AP Bio Photosynthesis Quiz
Questions: 16 · 10 minutes
1. A leaf is illuminated separately with equal intensities of blue, green, and red light. Photosynthesis is slowest under green light. Which explanation best accounts for this result?
Green light immediately closes most stomata
Green photons lack enough energy to excite electrons
Green light is absorbed primarily by Rubisco rather than chlorophyll
Major leaf pigments absorb less green light and reflect or transmit more of it
2. What is the direct carbon-fixation role of Rubisco in the Calvin cycle?
It splits water to provide electrons and protons
It catalyzes the attachment of carbon dioxide to RuBP
It transfers electrons from photosystem I to NADP+
It converts G3P directly into carbon dioxide
3. In an experiment, raising light intensity no longer increases a plant's photosynthetic rate, but increasing carbon dioxide concentration does. What is the best inference under these conditions?
Light has permanently damaged every photosynthetic pigment
Water must be the only limiting factor
Carbon dioxide availability, rather than light intensity, is limiting the rate
Oxygen has replaced carbon dioxide as Rubisco's preferred substrate
4. A chloroplast has sufficient NADPH but needs additional ATP for carbon fixation. Which adjustment would most directly help meet this need?
Increasing water splitting without activating either photosystem
Sending more electrons from photosystem II directly to the Calvin cycle
Increasing cyclic electron flow around photosystem I
Stopping proton movement through ATP synthase
5. A labeled carbon atom from carbon dioxide enters the Calvin cycle and later leaves the cycle in its net carbohydrate product. In which molecule does it leave?
RuBP
G3P
ATP
NADPH
6. Where are the photosystems and electron transport chains of photosynthesis primarily located in a chloroplast?
The thylakoid membrane
The outer chloroplast membrane
The stroma
The space between the chloroplast membranes
7. An herbicide blocks electron transfer from photosystem II to plastoquinone. After existing electron carriers adjust to the blockage, which outcome is most likely?
Oxygen production rises while NADPH production remains unchanged
The Calvin cycle accelerates because more RuBP is available
Photosystem I splits water to maintain normal linear electron flow
Linear electron flow declines, reducing both oxygen evolution and NADPH production
8. Plants receive water containing oxygen-18 while their carbon dioxide contains ordinary oxygen. Where should most oxygen-18 appear as the light reactions proceed?
Only in carbon dioxide regenerated by photorespiration
Only in glucose produced by the Calvin cycle
In NADPH but not in released oxygen gas
In the oxygen gas released by the plants
9. Ignoring later carbohydrate assembly, what energy input is required for the Calvin cycle to produce one net G3P from three carbon dioxide molecules?
3 ATP and 3 NADPH
6 ATP and 9 NADPH
9 ATP and 6 NADPH
18 ATP and 12 NADPH
10. An illuminated chloroplast maintains a higher proton concentration inside the thylakoid lumen than in the stroma. What happens when protons move through ATP synthase down this gradient?
ATP is synthesized on the stromal side of the thylakoid membrane
Carbon dioxide is reduced directly in the thylakoid membrane
NADPH is oxidized inside the lumen
Water is split by ATP synthase to replace electrons
11. Which sequence correctly traces linear electron flow during the light-dependent reactions?
Water → photosystem II → electron transport chain → photosystem I → NADP+
Photosystem I → photosystem II → water → NADP+
NADPH → photosystem I → electron transport chain → photosystem II → oxygen
Water → photosystem I → Calvin cycle → photosystem II → NADP+
12. A plant first fixes carbon dioxide into a four-carbon compound in mesophyll cells, then transports it to bundle-sheath cells where carbon dioxide is released for the Calvin cycle. What adaptation is illustrated?
C4 photosynthesis with spatial separation of initial fixation and the Calvin cycle
CAM photosynthesis with nighttime sugar production
C3 photosynthesis with cyclic electron flow
Photorespiration with spatial separation of the two photosystems
13. A desert plant opens its stomata at night, stores carbon in organic acids, and releases carbon dioxide internally during the day. Which description best fits this strategy?
C4 photosynthesis, because initial fixation and the Calvin cycle occur in different cell types
CAM photosynthesis, because initial fixation and the Calvin cycle are separated by time
C3 photosynthesis, because Rubisco fixes oxygen only at night
Cyclic electron flow, because carbon dioxide replaces water as an electron source
14. On a hot, dry afternoon, a C3 plant closes many of its stomata. Which internal change most directly promotes photorespiration?
Carbon dioxide rises while oxygen falls inside the leaf
RuBP production stops because all chlorophyll is degraded
Carbon dioxide falls relative to oxygen, increasing Rubisco's oxygenase activity
Rubisco gains a new ability to split water
15. A student measures oxygen production by an alga under equal intensities of different wavelengths. What does the resulting graph represent?
The emission spectrum of chlorophyll a
An action spectrum relating wavelength to photosynthetic activity
The fluorescence spectrum of carotenoids
The absorption spectrum of carbon dioxide
16. A researcher isolates several pigments from a plant. Which pigment is found in the reaction centers of both photosystems and directly donates energized electrons?
A xanthophyll only
Chlorophyll b
A carotenoid
Chlorophyll a