Biology
5th Edition
ISBN: 9781260487947
Author: BROOKER
Publisher: MCG
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Textbook Question
Chapter 8.2, Problem 5CC
Why does cyclic photophosphorylation provide an advantage to a plant over using only linear electron flow?
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The Calvin cycle, the "dark reaction" or Carbon fixation reactions of photosynthesis, cannot occur at night in a living plant. Which of the following best describes why this is true?
A) The stomata are incapable of opening at night, thus CO2 cannot enter the leaf
B) The reactions of the Calvin cycle are dependent on light reactions for high-energy compounds
C) Several enxymes necessary for Calvin cycle activity have been degraded during the day and must be replaced
D) Light is required to transport the water necessary for the cycle
E) Cooler temperatures at night slow enzyme activity and rates of substrate diffusion
DRAW a curved arrow mechanism for photosynthesis with the following steps.
Step 1: Absorption of sunlight and excitation of chlorophyll molecules
Step 2: Transfer of energy to reaction center chlorophylls, which lose an electron and become oxidized.
Step 3: Electron transfer from oxidized chlorophylls to an electron acceptor, such as a quinone molecule
Step 4: Electron transfer from the quinone molecule to a chain of electron carriers, such as cytochromes, which generate a proton gradient across the thylakoid membrane
Step 5: ATP synthesis by ATP synthase using the energy of the proton gradient.
Step 6: Transfer of electrons from the electron carriers to the enzyme rubisco, which catalyzes the carboxylation of ribulose bisphosphate (RuBP) with CO2, forming an unstable 6-carbon intermediate.
Step 7: Cleavage of the 6-carbon intermediate into two 3-carbon molecules, which are phosphorylated by ATP and reduced by NADPH to form glyceraldehyde-3-phosphate (G3P)
Step 8: Conversion of G3P to…
What are the two places where light energy is required in the light reaction of photosynthesis? Why must energy be supplied at precisely these points?
Chapter 8 Solutions
Biology
Ch. 8.1 - Core Skill: Modeling The goal of this modeling...Ch. 8.1 - Prob. 2CSCh. 8.1 - Can the Calvin cycle occur in the dark?Ch. 8.2 - Prob. 1CCCh. 8.2 - Prob. 2CCCh. 8.2 - Prob. 3CCCh. 8.2 - Prob. 4CCCh. 8.2 - Why does cyclic photophosphorylation provide an...Ch. 8.2 - Prob. 6CCCh. 8.3 - Prob. 1CC
Ch. 8.4 - Prob. 1CCCh. 8.4 - Prob. 1EQCh. 8.4 - Prob. 2EQCh. 8.4 - Prob. 3EQCh. 8.5 - Prob. 1CCCh. 8.5 - Prob. 2CCCh. 8 - The water necessary for photosynthesis a. is split...Ch. 8 - In PSII, P68o differs from the pigment molecules...Ch. 8 - Prob. 3TYCh. 8 - Prob. 4TYCh. 8 - Prob. 5TYCh. 8 - Prob. 6TYCh. 8 - Prob. 7TYCh. 8 - Prob. 8TYCh. 8 - Prob. 9TYCh. 8 - Prob. 10TYCh. 8 - Prob. 1CQCh. 8 - Prob. 2CQCh. 8 - Prob. 3CQCh. 8 - Discuss the advantages and disadvantages of being...Ch. 8 - Biotechnologists are trying to genetically modify...
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- Identify the chemical basis for ApH and AY across the chloroplast thylakoid membrane by dragging the descriptions to their targets. Be sure to notice that the upper arrow iindicates ApH and the lower arrow indicates ΔΨ. ATP synthase complex H+ N ADP + P₁ Light energy ATP H*N Photosystem I/II- Chloroplast N side Aus PN ApH T + Thylakoid membrane HTp H+p Lumen Stroma P side Proton circuit A B High H concentration Low positive charge High positive charge Low H+ concentration Within the image, identify the types of proton translocation by dragging each label to its target. O XH₂ 2H+ + Z 2 H* ZH₂ O XH₂ Z 2H+ ZH₂ 2H+ C A B Proton pump Redox looparrow_forwardIn photosystem I, how can a proton gradient be formed during cyclic photophosphorylation?arrow_forwardTypically the CO2 necessary for photosynthesis enters through the stomata of the plant leaves suppose petroleum jelly was used to coat the leaves out of this tomato blocked or closed a) what effect will this have on the light reactions in these leaf cells b) what effect will this have on the Calvin cycle in these leaf cellsarrow_forward
- In chloroplasts, the light reactions power the creation of ATP via chemiosmosis. In relation to this process, which of the following is true? a) ATP synthase breaks ATP down into ADP, creating energy to fuel chemiosmosis. b) Oxygen is used as a source of electrons to replace those lost in photosystem II. c) Chemiosmosis during the light reactions is also used in the reduction of NADPH and FADH2. d) As excited electrons fall back down to a lower energy state, they create a proton gradient that is used to fuel the phosphorylation of ADP.arrow_forwardWhich of the following statements about the light reactions of photosynthesis are correct? 1. Absorption of light does one thing: it makes chlorophyll easier to oxidize. 2. In PSII, the rate of damage to the D1 protein can never exceeds the rate of repair. 3. Electron transport is spontaneous (exergonic) as electrons move from P680* to P700+. 4. Compared to anoxygenic photosynthesis, in oxygenic photosynthesis less light needs to be absorbed to reduce NADP+. A. 1,2 and 3 B. 1 and 3 C. 2 and 4 D. 4 only E. All of 1,2,3 and 4 are correctarrow_forwardIn the light-dependent reaction of photosynthesis, what specifically happens in the electron transport chain between Photosystem II and Photosystem I? The excited electron accepted by the primary acceptor in Photosystem II is transferred to pheophytin and plastoquinones, then to cytochrome complex, and finally to plastocyanin. Plastocyanin then transfers the electron to the P700 in the reaction center complex of Photosystem I. The excited electron accepted by the primary acceptor in Photosystem I is transferred to pheophytin and plastoquinones, then to cytochrome complex, and finally to plastocyanin. Plastocyanin then transfers the electron to the P700 in the reaction center complex of Photosystem II. The excited electron accepted by the primary acceptor in Photosystem I is transferred to plastocyanin, then to cytochrome complex, and finally to pheophytin and plastoquinones. Plastoquinone then transfers the electron to the P700 in the reaction center complex of Photosystem II.…arrow_forward
- How many water molecules have to be split as part of the light reactions to produce enough ATP and NADPH for the Calvin cycle to produce one molecule of glyceraldehyde-3-phosphate (G3P)? STROMA (low H+ concentration) Light THYLAKOID SPACE (high H+ concentration) STROMA (low H+ concentration) Photosystem II 4 H+ H₂O 1 1/2 0₂ +2 H+ Thylakoid membrane Cytochrome complex Light Pq 4 H+ Photosystem I Pc ATP synthase ADP + H+ Fd M ATP NADP+ reductase NADP+ + H+ NADPH To Calvin Cyclearrow_forward1) When a leaf on an oak tree absorbs 15,440 photons, how many glyceraldehyde-3-phosphate molecules can be produced by the Calvin cycle? b)When a leaf on an oak tree absorbs 15,440 photons, how many glyceraldehyde-3-phosphate molecules can be produced by the Calvin cycle?arrow_forwardAtrazine is one of the world’s most used herbicides. It functions by bonding to and disabling a protein in photosystem II. Plants treated with this herbicide die via starvation. Based on this information, what is also true about atrazine-treated plants? a) Only non-cyclic electron flow is possible. b) There is not enough ATP created to fuel the Calvin cycle. c) The plants can switch to C4 pathways. d) The chloroplast is disabled.arrow_forward
- For the following questions, choose one to discuss: chloroplast/photosynthesis State at the outset which one you will discuss. A) What role do proton gradients play in the process of photosynthesis proton gradients allow B) Where are proton gradients formed? Within what structures are they seen in chloroplasts How do the structures help them to maintain a gradient? C) Explain where and how the chloroplast or mitochondria uses passive transport and active transport to complete photosynthesis or cellular respiration.arrow_forwardWhich of the following best describes the products of the photochemical reactions of photosynthesis?A) NADH and ATP are made in the stromaB) NADPH and ATP are made in the stromaC) NADH and ATP are made in the thylakoid lumenD) NADPH is made in the stroma and ATP is made in the thylakoid lumenE) NADPH and ATP are made in the thylakoid lumenarrow_forwardWhat is so special about thylakoid membranes (and chloroplasts in general) that allow it to be the site for photosynthetic activity in plants?arrow_forward
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