Photosystems I and II are numbered in the order they were discovered, not in the order in which they act.
Correct Answer
True
True. Photosystem II acts first in the linear electron pathway, and photosystem I acts second, but photosystem I was discovered first and so received the lower number.
Category: Light-Dependent Reactions
Question 2
During electron transport in the chloroplast, hydrogen ions are pumped from the thylakoid space into the stroma.
Correct Answer
False
False. Electron transport pumps hydrogen ions from the stroma into the thylakoid space, building a high concentration there. The ions then flow back to the stroma through ATP synthase.
Category: Light-Dependent Reactions
Question 3
ADP and NADP+ released by the Calvin cycle return to the light-dependent reactions to be recharged.
Correct Answer
True
True. The Calvin cycle spends ATP and NADPH, leaving ADP and NADP+. These go back to the thylakoids, where the light-dependent reactions turn them into ATP and NADPH again.
Category: Calvin Cycle
Question 4
Longer wavelengths of light carry more energy than shorter wavelengths.
Correct Answer
False
False. Shorter wavelengths carry more energy. That is why violet and blue light carry more energy per photon than red light.
Category: Light and Pigments
Question 5
The Calvin cycle uses 6 molecules of NADPH to build one glucose molecule.
Correct Answer
False
False. Building one glucose takes six turns of the cycle, and the reduction stage uses 2 NADPH per turn, for a total of 12 NADPH.
Category: Calvin Cycle
Question 6
Carbohydrates are a more stable form of energy storage than ATP.
Correct Answer
True
True. ATP is used quickly for immediate energy needs, while carbohydrates such as glucose and starch store energy stably over longer periods. Cells break the carbohydrates down later to make ATP as needed.
Category: Energy Cycle
Question 7
G3P, the sugar produced by the Calvin cycle, contains six carbon atoms.
Correct Answer
False
False. G3P is a three-carbon sugar. Two G3P molecules together supply the six carbons of a glucose molecule.
Category: Calvin Cycle
Question 8
NADPH is formed after electrons are re-energized by light at photosystem I.
Correct Answer
True
True. Electrons arriving at photosystem I absorb more light energy, and that energy is used to reduce NADP+ to NADPH, the electron carrier sent to the Calvin cycle.
Category: Light-Dependent Reactions
Question 9
Heterotrophs depend on autotrophs, either directly or indirectly, for their energy.
Correct Answer
True
True. A heterotroph cannot make its own food, so its energy traces back to photosynthesis. A deer eats plants directly, and a wolf that eats the deer gets plant-derived energy indirectly.
Category: Photosynthesis Overview
Question 10
Cyanobacteria lack chloroplasts but still carry out photosynthesis using internal thylakoid membranes.
Correct Answer
True
True. Cyanobacteria are prokaryotes, so they have no chloroplasts. Their photosynthetic pigments sit in internal thylakoid membranes that work much like the thylakoids of a chloroplast.
Category: Leaf and Chloroplast
Question 11
Carbon fixation converts organic carbon into inorganic carbon dioxide.
Correct Answer
False
False. Carbon fixation does the reverse: it converts inorganic carbon in CO2 into organic molecules when RuBisCO attaches CO2 to RuBP.
Category: Calvin Cycle
Question 12
Some plants of hot, dry climates take in CO2 at night, when cooler air reduces water loss, and store it for the Calvin cycle to use the next day.
Correct Answer
True
True. Taking in CO2 at night lets these plants keep their stomata closed during the hot day, saving water while still supplying the carbon the Calvin cycle needs to build sugar.
Category: Leaf and Chloroplast
Question 13
Photosynthesis converts the chemical energy in sugar into light energy.
Correct Answer
False
False. Photosynthesis converts light energy into chemical energy stored in sugar. Releasing energy from sugar is the job of cellular respiration.
Category: Photosynthesis Overview
Question 14
Chlorophyll is located in the outer membrane of the chloroplast.
Correct Answer
False
False. Chlorophyll is embedded in the thylakoid membranes inside the chloroplast, where the light-dependent reactions occur, not in the outer envelope membrane.
Category: Leaf and Chloroplast
Question 15
The Calvin cycle does not use light directly but depends on products of the light-dependent reactions.
Correct Answer
True
True. The Calvin cycle runs on ATP and NADPH rather than absorbing light itself, so it stops soon after the light-dependent reactions stop supplying those carriers.
Category: Calvin Cycle
Question 16
Splitting one water molecule in the light-dependent reactions supplies two electrons.
Correct Answer
True
True. Each water molecule split releases a pair of electrons, along with hydrogen ions and oxygen. Those electrons replace ones lost from chlorophyll in photosystem II.
Category: Light-Dependent Reactions
Question 17
Oxygen produced by photosynthesis is used as a reactant in cellular respiration.
Correct Answer
True
True. Photosynthesis releases oxygen and respiration consumes it, while respiration releases the CO2 that photosynthesis consumes. Each process supplies a reactant for the other.
Category: Energy Cycle
Question 18
Each turn of the Calvin cycle fixes three molecules of carbon dioxide.
Correct Answer
False
False. Each turn fixes one molecule of carbon dioxide, which is why six turns are needed to supply the six carbons of one glucose.
Category: Calvin Cycle
Question 19
ATP synthase breaks ATP down into ADP during the light-dependent reactions.
Correct Answer
False
False. In the light-dependent reactions ATP synthase builds ATP, adding a phosphate to ADP using energy from hydrogen ions flowing through it. This is called photophosphorylation.
Category: Light-Dependent Reactions
Question 20
In the reduction stage of the Calvin cycle, G3P is converted into 3-PGA.
Correct Answer
False
False. The conversion runs the other way: ATP and NADPH convert 3-PGA into G3P. Some G3P then leaves to build sugars, and the rest regenerates RuBP.
Category: Calvin Cycle