Chapter 10
Photosynthesis
Vocabulary: photosynthesis, autotroph, heterotroph, chlorophyll, mesophyll, stroma, thylakoid, light reactions, Calvin cycle, NADP+, photophosphorylation, carbon fixation, electromagnetic spectrum, wavelength, photons, spectrophotometer, absorption spectrum, action spectrum, carotenoids, photosytem, reaction-center complex, light harvesting complex, primary electron acceptor, linear electron flow, cyclic electron flow, photorespiration, bundle-sheath cells, C3 plants, C4 plants, CAM plants
Objectives:
After attending lectures and studying the chapter, the student should be able to:
1. Distinguish between autotrophic and heterotrophic modes of nutrition.
2. Distinguish between photoautotrophs and chemoautotrophs.
3. Define photosynthesis and write the general chemical equation for photosynthesis.
4. State which organisms undergo photosynthesis.
5. Distinguish between the site of photosynthesis in prokaryotic cells and in eukaryotic cells.
6. Describe the structure of the chloroplast in eukaryotic cells and describe where in the chloroplast the photosynthetic pigments are located.
7. Distinguish between radiant energy and chemical energy and relate both to the process of photosynthesis.
8. Distinguish between the electromagnetic spectrum, the visible spectrum, and an absorption spectrum.
9. State which colors of the visible spectrum are absorbed by chlorophylls and which color is reflected.
10. State which chlorophyll is required for the process of photosynthesis and is therefore found in all photosynthetic organisms.
11. State which chlorophylls are found in all plants and which other photosynthetic pigments are commonly found in plants.
12. Distinguish between the light-dependent reactions and the light-independent reactions of photosynthesis and describe the relationship between the two sets of reactions.
13. Relating to the light-dependent reactions (light reactions) of photosynthesis in eukaryotic cells (e.g. plants):
a. State the membrane and the two fluid areas in the chloroplast where the light reactions occur.
b. State and distinguish between the two different energy-storing molecules that are produced by the light reactions of photosynthesis.
c. Describe a photosystem, state the two photosystems involved in the linear (noncyclic) photophosphorylation process, and state the reaction center chlorophylls in each photosystem.
d. Explain how light energy causes the reaction center chlorophyll in a photosystem to
release an electron to a primary electron acceptor.
e. Explain why chlorophyll a is considered the main photosynthetic pigment in plants and
chlorophyll b and other pigments are considered accessory.
f. Describe where the electron given off by photosystem I goes and where the electron
given off by photosystem II goes.
g. Relate the redox reactions of an electron transport chain to the active transport of
hydrogen ions (H+) across a membrane.
h. Relate the active transport of H+ ions across a membrane to the formation of an
electrochemical gradient.
i. Relate facilitated diffusion of H+ ions through the ATP synthase protein channel to the
making of ATP.
j. State the source of a replacement electron for the one given off by the reaction center
chlorophyll P680 and the source of a replacement electron for the one given off by the
reaction center chlorophyll P700.
14. Relating to the light-independent reactions (Calvin cycle) of photosynthesis in eukaryotic cells (e.g. plants):
a. State the site of the Calvin cycle in the chloroplast.
b. State the energy-storing molecules which were produced by the light reactions and which
are used as an energy source for the Calvin cycle.
c. Show the steps of the Calvin cycle, including the major molecules involved, and explain
why the Calvin cycle is considered a cycle.
d. State the 3-carbon product of the Calvin cycle and relate it to the production of glucose.
15. Describe the major functions of glucose in photosynthetic organisms.
16. Explain the role in photosynthesis of stomata in plant leaves.
17. Distinguish the major differences between C3, C4, and CAM plants.
| 1901050321 | Photosynthesis converts light energy to the chemical energy of food | ... |  | 0 |
| 1901050329 | Autotrophic | produce their organic molecules from CO2 and other raw material from the environment. | 1 | |
| 1901050330 | Chloroplasts | absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water. | 2 | |
| 1901050322 | Thylakoids | A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy. |  | 3 |
| 1901050331 | Photosynthesis | The conversion of light energy to chemical energy that is stored in glucose or other organic compounds; occurs in plants, algae, and certain prokaryotes. | 4 | |
| 1901050332 | Autotrophs | produce their own organic molecules from CO2 | 5 | |
| 1901050333 | Heterotrophs | An organism that obtains organic food molecules by eating other organisms or substances derived from them. | 6 | |
| 1901050334 | Mesophyll | specialized for photosynthesis. In C3 and CAM plants, mesophyll cells are located between the upper and lower epidermis; in C4 plants, they are located between the bundle-sheath cells and the epidermis. | 7 | |
| 1901050335 | Stomata | pores on the leaf where O2 exits and CO2 enters | 8 | |
| 1901050336 | Stroma | The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water. | 9 | |
| 1901050337 | Thylakoids | A flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular "machinery" used to convert light energy to chemical energy. | 10 | |
| 1901050338 | Chlorophyll | A green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes. Chlorophyll a participates directly in the light reactions, which convert solar energy to chemical energy. | 11 | |
| 1901050339 | What are the two stages of photosynthesis | light dependent and light independent | 12 | |
| 1901050340 | Light Reactions | The first of two major stages in photosynthesis (preceding the Calvin cycle). These reactions, which occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process. | 13 | |
| 1901050341 | Calvin cycle | The second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric CO2 and reduction of the fixed carbon into carbohydrate. | 14 | |
| 1901050342 | NADP | Nicotinamide adenine dinucleotide phosphate, an electron acceptor that, as NADPH, temporarily stores energized electrons produced during the light reactions. | 15 | |
| 1901050343 | Photophosphorylation | The process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certain prokaryotes during the light reactions of photosynthesis. | 16 | |
| 1901050344 | Carbon Fixation | The initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic prokaryote). | 17 | |
| 1901050345 | Carotenoids | An accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis. | 18 | |
| 1901050323 | Describe a chlorophyll molecule | ... |  | 19 |
| 1901050346 | Photosystem | A light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes. There are two types of photosystems, I and II; they absorb light best at different wavelengths. | 20 | |
| 1901050347 | Reaction-center complex | A complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. Excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain. | 21 | |
| 1901050348 | Light harvesting complex | A complex of proteins associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem. | 22 | |
| 1901050349 | Primary electron acceptor | In the thylakoid membrane of a chloroplast or in the membrane of some prokaryotes, a specialized molecule that shares the reaction-center complex with a pair of chlorophyll a molecules and that accepts an electron from them. | 23 | |
| 1901050350 | Photo system II | One of two light-capturing units in a chloroplast's thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P680 chlorophyll a at its reaction center. Pheophytin = primary electron acceptor Electrons recovered by splitting H2O Mn complex catalyzes splitting of H2O | 24 | |
| 1901050351 | Photosystem I | A light-capturing unit in a chloroplast's thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P700 chlorophyll a at its reaction center. remaining pigments = antenna pigments | 25 | |
| 1901050324 | 10.3 The Calvin Cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar | ... |  | 26 |
| 1901050352 | Glyceraldehyde 3-phosphate (G3P) | A three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis. | 27 | |
| 1901050353 | What are the three phases of The Calvin cycle? | Carbon Fixation Energy Consumption and Redox Release of G3P; Regeneration of RuBP | 28 | |
| 1901050354 | C3 plants | A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate. | 29 | |
| 1901050355 | Photorespiration | A metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output. Photorespiration generally occurs on hot, dry, bright days, when stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco. | 30 | |
| 1901050356 | C4 Plants | A plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle. | 31 | |
| 1901050357 | Bundle-sheath cells | In C4 plants, a type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf. | 32 | |
| 1901050358 | PEP carboxylase | An enzyme that adds CO2 to phosphoenolpyruvate (PEP) to form oxaloacetate in mesophyll cells of C4 plants. It acts prior to photosynthesis. | 33 | |
| 1901050359 | CAM plants | A plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions. In this process, carbon dioxide entering open stomata during the night is converted to organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed. | 34 | |
| 1901050360 | Which of the following sequences correctly represents the flow of electrons during photosynthesis? NADPH → chlorophyll → Calvin cycle H2O → NADPH → Calvin cycle NADPH → O2 → CO2 NADPH → electron transport chain → O2 H2O → photosystem I → photosystem II | H2O → NADPH → Calvin cycle | 35 | |
| 1901050361 | Which of the following statements is a correct distinction between autotrophs and heterotrophs? Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic. Only heterotrophs require oxygen. Cellular respiration is unique to heterotrophs. Only heterotrophs have mitochondria. Only heterotrophs require chemical compounds from the environment. | Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic. | 36 | |
| 1901050362 | Which of the following does not occur during the Calvin cycle? release of oxygen regeneration of the CO2 acceptor oxidation of NADPH consumption of ATP carbon fixation | release of oxygen | 37 | |
| 1901050363 | Which process is most directly driven by light energy? creation of a pH gradient by pumping protons across the thylakoid membrane removal of electrons from chlorophyll molecules reduction of NADP+ molecules ATP synthesis carbon fixation in the stroma | removal of electrons from chlorophyll molecules | 38 | |
| 1901050364 | The light reactions of photosynthesis supply the Calvin cycle with | ATP and NADPH. | 39 | |
| 1901050365 | How is photosynthesis similar in C4 plants and CAM plants? | In both cases, rubisco is not used to fix carbon initially. | 40 | |
| 1901050366 | In mechanism, photophosphorylation is most similar to | oxidative phosphorylation in cellular respiration. | 41 | |
| 1901050325 | Which of the following equations represents photosynthesis? 6CO2 + 6O2 → C6H12O6 + 6H2O 6H2O + 6O2 → C6H12O6 + 6CO2 C6H12O6 + 6O2 → 6CO2 + 6H2O C6H12O6 + 6CO2 → 6O2 + 6H2O 6CO2 + 6H2O → C6H12O6 + 6O2 | 6CO2 + 6H2O → C6H12O6 + 6O2 Photosynthesis requires carbon dioxide and water for the production of sugar and oxygen. |  | 42 |
| 1901050326 | In which of the following organelles does photosynthesis take place? Chloroplast Mitochondrion Ribosome Central vacuole Nucleus | Chloroplast Chloroplasts use energy from light to transform carbon dioxide and water into sugar and oxygen. |  | 43 |
| 1901050327 | What connects the two photosystems in the light reactions? Chlorophyll A thylakoid An electron transport chain A chain of glucose molecules The Calvin cycle | An electron transport chain |  | 44 |
| 1901050328 | What two molecules are produced by the light reactions and used to power the Calvin cycle? CO2 and O2 C6H12O6 and O2 C6H12O6 and RuBP ATP and NADPH G3P and H2O | ATP and NADPH ATP and NADPH are both products of the light reactions and are used to power the Calvin cycle. |  | 45 |
| 1901050367 | What provides electrons for the light reactions? CO2 The Calvin cycle H2O Light O2 | H2O Electrons are stripped from water in the light reactions of photosynthesis. Light provides the energy to excite electrons. | 46 | |
| 1901050368 | What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle? Sucrose (C12H22O11) RuBP Carbon dioxide (CO2) Glucose (C6H12O6) G3P (C3H6O3) | Carbon dioxide (CO2) Carbon dioxide provides the carbon atoms that are incorporated into sugars in photosynthesis. Carbon dioxide initially combines with RuBP, and RuBP is regenerated to continue the Calvin cycle. | 47 | |
| 1901050369 | What transports electrons from the light reactions to the Calvin cycle? NADH NADPH An electron transport chain FADH2 Chlorophyll | NADPH NADPH is an electron carrier that picks up electrons in the light reactions and releases them in the Calvin cycle. An electron transport chain conveys electrons from one photosystem to the other within the light reactions. | 48 | |
| 1901050370 | The light reactions take place in the _________ and the Calvin cycle takes place in the _________. stroma; thylakoids thylakoids; stroma inner membrane; outer membrane chloroplasts; mitochondria mitochondria; chloroplasts | thylakoids; stroma Within the chloroplast, the light reactions take place in the flattened sacs called thylakoids and the Calvin cycle takes place in the thick fluid called the stroma. | 49 | |
| 1901050371 | Where does the Calvin Cycle take place? | The Calvin cycle is a complex series of chemical reactions carried out in the stroma. | 50 | |
| 1901050372 | Describe Carbon Fixation in the Calvin Cycle | Three molecules of carbon dioxide are added to three molecules of a five-carbon sugar abbreviated RuBP. These molecules are then rearranged to form six molecules called 3-PGA, which have three carbons each. | 51 | |
| 1901050373 | How did Jan Bautista van Helmont contribute to the elucidation of photosynthesis? | Demonstrated that the substance of plant was not produced only from the soil by weighing his plants and tracking how much he watered them. | 52 | |
| 1901050374 | How did Joseph Priestly contribute to the elucidation of photosynthesis? | Living vegetation adds something to the air (02). "Injured air" could not support life. | 53 | |
| 1901050375 | How did Jan Ingen-Houz contribute to the elucidation of photosynthesis? | Proposed plants carry out a process that uses sunlight to split carbon dioxide into carbon and oxygen gas. | 54 | |
| 1901050376 | How did J. F. Blackman contribute to the elucidation of photosynthesis? | Photosynthesis is a multistage process and only portion uses light directly. | 55 | |
| 1901050377 | How did C. B. Van Neil contribute to the elucidation of photosynthesis? | Found purple sulfur bacteria do not release O2 but accumulate sulfur. Proposed general formula for photosynthesis and later researchers found O2 produced comes from water. | 56 | |
| 1901050378 | How did Robin Hill contribute to the elucidation of photosynthesis? | Demonstrated that Neil was right that light energy could be harvested and used in reduction reaction without CO2. | 57 | |
| 1901050379 | What did Engelmann elucidate? | Action spectrum of chlorophyll. Not all wavelengths of light created equally when it comes to photosynthesis. | 58 | |
| 1901050380 | Chlorophyll a | all photosynthetic organisms | 59 | |
| 1901050381 | chlorophyll b | accessory pigment | 60 | |
| 1901050382 | carotenoids | accessory pigment | 61 | |
| 1901050383 | With regard to the structure of chlorophyll a, what is the significance of the hydrophobic tail? | all these pigments end up embedded in membranes. | 62 | |
| 1901050384 | In general, photosynthesis: | 1. 200-400 pigment molecules linked together in antenna array 2. 1 pair of chlorophyll a molecules in reaction center which are able to transfer electrons. 3. Resonance energy transfer between array of pigments and reactions center. | 63 | |
| 1902354990 | Ferrodoxin | Primary electron acceptor in Photosystem I. If there is no NADP+, electrons go to cytochrome b6f | 64 | |
| 1902354991 | Pheophytin | Primary electron acceptor in Photosystem II. | 65 | |
| 1902354992 | Cytochrome b6f complex | H+ pump Establishes H+ gradient used to manufacture ATP | 66 | |
| 1902354993 | What is the role of Rubisco in the presence of CO2? | Combines RuBP with CO2 and H2O into a short lived 6C compound; results in the formation of 2 molecules of PGA | 67 | |
| 1902354994 | What is the role of Rubisco in the presence of O2? | Combines RuBP with O2 and H2O resulting: 1 molecule of PGA (3C) 1 molecule of Glycolic acid (2C) | 68 | |
| 1902355006 | What happens to the products of photorespiration? | 1. Glycolic acid shipped to peroxisome and metabolized into glycine 2. Glycine is sent to the mitochondria and metabolized into serine 3. Serine is sent back to peroxisome and metabolized into glycerate 4. Glycerate is shipped to chloroplast and enter Calvin Cycle as PGA |  | 69 |
| 1902354995 | What is the cost of photorespiration? | 2 NADH and 1 ATP | 70 | |
| 1902354996 | What is photorespiration? | O2 out competes CO2 at active site of Rubisco resulting in 1 PGA and 1 Glycolic Acid | 71 | |
| 1902354997 | What is the advantage of photorespiration? | Helps C3 plants survive under hot dry conditions | 72 | |
| 1902354998 | C4 pathway | Decouples light reactions and carbon fixation reactions. CO2 converted to 4C organic acid in MESOPHYLL cells. | 73 | |
| 1902354999 | C4 pathway: What enzyme is the primary enzyme? | PEP carboxylase adds a CO2 to PEP forming oxaloacetate which can be converted to malate and asparate. | 74 | |
| 1902355000 | C4 pathway: Where is CO2 released from the 4C organic acid? | Bundle sheath cell. This is the site of carbon fixation. | 75 | |
| 1902355001 | Pros and Cons of C4 pathway: | PRO: PEP carboxylase has no affinity for O2; NO photorespiration in hot, dry, very bright conditions therefore able to outcompete C3 plants in these conditions. CON: Very expensive for the plant | 76 | |
| 1902355002 | What does CAM stand for? | Crassulacean Acid Metabolism; ie succulents like jade | 77 | |
| 1902355003 | CAM Photosynthesis | At night, stomata are open. CO2 combined with PEP to form 4C organic acids, which accumulate at night. During the day when stomates are closed, CO2 is released and enters carbon fixation reactions. | 78 | |
| 1902355004 | How do CAM and C4 plants differ? | C4: light and dark reactions separated by space CAM: light and dark reactions separated by time | 79 | |
| 1902355005 | What is the advantage of CAM metabolism? | Allows plants to function well under limited water supply as well as high light intensity. | 80 |
