same cells.
Which of the following sequences correctly represents the flow of electrons during photosynthesis?
H2O → NADPH → Calvin cycle
How is photosynthesis similar in C4 plants and CAM plants?
In both cases, rubisco is not used to fix carbon initially
Which of the following statements is a correct distinction between autotrophs and heterotrophs?
Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.
Which of the following does NOT occur during the Calvin cycle?
Release of oxygen
Which process is most directly driven by light energy?
removal of electrons from chlorophyll molecules
What is the basic role of CO2 in photosynthesis?
CO2 is fixed or incorporated into organic molecules.
Select the correct molecule that is the main product of the Calvin cycle.
G3P -Glucose is discussed as the product of photosynthesis primarily for convenience. In fact, very little free glucose is produced by or transported from photosynthetic cells. Read about the Calvin cycle.
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. -Read about the light reactions of photosynthesis.
Select the correct statement about the Calvin cycle.
The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of RuBP.
Why are plants classified as producers?
Plants are classified as producers because they fix inorganic carbon into organic molecules