Biology Chap 10
Which of the following occurs during the Calvin cycle? (Concept 10.3) SHOW HINT ATP is reduced and NADPH is oxidized. Linear electron flow produces the materials required for the fixation of carbon from carbon dioxide. Light energy is converted to chemical energy. ATP is oxidized and NADPH is reduced. ATP is hydrolyzed and NADPH is oxidized.
ATP is hydrolyzed and NADPH is oxidized. right answer feedback: Correct. The hydrolysis of ATP releases energy to drive the endergonic reactions of the Calvin cycle, and the oxidation of NADPH provides high-energy electrons for the reduction of the carbon from carbon dioxide.
Glyceraldehyde-3-phosphate (G3P) is produced in the stroma of chloroplasts. Which of the following statements is most accurate regarding this compound? (Concept 10.3) SHOW HINT It is a three-carbon sugar. It is produced from glucose during glycolysis. For every three molecules of CO2, six molecules of G3P are formed but five molecules must be recycled to regenerate three molecules of RuBP For every three molecules of CO2 reduced in the Calvin cycle, six molecules of G3P are formed but only one of these molecules exits the cycle to be used by the plant cell. All of the listed responses are correct.
All of the listed responses are correct.
The use of non-C3 and non-CAM plants as crops may be limited in some regions because on hot, dry days, they close their stomata. What happens as a result of closing their stomata? (Concept 10.4) SHOW HINT Water loss is reduced. Oxygen from the light reactions in the leaf builds up. In a process called photorespiration, rubisco binds oxygen instead of carbon dioxide. Carbon dioxide is prevented from entering the leaf. All of the listed responses are correct.
All of the listed responses are correct.
Of the following, which occurs during the Calvin cycle? (Concept 10.3) SHOW HINT Light energy is converted to chemical energy. Photons are absorbed. CO2 is reduced. Excited electrons are conveyed from chlorophyll to an electron acceptor. ATP and NADPH are synthesized.
CO2 is reduced.
During photosynthesis in chloroplasts, O2 is produced from __________ via a series of reactions associated with __________. (Concept 10.2) SHOW HINT H2O ... photosystem II CO2 ... the Calvin cycle CO2 ... photosystem II H2O ... photosystem I CO2 ... both photosystem I and the Calvin cycle
H2O ... photosystem II Correct. When photosystem II absorbs light, the electron that is excited to a higher energy level in the special chlorophyll leaves a "hole" that is filled when an enzyme extracts electrons from the hydrogen of water, releasing oxygen. Question 19
What is the role of NADP+ in photosynthesis? (Concept 10.1) SHOW HINT It forms part of photosystem II. It forms NADPH to be used in the Calvin cycle. It absorbs light energy. It is the primary electron acceptor. It helps produce ATP from the light reactions.
It forms NADPH to be used in the Calvin cycle.
What is the role of NADP+ in photosynthesis? (Concept 10.2) SHOW HINT As part of the electron transport chain, it manufactures ATP. As a component of photosystem II, it catalyzes the hydrolysis of water. It is reduced and then carries electrons to the Calvin cycle. It acts as the primary electron acceptor for the photosystems. It assists chlorophyll in capturing light.
It is reduced and then carries electrons to the Calvin cycle. Correct. Electrons received from photosystem I reduce NADP+ to NADPH, which then carries them to the Calvin cycle.
The light reactions of photosynthesis generate high-energy electrons, which end up in __________ through linear electron flow. The light reactions also produce __________ and __________. (Concept 10.2) SHOW HINT chlorophyll ... ATP ... NADPH ATP ... NADPH ... oxygen oxygen ... sugar ... ATP water ... sugar ... oxygen NADPH ... ATP ... oxygen
NADPH ... ATP ... oxygen right answer feedback: Correct. The electrons are transferred to NADP+, forming NADPH. ATP is formed via photophosphorylation, and oxygen is produced when water molecules are split.
The reactions of the Calvin cycle are NOT directly dependent on light, but they usually do NOT occur at night. Why? (Concept 10.1) SHOW HINT At night, no water is available for the Calvin cycle. The Calvin cycle requires products only produced when the photosystems are illuminated. Plants usually open their stomata at night. It is often too cold at night for these reactions to take place. Carbon dioxide concentrations decrease at night.
The Calvin cycle requires products only produced when the photosystems are illuminated. Correct. The ATP and NADPH produced during the light reactions are necessary for the Calvin cycle.
Which of the following statements correctly describes the relationship between the light reactions and the Calvin cycle? (Concept 10.3) SHOW HINT The light reactions produce ADP and NADP+, both of which are used in the Calvin cycle. The light reactions produce carbon dioxide and water, both of which are used in the Calvin cycle. The light reactions produce ATP and NADPH, both of which are used in the Calvin cycle. The light reactions produce water, ATP, and NADPH, all of which are used in the Calvin cycle. The light reactions produce carbon dioxide, ATP, and NADPH, all of which are used in the Calvin cycle.
The light reactions produce ATP and NADPH, both of which are used in the Calvin cycle. Correct. NADPH provides reducing power by donating electrons and ATP provides energy when it is converted to ADP.
Why are C4 plants more suited to hot climates than C3 plants? (Concept 10.4) SHOW HINT They suspend photosynthesis in the heat. They do not close their stomata in hot, dry weather. The same cells that bind carbon dioxide perform the Calvin cycle. They evolved in cold weather but migrated to the tropics, where they were more suitable. Unlike C3 plants, they keep fixing carbon dioxide even when the concentration of carbon dioxide in the leaf is low.
Unlike C3 plants, they keep fixing carbon dioxide even when the concentration of carbon dioxide in the leaf is low. right answer feedback: Correct. They continue to fix carbon dioxide under low concentrations of the gas. Photosynthesis can continue even if the stomata are closed and the concentration of carbon dioxide diminishes.
You have a large, healthy philodendron that you carelessly leave in total darkness while you are away on vacation. You are surprised to find that it is still alive when you return. What has the plant been using for an energy source while in the dark? (Concept 10.4) SHOW HINT When light energy is not available, plants can derive energy from inorganic molecules. Even though it cannot carry out the light reactions, the plant can still produce sugars because the Calvin cycle does not require light. Even though the plant received no visible light, it was able to use the short-wave part of the electromagnetic spectrum (gamma rays and X-rays) to carry out photosynthesis. While it did have access to light, the plant stored energy in the form of sugars or starch, and it was able to derive energy from the stored molecules during your vacation. None of the listed responses is correct.
While it did have access to light, the plant stored energy in the form of sugars or starch, and it was able to derive energy from the stored molecules during your vacation. Correct. Because plants make more organic material each day than they need to use as respiratory fuel and precursors for biosynthesis, the extra sugar is stockpiled as starch stored in chloroplasts, as well as in roots, tubers, seeds, and fruits.
In the Calvin cycle, CO2 is combined with __________. (Concept 10.3) SHOW HINT a two-carbon compound to form a three-carbon compound a five-carbon compound to form a stable six-carbon compound that can be converted directly to glucose two two-carbon compounds to form a five-carbon compound a seven-carbon compound to form two four-carbon compounds a five-carbon compound to form an unstable six-carbon compound, which decomposes into two three-carbon compounds
a five-carbon compound to form an unstable six-carbon compound, which decomposes into two three-carbon compounds right answer feedback: Correct. Rubisco catalyzes the first step of the Calvin cycle—the incorporation of a molecule of carbon dioxide with a five-carbon sugar. The six-carbon product is so unstable that it decomposes immediately into two three-carbon phosphoglycerates.
Based on the work of Engelmann, a plot of photosynthetic activity versus wavelength of light is referred to as __________. (Concept 10.2) SHOW HINT a visible light spectrum an effective spectrum an electromagnetic spectrum an action spectrum an absorption spectrum
an action spectrum Correct. An action spectrum plots the effectiveness of different wavelengths of light in driving photosynthesis.
A photon of which of these colors would carry the most energy? (Concept 10.2) SHOW HINT yellow green blue orange red
blue Correct. The shorter the wavelength, the greater the energy content.
What is the range of wavelengths of light that are absorbed by the pigments in the thylakoid membranes? (Concept 10.2) SHOW HINT the range absorbed by carotenoids the infrared the entire spectrum of white light blue-violet and red-orange green, which is why plants are green
blue-violet and red-orange
The most important role of pigments in photosynthesis is to __________. (Concept 10.2) SHOW HINT catalyze the synthesis of ATP screen out harmful ultraviolet rays store energy capture light energy catalyze the hydrolysis of water
capture light energy Correct. The pigments absorb the energy required for the light reactions.
In photosynthesis, plants use carbon from __________ to make sugar and other organic molecules. (Concept 10.0) SHOW HINT water chlorophyll soil carbon dioxide the sun
carbon dioxide Correct. Less than 1% of the atmosphere is CO2, but that is enough to support photosynthesis.
Which of the following is cycled in the cyclic variation of the light reactions? (Concept 10.2) SHOW HINT NADPH ribulose bisphosphate protons ATP electrons
electrons right answer feedback: Correct. During the light reactions of photosynthesis, there are two possible routes for electron flow: cyclic and linear.
You could distinguish a thylakoid membrane from an inner mitochondrial membrane because the thylakoid membrane would __________. (Concept 10.2) SHOW HINT contain protein but not lipids have photosynthetic pigments be inside a mitochondrion function in energy transformation have all of the listed characteristics
have photosynthetic pigments Correct. The photosynthetic pigment chlorophyll is anchored in the thylakoid membrane.
In photosynthesis, what is the fate of the oxygen atoms present in CO2? They end up __________. (Concept 10.1) SHOW HINT in water in sugar molecules and in water as molecular oxygen and in sugar molecules in sugar molecules as molecular oxygen
in sugar molecules and in water Correct. The oxygen atoms present in carbon dioxide appear in sugar and water.
Molecular oxygen is produced during __________. (Concept 10.1) SHOW HINT glycolysis the Calvin cycle linear electron flow during the light reactions cyclic electron flow during the light reactions re-energization of electrons by PSI
linear electron flow during the light reactions Correct. The light reactions of photosynthesis generate molecular oxygen when water is split.
The energy used to produce ATP in the light reactions of photosynthesis comes from __________. (Concept 10.2) SHOW HINT fluorescence splitting water carbon fixation the oxidation of sugar molecules movement of H+ through a membrane
movement of H+ through a membrane right answer feedback: Correct. Termed "chemiosmosis," the diffusion of hydrogen ions through ATP synthase provides the energy to produce ATP.
The Calvin cycle occurs in the __________. (Concept 10.1) thylakoid membrane stroma thylakoid lumen stomata matrix
stroma Correct. The thylakoids of the chloroplast are the sites of the light reactions, whereas the Calvin cycle occurs in the stroma.
Rubisco is __________. (Concept 10.3) SHOW HINT the enzyme that forms a four-carbon compound in CAM photosynthesis the enzyme responsible for splitting H2O to produce O2 in photosynthesis the enzyme in plants that captures CO2 to begin the Calvin cycle the first stable intermediate in C4 photosynthesis the five-carbon sugar molecule that reacts with CO2 to begin the Calvin cycle
the enzyme in plants that captures CO2 to begin the Calvin cycle Correct. The enzyme that catalyzes the first step of the Calvin cycle (incorporation of a molecule of carbon dioxide by attaching it to a five-carbon sugar, named ribulose biphosphate, or RuBP) is RuBP carboxylase, or rubisco.
What structure is formed by the reaction center, light-harvesting complexes, and primary electron acceptors that cluster, and is located in the thylakoid membrane? (Concept 10.2) SHOW HINT the photosystem the fluorescence center the electron transport chain ATP synthase NADP+ reductase
the photosystem
When chloroplast pigments absorb light, __________. (Concept 10.2) the Calvin cycle is triggered the pigments lose potential energy the pigments' electrons become excited the pignments' photons become excited the pigments become reduced
the pigments' electrons become excited Correct. When a molecule absorbs a photon of light, one of the molecule's electrons is elevated to an orbital where it has more potential energy.
How does carbon dioxide enter the leaf? (Concept 10.1) SHOW HINT through the chloroplasts through the roots through the stomata through the thylakoids through the vascular system
through the stomata Correct. These are the openings in the leaf for gas exchange.
During photosynthesis in a eukaryotic cell, an electrochemical gradient is formed across the __________. (Concept 10.2) SHOW HINT cristae chloroplast outer membrane stomata chloroplast inner membrane thylakoid membrane
thylakoid membrane right answer feedback: Correct. In chloroplasts, the electron transport chain pumps protons from the stroma to the thylakoid space; these locations are separated by the thylakoid membrane.
Chlorophyll molecules are in which part of the chloroplast? (Concept 10.1) SHOW HINT thylakoid lumen stomata plasma membrane thylakoid membranes stroma
thylakoid membranes Correct. The chlorophyll molecules are embedded in the thylakoid membranes of the chloroplasts.
In a rosebush, chlorophyll is located in __________. (Concept 10.1) SHOW HINT chloroplasts, which are in mesophyll cells in the thylakoids of a leaf thylakoids, which are in chloroplasts in the mesophyll cells of a leaf thylakoids, which are in mesophyll cells in the chloroplasts of a leaf chloroplasts, which are in thylakoids in the mesophyll cells of a leaf mesophyll cells, found within the thylakoids of a leaf's chloroplasts
thylakoids, which are in chloroplasts in the mesophyll cells of a leaf Correct. Thylakoids are arranged in stacks within the 30-40 chloroplasts per typical mesophyll cell.
Both mitochondria and chloroplasts __________. (Concept 10.2) SHOW HINT are surrounded by a single membrane obtain electrons from water release oxygen as a by-product use chemiosmosis to produce ATP reduce NAD+, forming NADP
use chemiosmosis to produce ATP orrect. Chloroplasts and mitochondria both generate ATP by chemiosmosis. An electron transport chain in the membrane pumps protons across the membrane as electrons are passed through a series of carriers that are progressively more electronegative. Built into the same membrane is an ATP synthase that couples the diffusion of hydrogen ions down their gradient to the phosphorylation of ADP.
The source of the oxygen produced by photosynthesis has been identified through experiments using radioactive tracers. The oxygen comes from __________. (Concept 10.1) SHOW HINT light radioisotopes glucose carbon dioxide water
water right answer feedback: Correct. The oxygen produced by photosynthesis comes from the splitting of water. Question 6
Where do the electrons entering photosystem II come from? (Concept 10.2) SHOW HINT ATP light chlorophyll molecules in the antenna complex the electron transport chain water
water right answer feedback: Correct. The splitting of water molecules provides the source of electrons for photosystem II.
