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.
| 1861241069 | 10.1 Photosynthesis converts light energy to the chemical energy of food | ... |  | 0 |
| 1861241077 | Autotrophic | ... | 1 | |
| 1861241078 | Chloroplasts | An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water. | 2 | |
| 1861241070 | Thylakoids | A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy. |  | 3 |
| 1861241079 | 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 | |
| 1861241080 | Autotrophs | ... | 5 | |
| 1861241081 | Heterotrophs | An organism that obtains organic food molecules by eating other organisms or substances derived from them. | 6 | |
| 1861241082 | Mesophyll | Leaf cells 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 | |
| 1861241083 | Stomata | ... | 8 | |
| 1861241084 | Stroma | The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water. | 9 | |
| 1861241085 | 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 | |
| 1861241086 | 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 | |
| 1861241087 | What are the two stages of photosynthesis | ... | 12 | |
| 1861241088 | 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 | |
| 1861241089 | 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 | |
| 1861241090 | NADP | Nicotinamide adenine dinucleotide phosphate, an electron acceptor that, as NADPH, temporarily stores energized electrons produced during the light reactions. | 15 | |
| 1861241091 | 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 | |
| 1861241092 | 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 | |
| 1861241093 | 10.2 The light reactions convert solar energy to thee chemical energy of ATP and NADPH | ... | 18 | |
| 1861241094 | Wavelength | The distance between crests of waves, such as those of the electromagnetic spectrum. | 19 | |
| 1861241095 | Electromagnetic Spectrum | The entire spectrum of electromagnetic radiation, ranging in wavelength from less than a nanometer to more than a kilometer. | 20 | |
| 1861241096 | Visible light | That portion of the electromagnetic spectrum that can be detected as various colors by the human eye, ranging in wavelength from about 380 nm to about 750 nm. | 21 | |
| 1861241097 | Photons | A quantum, or discrete quantity, of light energy that behaves as if it were a particle. | 22 | |
| 1861241098 | Spectrophotometer | ... | 23 | |
| 1861241099 | Absorption spectrum | ... | 24 | |
| 1861241100 | Chlorophyll a | A photosynthetic pigment that participates directly in the light reactions, which convert solar energy to chemical energy. | 25 | |
| 1861241101 | Chlorophyll b | An accessory photosynthetic pigment that transfers energy to chlorophyll a. | 26 | |
| 1861241102 | 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. | 27 | |
| 1861241071 | Describe a chlorophyll molecule | ... |  | 28 |
| 1861241103 | 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. | 29 | |
| 1861241104 | 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. | 30 | |
| 1861241105 | 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. | 31 | |
| 1861241106 | 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. | 32 | |
| 1861241107 | 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. | 33 | |
| 1861241108 | 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. | 34 | |
| 1861241109 | Cyclic electron flow | A route of electron flow during the light reactions of photosynthesis that involves only photosystem I and that produces ATP but not NADPH or O2. | 35 | |
| 1861241072 | 10.3 The Calvin Cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar | ... |  | 36 |
| 1861241110 | Glyceraldehyde 3-phosphate (G3P) | A three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis. | 37 | |
| 1861241111 | What are the three phases of The Calvin cycle? | Carbon Fixation Energy Consumption and Redox Release of G3P; Regeneration of RuBP | 38 | |
| 1861241112 | 10.4 Alternative mechanisms of carbon fixation have evolved in hot, arid climates | ... | 39 | |
| 1861241113 | 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. | 40 | |
| 1861241114 | 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. | 41 | |
| 1861241115 | 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. | 42 | |
| 1861241116 | Bundle-sheath cells | In C4 plants, a type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf. | 43 | |
| 1861241117 | PEP carboxylase | An enzyme that adds CO2 to phosphoenolpyruvate (PEP) to form oxaloacetate in mesophyll cells of C4 plants. It acts prior to photosynthesis. | 44 | |
| 1861241118 | Crassulacean acid metabolism (CAM) | An adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. In this process, a plant takes up CO2 and incorporates it into a variety of organic acids at night; during the day, CO2 is released from organic acids for use in the Calvin cycle. | 45 | |
| 1861241119 | 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. | 46 | |
| 1861241120 | Chromatography | ... | 47 | |
| 1861241121 | Word Roots: auto- | self; (autotroph: an organism that obtains organic food molecules without eating other organisms) | 48 | |
| 1861241122 | Word Roots: chloro- | green; | 49 | |
| 1861241123 | Word Roots: electro- | = electricity; | 50 | |
| 1861241124 | Word Roots: hetero- | = other (heterotroph: an organism that obtains organic food molecules by eating other organisms or their by-products) | 51 | |
| 1861241125 | Word Roots: meso- | = middle (mesophyll: the green tissue in the middle, inside of a leaf) | 52 | |
| 1861241126 | Word Roots: photo- | = light (photosystem: cluster of pigment molecules) | 53 | |
| 1861241127 | Word Roots: -troph | = food (autotroph: an organism that obtains organic food molecules without eating other organisms) | 54 | |
| 1861241128 | Word Roots: -phyll | = leaf (chlorophyll: photosynthetic pigment in chloroplasts) | 55 | |
| 1861241129 | Word Roots: magnet- | = magnetic (electromagnetic spectrum: the entire spectrum of radiation) | 56 | |
| 1861241130 | 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 | 57 | |
| 1861241131 | 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. | 58 | |
| 1861241132 | 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 | 59 | |
| 1861241133 | 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 | 60 | |
| 1861241134 | The light reactions of photosynthesis supply the Calvin cycle with | ATP and NADPH. | 61 | |
| 1861241135 | How is photosynthesis similar in C4 plants and CAM plants? | In both cases, rubisco is not used to fix carbon initially. | 62 | |
| 1861241136 | In mechanism, photophosphorylation is most similar to | oxidative phosphorylation in cellular respiration. | 63 | |
| 1861241073 | 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. |  | 64 |
| 1861241074 | 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. |  | 65 |
| 1861241075 | 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 |  | 66 |
| 1861241076 | 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. |  | 67 |
| 1861241137 | 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. | 68 | |
| 1861241138 | 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. | 69 | |
| 1861241139 | 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. | 70 | |
| 1861241140 | 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. | 71 | |
| 1861241141 | Where does the Calvin Cycle take place? | The Calvin cycle is a complex series of chemical reactions carried out in the stroma. | 72 | |
| 1861241142 | 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. | 73 |
