Question 1

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 and 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)free radicals induce the synthesis of carotenoids in chloroplasts
D)carotenoids communicate directly with the immune system of plants

Accepted Answer

The presence of carotenoids in chloroplasts suggests that they have a protective function in the cell by stabilizing free radicals, which are highly reactive and can degrade and destroy other compounds in their vicinity. Therefore, option B is the best choice. Option A is incorrect as it is not necessary that destruction of chloroplasts would lead to destruction of the entire cell. Option C is incorrect as there is no evidence for free radicals inducing the synthesis of carotenoids. Option D is incorrect as there is no evidence of carotenoids communicating directly with the immune system in plants.

Question 2

Which of the following 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 a Mg in its ring structure,whereas chlorophyll b contains iron.
D)Chlorophyll a and b absorb light energy at slightly different wavelengths.

Accepted Answer

Chlorophyll a and b differ in their absorption spectra, with chlorophyll a absorbing more at 680 nm and chlorophyll b absorbing more at 640 nm. This allows plants to utilize a wider range of light energy for photosynthesis. Option A is incorrect as chlorophyll b is also a pigment, and Option C is incorrect as both chlorophylls contain Mg in their ring structure. Option B is incorrect as chlorophyll a absorbs mostly red and blue light, not yellow.

Question 3

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 temporarily shut down photosynthesis
C)their ability to reflect ultraviolet light
D)their ability to absorb ultraviolet light

Accepted Answer

Flavonoids have the capability to absorb ultraviolet light, which is the reason why they are able to protect plant leaves from damage caused by UV radiation. This capability is due to the specific chemical structure of flavonoids that allows them to absorb UV light and dissipate its energy, thereby preventing it from causing damage to the plant's DNA and other important molecules.

Question 4

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

Accepted Answer

The oxygen produced during photosynthesis comes from water, which is split during the light-dependent reactions of photosynthesis. This process is known as photolysis or water splitting, and it produces oxygen gas as a byproduct.

Question 5

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

Accepted Answer

Chloroplasts are a type of plastid and are therefore related to other types of plastids such as chromoplasts and leucoplasts.

Question 6

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 considered to be part of the reaction center of photosystem I
D)absorb the same wavelengths of light as their associated chlorophylls

Accepted Answer

The proteins of the electron transport chain in the light-dependent reactions are membrane proteins present in the thylakoid.

Question 7

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

Accepted Answer

Photosynthesis is believed to have originated in ancient prokaryotes such as cyanobacteria, which were able to convert light energy into chemical energy through photosynthesis. This process eventually evolved and was used by plants, algae, and other organisms.

Question 8

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 changes color
C)water supply to the leaves has been reduced
D)the cells of the leaves begin to die

Accepted Answer

In autumn, the chlorophyll in leaves breaks down as the days get shorter and cooler. As a result, the green color fades, revealing the colors of other pigments such as carotenoids (yellow, orange and brown) and anthocyanins (reds and purples) that have been present in the leaves all along. So, option A is the correct answer.

Question 9

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 chlorophyll (or other pigment molecules of the antenna complex) absorb energy, an electron is excited to a higher energy level. This is called photoexcitation, and it is the event that accompanies energy absorption by chlorophyll. This event ultimately leads to the transfer of energy to reaction centers, where it can be used to drive photosynthesis. ATP synthesis, carboxylation reactions, and NADPH electron stripping are all processes that occur downstream of energy absorption and photoexcitation.

Question 10

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 are correct.

Accepted Answer

PQ is a small molecular weight electron carrier that is lipid-soluble and can move freely within the thylakoid membrane. It shuttles electrons between photosystem II and the cytochrome b6f complex in the electron transport chain. Therefore, both options A and B are correct.

Question 11

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)violet and red light
D)red and blue light

Accepted Answer

Red and blue light are most effectively absorbed by chlorophyll, the primary pigment in the antenna complex, leading to higher rates of photosynthesis and oxygen production.

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)the wavelengths of light that are transmitted by the plant
C)the wavelengths of light to which the plant's pigments respond
D)the surface area of the plant's leaves

Accepted Answer

The absorption spectrum depends on the wavelengths of light to which the plant's pigments respond. Different pigments in the plant, such as chlorophyll and carotenoids, have different absorption spectra which determine which wavelengths of light the plant can absorb for photosynthesis. The wavelengths that are absorbed are used to power the plant's metabolic processes, while the wavelengths that are not absorbed are reflected or transmitted, giving the plant its characteristic color.

Question 13

The electrons of photosystem II are excited and transferred to electron carriers.From which molecule or structure do the photosystem II replacement electrons come?
A)the electron carrier,plastocyanin
B)photosystem I
C)water
D)oxygen

Accepted Answer

The replacement electrons for photosystem II come from the splitting of water during the light-dependent reactions of photosynthesis. This process is called photolysis, and it results in the release of oxygen gas as a byproduct.

Question 14

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 system of electron carriers associated with photosystem II is used to establish and maintain a proton gradient. This proton gradient is essential for ATP synthesis during the light-dependent reactions of photosynthesis.

Question 15

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

Accepted Answer

Pigment molecules, such as chlorophyll, are responsible for capturing light energy and initiating the process of photosynthesis. Therefore, thylakoid membranes must contain a large number of pigment molecules in the reaction centers to harvest light energy. Proteins, phospholipids, and water are also present in thylakoid membranes, but they do not play the primary role in capturing light energy. Electron carriers are important in the transport of electrons during photosynthesis, but they are not directly involved in harvesting light energy at the reaction centers.

Question 16

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 light energy of 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

Having several structurally different pigments in the reaction centers of photosystems enables the plant to absorb light energy of a variety of wavelengths, which increases the efficiency of photosynthesis. Different pigments absorb light of different wavelengths and transfer the energy to the reaction center, where it is used to drive electron transfer reactions.

Question 17

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 that particular plant.
B)Paper chromatography would separate the pigments from a particular plant into several bands.
C)The isolated pigments would always be some shade of green.
D)Paper chromatography would isolate only the pigments that reflect green light.

Accepted Answer

Paper chromatography is a technique used to separate compounds or molecules based on their physical and chemical properties. In the case of plant pigments, different types of pigments (chlorophylls, carotenoids) have different physical and chemical properties and therefore would be separated into different bands on the chromatography paper. Therefore, it is most believable that paper chromatography would separate the pigments from a particular plant into several bands.

Question 18

The final electron acceptor(s)associated with photosystem I is/are _____.
A)oxygen
B)water
C)NADP
D)NADPH

Accepted Answer

The final electron acceptor associated with photosystem I is NADP. This is because photosystem I generates NADPH, which is used in the Calvin cycle to reduce carbon dioxide and synthesize glucose.

Question 19

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

Accepted Answer

The answer of Chlorophylls absorb light in which colors of...

Question 20

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

The main difference between NAD⁺ and NADP is that NADP has an additional phosphate group, while NAD⁺ does not. Both NAD⁺ and NADP function as electron carriers in metabolic reactions, but NADP is primarily involved in anabolic reactions, such as photosynthesis and fatty acid synthesis, where it provides reducing power in the form of electrons and hydrogen ions. The phosphate group on NADP enables it to carry two electrons and a proton, making it more suitable for biosynthetic reactions, whereas NAD⁺ can only carry one electron at a time.

Quiz 10: Photosynthesis

Which of the following is a difference between chlorophyll a and chlorophyll b?

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

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

Which of the following statements concerning chloroplasts is false?

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

The process of photosynthesis probably originated _____.

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

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

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 _____.

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?

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

The electrons of photosystem II are excited and transferred to electron carriers.From which molecule or structure do the photosystem II replacement electrons come?

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

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

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

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

The final electron acceptor(s) associated with photosystem I is/are _____.

Chlorophylls absorb light in which colors of the visible range?

What is the difference between NAD⁺ and NADP?