Chapter 8.1 & 8.2 reading guide PDF

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Chapter 8 Reading Guide: Photosynthesis Using Sunlight to Build Carbohydrates The targeted reading is created to guide your study, directing your attention to the content that will help you meet the learning objectives. There are detailed Learning Objectives at the end of the document if you need extra guidance. The answers to the Self-Assessment Questions are also included.

8.1 An Overview of Photosynthesis (p. 157-160) Photosynthesis is the major pathway by which energy and carbon are incorporated into carbohydrates. LO 8.1 Interpret the chemical pathways of photosynthesis as reactions that result in the formation of carbohydrates. Terminology: Reduction: a reaction in which a molecule gains electrons Oxidation: a reaction in which a molecule loses electrons Photosynthetic electron transport chain: a series of redox reactions in which light energy absorbed by chlorophyll is used to power the movement of electrons; in oxygenic photosynthesis, the electrons ultimately come from water and the terminal electron acceptor is NADP+ Nicotinamide adenine dinucleotide phosphate (NADPH): an important cofactor in many biosynthetic reactions; the reducing agent used in the Calvin cycle Calvin Cycle: the process in which carbon dioxide is reduced to synthesize carbohydrates, with ATP and NADPH as the energy sources Thylakoid membrane: a highly folded membrane in the center of the chloroplast that contains lightcollecting pigments and that is the site of photosynthetic electron transport chain Grana: interlinked structures resembling flattened sacs that form the thylakoid membrane Lumen: in eukaryotes, the continuous interior of the endoplasmic reticulum; in plants, a fluid-filled compartment enclosed by the thylakoid membrane; generally, the interior of any tubelike structure Stroma: the region of the chloroplast that surrounds the thylakoid, where the Calvin cycle takes place Self-Assessment Questions: 1. Write the overall reaction for photosynthesis. Which molecules are oxidized and which molecules are reduced?

6 C O 2 +12 H 2 O → C 6 H 12 O6 + 6 O 2 +6 H 2 O CO2 is reduced to C6H12O6, and H2O is oxidized to O2 2. If you want to produce carbohydrates that contain the heavy oxygen ( 18O) isotope, should you water your plants with H218O or inject C18O2 into the air? You should inject C18O2 into the air, since the entire CO2 molecule is used in synthesizing carbohydrates. 3. How are the overall reactions for photosynthesis and cellular respiration similar and how are they different? Photosynthesis uses energy from sunlight to make carbohydrates from CO2, while celllular respiration uses carbohydrates that are oxidized to CO2 to release energy to synthesize ATP. H2O is used as the ultimate electron donor in photosynthesis, which leaves O2 as a by-product, while cellular respiration uses O2 as the utimaate electron acceptor, leaving H2O as a by-product. 4. In the chloroplasts of plant cells, the absorption of light energy and the movement of electrons

along an electron transport chain occur in the _____, and the synthesis of carbohydrates takes place in the _____.

A. B. C. D. E.

inner membrane; matrix

thylakoids; stroma thylakoids; matrix inner membrane; cytoplasm inner membrane; stroma

5. With the endosymbiotic hypothesis in mind, what structure within modern-day chloroplasts is

likely derived from the plasma membrane of ancestral cyanobacteria that took up residence within a eukaryotic cell?

A. B. C. D. E.

inner membrane

grana lumen thylakoid membrane stroma

8.2 The Calvin Cycle: (p. 160-163) The Calvin cycle is a three-step process that uses carbon dioxide to synthesize carbohydrates. LO 8.2 Interpret the Calvin cycle as a three-phase process that uses carbon dioxide to synthesize carbohydrates. Terminology: Carboxylation: a chemical reaction in which carbon dioxide is added to another molecule and a carboxylic acid group is produced. It occurs, for example, in the Calvin cycle when carbon dioxide is added to a 5carbon molecule Reduction: a reaction in which a molecule gains electrons Regeneration: in the context of photosynthesis, the third step of the Calvin cycle, in which the 5-carbon molecule needed for carboxylation is produced Ribulose 1,5-bisphosphate (RuBP): the 5-carbon sugar to which carbon dioxide is added by the enzyme rubisco Ribulose bisphosphate carboxylase oxygenase (rubisco): the enzyme that catalyzes the carboxylation reaction in the Calvin cycle 3-phosphoglycerate (3-PGA): a 3-carbon molecule; during the Calvin cycle, two molecules of 3-PGA are the first stable products following the addition of carbon dioxide. Triose phosphates: a 3-carbon carbohydrate molecule, produced by the Calvin cycle and exported from the chloroplast Self-Assessment Questions: 6. What are the major inputs and outputs of the Calvin cycle? The major inputs of the Calvin cycle are CO2, ATP, and NADPH. The major outputs from the Calvin cycle are ADP, NADP+, and carbohydrates. 7. What are the three major steps in the Calvin cycle and the role of the enzyme rubisco? First CO2 eenters and is added to the 5-carbon compound RuBP, due to the catalyst, rubisco, creating 3phosphoglycerate (3-PGA). Second, the 3-PGA is reduced because, by going through ATP to ADP and NADPH to NADP+, leaving triose phosphate. Third, triose phosphate is used to create RuBP through reactions with ATP. 8. The Calvin cycle requires both ATP and NADPH. Which of these molecules provides the major input of energy needed to synthesize carbohydrates? The major input of energy needed to synthesize carbohydrates comes from NADPH.

9. Which of the answer choices correctly lists the three phases of the Calvin cycle? A. B. C. D.

carboxylation, reduction, and regeneration

oxidation, reduction, and carboxylation carboxylation, ATP synthesis, and regeneration reduction of CO2, reduction of NADPH, regeneration of RuBP

10. For every six CO2 molecules incorporated into carbohydrate molecules, how many triose

phosphates can be exported from the chloroplast? A. 10 B. C. D. E.

12 2 6 1...