Homework 7

In plants and algae, _____ is the source of the electrons needed for photosynthesis. NADPH H2O O2 CO2 H+

H2O

How would subjecting a CAM plant at night to normal daytime temperatures affect its water use efficiency (CO₂ captured /H₂O lost)? CO₂ capture would increase, due to a temperature-induced increase in PEP carboxylase activity, which is enough to increase water use efficiency. Water use efficiency would decrease due to an increasing concentration gradient for diffusion of water out of the leaf at night. Water use efficiency would increase due to more rapid diffusion of CO₂during the day. CO₂ capture would decrease due to temperature inhibition of rubisco, which would decrease water use efficiency.

Water use efficiency would decrease due to an increasing concentration gradient for diffusion of water out of the leaf at night.

Which of the following are produced directly as a result of the movement of electrons through the photosynthetic electron transport chain? water and carbohydrates oxygen and carbohydrates carbohydrates and ATP ATP and NADPH

ATP and NADPH

Suppose you discovered a mutant strain of spinach in which the thylakoid membranes were slightly permeable to protons, thus allowing a slow leakage. (Remember that normal membranes are not permeable to protons at all.) How might this defect affect the yield of ATP and/or NADPH from the light reactions? NADPH yield would decrease. ATP yield would increase. There would be no change. NADPH yield would increase. ATP yield would decrease.

ATP yield would decrease

Why is the photosynthetic electron transport chain sometimes referred to as the "Z scheme"? Because the energy level of the electrons increases and decreases and increases and decreases. Because the electrons zigzag through the antenna chlorophyll molecule to get to the reaction center. Because the electrons zigzag through the electron transport chain as they travel from one photosystem to another in the thylakoid membrane.

Because the energy level of the electrons increases and decreases and increases and decreases.

Which of the following statements is TRUE regarding CO2 capture and the Calvin cycle in CAM plants? (Select all that apply.) CO2 is captured in mesophyll cells, and the Calvin cycle occurs in bundle-sheath cells. CO2 capture and the Calvin cycle both occur in the same cell. CO2 capture and the Calvin cycle both occur during the day (in sunlight). CO2 capture occurs at night, and the Calvin cycle takes place in the day.

CO2 capture and the Calvin cycle both occur in the same cell. CO2 capture occurs at night, and the Calvin cycle takes place in the day.

In animal cells, most ATP synthesis takes place in mitochondria, but in plant cells, most of the ATP used by plant cells is made in the chloroplasts. False True

False

Two cells are adjacent to one another. Cell A has a solute potential = -1.4 and a pressure potential = 0.6. Cell B has a solute potential = -1.6 and a pressure potential of 1.0. Which way will water flow? Both ways at equal rates. You need more information. From A to B. From B to A

From B to A

The reducing agent during the Calvin cycle is: ATP. NADPH. NADH. oxygen. FADH2.

NADPH.

During photorespiration, which of the following molecules acts as a substrate for the rubisco enzyme? O2 CO2 N2 H2O

O2

In plants and algae, which of the following is a by-product of photosynthesis? CO2 carbohydrates H+ C6H12O6 O2

O2

You are evaluating novel varieties of C3 rice that express PEP carboxylase and rubisco in both mesophyll and bundle-sheath cells for a project to develop rice plants that are capable of C4 photosynthesis. Your MOST promising candidates are those for which the enzyme levels of: both enzymes are highly expressed in both cell types. both enzymes are higher in bundle-sheath cells than in mesophyll cells. PEP carboxylase levels are higher in mesophyll cells than in bundle-sheath cells. rubisco levels are lower in bundle-sheath cells than in mesophyll cells.

PEP carboxylase levels are higher in mesophyll cells than in bundle-sheath cells.

Which one of the following statements BEST represents the relationship between cellular respiration and photosynthesis? Respiration occurs only in animals and photosynthesis occurs only in plants. Photosynthesis reverses the biochemical pathways of respiration. Photosynthesis occurs only during the day and respiration occurs only at night. Respiration stores energy in organic molecules, while photosynthesis releases it. Photosynthesis stores energy in organic molecules, while respiration releases it.

Photosynthesis stores energy in organic molecules, while respiration releases it.

Which of the following CORRECTLY describes the role of rubisco in the Calvin cycle? Rubisco uses NADPH to reduce 3-phosphoglycerate to a three-carbon sugar. R.ubisco incorporates CO2 from the atmosphere into an organic molecule Rubisco uses ATP to regenerate RUBP. None of the other answer options is correct.

Rubisco incorporates CO2 from the atmosphere into an organic molecule

Which of the following statements must be true in order for ATP synthase present in chloroplasts to function properly? The pH of the stroma must be higher than the pH of the thylakoid lumen. The pH of the stroma must be lower than the pH of the thylakoid lumen. There must be no difference in pH between the stroma of the chloroplast and the thylakoid lumen.

The pH of the stroma must be higher than the pH of the thylakoid lumen.

Which of the following is TRUE concerning the Calvin cycle and light-harvesting reactions of photosynthesis? They take place in different types of cells in the plant. They take place in different organelles. They take place in different compartments of the same organelle. None of the other answer options is correct.

They take place in different compartments of the same organelle.

.Two plant cells are adjacent to one another. If cell A has a solute potential =- 0.5 MPa and Cell B has a solute potential = -1.0 MPa, then water molecules will: Move from B to A Move from A to B You can't tell, you need more information Move at equal rater in both directions

You can't tell, you need more information

In C4 plants, the Calvin cycle is performed in _____; CO2 is captured during the C4 cycle in _____. mesophyll cells; bundle-sheath cells bundle-sheath cells; mesophyll cells the night; the day the day; the night

bundle-sheath cells; mesophyll cells

How does the plant cell protect itself from harmful reactive oxygen species formed by the interaction of high-energy electrons with oxygen molecules? by decreasing the production of ATP by increasing the amount of NADP by increasing the amount of e- donated to ferredoxin by producing antioxidants

by producing antioxidants

During photosynthesis, _____ is reduced to _____. carbon dioxide; oxygen sugar; oxygen oxygen; water carbon dioxide; sugar water; carbon dioxide

carbon dioxide; sugar

Beginning with the step catalyzed by rubisco, arrange the steps in the Calvin cycle in the proper sequence in which they occur. reduction, carboxylation, regeneration reduction, regeneration, carboxylation regeneration, carboxylation, reduction carboxylation, reduction, regeneration carboxylation, regeneration, reduction

carboxylation, reduction, regeneration

Leaves absorb the LEAST amount of light in the _____ range of the visible spectrum. blue violet yellow green orange

green

Openings between _____ cells create pores in the leaf epidermis that play a critical role in photosynthesis by providing openings for atmospheric CO2 to enter a leaf's interior. mesophyll companion bundle-sheath guard

guard

Where is are the chlorophyll molecules located in plant cells that carry out photosynthesis? in the cytoplasm in the stroma of the chloroplasts in the plasma membrane in the lumen of the thylakoids in the chloroplasts in the thylakoid membranes

in the stroma of the chloroplasts

The fluid-filled interior compartment of the thylakoid network is referred to as the: lumen. cytoplasm. stroma. grana. intermembrane space.

lumen.

In a thylakoid membrane, absorbed light energy is passed from one chlorophyll molecule to another until it is: released as fluorescence. both dissipated as heat and released as fluorescence. All these choices are correct. dissipated as heat. passed to a reaction center.

passed to a reaction center.

Which step of the Calvin cycle would be affected first by a lack of NADPH? regeneration carboxylation reduction All of these choices are correct.

reduction

What is the MOST abundant protein on Earth? 3-PGA NADPH CO2 rubisco

rubisco

A new experimental pesticide is being tested by a large agricultural chemical company. An unfortunate side effect in plants treated with this new product is a decrease in ATP production in the chloroplasts. (Interestingly, production of ATP in the mitochondria is unaffected.) Given this observation, which of the following would you expect to be DIRECTLY affected by the new pesticide? the oxidation of RuBP by rubisco the carboxylation of RuBP by rubisco the rate of photorespiration the transport of electrons along the photosynthetic electron transport chain

the rate of photorespiration

In the chloroplasts of plant cells, the absorption of light energy and the movement of electrons along an electron transport chain occurs in the _____ and the synthesis of carbohydrates takes place in the _____. thylakoids; stroma thylakoids; matrix inner membrane; cytoplasm inner membrane; matrix inner membrane; stroma

thylakoids; stroma

Plants lose a great deal of water from their leaves in a process referred to as: transfection. transpiration. transformation. transduction.

transpiration.

Which of the following is a product of the Calvin cycle of photosynthesis? oxygen starch glucose triose phosphate

triose phosphate

Which of the following CORRECTLY lists the path taken by electrons through the light dependent reactions of photosynthesis? water → photosystem II → cytochrome b6f → photosystem I → NADPH water → photosystem I → cytochrome b6f → photosystem II → NADPH NADPH → photosystem I → cytochrome b6f → photosystem II → water NADPH → photosystem II → cytochrome b6f → photosystem I → water

water → photosystem II → cytochrome b6f → photosystem I → NADPH