chapter 10 mastering biology hwk

Which statement correctly describes how O2 production would be affected? (Assume that the light intensity does not change.) a) The rate of O2 production would decrease because the rate of ADP and NADP+ production by the Calvin cycle would decrease. b) The rate of O2 production would remain the same because the light intensity did not change. c) The rate of O2 production would decrease because the rate of G3P production by the Calvin cycle would decrease. d)The rate of O2 production would remain the same because the light reactions are independent of the Calvin cycle.

a) The rate of O2 production would decrease because the rate of ADP and NADP+ production by the Calvin cycle would decrease.

For every molecule of O2 that is released by photosystem II, _________ H2O molecules are needed, which together pass _________ electrons to the PS II reaction-center complex.

2,4

The electrons derived from this oxidation reaction in the light reactions are used to reduce ___________ to ______________.

NADP+, NADPH

In C3 plants the conservation of water promotes _____. a) photorespiration b) the light reactions c) photosynthesis d) a shift to C4 photosynthesis the opening of stomata

a) photorespiration

In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells. a) stomata b) stroma c) cytoplasm d) thylakoids e) grana

c) cytoplasm

In the light reactions, light energy is used to oxidize __________ to _______.

H2O, O2

The Calvin cycle oxidizes the light-reactions product ___________ to ___________.

NADPH, NADP+

How many electrons at a time are passed between the pigment molecules in the light-harvesting complexes? a) 0 b) 1 c) 2 d) 3 e) 4

a) 0

C4 plants differ from C3 and CAM plants in that C4 plants _____. a) are better adapted to wet conditions b) use PEP carboxylase to fix carbon dioxide c) use malic acid to transfer carbon dioxide to the Calvin cycle d) transfer fixed carbon dioxide to cells in which the Calvin cycle occurs e) open their stomata only at night

d) transfer fixed carbon dioxide to cells in which the Calvin cycle occurs

The electrons derived from this oxidation reaction in the Calvin cycle are used to reduce _________ to ___________.

CO2, G3P

Why is it correct to say that the linear electron flow of the light reactions directly captures energy in NADPH but only indirectly captures energy in ATP? a) Electrons are directly transferred to NADP+ to form NADPH, but electron flow is used to generate a proton gradient for ATP synthesis. Electrons are not directly transferred to ATP. b) Electrons used to generate ATP are extracted from water, but electrons used to generate NADPH come directly from PS I. c) NADPH is generated directly in the chloroplast, but ATP is synthesized in the mitochondrion. d) Light energy is used to excite electrons used to generate NADPH, but the energy used to make ATP comes from the cytochrome complex. e) Electrons are directly transferred to NADP+ to form NADPH in the electron transport chain after PS I, but ATP synthesis requires electrons that have flowed through both photosystems.

a) Electrons are directly transferred to NADP+ to form NADPH, but electron flow is used to generate a proton gradient for ATP synthesis. Electrons are not directly transferred to ATP.

Which of the following is the correct order of electron flow in the light reactions of photosynthesis? a) O2 → P680 chlorophyll a pair → PS I primary electron acceptor → Pq → cytochrome complex → Pc → P700 chlorophyll a pair → PS II primary electron acceptor → Fd → NADPH b) H2O → P680 chlorophyll a pair → PS II primary electron acceptor → Pq → cytochrome complex → Pc → P700 chlorophyll a pair → PS I primary electron acceptor → Fd → NADPH c) H2O → P700 chlorophyll a pair → PS I primary electron acceptor → Pc → cytochrome complex → Pq → P680 chlorophyll a pair → PS II primary electron acceptor → Fd → NADPH d) H2O → P680 chlorophyll a pair → PS II primary electron acceptor → Pq → cytochrome complex → Pc → P700 chlorophyll a pair → PS I primary electron acceptor → Fd → ATP e) H2O → P680 chlorophyll a pair → PS II primary electron acceptor → Pq → ATP → Pc → P700 chlorophyll a pair → PS I primary electron acceptor → Fd → NADPH

b) H2O → P680 chlorophyll a pair → PS II primary electron acceptor → Pq → cytochrome complex → Pc → P700 chlorophyll a pair → PS I primary electron acceptor → Fd → NADPH

If the Calvin cycle slows down, what will happen to the rate of O2 production in PS II, and why? a) O2 production will not change because light energy will still be absorbed by the pigment molecules and excite the PS II chlorophyll a pair. b) O2 production will slow down because less NADP+ will be regenerated in the Calvin cycle. c) O2 production will speed up because not as much NADPH will be used in the Calvin cycle and so it will accumulate in the chloroplast. d) O2 production will not change because the Calvin cycle is a separate process from the light reactions. e) O2 production will slow down because the chloroplast will need less light energy to send to the Calvin cycle.

b) O2 production will slow down because less NADP+ will be regenerated in the Calvin cycle.

When a pigment molecule in a light-harvesting complex absorbs a photon of light, what happens to its excited-state electron? a) The excited-state electron is passed to electron acceptors P680 or P700. b) The electron falls back to its ground state, while passing its excited-state energy to an electron in a nearby pigment molecule. c) The excited-state electron excites electrons in other pigments around it, so that multiple pigments can send electrons to P680 or P700. d) The excited-state electron is removed and transferred to a nearby pigment molecule, causing the next pigment to enter an excited state.

b) The electron falls back to its ground state, while passing its excited-state energy to an electron in a nearby pigment molecule.