Deck 10: Photosynthesis

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

Answer 1

B

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.

Answer 2

D

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

Answer 3

D

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

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.

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

Question 7

The process of photosynthesis probably originated _____.

A)in plants
B)in prokaryotes
C)in fungi
D)three separate times during evolution

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

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.

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.

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

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

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

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.

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

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.

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.

Question 18

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

A)oxygen
B)water
C)NADP
D)NADPH

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

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.

Question 21

CAM plants function using crassulacean acid metabolism.Like C₄ plants,CAM plants provide a preparatory step for the Calvin cycle.CAM plants are found in hot,dry environments;to prevent desiccation,they keep their stomata closed during the day.They take in carbon dioxide at night while stomata are open.To increase the concentration of carbon dioxide available to the enzyme rubisco and minimize the degree of photorespiration,the CAM plants carboxylate _____.

A)phosphoenolpyruvate
B)oxaloacetate
C)organic acids
D)ribose

Question 22

Which of the following statements most accurately compares photosynthesis and respiration?

A)ATP generated during photosynthesis is a fundamentally different process than ATP generated during respiration.
B)Photosynthesis is just respiration in reverse.
C)Photosynthesis requires ATP,but respiration does not.
D)Photosynthesis stores energy in complex organic molecules;respiration releases the energy stored in complex organic molecules.

Question 23

How does carbon fixation differ between C₃ and C₄ plants?

A)C₄ plants undergo carbon fixation by carboxylation of a four-carbon substrate (oxaloacetate),while in C₃ plants,a three-carbon compound (phosphoglycerate)is carboxylated.
B)Both C₃ and C₄ plants involve carboxylation of ribulose-1,5-bisphosphate by rubisco;but in C₃ plants,the first stable intermediate is 3-phosphoglycerate,and in C₄ plants,it is oxaloacetate.
C)C₃ plants don't undergo photorespiration,but C₄ plants do.
D)Rubisco is the primary enzyme that catalyzes carbon fixation in C₃ plants,and phosphoenolpyruvate carboxylase can catalyze carbon fixation in C₄ plants.

Question 24

Photorespiration is _____.

A)a process that rarely occurs in photosynthetic organisms
B)a process involving addition of oxygen to ribulose-1,5-bisphosphate and the formation of ribose-1,5-diphosphate
C)a process involving the addition of oxygen to ribulose-1,5-bisphosphate and the formation of the products 3-phosphoglycerate and 2-phosphoglycolate
D)a process involving the carboxylation of ribulose-1,5-bisphosphate

Question 25

Data suggest that rubisco (ribulose-1,5-bisphosphate carboxylase)makes up 10% of the total protein found in spinach leaves.Research elucidating the structure of rubisco shows that it has four active sites.Why,with four active sites,might there be such a large concentration of rubisco in plant matter?

A)All heterotrophic organisms depend on plants,either directly or indirectly,for their food supply.
B)Rubisco is a very slow enzyme;what it lacks in speed,it makes up in quantity.
C)Rubisco catalyzes four of the six reactions found in the Calvin cycle.
D)Three of the four active sites bind carbon dioxide;only one binds ribulose-1,5-bisphosphate.

Question 26

How are the light-dependent and light-independent reactions of photosynthesis related?

A)The products of the light-independent reactions are used in the light-dependent reactions.
B)The products of light-dependent reactions are used in light-independent reactions.
C)The products of light-independent reactions must be present for light-dependent reactions to take place.
D)They are not related.

Question 27

What is the main purpose of the light-dependent reactions of photosynthesis?

A)to generate oxygen by "splitting" H₂O
B)to produce NADPH for use in respiration
C)to produce NADPH and ATP
D)to use ATP to make glucose

Question 28

Purple photosynthetic bacteria do not contain chloroplasts.They have an antenna system that includes two light-harvesting protein complexes,both of which are integral membrane proteins.The bacteriochlorophyll a molecules contain Mg²⁺ and absorb light at 800 nm.Which of the following statements comparing photosynthesis in purple bacteria and plant chloroplasts is true?

A)Because purple bacteria do not have chloroplasts,there is no electron transport associated with photosynthesis.
B)Bacteriochlorophyll a is a molecule containing Mg²⁺,whereas chlorophyll a from chloroplasts contains Fe²⁺.
C)Bacteriochlorophyll a absorbs light most efficiently in the ultraviolet range,at a significantly shorter wavelength than that for chlorophyll a of chloroplasts.
D)Plant chlorophyll a absorbs in the visible light range,whereas purple photosynthetic bacteriochlorophyll a absorbs light at a longer wavelength.

Question 29

In the carbon fixation step of the Calvin cycle,ribulose-1,5-bisphosphate (a five-carbon compound)is carboxylated to produce _____.

A)5 molecules of carbon dioxide
B)2 three-carbon compounds
C)acetyl CoA (two carbons)and oxaloacetate (four carbons)
D)glucose

Question 30

Most of the enzymes of the Calvin cycle also function in other metabolic pathways.This should not be a surprising finding,because _____.

A)metabolic reactions are catalyzed by enzymes that have multiple functions
B)there is a close relationship between carbohydrate synthesis and carbohydrate metabolism
C)the Calvin cycle is nearly ubiquitous in cells,as are metabolic pathways
D)the Calvin cycle probably evolved at the same time as did glycolysis

Question 31

Which of the following procedures would identify the enzyme that catalyzes the carboxylation of ribulose-1,5-bisphosphate?

A)irradiating a leaf extract with red light
B)introducing radiolabeled carbon dioxide into a plant extract and determining which molecules become radiolabeled
C)purifying a variety of proteins from plant extracts and testing each protein individually to see if it can carboxylate ribulose-1,5-bisphosphate
D)differential sedimentation of a protein extract

Question 32

The light-independent reactions of plants function to make organic molecules using carbon dioxide as a carbon source.What is the electron source that helps reduce carbon dioxide to sugars and other organic molecules?

A)NADH
B)NADPH
C)ATP
D)electrons from oxygen