AP Biology - Photosynthesis practice questions

The energy required to run the Calvin cycle reactions of photosynthesis comes from which two substances produced during the light-dependent reactions? A) ATP and NADPH B) ADP and PO4 C) H+ and PO2 D) O2 and CO2 E) H2O and CO2

A) ATP and NADPH

Scientists investigated the effect of oxygen levels on the net rate of carbon fixation in two types of plants. The plants were grown in either well-watered soil (control) or dry soil and then exposed to either 21% or 1% O2. The net rate of CO2 fixation for both types of plants was measured. Data are shown in Figure 1 and Figure 2. Figure 1. Net rate of CO2 fixation in two types of plants grown in wet (control) or dry soil at 21% O2 Figure 2. Net rate of CO2CO2 fixation in two types of plants grown in wet (control) or dry soil at CO2 Which of the following statements about the rate of CO2CO2 fixation in the two types of plants is supported by the data shown in the figures? A) At 21% O2, plant type 2 has a lower rate of CO2 fixation than plant type 1 does in both types of soil. B) At 1% O2, plant type 2 has a higher rate of CO2 fixation than plant type 1 does in the dry soil but not in the control soil. C) Plant types 1 and 2 have a statistically different rate of CO2 fixation in both soil types at both oxygen levels. D) The rate of CO2 fixation is the same in both types of plants in the control soil at both oxygen levels.

A) At 21%21% O2O2, plant type 22 has a lower rate of CO2CO2 fixation than plant type 11 does in both types of soil.

In chloroplasts, ATP is synthesized from ADP plus inorganic phosphate (Pi)(Pi) in a reaction catalyzed by ATP synthase molecules that are embedded in the thylakoid membrane. Which of the following statements provides evidence to support the claim that no ATP will be synthesized in the absence of a proton gradient across the thylakoid membrane? A) Blocking electron flow from one carrier to the next in the electron transport chains blocks formation of a proton gradient in the thylakoid. B) Increasing the proton concentration difference across the thylakoid membrane is not associated with a parallel increase in the rate of ATP synthesis. C) No ATP is synthesized when channel proteins that allow the free passage of protons are inserted into the thylakoid membrane. D) No ATP is synthesized while the Calvin cycle is synthesizing carbohydrates and using ATP and NADPH at a high rate.

A) Blocking electron flow from one carrier to the next in the electron transport chains blocks formation of a proton gradient in the thylakoid.

For following group of questions first study the description of the situation and diagrams and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet. A student studied the effects of light intensity on oxygen production in green algae. The algae were suspended in water inside a sealed glass jar, and the jar was placed into a constant-temperature, lightproof box containing a light source. A probe was inserted into the jar to record the concentration of oxygen. The probe was connected to a recording device. The setup is shown below. The student decreased the intensity of the light hourly and recorded the corresponding changes in oxygen concentration. The graph below shows the results from the recording device. An increase in the rate of oxygen production by algae would be accompanied by a comparable increase in the rate of production of which of the following substances? A) C6H12O6 B) CO2 C) CH4 D) NH3 E) H2O

A) C6H12O6

Dichlorophenolindophenol (DCPIP) is a chemical dye. When DCPIP is chemically reduced, it changes color from blue to clear. DCPIP can be used as an electron acceptor in experiments that measure the rate of electron transport through the electron transport chain. A student performed an experiment to study the effects of a chemical, DCMU, on photosynthesis. The student prepared four tubes with a liquid buffer and chloroplasts that had been extracted from spinach leaves. The student then added DCPIP to three of the tubes and added DCMU to one of them. Additionally, tube 33 was wrapped in tin foil. The contents of each tube are shown in the table. The student then incubated each tube for 60 minutes and measured the absorbance (A600) of each solution at five-minute intervals. The absorbance readings of each solution are shown in Figure 1. Tube 1 Buffer and water Tube 2 DCPIP, buffer, and water Tube 3 DCPIP, buffer, and water (wrapped in foil) Tube 4 DCPIP, buffer, and 1.0m MDCMU Figure 1. Absorbance readings of four prepared tubes with various solutions over a 60-minute period. Which of the following claims is best supported by the experimental results? A) Light is required for the electron transport chain to transfer electrons. B) Water, not carbon dioxide, is the source of electrons used in the light-dependent reaction of photosynthesis. C) Carbon dioxide is the source of carbon used by green plants to build carbohydrates. D) DCPIP provides a significant source of electrons to the electron transport chain of the light reaction in the absence of light.

A) Light is required for the electron transport chain to transfer electrons.

A student placed 20 tobacco seeds of the same species on moist paper towels in each of two petri dishes. Dish A was wrapped completely in an opaque cover to exclude all light. Dish B was not wrapped. The dishes were placed equidistant from a light source set to a cycle of 14 hours of light and 10 hours of dark. All other conditions were the same for both dishes. The dishes were examined after 7 days and the opaque cover was permanently removed from dish A. Both dishes were returned to the light and examined again at 14 days. The following data were obtained. According to the results of this experiment, germination of tobacco seeds during the first week is A) increased by exposure to light B) unaffected by light intensity C) prevented by paper towels D)accelerated in green-leaved seedlings

A) increased by exposure to light

A student placed 20 tobacco seeds of the same species on moist paper towels in each of two petri dishes. Dish A was wrapped completely in an opaque cover to exclude all light. Dish B was not wrapped. The dishes were placed equidistant from a light source set to a cycle of 14 hours of light and 10 hours of dark. All other conditions were the same for both dishes. The dishes were examined after 7 days, and the opaque cover was permanently removed from dish A. Both dishes were returned to the light and examined again at 14 days. The following data were obtained. According to the results of this experiment, germination of tobacco seeds during the first week is A) increased by exposure to light B) unaffected by light intensity C) prevented by paper towels D) accelerated in green-leaved seedlings

A) increased by exposure to light

To test the hypothesis that a particular plant synthesizes storage lipids by using glyceraldehyde 3-phosphate (G3P) from photosynthesis, a researcher plans to use radiolabeled precursors to track the molecules through the biosynthetic pathway. Which of the following radiolabeled precursors is most appropriate for the researcher to use? A) 15N-labeled N2, because atmospheric nitrogen is fixed to amino acids by photosynthesis B) 14C-labeled CO2, because atmospheric carbon is fixed to carbohydrates by photosynthesis C) 35S-labeled methionine, because amino acids are incorporated into lipids during photosynthesis D) 32P-labeled phosphate, because lipids are stored in plants as phospholipids

B) 14C-labeled CO2, because atmospheric carbon is fixed to carbohydrates by photosynthesis

The chemical reaction for photosynthesis is 6 CO2 + 12 H2O + light energy → C6H12O6 + 6 O2 + 6 H2O If the input water is labeled with a radioactive isotope of oxygen, 18O, then the oxygen gas released as the reaction proceeds is also labeled with 18O. Which of the following is the most likely explanation? A) During the light reactions of photosynthesis, water is split, the hydrogen atoms combine with the CO2, and oxygen gas is released. B) During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released. C) During the Calvin cycle, water is split, regenerating NADPH from NADP+, and oxygen gas is released. D) During the Calvin cycle, water is split, the hydrogen atoms are added to intermediates of sugar synthesis, and oxygen gas is released.

B) During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released.

A scientist claims that Elysia chlorotica, a species of sea slug, is capable of photosynthesis. Which of the following observations provides the best evidence to support the claim? A) Elysia chlorotica will die if not exposed to light. B) Elysia chlorotica grows when exposed to light in the absence of other food sources. C) Elysia chlorotica grows faster when exposed to light than when placed in the dark. D) Elysia chlorotica grows in the dark when food sources are available.

B) Elysia chlorotica grows when exposed to light in the absence of other food sources.

The O2 released during photosynthesis comes from A) CO2 B) H2O C) NADPH D) RuBP (RuDP) E) C6H12O6

B) H2O

Which of the following questions is most relevant to understanding the Calvin cycle? A) How does chlorophyll capture light? B) How is ATP used in the formation of 3-carbon carbohydrates? C) How is NADP+ reduced to NADPH? D) How is ATP produced in chemiosmosis?

B) How is ATP used in the formation of 3-carbon carbohydrates?

For following group of questions first study the description of the situation and diagrams and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet. A student studied the effects of light intensity on oxygen production in green algae. The algae were suspended in water inside a sealed glass jar, and the jar was placed into a constant-temperature, lightproof box containing a light source. A probe was inserted into the jar to record the concentration of oxygen. The probe was connected to a recording device. The setup is shown below. The diagram of the setup shows a box that contains a light bulb and algae in a jar, with a probe sticking into the algae and connected to a recording device outside of the box. The student decreased the intensity of the light hourly and recorded the corresponding changes in oxygen concentration. The graph below shows the results from the recording device. There is a graph with x-axis labeled time in hours from zero to four and y-axis labeled oxygen concentration from low to high at the top. There is a data point on every hour labeled G through K. Hour zero is G with a high concentration. Hour one is H with a much lower concentration. Hour two is I with a lower concentration. Hour three is J with a slightly lower concentration. Hour four is K with the same concentration as J. Based on the data shown, changes in the light intensity resulted in changes in the rate of which of the following processes? A)Excretion B) Photosynthesis C) Respiration D) Translation E) Transcription

B) Photosynthesis

A researcher is investigating the effects of a chemical that makes thylakoid membranes permeable to hydrogen ions (H+). Which of the following is the most likely direct effect of adding the chemical to plant cells? A) The plant cells will produce less NADPH. B) The chloroplasts will generate less ATP. C) Chlorophyll will require less light energy to excite its electrons. D) The plant cells will split fewer water molecules into hydrogen ions and oxygen.

B) The chloroplasts will generate less ATP.

Which of the following best describes the role of water in photosynthesis? A) Water is the only source of protons for the formation of a proton gradient. B) Water molecules donate electrons to the electron transport chain. C) Water molecules combine with stored carbon molecules to produce glucose. D) Water is the terminal electron acceptor for electrons that pass through the electron transport chain.

B) Water molecules donate electrons to the electron transport chain.

The carbon 'that makes up organic molecules in plants is derived directly from A) combustion of fuels B) carbon fixed in photosynthesis C) carbon dioxide produced in respiration D) carbon in the lithosphere E) coal mines

B) carbon fixed in photosynthesis

Carbohydrate-synthesizing reactions of photosynthesis directly require A) light B) products of the light reactions C) darkness D) O2 and H2O E) chlorophyll and CO2

B) products of the light reactions

Directions: This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. (A) Glycolysis (B) Krebs cycle (citric acid cycle) (C) Calvin cycle (light-independent reactions of photosynthesis) (D) Light-dependent reactions of photosynthesis (E) Chemiosmosis Process in which carbon from CO2 is incorporated into organic molecules A) A B) B C) C D) D E) E

C) C

A student placed 20 tobacco seeds of the same species on moist paper towels in each of two petri dishes. Dish A was wrapped completely in an opaque cover to exclude all light. Dish B was not wrapped. The dishes were placed equidistant from a light source set to a cycle of 14 hours of light and 10 hours of dark. All other conditions were the same for both dishes. The dishes were examined after 7 days and the opaque cover was permanently removed from dish A. Both dishes were returned to the light and examined again at 14 days. The following data were obtained. Additional observations were made on day 21, and no yellow-leaved seedlings were found alive in either dish. This is most likely because A) yellow-leaved seedlings were unable to absorb water from the paper towels B) taller green-leaved seedlings blocked the light and prevented photosynthesis C) yellow-leaved seedlings were unable to convert light energy to chemical energy D) a higher rate of respiration in yellow-leaved seedlings depleted their stored nutrients

C) yellow-leaved seedlings were unable to convert light energy to chemical energy

A student placed 20 tobacco seeds of the same species on moist paper towels in each of two petri dishes. Dish A was wrapped completely in an opaque cover to exclude all light. Dish B was not wrapped. The dishes were placed equidistant from a light source set to a cycle of 14 hours of light and 10 hours of dark. All other conditions were the same for both dishes. The dishes were examined after 7 days, and the opaque cover was permanently removed from dish A. Both dishes were returned to the light and examined again at 14 days. The following data were obtained. Additional observations were made on day 21, and no yellow-leaved seedlings were found alive in either dish. This is most likely because A) yellow-leaved seedlings were unable to absorb water from the paper towels B) taller green-leaved seedlings blocked the light and prevented photosynthesis C) yellow-leaved seedlings were unable to convert light energy to chemical energy D) a higher rate of respiration in yellow-leaved seedlings depleted their stored nutrients

C) yellow-leaved seedlings were unable to convert light energy to chemical energy

A researcher claims that increased atmospheric carbon dioxide levels cause increased growth rates in plants. Which of the following statements best supports the researcher's claim? A)Atmospheric carbon dioxide is produced by the burning of fossil fuels, which are formed from the remains of living organisms such as plants. B) Atmospheric carbon dioxide is a byproduct of cellular respiration, which is a metabolic process that occurs in plants and other living organisms. C) Atmospheric carbon dioxide typically enters plant leaves through stomata, which plants rely on for regulating gas exchange with the atmosphere. D) Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

D) Atmospheric carbon dioxide is the raw material for photosynthesis, which plants rely on for producing sugars and other organic compounds.

Directions: This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. (A) Glycolysis (B) Krebs cycle (citric acid cycle) (C) Calvin cycle (light-independent reactions of photosynthesis) (D) Light-dependent reactions of photosynthesis (E) Chemiosmosis Process in which O2 is released as a by-product of oxidation-reduction reactions A) A B) B C) C D) D E) E

D) D

Dichlorophenolindophenol (DCPIP) is a chemical dye. When DCPIP is chemically reduced, it changes color from blue to clear. DCPIP can be used as an electron acceptor in experiments that measure the rate of electron transport through the electron transport chain. A student performed an experiment to study the effects of a chemical, DCMU, on photosynthesis. The student prepared four tubes with a liquid buffer and chloroplasts that had been extracted from spinach leaves. The student then added DCPIP to three of the tubes and added DCMU to one of them. Additionally, tube 33 was wrapped in tin foil. The contents of each tube are shown in the table. The student then incubated each tube for 60 minutes and measured the absorbance (A600) of each solution at five-minute intervals. The absorbance readings of each solution are shown in Figure 1. Tube 1 Buffer and water Tube 2 DCPIP, buffer, and water Tube 3 DCPIP, buffer, and water (wrapped in foil) Tube 4 DCPIP, buffer, and 1.0m MDCMU Figure 1. Absorbance readings of four prepared tubes with various solutions over a 60-minute period. Which of the following best justifies the use of tube 22 as a control treatment? A) It was a negative control for the accuracy of the spectrophotometer, ensuring that an accurate reading for treatment cuvette 22 would be made. B) It was a negative control for the chemical stability of the chlorophyll suspension, ensuring that changes in absorbance could only be attributed to changes in chlorophyll content. C) It was a positive control for the change in DCPIP color associated with changes in light intensity. D) It was a positive control for measuring the effect of DCMU on the reaction.

D) It was a positive control for measuring the effect of DCMU on the reaction.

For following group of questions first study the description of the situation and diagrams and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet. A student studied the effects of light intensity on oxygen production in green algae. The algae were suspended in water inside a sealed glass jar, and the jar was placed into a constant-temperature, lightproof box containing a light source. A probe was inserted into the jar to record the concentration of oxygen. The probe was connected to a recording device. The setup is shown below. The student decreased the intensity of the light hourly and recorded the corresponding changes in oxygen concentration. The graph below shows the results from the recording device. The rate of oxygen production equaled the rate of oxygen consumption during which of the following time periods? A) G to H B) H to I C) I to J D) J to K E) G to K

D) J to K

What most likely causes the trends in oxygen concentration shown in the graph above? A) The water becomes colder at night and thus holds more oxygen. B) Respiration in most organisms increases at night. C) More organisms are respiring at night than during the day. D) Photosynthesis produces more oxygen than is consumed by respiration during the day.

D) Photosynthesis produces more oxygen than is consumed by respiration during the day.

Which of the following is an important difference between light-dependent and light-independent reactions of photosynthesis? A) The light-dependent reactions occur only during the day; the light-independent reactions occur only during the night. B) The light-dependent reactions occur in the cytoplasm; the light-independent reactions occur in chloroplasts. C) The light-dependent reactions utilize CO2 and H2O; the light-independent reactions produce CO2 and H2O. D) The light-dependent reactions depend on the presence of both photosystems I and II; the light-independent reactions require only photosystem I. E) The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH.

E) The light-dependent reactions produce ATP and NADPH; the light-independent reactions use energy stored in ATP and NADPH.