Question 1

Plastoquinone (PQ),an electron carrier of small molecular weight,is found in the electron transport chain associated with photosystem II.If PQ is not directly anchored to other membrane or cytoplasmic structures,it is probably
A)mobile in the thylakoid membrane.
B)lipid soluble.
C)a molecule that serves as a shuttle between the electron transport chain and ATP synthase.
D)both A and B.

Accepted Answer

Since PQ is a small molecule and not directly anchored to other structures, it is likely to be mobile within the thylakoid membrane. Additionally, PQ is known to be lipid soluble due to its ability to move through the hydrophobic region of the membrane. Therefore, both options A and B are correct. PQ does not serve as a shuttle between the electron transport chain and ATP synthase, so option C is not correct.

Question 2

Chlorophylls absorb light in which colors of the visible range?
A)green and blue
B)blue and red
C)green and red
D)orange and blue

Accepted Answer

Chlorophylls primarily absorb light in the blue and red regions of the visible spectrum, reflecting green light, which is why plants appear green.

Question 3

Which of the following statements about photosynthesis and cellular respiration is TRUE?
A)Photosynthesis is a catabolic process;cellular respiration is an anabolic process.
B)Photosynthesis occurs in plants and some prokaryotes;cellular respiration occurs in animals,but not plants.
C)Organelles are required to carry out photosynthesis and cellular respiration in eukaryotes.
D)Both photosynthesis and cellular respiration require CO₂ as an input.

Accepted Answer

Photosynthesis occurs in chloroplasts and cellular respiration occurs in mitochondria, both of which are organelles in eukaryotic cells.

Question 4

The process of photosynthesis probably originated
A)in plants.
B)in prokaryotes.
C)in fungi.
D)three separate times.

Accepted Answer

The process of photosynthesis likely originated in prokaryotes such as cyanobacteria, which have been performing photosynthesis for billions of years before the evolution of plants.

Question 5

What is the difference between NAD⁺ and NADP?
A)NAD⁺ functions as an electron transporter,whereas NADP does not.
B)NAD⁺ functions as a free energy source for cells,whereas NADP does not.
C)Both function as electron carriers,but NADP has a phosphate group and NAD⁺ does not.
D)Both transport electrons to the electron transport chain (ETC)found on the inner mitochondrial membrane,but NADP transfers its electrons to the ETC at a higher energy level.

Accepted Answer

Both NAD⁺ and NADP function as electron carriers, but NADP has an additional phosphate group attached to its ribose ring. This phosphate group allows NADP to be involved in different metabolic pathways compared to NAD⁺, such as in the biosynthesis of fatty acids and steroids.

Question 6

What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?
A)ATP is synthesized from the energy absorbed.
B)A carboxylation reaction of the Calvin cycle occurs.
C)Electrons are stripped from NADPH.
D)An electron is excited.

Accepted Answer

When energy is absorbed by chlorophyll or other pigment molecules in the antenna complex, an electron becomes excited, jumping to a higher energy level. This electron is then passed on to the reaction center of the photosystem, beginning the process of converting light energy into chemical energy.

Question 7

As electrons are passed through the system of electron carriers associated with photosystem II,they lose energy.What happens to this energy?
A)It excites electrons of the reaction center of photosystem I.
B)It is lost as heat.
C)It is used to establish and maintain a proton gradient.
D)It is used to phosphorylate NAD⁺ to NADPH,the molecule that accepts electrons from photosystem I.

Accepted Answer

The energy lost by electrons as they pass through the electron carriers of photosystem II is used to establish and maintain a proton gradient, which is necessary for the generation of ATP during photophosphorylation. This proton gradient is created by pumping protons from the stroma into the thylakoid lumen by the electron transport chain associated with photosystem II, and the energy lost by the electrons is used to power this process. Eventually, the protons flow back down their electrochemical gradient through ATP synthase, which uses the energy to phosphorylate ADP to ATP.

Question 8

The proteins of the electron transport chain active in the light-dependent reactions
A)are membrane proteins present in the thylakoid.
B)are free proteins present in the thylakoid lumen.
C)are part of the reaction center of photosystem I.
D)have hydrophilic exterior surfaces.

Accepted Answer

The electron transport chain proteins involved in the light-dependent reactions of photosynthesis are membrane proteins located in the thylakoid membrane. They are embedded within the membrane and therefore cannot be free proteins in the thylakoid lumen. Additionally, they are not part of the reaction center of photosystem I or II and have hydrophilic and hydrophobic regions, with the hydrophilic regions facing either the stroma or the thylakoid lumen.

Question 9

Based on what you know about the structure and function of the antenna complex,irradiating a leaf with which of the following light types would result in the release of the greatest quantities of oxygen?
A)red and orange light
B)green and blue light
C)blue and orange light
D)red and blue light

Accepted Answer

The antenna complex contains pigments that absorb light of specific wavelengths and transfer the energy to the reaction center for photosynthesis to occur. The pigments that are most effective at absorbing light for photosynthesis are chlorophyll a and chlorophyll b, which absorb light most effectively in the blue and red regions of the spectrum. Therefore, irradiating a leaf with red and blue light would result in the release of the greatest quantities of oxygen.

Question 10

Besides proteins,thylakoid membranes must contain a large number of ________ molecules in the reaction centers in order to harvest light energy.
A)phospholipid
B)oligosaccharide
C)pigment
D)electron carrier

Accepted Answer

Thylakoid membranes contain pigments such as chlorophyll and carotenoids, which are essential for capturing and absorbing light energy during photosynthesis. These pigments are found in the reaction centers of the thylakoid membrane, where they work in conjunction with proteins and electron carriers to convert light energy into chemical energy.

Question 11

In autumn,the leaves of deciduous trees change colors.This is because the chlorophyll is degraded,and
A)the carotenoids and other pigments are still present in the leaves.
B)degraded chlorophyll becomes a pigment with different colors.
C)water supply to the leaves has been reduced.
D)the cells of the leaves begin to die.

Accepted Answer

During autumn, the chlorophyll in the leaves of deciduous trees degrades, causing the green pigment to disappear. This allows the other pigments such as carotenoids and anthocyanins, which are still present, to become visible and produce the vibrant colors of fall.

Question 12

The absorption spectrum of a plant shows what wavelengths of light the plant absorbs.The absorption spectrum depends on
A)the wavelengths of light that hit the plant.
B)wavelengths of light that are transmitted by the plant.
C)wavelengths of light to which the plant's pigments respond.
D)the thickness of the plant's leaves.

Accepted Answer

The absorption spectrum shows which wavelengths of light the plant's pigments absorb, indicating which wavelengths are being used for photosynthesis. The plant pigments, such as chlorophyll, respond to specific wavelengths of light, resulting in the absorption of energy from those wavelengths. The other choices (A, B, and D) are not relevant to determining the absorption spectrum of a plant.

Question 13

What is a difference between chlorophyll a and chlorophyll b?
A)Chlorophyll a is a pigment,and chlorophyll b is the enzyme that transfers excited electrons from chlorophyll a to electron carriers of the thylakoid membrane.
B)Chlorophyll a absorbs yellow light,and chlorophyll b absorbs green.
C)Chlorophyll a contains Mg⁺⁺ in a ring structure,whereas chlorophyll b contains iron.
D)Chlorophyll a and b absorb light energy at slightly different wavelengths.

Accepted Answer

Chlorophyll a and chlorophyll b differ in the wavelengths of light they absorb most efficiently. Chlorophyll a absorbs most light in the blue to violet and red parts of the spectrum, while chlorophyll b absorbs most light in the blue and orange parts of the spectrum. This difference in absorption spectra allows plants to utilize a wider range of wavelengths for photosynthesis.

Question 14

If pigments from a particular species of plant are extracted and subjected to paper chromatography,which of the following is the most believable result?
A)Paper chromatography for the plant would isolate a single band of pigment that is characteristic of the particular plant.
B)Paper chromatography would separate the pigments from a particular plant into several bands.
C)The single band of pigment that is isolated is always some shade of green.
D)Paper chromatography isolates only the pigments that reflect green light.

Accepted Answer

Paper chromatography separates pigments based on their solubility and polarity, so it is likely that pigments from a particular plant will separate into several bands. The number and location of the bands will depend on the specific pigments present in the plant. Therefore, it is unlikely that a single band of pigment characteristic of the plant will be isolated. Additionally, while some plant pigments may reflect green light, not all of them do, so option D is not a reliable statement. Option C is also not reliable, as not all plant pigments are green - there are many different types of pigments that contribute to the overall color of a plant.

Question 15

Why are there several structurally different pigments in the reaction centers of photosystems?
A)Excited electrons must pass through several pigments before they can be transferred to electron acceptors of the electron transport chain.
B)This setup enables the plant to absorb energy from sunlight from a variety of wavelengths.
C)They enable the plant to absorb more photons from light energy,all of which are at the same wavelength.
D)They enable the reaction center to excite electrons to a higher energy level.

Accepted Answer

The presence of several structurally different pigments in the reaction centers of photosystems enables the plant to absorb energy from sunlight from a variety of wavelengths. This increases the efficiency of photosynthesis as the plant can capture more energy from different parts of the visible spectrum of light.

Question 16

Which of the following statements concerning chloroplasts is false?
A)They are unrelated to plastids.
B)They have outer and inner membranes.
C)They have their own DNA.
D)They have an internal membrane system known as the thylakoids.

Accepted Answer

Chloroplasts are a type of plastid and are derived from the same ancestral lineage as other plastids such as amyloplasts and chromoplasts. Therefore, statement A is false.

Question 17

Which of the following is FALSE regarding photosynthesis?
A)It first appeared in ancient prokaryotes.
B)The earliest form of photosynthetic reactions oxidized (used)H₂O and yielded O₂.
C)Development of oxygenic photosynthesis led to atmospheric changes that allowed evolution of cells/organisms able to use aerobic respiration.
D)Some forms of photosynthesis involve oxidizing compounds such as ferrous iron or H₂S.

Accepted Answer

The earliest form of photosynthetic reactions did not produce O₂, but rather used other compounds such as H₂S. The development of oxygenic photosynthesis, which first appeared in cyanobacteria, was responsible for the production of oxygen.

Question 18

Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide.In fact,it comes from
A)water.
B)glucose.
C)H₂S.
D)electrons from NADPH.

Accepted Answer

Oxygen produced by photosynthetic plants comes from water, not carbon dioxide. During photosynthesis, water is split into oxygen, protons, and electrons. The oxygen is released into the atmosphere as a byproduct.

Question 19

What capability of flavonoids,found in plants,protects their leaves from damage due to ultraviolet light?
A)their ability to stabilize free radicals
B)their ability to absorb visible light
C)their ability to absorb infrared light
D)their ability to absorb ultraviolet light

Accepted Answer

Flavonoids have the ability to absorb ultraviolet light, which helps to protect plants' leaves from damage caused by exposure to UV radiation. This is particularly important for plants that grow in areas with high levels of UV radiation, such as at high altitudes or in regions with thin ozone layers. The absorption of UV light by flavonoids is due to their unique chemical structure, which enables them to act as natural sunscreens for plants.

Question 20

Energy from sunlight can excite electrons,kicking them out of their orbitals and creating free radicals.Free radicals are highly reactive atoms or molecules that have unpaired electrons.They degrade and destroy other compounds in their vicinity.Carotenoids,one of the pigments present in most chloroplasts,can stabilize these free radicals.This suggests that
A)once chloroplasts are destroyed,the free radicals will destroy the cell.
B)carotenoids probably have a protective function in the cell.
C)other pigments (besides carotenoids and chlorophyll)are essential for the health of a plant cell.
D)carotenoids communicate directly with the immune system of plants.

Accepted Answer

The fact that carotenoids can stabilize free radicals suggests that they have a protective function in the cell, helping to prevent damage to other compounds. Therefore, option B is the best choice. Option A is incorrect because it assumes that the destruction of chloroplasts will inevitably lead to the destruction of the cell, which may not always be the case. Option C is also incorrect because the passage does not provide any evidence to support the idea that other pigments are essential for the health of a plant cell. Option D is incorrect because there is no mention of carotenoids communicating with the immune system of plants in the passage.

Quiz 10: Photosynthesis

Plastoquinone (PQ) ,an electron carrier of small molecular weight,is found in the electron transport chain associated with photosystem II.If PQ is not directly anchored to other membrane or cytoplasmic structures,it is probably

Chlorophylls absorb light in which colors of the visible range?

Which of the following statements about photosynthesis and cellular respiration is TRUE?

The process of photosynthesis probably originated

What is the difference between NAD⁺ and NADP?

What event accompanies energy absorption by chlorophyll (or other pigment molecules of the antenna complex) ?

As electrons are passed through the system of electron carriers associated with photosystem II,they lose energy.What happens to this energy?

The proteins of the electron transport chain active in the light-dependent reactions

Based on what you know about the structure and function of the antenna complex,irradiating a leaf with which of the following light types would result in the release of the greatest quantities of oxygen?

Besides proteins,thylakoid membranes must contain a large number of ________ molecules in the reaction centers in order to harvest light energy.

In autumn,the leaves of deciduous trees change colors.This is because the chlorophyll is degraded,and

The absorption spectrum of a plant shows what wavelengths of light the plant absorbs.The absorption spectrum depends on

What is a difference between chlorophyll a and chlorophyll b?

If pigments from a particular species of plant are extracted and subjected to paper chromatography,which of the following is the most believable result?

Why are there several structurally different pigments in the reaction centers of photosystems?

Which of the following statements concerning chloroplasts is false?

Which of the following is FALSE regarding photosynthesis?

Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide.In fact,it comes from

What capability of flavonoids,found in plants,protects their leaves from damage due to ultraviolet light?