Biology Test 3 Part II

The light reactions of photosynthesis involve

reduction of NADP+ NADP+ is reduced during the light reactions, and these electrons are later used to reduce CO2 to carbohydrates in the Calvin cycle.

Carbon dioxide enters a leaf through the _____.

stomata These are the openings for gas exchange in the leaf.

The photosynthetic event known as the Calvin cycle occurs in the

stroma The thylakoids of the chloroplast are the sites of the light reactions, whereas the Calvin cycle occurs in the stroma.

Cellular respiration and photosynthesis are similar in that both involve _____.

oxidation-reduction (redox) reactions Both cellular respiration and photosynthesis involve a series of oxidation-reduction events.

In simple summary form, the input of the Calvin cycle for every product is __________, and the output is __________ used for glucose synthesis.

3 CO2 ...; a three-carbon molecule For every six molecules of G3P produced, 3 CO2 enter the cycle. (One G3P leaves the cycle as an output. The other five remain and are rearranged to form RuBP.) In addition, glyceraldehyde-3-phosphate (G3P), a three-carbon molecule, is shunted off the cycle for glucose synthesis.

Which of the following is NOT a greenhouse gas?

Carbon dioxide, water vapor, and methane are all important greenhouse gases.

Blue-Violet and Red-Orange

Considering the wavelengths of light shown below, the pigments in the granum absorb mainly in which range? These are the wavelengths of light that plant pigments absorb.

Which of the following statements regarding the reduction of CO2 to sugar during photosynthesis is true?

Electrons (with accompanying protons) are added to CO2 during photosynthesis. Reductions involve the addition of electrons, often with accompanying protons.

Which statement regarding the light reactions is true?

Electrons are supplied to chlorophyll P680 as it reduces the primary electron acceptor. As the excited electrons of chlorophyll P680 are donated to the primary electron acceptor, they are replaced by the splitting of water. Provide Feedback

The splitting of water molecules provides the source of electrons for photosystem II.

H2O ... photosystem II When photosystem II absorbs light, the electron that is excited to a higher energy level in the chlorophyll leaves a "hole." This is filled when an enzyme extracts electrons from the hydrogen of water, releasing oxygen.

What is the main cause of the current amplification of global climate change?

Human activity is increasing the concentration of greenhouse gases, which delays the escape of heat from the planet. There are multiple consequences of this increased energy, including increased average temperatures, melting polar ice, increased incidence of extreme weather, and increased extinction rates.

Oxygen is the final electron acceptor for cellular respiration. What is the final electron acceptor in the light reactions of photosynthesis?

NADP+ NADP+ is the final electron acceptor in the light reactions of photosynthesis. The product is NADPH.

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 The electrons are transferred to NADP+, forming NADPH. ATP is formed via photophosphorylation, and oxygen is produced when water molecules are split.

The reaction center, antenna molecules, and primary electron acceptors that cluster in the thylakoid membrane form which structure?

photosystem The above combination describes the photosystem.

Although the reactions of the Calvin cycle are not directly dependent on light, they usually do not occur at night. Why?

The Calvin cycle depends on products of the light reactions The ATP and NADPH produced during the light reactions are necessary to provide energy and high-energy electrons for the Calvin cycle.

A red chemical dye known as phenol red changes to yellow when CO2 is present. A small green plant seedling is placed in phenol red and then placed in the dark. Which of the following is most likely to occur?

The solution is red to begin with, and it will turn yellow because respiration is occurring. Plants will not conduct photosynthesis in the dark, but they will continue with cellular respiration, releasing carbon dioxide, which should turn the chemical yellow.

Where do the electrons needed by photosystem II originate?

Water The splitting of water molecules provides the source of electrons for photosystem II.

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?

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. Because plants can make more organic material each day than they need to use as respiratory fuel and precursors for biosynthesis, they stockpile the extra sugar as starch, storing some in chloroplasts, as well as in roots, tubers, seeds, and fruits.

The primary function of light absorption by photosystems I and II is to produce __________.

a free, energized electron These free, energized electrons power the electron transport chain to generate ATP and ultimately be "handed off" to NADP+ to make NADPH for use in the Calvin cycle.

The Calvin cycle is a series of reactions that _____.

assemble sugar molecules by fixing carbon The Calvin cycle uses carbon supplied by CO2 and energy and high-energy electrons supplied by ATP and NADPH, respectively, generated during the light reactions to assemble sugar molecules.

Which of the following colors of light are useful during the process of photosynthesis?

blue, red, and violet We do not see the absorbed wavelengths, only those that are reflected. Plants appear green as they absorb these colors and reflect mostly green light.

The most important role of pigments in photosynthesis is to _____.

capture light energy The wavelengths most effectively absorbed by pigments are the colors most useful as energy for the light reactions.

In the Calvin cycle carbon dioxide provides _____, whereas ATP and NADPH provide _____ and _____, respectively.

carbon ... energy ... high-energy electrons However, the ultimate source of energy for the entire process is the sun.

The conversion of NADP+ to NADPH occurs with the assistance of

electrons from water and energy from sunlight Water is necessary because it is the splitting of water molecules that provides plant cells with electrons and an electron to reduce NADP+ to NADPH. Light energy is required to drive the transfer of the electrons to NADP+.

Photosynthesis is an __________ process in which carbon is __________, whereas cellular respiration is an __________ process in which carbon is __________.

endergonic : reduced : exergonic : oxidized Photosynthesis is an endergonic process in which electrons from water are transferred to carbon dioxide, reducing it to sugar. During the exergonic process of respiration, energy is released from sugar when the sugar is oxidized.

Which of the following colors is most strongly reflected by chlorophyll?

green Chlorophyll reflects green light, which is why leaves appear green.

Solar radiation warms the surface of the planet and then is radiated back in the form of __________.

heat Heat is radiated as the planet warms. Some of this energy is then absorbed by atmospheric gases, and some of that heat is reflected back to Earth.

The "photo-" part of the word photosynthesis refers to the _____, whereas "-synthesis" refers to _____.

light reactions that occur in the thylakoids : carbon fixation Events in the thylakoids are termed the "light reactions," and "carbon fixation" refers to the incorporation of carbon into organic molecules.

Which of the following is NOT an aspect of global climate change?

net growth of polar ice caps Quite the opposite is happening as a component of climate change: polar ice caps are shrinking.

When chloroplast pigments absorb light, _____.

their electrons become excited The absorbed energy moves the electrons to a more energetic orbital.

How many turns of the Calvin cycle are required to produce one G3P molecule?

three It requires three turns of the Calvin cycle to fix three molecules of carbon dioxide that form G3P molecule.

Chlorophyll molecules are found in which part of the chloroplast?

thylakoid membrane Grana are stacks of thylakoids; thylakoid membranes contain chlorophyll molecules.

Chlorophyll is found in the __________ of chloroplasts.

thylakoid membranes This is where light absorption occurs during photosynthesis and therefore is the place where chlorophyll molecules are located.

Both mitochondria and chloroplasts _____.

use an H+ gradient to produce ATP Chloroplasts and mitochondria both generate ATP by chemiosmosis. An electron transport chain in the membrane pumps H+ across the membrane as electrons are passed through a series of carriers that are progressively more electronegative. ATP synthase is built into the same membrane and couples the diffusion of H+ down their gradient to the phosphorylation of ADP to ATP.