Photosynthesis

Question 1

) Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?
A) CO2 and glucose
B) H2O and O2
C) ADP, i, and NADP+
D) electrons and H+
E) ATP and NADPH

Answer 1

E) ATP and NADPH

Question 2

2) Where does the Calvin cycle take place?
A) stroma of the chloroplast
B) thylakoid membrane
C) cytoplasm surrounding the chloroplast
D) interior of the thylakoid (thylakoid space)
E) outer membrane of the chloroplast

Answer 2

A) stroma of the chloroplast

Question 3

3) In autotrophic bacteria, where are the enzymes located that can carry on carbon fixation (reduction of carbon dioxide to
carbohydrate)?
A) in chloroplast membranes
B) in chloroplast stroma
C) in the cytosol
D) in the nucleoid
E) in the infolded plasma membrane

Answer 3

C) in the cytosol

Question 4

When oxygen is released as a result of photosynthesis, it is a direct by-product of
A) reducing NADP+.
B) splitting water molecules.
C) chemiosmosis.
D) the electron transfer system of photosystem I.
E) the electron transfer system of photosystem II.

Answer 4

B) splitting water molecules

Question 5

Which of the events listed below occurs in the light reactions of photosynthesis?
A) NADP is produced.
B) NADPH is reduced to NADP+.
C) Carbon dioxide is incorporated into PGA.
D) ATP is phosphorylated to yield ADP.
E) Light is absorbed and funneled to reaction-center chlorophyll a.

Answer 5

E) Light is absorbed and funneled to reaction-center chlorophyll a.

Question 6

) Which statement describes the functioning of photosystem II?
A) Light energy excites electrons in the thylakoid membrane electron transport chain.
B) Photons are passed along to a reaction-center chlorophyll.
C) The P680 chlorophyll donates a pair of protons to NADP+, which is thus converted to NADPH.
D) The electron vacancies in P680+ are filled by electrons derived from water.
E) The splitting of water yields molecular carbon dioxide as a by-product.

Answer 6

D) The electron vacancies in P680+ are filled by electrons derived from water.

Question 7

Which of the following are directly associated with photosystem I?
A) harvesting of light energy by ATP
B) receiving electrons from the thylakoid membrane electron transport chain
C) generation of molecular oxygen
D) extraction of hydrogen electrons from the splitting of water
E) passing electrons to the thylakoid membrane electron transport chain

Answer 7

B) receiving electrons from the thylakoid membrane electron transport chain

Question 8

What are the products of linear photophosphorylation?
A) heat and fluorescence
B) ATP and P700
C) ATP and NADPH
D) ADP and NADP
E) P700 and P680

Answer 8

C) ATP and NADPH

Question 9

What does the chemiosmotic process in chloroplasts involve?
A) establishment of a proton gradient across the thylakoid membrane
B) diffusion of electrons through the thylakoid membrane
C) reduction of water to produce ATP energy
D) movement of water by osmosis into the thylakoid space from the stroma
E) formation of glucose, using carbon dioxide, NADPH, and ATP

Answer 9

A) establishment of a proton gradient across the thylakoid membrane

Question 10

In a plant cell, where are the ATP synthase complexes located?
A) thylakoid membrane only
B) plasma membrane only
C) inner mitochondrial membrane only
D) thylakoid membrane and inner mitochondrial membrane
E) thylakoid membrane and plasma membrane

Answer 10

D) thylakoid membrane and inner mitochondrial membrane

Question 11

Which of the following statements best describes the relationship between photosynthesis and respiration?
A) Respiration runs the biochemical pathways of photosynthesis in reverse.
B) Photosynthesis stores energy in complex organic molecules, whereas respiration releases it.
C) Photosynthesis occurs only in plants and respiration occurs only in animals.
D) ATP molecules are produced in photosynthesis and used up in respiration.
E) Respiration is anabolic and photosynthesis is catabolic

Answer 11

B) Photosynthesis stores energy in complex organic molecules, whereas respiration releases it.

Question 12

Where are the molecules of the electron transport chain found in plant cells?
A) thylakoid membranes of chloroplasts
B) stroma of chloroplasts
C) outer membrane of mitochondria
D) matrix of mitochondria
E) cytoplasm

Answer 12

A) thylakoid membranes of chloroplasts

Question 13

Reduction of oxygen to form water occurs during
A) photosynthesis only.
B) respiration only.
C) both photosynthesis and respiration.
D) neither photosynthesis nor respiration.
E) photorespiration only

Answer 13

B) respiration only

Question 14

Reduction of NADP+ occurs during
A) photosynthesis.
B) respiration.
C) both photosynthesis and respiration.
D) neither photosynthesis nor respiration.
E) photorespiration.

Answer 14

A) photosynthesis.

Question 15

Generation of proton gradients across membranes occurs during
A) photosynthesis.
B) respiration.
C) both photosynthesis and respiration.
D) neither photosynthesis nor respiration.
E) photorespiration

Answer 15

C) both photosynthesis and respiration.

Question 16

P680+ is said to be the strongest biological oxidizing agent. Why?
A) It is the receptor for the most excited electron in either photosystem.
B) It is the molecule that transfers electrons to plastoquinone (Pq) of the electron transfer system.
C) It transfers its electrons to reduce NADP+ to NADPH.
D) This molecule has a stronger attraction for electrons than oxygen, to obtain electrons from water.
E) It has a positive charge.

Answer 16

D) This molecule has a stronger attraction for electrons than oxygen, to obtain electrons from water.

Question 17

In thylakoids, protons travel through ATP synthase from the thylakoid space to the stroma. Therefore, the catalytic “knobs” of ATP
synthase would be located
A) on the side facing the thylakoid space.
B) on the ATP molecules themselves.
C) on the pigment molecules of photosystem I and photosystem II.
D) on the stromal side of the membrane.
E) built into the center of the thylakoid stack (granum).

Answer 17

D) on the stromal side of the membrane.

Question 18

The reactions that produce molecular oxygen (O2) take place in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but are not part of photosynthesis

Answer 18

A) the light reactions alone.

Question 19

Where do the enzymatic reactions of the Calvin cycle take place?
A) stroma of the chloroplast
B) thylakoid membranes
C) matrix of the mitochondria
D) cytosol around the chloroplast
E) thylakoid space

Answer 19

A) stroma of the chloroplast

Question 20

What is the primary function of the Calvin cycle?
A) use ATP to release carbon dioxide
B) use NADPH to release carbon dioxide
C) split water and release oxygen
D) transport RuBP out of the chloroplast
E) synthesize simple sugars from carbon dioxide

Answer 20

E) synthesize simple sugars from carbon dioxide

Question 21

In C3 photosynthesis, the reactions that require ATP take place in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but is not part of photosynthesis.

Answer 21

B) the Calvin cycle alone.

Question 22

The NADPH required for the Calvin cycle comes from
A) reactions initiated in photosystem I.
B) reactions initiated in photosystem II.
C) the citric acid cycle.
D) glycolysis.
E) oxidative phosphorylation.

Answer 22

A) reactions initiated in photosystem

Question 23

Reactions that require CO2 take place in
A) the light reactions alone.
B) the Calvin cycle alone.
C) both the light reactions and the Calvin cycle.
D) neither the light reactions nor the Calvin cycle.
E) the chloroplast, but is not part of photosynthesis

Answer 23

B) the Calvin cycle alone.

Question 24

Which of the following statements best represents the relationships between the light reactions and the Calvin cycle?
A) The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, i, and NADP+ to the light
reactions.
B) The light reactions provide ATP and NADPH to the carbon fixation step of the Calvin cycle, and the cycle provides water and
electrons to the light reactions.
C) The light reactions supply the Calvin cycle with CO2 to produce sugars, and the Calvin cycle supplies the light reactions with sugars
4
to produce ATP.
D) The light reactions provide the Calvin cycle with oxygen for electron flow, and the Calvin cycle provides the light reactions with
water to split.
E) There is no relationship between the light reactions and the Calvin cycle.

Answer 24

A) The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, i, and NADP+ to the light
reactions.

Question 25

In the process of carbon fixation, RuBP attaches a CO2 to produce a six-carbon molecule, which is then split to produce two
molecules of 3-phosphoglycerate. After phosphorylation and reduction produces glyceraldehyde 3-phosphate (G3P), what more needs
to happen to complete the Calvin cycle?
A) addition of a pair of electrons from NADPH
B) inactivation of RuBP carboxylase enzyme
C) regeneration of ATP from ADP
D) regeneration of RuBP
E) regeneration of NADP+

Answer 25

D) regeneration of RuBP

Question 26

Photorespiration occurs when rubisco reacts RuBP with
A) CO2.
B) O2.
C) glyceraldehyde 3-phosphate.
D) 3-phosphoglycerate.
E) NADPH.

Answer 26

B) O2.

Question 27

Why are C4 plants able to photosynthesize with no apparent photorespiration?
A) They do not participate in the Calvin cycle.
B) They use PEP carboxylase to initially fix CO2.
C) They are adapted to cold, wet climates.
D) They conserve water more efficiently.
E) They exclude oxygen from their tissues.

Answer 27

B) They use PEP carboxylase to initially fix CO2.

Question 28

CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because they
A) fix CO2 into organic acids during the night.
B) fix CO2 into sugars in the bundle-sheath cells.
C) fix CO2 into pyruvate in the mesophyll cells.
D) use the enzyme phosphofructokinase, which outcompetes rubisco for CO2.
E) use photosystem I and photosystem II at night.

Answer 28

A) fix CO2 into organic acids during the night.

Question 29

The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why?
A) Each one minimizes both water loss and rate of photosynthesis.
B) C4 compromises on water loss and CAM compromises on photorespiration.
C) Both minimize photorespiration but expend more ATP during carbon fixation.
D) CAM plants allow more water loss, while C4 plants allow less CO2 into the plant.
E) C4 plants allow less water loss but CAM plants allow more water loss.

Answer 29

C) Both minimize photorespiration but expend more ATP during carbon fixation

Question 30

Compared to C3 plants, C4 plants
A) can continue to fix CO2 even at relatively low CO2 concentrations and high oxygen concentrations.
B) have higher rates of photorespiration.
C) do not use rubisco for carbon fixation.
D) grow better under cool, moist conditions.
E) make a four-carbon compound, oxaloacetate, which is then delivered to the citric acid cycle in mitochondria

Answer 30

A) can continue to fix CO2 even at relatively low CO2 concentrations and high oxygen concentrations

Question 31

How is photosynthesis similar in C4 plants and CAM plants?
A) In both cases, only photosystem I is used.
B) Both types of plants make sugar without the Calvin cycle.
C) In both cases, rubisco is not used to fix carbon initially.
D) Both types of plants make most of their sugar in the dark.
E) In both cases, thylakoids are not involved in photosynthesis

Answer 31

C) In both cases, rubisco is not used to fix carbon initially.

Question 32

While C-4 plants have carbon dioxide fixation and carbon dioxide uptake separated by location within the plant, CAM plants:
A) have these processes separated by time
B) fix much greater amounts of carbon dioxide than C-4 plants
C) are found in tropical regions where nutrients are abundant
D) all of the choices are correct

Answer 32

A) have these processes separated by time.