Chapter 10: Photosynthesis Flashcards
Van Niel’s experiments with purple sulfur bacteria led to which of the following hypotheses?
A) During plant photosynthesis, the oxygen gas released comes from carbon dioxide.
B) Hydrogen sulfide is required for plant photosynthesis.
C) During plant photosynthesis, the oxygen gas released comes from water.
D) Purple sulfur bacteria are incapable of photosynthesis because they don’t release oxygen gas.
C) During plant photosynthesis, the oxygen gas released comes from water.
During photosynthesis, which of the following reactions occurs?
A) Water acts as an electron acceptor.
B) Light energy is used to raise the potential energy of electrons.
C) Carbon dioxide becomes oxidized to sugar.
D) ATP is produced in the cytoplasm of plant cells.
B) Light energy is used to raise the potential energy of electrons.
Predict the colour of a pigment that absorbs light of green, yellow, and red wavelengths.
A) The pigment will appear blue.
B) The pigment will appear white.
C) The pigment will appear black.
D) The pigment will appear a mixture of green and orange.
A) The pigment will appear blue.
Why are summer leaves green, even though carotenoids are present?
A) During summer, chlorophyll is more abundant than carotenoids in leaves.
B) The carotenoids are located in different compartments of the leaves than chlorophyll.
C) Carotenoids absorb green light.
D) Carotenoids reflect green light.
A) During summer, chlorophyll is more abundant than carotenoids in leaves.
Chlorophyll consists of a magnesium-containing head and a long, hydrophobic hydrocarbon tail. Why is the tail region important to the molecule’s function?
A) The tail region anchors chlorophyll in the thylakoid membrane.
B) The tail region donates electrons to an electron acceptor.
C) The tail region captures the energy in sunlight.
D) The tail region anchors chlorophyll in the nuclear membrane.
A) The tail region anchors chlorophyll in the thylakoid membrane.
Why is the chemical reduction of an electron acceptor in the photosynthetic reaction centre important to plant function?
A) It allows the energy of absorbed light to be trapped and converted to chemical energy.
B) It provides electrons to be excited by the absorbed light.
C) It changes the wavelength of chlorophyll fluorescence so that it will not interfere with the absorption of light.
D) It adjusts the energy level of chlorophyll electrons to match the energy of light illuminating the leaf.
A) It allows the energy of absorbed light to be trapped and converted to chemical energy.
What is the evidence for two photosystems?
A) Two different high-energy molecules are produced during the light-dependent reactions of photosynthesis: ATP and NADPH.
B) The combination of light at 680 nm and 700 nm is much more effective in stimulating photosynthesis than is either wavelength alone.
C) Microscopy reveals two colours of chloroplast within the same leaf cell.
D) Chlorophyll absorbs light of two different wavelengths: blue and red.
B) The combination of light at 680 nm and 700 nm is much more effective in stimulating photosynthesis than is either wavelength alone.
Why is pheophytin an important component of photosystem II?
A) It transforms light energy by acting as the initial electron acceptor.
B) It absorbs photons with a wavelength of 680 nm.
C) It protects chlorophyll from destruction by free radicals.
D) It carries electrons to photosystem I.
A) It transforms light energy by acting as the initial electron acceptor.
Isolated thylakoids were incubated in an acidic solution at pH 4 until the pH was equilibrated across the thylakoid membrane. The thylakoids were then transferred to a buffer at pH 8 with ADP and inorganic phosphate. ATP was synthesized. Did this experiment require light to generate the ATP?
A) No, because ATP synthesis depends only on the presence of a hydrogen ion gradient and does not require light directly.
B) Yes, because the hydrogen ion gradient is generated through the transfer of electrons in photosystem II.
C) Yes, because ATP synthase requires high-energy electrons from photosystem II.
D) No, because ATP synthesis is not part of the light-dependent reactions of photosynthesis.
A) No, because ATP synthesis depends only on the presence of a hydrogen ion gradient and does not require light directly.
The primary biochemical outcome of the activity of photosystem I is to _____.
A) reduce NADP+
B) phosphorylate ADP
C) oxidize NADPH
D) hydrolyze ATP
A) reduce NADP+
Electrons excited by the absorption of light in photosystem I are transferred to iron–sulfur electron acceptors and therefore must be replaced. The replacement electrons come directly from _____.
A) ATP
B) water
C) NADP+
D) plastocyanin
D) plastocyanin
Electrons excited by absorption of light in photosystem II are transferred to plastoquinone and therefore must be replaced. The replacement electrons come from _____.
A) oxygen
B) cytochrome
C) water
D) photosystem I
C) water
The Calvin cycle uses six ATP molecules to produce one 3-carbon sugar (glyceraldehyde-3-phosphate, 3GP) from three molecules of RuBP and three molecules of carbon dioxide. Yet the Calvin cycle actually requires nine ATP molecules to function. Why?
A) Three additional ATP molecules are used to phosphorylate carbon dioxide for the next cycle.
B) Three additional ATP molecules are used to regenerate RuBP.
C) Three additional ATP molecules are hydrolyzed to keep enough heat available for the reaction to continue.
D) Three additional ATP molecules are used to reduce NADP+ to NADPH.
B) Three additional ATP molecules are used to regenerate RuBP.
Why is it critical for plants to maintain a high concentration of carbon dioxide in the leaves?
A) Oxygen will not be produced without it.
B) It is the only substrate for rubisco.
C) It helps prevent photorespiration.
D) It is necessary for regeneration of RuBP from G3P.
C) It helps prevent photorespiration.
Rubisco differs from PEP carboxylase in that _____.
A) rubisco can “fix” CO2, catalyzing its attachment to an organic compound
B) rubisco can use oxygen gas as a substrate
C) rubisco is only found in C3 plants
D) rubisco is located in the leaves of plants
B) rubisco can use oxygen gas as a substrate
