Chapter 8 Mastering Biology

True or false? The chemiosmotic hypothesis states that the synthesis of ATP generates a proton gradient that leads to electron flow through an electron transport chain.

False. (The chemiosmotic hypothesis states that the flow of electrons through an electron transport chain generates a proton gradient that leads to the synthesis of ATP.)

True or false? The region of ATP synthase that catalyzes the production of ATP from ADP and inorganic phosphate spans the chloroplast membrane.

False. (The region of ATP synthase that catalyzes ATP production protrudes out of, but does not span, the chloroplast membrane; the region that spans the membrane is an ion channel through which protons can pass.)

Why are plants classified as producers?

Plants are classified as producers because they fix inorganic carbon into organic molecules.

Which of the following particles can pass through the ATP synthase channel?

Protons

Generation of proton gradients across membranes occurs during ________.

both photosynthesis and cellular respiration.

In the thylakoid membranes, what is the main role of the pigment molecules in a light-harvesting complex?

transfer light energy to the reaction-center chlorophyll

Which of these phosphorylates ADP to make ATP?

ATP synthase

In C3 plants the conservation of water promotes _______.

photorespiration (Conserving water simultaneously reduces the amount of carbon dioxide available to the plant.)

Which of the following is directly associated with photosystem I?

receiving electrons from the thylakoid membrane electron transport chain

In a plant cell, where are ATP synthase complexes located?

thylakoid membrane and inner mitochondrial membranes

Where are the molecules of the electron transport chain associated with photophosphorylation located in plant cells?

thylakoid membranes of chloroplasts

Which of the following events occurs in the light reactions of photosynthesis?

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

Carbon fixation involves the addition of carbon dioxide to ________.

RuBP

True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.

True. (The water molecules are split to replenish electrons in photosystem II, leaving behind protons, which are used to generate a proton gradient for the formation of ATP, and oxygen, which is released as a by-product.)

In C4 and CAM plants carbon dioxide is fixed in the _______ of mesophyll cells.

cytoplasm

The overall function of the Calvin cycle is __________.

making sugar

In the process of carbon fixation, three molecules of RuBP combine with three molecules of CO2 to produce three six-carbon molecules, which are then split to produce 12 molecules of 3-phosphoglycerate. After phosphorylation and reduction produce 12 glyceraldehyde 3-phosphate (G3P), what more needs to happen to complete the Calvin cycle?

release of one G3P to make sugars and regeneration of RuBP

The ultimate source of energy to support most life on Earth is _______.

sunlight

Which term describes ATP production resulting from the capture of light energy by chlorophyll?

Photophosphorylation (The excitation of chlorophyll by light energy initiates a chain of events that leads to ATP production.)

Which process produces oxygen?

Photosynthesis

Energized electrons from _______ enter an electron transport chain and are then used to reduce NADP+.

Photosystem I

Chlorophyll can be found in _______.

Photosystem I and II

_______ splits water into 1/2 O2, H+, and e- .

Photosystem II

In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?

3

How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?

6 (Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.)

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?

ATP and NADPH

What is the basic role of CO2 in photosynthesis?

CO2 is fixed or incorporated into organic molecules.

Which of the following statements about the relationship between photosynthesis and cellular respiration is true?

Cellular respiration is catabolic and photosynthesis is anabolic.

Select the correct molecule that is the main product of the Calvin cycle.

G3P

Which of the following sequences correctly represents the flow of electrons during photosynthesis?

H2O → NADPH → Calvin cycle

How is photosynthesis similar in C4 plants and CAM plants?

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

Which of the following products of the light reactions of photosynthesis is used during the Calvin cycle?

NADPH

What compound provides the reducing power for the Calvin cycle reactions?

NADPH

Photorespiration occurs when rubisco combines RuBP with ________.

O2

According to the chemiosmotic hypothesis, what provides the energy that directly drives ATP synthesis?

Proton gradient (A proton gradient across chloroplast and mitochondrial membranes drives ATP synthesis by the enzyme ATP synthase.)

Select the correct statement about the Calvin cycle.

The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of RuBP.

Select the most accurate statement describing the basic function of the light reactions of photosynthesis.

The basic function of the light reactions of photosynthesis is the conversion of solar energy to chemical energy.

What is the biological significance of the light-independent reactions of photosynthesis?

They convert carbon dioxide to sugar.

Plants are photoautotrophs. What does this mean?

They use light energy to drive the synthesis of organic molecules from inorganic materials.

Compared to C3 plants, C4 plants ________.

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

The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during ________.

neither photosynthesis nor respiration.

Photosynthesis is a redox reaction. This means that H2O is _______ during the light reactions and CO2 is _______ during the Calvin cycle.

oxidized...reduced

Which process is most directly driven by light energy?

removal of electrons from chlorophyll molecules

Where does the Calvin cycle take place?

stroma of the chloroplast

C4 plants differ from C3 and CAM plants in that C4 plants _______.

transfer fixed carbon dioxide to cells in which the Calvin cycle occurs (In C3 and CAM plants carbon dioxide fixation and the Calvin cycle occur in the same cells.)

Which of the following does NOT occur during the Calvin cycle?

release of oxygen

Which set of reactions uses H2O and produces O2?

The light-dependent reactions

Chloroplast membrane vesicles are equilibrated in a simple solution of pH 5‎ . The solution is then adjusted to pH 8‎ . Which of the following conclusions can be drawn from these experimental conditions?

ATP will not be produced because there is no ADP and inorganic phosphate in the solution. (This statement is true; although the proton gradient is present, ADP and inorganic phosphate are required to make ATP and were not added to the reaction.)

Which of the following statements is a correct distinction between autotrophs and heterotrophs?

Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic.

After 3-PGA is phosphorylated, it is reduced by ________.

NADPH (NADPH supplies the electrons that reduce the phosphorylated 3-PGA.)

Which of the following molecules is the primary product of photosystem I?

NADPH (The NADPH produced by photosystem I is used to supply energy for the production of sugars during photosynthesis.)

_______ has a longer wavelength than _______.

Red ... green

Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose?

Regneration of RuBP (The regeneration of RuBP ensures that the Calvin cycle can proceed indefinitely, since RuBP fixes carbon dioxide into an organic molecule that is used to produce sugar.)

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?

The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.

What is the importance of the light-independent reactions in terms of carbon flow in the biosphere?

The light-independent reactions turn CO2, a gas, into usable carbon in the form of sugars. (CO2 is unusable until plants have "fixed" this carbon into sugar.)

CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because they ________.

fix CO2 into organic acids during the night when temperatures are cooler.

There is graph with 2 curves on it. The first curve shows the absorbance of chlorophyll a as a function of the wavelength of light and the second curve shows of the rate of photosynthesis as a function of the wavelength of light. Maximums of the first curve are at 450 and 660 nanometers, however maximums of the second curve are at 420 and 680 nanometers. The minimum of the second curve is at 560 nanometers. Violet color is from 380 to 440 nanometers, blue color from 440 to 500 nanometers, green color is from 500 to 550 nanometers, yellow color is from 550 to 600nanometers, orange color is from 600 to 620 nanometers, red color is from 620 to 770 nanometers. The figure shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. What colors of light are least effective in driving photosynthesis?

green-yellow

C4 plants occur more commonly in desert conditions because __________.

they can fix carbon at the lower CO2 concentrations that develop when the stomata are closed (To conserve water during hot, dry conditions, the stomata are fully or partially closed, preventing CO2 from reaching high concentrations.)