Chapter 7: Photosynthesis

Which of the following statements regarding the reduction of CO2 to sugar during photosynthesis is true? View Available Hint(s) Oxygen is removed from CO2 during photosynthesis. Hydrogen is added to CO2 during photosynthesis. Electrons (with accompanying protons) are removed from CO2 during photosynthesis and added to water molecules to form sugar. Electrons (with accompanying protons) are added to CO2 during photosynthesis.

Electrons (with accompanying protons) are added to CO2 during photosynthesis.

Which statement regarding the light reactions is true? View Available Hint(s) Photoexcited electrons pass from photosystem I to photosystem II. Glucose is a product of the light reactions. Electrons "falling" down the electron transport chain are deposited on ADP to form ATP. Electrons are supplied to chlorophyll P680 as it reduces the primary electron acceptor.

Electrons are supplied to chlorophyll P680 as it reduces the primary electron acceptor.

How many turns of the Calvin cycle are required to produce one G3P molecule? View Available Hint(s) one two three six

3

In simple summary form, the input of the Calvin cycle for every product is __________, and the output is __________ used for glucose synthesis. View Available Hint(s) NADP+ ...; NADPH ADP ... ATP 6 CO2 ...; glucose 3 CO2 ...; a three-carbon molecule

3 CO2 ...; a three-carbon molecule

Which of the following equations represents photosynthesis? View Available Hint(s) C6H12O6 + 6CO2 → 6O2 + 6H2O 6CO2 + 6H2O → C6H12O6 + 6O2 C6H12O6 + 6O2 → 6CO2 + 6H2O 6CO2 + 6O2 → C6H12O6 + 6H2O 6H2O + 6O2 → C6H12O6 + 6CO2

6CO2 + 6H2O → C6H12O6 + 6O2

It has been suggested that scientists should attempt to genetically engineer a plant to have black leaves so that it would perform photosynthesis more efficiently. What is the likely reason behind this idea? A black plant would reflect all wavelengths and therefore have more energy to drive photosynthesis. A black plant would absorb all wavelengths and therefore absorb more light energy that powers photosynthesis. A black plant would absorb green wavelengths like most plants, but would absorb them more efficiently. Black plants would heat up faster and therefore all chemical reactions including photosynthesis would operate faster.

A black plant would absorb all wavelengths and therefore absorb more light energy that powers photosynthesis.

Which of the following are produced during the light reactions of photosynthesis? glucose, ADP, NADP+, CO2 ADP, NADP+, O2 glucose, ADP, NADP+ ATP, NADPH, O2

ATP, NADPH, O2

It has been suggested that global warming could be halted by fertilizing the oceans to increase the growth of algae. How might this affect the greenhouse effect? Algal photosynthesis would produce more O2, which blocks light. Algae photosynthesis would use heat in place of photons. Algal photosynthesis would be inhibited by the addition of fertilizer. Algal photosynthesis would use up more CO2, which traps heat.

Algal photosynthesis would use up more CO2, which traps heat.

CAM plants have adapted to arid environments by closing their stomata during the day. However, photosynthesis still occurs. This is because __________. View Available Hint(s) CO2 is fixed in the bundle-sheath cells CO2 is fixed at night when the stomata are open some CO2 leaks through the closed stomata photosynthesis occurs at night

CO2 is fixed at night when the stomata are open

Why are most plants green? Chlorophyll a absorbs green light. Chlorophyll a reflects green light. Green helps plants blend into their environment as a sort of camouflage. Chlorophyll b primarily uses green light as the source of energy for photosynthesis.

Chlorophyll a reflects green light.

In photophosphorylation, energy from electron flow is used to transport ________ from the ________ to the thylakoid compartment, generating a concentration gradient of ________. H+; grana; electrons H+; stroma; ATP electrons; grana; H+ H+; stroma; H+

H+; stroma; H+

As photosynthesis occurs in chloroplasts, O2 is produced from _____ via a series of reactions associated with _____. View Available Hint(s) H2O ... photosystem II H2O ... photosystem I CO2 ... Calvin cycle CO2 ... photosystem II

H2O ... photosystem II

What is the main cause of the current amplification of global climate change? View Available Hint(s) lowered sea levels Human activity is increasing the concentration of greenhouse gases, which delays the escape of heat from the planet. depletion of the ozone layer melting polar ice

Human activity is increasing the concentration of greenhouse gases, which delays the escape of heat from the planet.

The impact of a sufficiently large asteroid or comet is one of the theories that have been put forward to explain why dinosaurs, as well as many other plant and animal species, became extinct 65 million years ago. Why would this extinction-level event have had such a major impact on Life on Earth? View Available Hint(s) It produced dust and other particulates that would block out the sun. The toxic fumes produced meant that the dinosaurs could no longer breathe. It created enormous tidal waves and huge forest fires. It increased the temperature of the planet.

It produced dust and other particulates that would block out the sun

It has been argued that cutting old-growth forests and replacing them with plantations of young trees would help to alleviate the threat of global greenhouse warming. What important fact does this argument ignore? Most of the young trees would die within a few years. Young trees fix carbon at a lower rate per unit mass than old trees. Most of the biomass of the cut trees would be added to the atmosphere as CO2 within a few years. Forests play too minor a role in global CO2 dynamics, which are affected far more by marine algae.

Most of the biomass of the cut trees would be added to the atmosphere as CO2 within a few years.

Oxygen is the final electron acceptor for cellular respiration. What is the final electron acceptor in the light reactions of photosynthesis? View Available Hint(s) water NADP+ ATP light

NADP+

The light reactions of photosynthesis generate high-energy electrons, which end up in __________. The light reactions also produce __________ and __________. View Available Hint(s) NADPH : ATP : oxygen ATP : NADPH : oxygen oxygen : sugar : ATP chlorophyll : ATP : NADPH

NADPH : ATP : oxygen

Current evidence indicates that the process of photosynthesis arose more than three billion years ago. Its origin had a huge impact on existing organisms and on the physical characteristics of the biosphere. Which major physical change could be attributed to photosynthesis? View Available Hint(s) Photosynthesis drastically increased the oxygen content of the atmosphere. Photosynthesis drastically raised Earth's surface temperature. Photosynthesis drastically increased the carbon dioxide content of the atmosphere. Photosynthesis allowed much higher levels of ultraviolet light to reach Earth's surface.

Photosynthesis drastically increased the oxygen content of the atmosphere.

Hydrogen is a likely candidate in the search for a replacement for petroleum. However, removing hydrogen from water requires the investment of a great deal of energy. Why are plants considered to be one step ahead in the utilization of hydrogen as an alternative fuel source? View Available Hint(s) Plant cells break down carbohydrates to generate hydrogen. Plant cells possess water-splitting enzymes. Plant cells convert carbon to combustible hydrogen. Plant cells harness the ATP produced during photosynthesis to split water.

Plant cells possess water-splitting enzymes.

During photosynthesis, the light reactions convert light energy to chemical energy. Select the three true statements about the light reactions of photosynthesis. The light reactions take place after the Calvin Cycle. The light reactions produce chemical energy in the form of NADPH and ATP. One molecule of water is produced for every electron that moves through photosystem II. The light reactions take place inside the thylakoids of chloroplasts. Pigment molecules inside photosystem II and photosystem I absorb light energy from the sun.

The light reactions produce chemical energy in the form of NADPH and ATP. The light reactions take place inside the thylakoids of chloroplasts. Pigment molecules inside photosystem II and photosystem I absorb light energy from the sun.

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? View Available Hint(s) Even though it cannot carry out the light reactions, the plant can still produce sugars because the Calvin cycle does not require light. When light energy is not available, plants can derive energy from inorganic molecules. Even though the plant received no visible light, it was able to use the shortwave part of the electromagnetic spectrum (gamma rays and X-rays) to carry out photosynthesis. While it did have access to light before you left, the plant stored energy in the form of sugars or starch, and it was able to derive energy from those during your vacation.

While it did have access to light before you left, the plant stored energy in the form of sugars or starch, and it was able to derive energy from those during your vacation.

Which of the following colors of light are useful during the process of photosynthesis? View Available Hint(s) orange, red, and ultraviolet blue, green, and orange blue, red, and violet green, orange, and red

blue, red, and violet

In the Calvin cycle carbon dioxide provides _____, whereas ATP and NADPH provide _____ and _____, respectively. View Available Hint(s) hydrogen ... carbon ... energy high-energy electrons ... energy ... carbon carbon ... energy ... high-energy electrons energy ... carbon ... high-energy electrons

carbon ... energy ... high-energy electrons

Which of the following are photoautotrophs? View Available Hint(s) deep-sea vent organisms that make organic molecules using hydrogen sulfide as an energy source filamentous molds growing on bread bacteria found in the human digestive tract corn stalks just before harvest

corn stalks just before harvest

Sunlight is a type of ________ energy. chemical mechanical electromagnetic

electromagnetic

The conversion of NADP+ to NADPH occurs with the assistance of __________. View Available Hint(s) electrons from water and energy from sunlight electrons from carbon dioxide and energy from ATP electrons from water and energy from ATP electrons from carbon dioxide and energy from sunlight

electrons from water and energy from sunlight

Photosynthesis is an __________ process in which carbon is __________, whereas cellular respiration is an __________ process in which carbon is __________. View Available Hint(s) endergonic : reduced : exergonic : oxidized endergonic : oxidized : exergonic : reduced exergonic : reduced : endergonic : oxidized endergonic : oxidized : endergonic : reduced

endergonic : reduced : exergonic : oxidized

C4 plants have evolved different photosynthetic mechanisms. These plants _____. View Available Hint(s) conserve water more efficiently by shutting their stomata during the day are adapted to living in cold, wet climates where there is no water shortage fix CO2 into a four-carbon compound instead of a three-carbon compound do not fix CO2 through the Calvin cycle

fix CO2 into a four-carbon compound instead of a three-carbon compound

The primary function of light absorption by photosystems I and II is to produce __________. View Available Hint(s) free, energized electrons fluorescence heat oxygen

free, energized electrons

Solar radiation warms the surface of the planet and then is radiated back in the form of __________. View Available Hint(s) ozone CO2 UV radiation heat

heat

C4 and CAM plants have adapted to living in environments where water loss is a problem. C4 plants fix carbon dioxide _____, whereas CAM plants fix carbon at _____. View Available Hint(s) during different seasons ... different locations at different times of the day ... different seasons at different times of the day ... different locations within the leaf in different locations ... different times of the day

in different locations ... different times of the day

What is the source of energy that provides the boost for electrons during photosynthesis? ATP NADPH light cellular respiration Submit

light

Which of the following is NOT an aspect of global climate change? View Available Hint(s) rising sea levels net growth of polar ice caps increases in extreme weather events increased spread of tropical diseases

net growth of polar ice caps

Autotrophs that utilize light as their energy source are chemosynthetic autotrophs. fungi. photoautotrophs. heterotrophs.

photoautotrophs

Which of these types of organisms produces the biosphere's food supply? View Available Hint(s) photoautotrophs chemoheterotrophs photoheterotrophs chemoautotrophs

photoautotrophs

The reaction center, antenna molecules, and primary electron acceptors that cluster in the thylakoid membrane form which structure? View Available Hint(s) fluorescence center electron transport chain photosystem carbon-fixation unit

photosystem

1. In C3 plants, the first product of carbon fixation is the three-carbon compound 3-PGA formed in the Calvin cycle. 2. When such plants close their stomata on hot, dry days to conserve water, O2 builds up in the leaf and is added to RuBP in place of CO2. A two-carbon product of this reaction is broken down to CO2, consuming ATP and generating no sugar. 3. The apparently wasteful process described in sentence 2 is called photorespiration . 4. In C4 plants, CO2 is first fixed into a four-carbon compound, which moves into bundle-sheath cells and releases CO2 to the Calvin cycle. 5. In CAM plants, stomata are open at night, and CO2 is first fixed into a four-carbon compound, which releases CO2 to the Calvin cycle during the day. 6. In all three types of plants, the enzyme rubisco brings CO2 into the Calvin cycle.

read

Carbon dioxide enters a leaf through the _____. View Available Hint(s) stomata mesophyll chloroplasts thylakoids

stomata

The photosynthetic event known as the Calvin cycle occurs in the __________. View Available Hint(s) thylakoid membrane stroma thylakoid compartment stomata

stroma

The light reactions' production of oxygen during photosynthesis is important for life on Earth. Which of the following would prevent oxygen from being made? the inability of the electron transport chain to pump hydrogen ions from the stroma into the thylakoid space the inability of chlorophyll a in photosystem I to absorb light energy from the sun the inability of ATP synthase to use the gradient of hydrogen ions to make ATP the inability of water to donate its electrons to photosystem II

the inability of water to donate its electrons to photosystem II

When chloroplast pigments absorb light, _____. View Available Hint(s) they lose potential energy their electrons become excited they become reduced the Calvin cycle is triggered

their electrons become excited

Chlorophyll molecules are found in which part of the chloroplast? View Available Hint(s) thylakoid membrane stomata stroma plasma membrane

thylakoid membrane

Chlorophyll is found in the __________ of chloroplasts. View Available Hint(s) stroma thylakoid space outer membrane thylakoid membranes

thylakoid membranes

The oxygen released into the air as a product of photosynthesis comes from chlorophyll. water. glucose. carbon dioxide.

water