Chapter 8: Photosynthesis

Which of the answer choices is part of the photosynthetic electron transport chain between photosystems I and II? All of these choices are correct. plastoquinone plastocyanin cytochrome-b6f complex

All of these choices are correct.

Which statement is true regarding the earliest photosynthetic organisms on Earth? The organisms likely produced O2 as a waste product, resulting in Earth's current atmosphere. Given the abundance of H2O on early Earth, these organisms used H2O as an electron donor. These organisms likely possessed two photosystems. These organisms likely used both inorganic molecules and H2O as electron donors. The organisms likely used molecules other than H2O (that is, H2S) as electron donors.

The organisms likely used molecules other than H2O (that is, H2S) as electron donors.

The Calvin cycle requires 3 ATP and 2 NADH for each molecule of CO2 that is incorporated into carbohydrate products, a ratio of 3:2. The flow of electrons from water to NADPH in the photosynthetic electron transport system, however, yields a ratio of ATP to NADH of 1:1. Where does the additional ATP come from to power the Calvin cycle? plastocyanin photosystem II import from the cytoplasm triose phosphate cyclic electron flow

cyclic electron flow

How does the metabolism occurring in chloroplasts differ from that of mitochondria? different electron acceptors and electron sources one makes ATP, the other makes NADPH None of the other answer options is correct. different proton acceptors different proton sources

different electron acceptors and electron sources

Cyclic electron transport enhances ATP production because: photosystem I can pump more protons into the thylakoid lumen. the cycling of ADP to ATP is enhanced by transport. cyclic electron transport is more energy efficient than linear electron transport. protons are recycled into the thylakoid lumen. excited electrons are transferred from PS I back to plastoquinone.

excited electrons are transferred from PS I back to plastoquinone.

Which could likely result in a reduction of energy losses to photorespiration in plants? decreased light intensity increased O2 concentration decreased H2O supply increased CO2 concentration decreased CO2 concentration

increased CO2 concentration

Photorespiration and cellular respiration are unalike in that: photorespiration reactions consume O2 and release CO2, whereas cellular respiration reactions consume CO2 and release O2. photorespiration consumes ATP, and cellular respiration does not. photorespiration reactions consume CO2 and releases O2, whereas cellular respiration reactions consume O2 and release CO2. photorespiration occurs during daylight hours, and cellular respiration only occurs at night. photorespiration creates H2O by reducing O2, and cellular respiration creates H2O by reducing CO2.

photorespiration consumes ATP, and cellular respiration does not.

Organisms with only one photosystem cannot: reduce CO2. reduce NADP+. reduce H2O. produce O2. oxidize H2S.

produce O2.

Rubisco is characterized by: slow catalysis and the ability to use two substrates. fast catalysis. the ability to use three substrates and faster catalysis. the ability to use three substrates.

slow catalysis and the ability to use two substrates.

Photosystem I is a _____ than photosystem II. stronger oxidant and a stronger reductant weaker oxidant and weaker reductant weaker reductant stronger oxidant weaker oxidant and a stronger reductant

weaker oxidant and a stronger reductant