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138 Cards in this Set
- Front
- Back
- 3rd side (hint)
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True or false: life on earth is solar powered
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True
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What is photosynthesis?
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Is the process that converts solar energy into chemical energy
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The chloroplasts of plants use a process called _______ to capture light energy from the sun and convert it to chemical energy stored in sugars and other organic molecules
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Photosynthesis
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How does photosynthesis nourish almost all of the living world
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Directly or indirectly
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Organisms obtain organic compounds by one of two major modes. What are they called?
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1. Autotrophic nutrition
2. Heterotrophic nutrition |
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What are autotrophs and what are there functions?
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Are the producers of the biosphere; produce organic molecules from CO2 and other inorganic raw materials obtained from their environment
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True or false: almost all plants are autotrophs; the only nutrients they require are water and minerals from the soil and carbon dioxide from the air
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True
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What are plants?
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They are photo autotrophs, using light as a source of energy to synthesize organic compounds
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What are heterotrophs? How do they live?
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Are the consumers of the biosphere; they live organic compounds produced by other organisms
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What a
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______ are the sites of photosynthesis in plants
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Chloroplasts
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All green parts of a plant have chloroplasts but...
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Leaves are the major sites of photosynthesis for most plants
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O2 exists and CO2 enters the leaf through microscopic pores called _______ in the leaf
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Stomata
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A typical mesophyll cell has...
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30-40 chloroplasts
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Chloroplasts are found mainly in cells of ________, the tissue in the interior of the leaf
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Mesophyll
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Each chloroplasts has two membranes around a dense fluid called the
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Stroma
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Suspended within the stroma is an internal membranes of sacs called
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Thylakoids
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Thylakoids may be stacked in columns called
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Grams
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___________, the green pigment in the chloroplasts, is located in the thylakoids membranes
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Chlorophyll II
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Powered by light, photosynthesis produces
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Organic compounds and O2 from CO2 and H2O
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The equation describing the process of photosynthesis is
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6CO2+12H2O+ light energy ----> C6H12O6 + 6O2 + 6H2O
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True or false: evidence that chloroplasts split water molecules enabled researchers to track atoms through photosynthesis
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True
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One of the first clues to the mechanism of photosynthesis came from?
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The discovery that the O2 given off by plants come from H2O not CO2
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Plants split water as a source of _____ from _____ ____, releasing ______ as a by product.
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Electrons; hydrogen atoms; oxygen
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Hydrogen extracted from water is incorporated into _____, and ______ is released to the atmosphere
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Sugar; oxygen
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What type of reaction is photosynthesis?
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Redox
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True or false: photosynthesis reverses the direction of electron flow
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True
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In photosynthesis, water is split and electrons are ...
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Transferred with H+ from water to CO2 reducing it to sugar
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In photosynthesis, because the electrons increase in potential energy as they move from water to sugar....
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The process requires energy. The energy boost is provided by light
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True or false: photosynthesis is two processes, each with multiple steps: light reactions and the Calvin cycle
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True
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What is the function of light reactions ?
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Converts solar energy to chemical energy
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What is the function of the Calvin cycle
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Uses energy from the light reactions to incorporate CO2 from the atmosphere into sugar
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What happens in the light reactions of photosynthesis
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Water is split, providing a source of electrons and protons (H+ ions) and giving off O2 as a by-product
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Light absorbed by chlorophyll drives the transfer of electrons and hydrogen ions from water to NADP+ ...forming
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NADPH
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The light reactions also generate ATP using chemiosmosis in a process called
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Photophosphorylation
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Light energy is initially converted to chemical energy in the form of two compounds. What two compounds?
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NADPH and ATP
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What is NADPH?
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A source of electrons as reducing power that can be passed along to an electron acceptor
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What is ATP?
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The energy currency of cells
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The Calvin cycle begins with the incorporation of CO2 into organic molecules, a process known as
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Carbon fixation
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It is the Calvin cycle that makes sugar, but only ...
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With the help of ATP and NADPH from the light reactions
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True or false: the light reactions occur at the thylakoids, the Calvin cycle occurs in the stroma
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True
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________ are solar powered chemical factories
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Chloroplasts
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Chloroplasts' thylakoids transform light energy into ...
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The chemical energy of ATP and NADPH
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_____ is a form of electromagnetic energy or radiation
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Light
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How does light travel?
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Light travels in rhythmic waves
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The distance between crests of electromagnetic waves is called the...
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Wavelength
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Wavelengths of electromagnetic radiation range from shorter than a nanometer (gamma rays) to longer than a kilometer ( radio waves)
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The entire range of electromagnetic radiation is the
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Electromagnetic spectrum
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The most important segment of the electromagnetic spectrum for life is a narrow band, ______ _____, detected as colors by the human eye
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Visible light
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Although light travels as a wave, many of its roper ties are those of a discrete particle, a ________
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Photon
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True or false: photosynthetic pigments are light receptors
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True
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Substances that absorb visible light are known as
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Pigments
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True or false: different pigments absorb photons of different wavelengths, and the wavelengths that are absorbed disappear
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True
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Why does a leaf look green in color?
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A leaf looks green because chlorophyll, the dominant pigment, absorbs red and violet-blue light while transmitting and reflecting green light.
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What is the function of a spectrophotometer ?
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measures the ability of a pigment to absorb various wavelengths of light.
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How does a spectrophotometer function ?
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A spectrophotometer beams narrow wavelengths of light through a solution containing the pigment and then measures the fraction of light transmitted at each wavelength.
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What is the function of an absorption spectrum?
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Plots a pigment light absorption versus wavelength
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__________ ___ which participates directly in the light reactions, absorbs best in the red and violet-blue wavelengths and absorbs least in the green.
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Chlorophyll a
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An overall action spectrum for photosynthesis profiles ...
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the relative effectiveness of different wavelengths of radiation in driving the process.
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Accessory pigments such as ________ ____ , broadens the spectrum used for photosynthesis
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Chlorophyll b
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Accessory pigments called _______ absorb excessive light that would damage chlorophyll
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Carotenoids
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True or false: when chlorophyll and other pigments absorb light, an electron is boosted to an excite state
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True
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What happens when a pigment absorbs light?
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It goes from a ground state to an excited state, which is unstable
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When excited electrons fall back to the ground state, photons are given off, an afterglow called
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Fluorescence
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If illuminated a isolated solution of chlorophyll will....
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Fluoresce, giving off light and heat
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In the thylakoid membrane, chlorophyll is organized along with proteins and smaller organic molecules into ...
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Photo systems
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What is a photo system composed of?
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A reaction-center complex surrounded by several light harvesting complexes
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What is the reaction center complex?
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It is an organized association of proteins holding a special pair of chlorophyll 'a' molecules
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What does each light harvesting complex consist of?
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Pigment molecules ( which may include chlorophyll 'a', chlorophyll 'b' and carotenoids) bound to proteins
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At the reaction center is a ______ _____ _____, which accepts an excited electron from the reaction center chlorophyll 'a'
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Primary electron acceptor
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What is the first step of the light reactions?
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The solar powered transfer of an electron from a special chlorophyll 'a' molecule to the primary electron acceptor
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How does each photo system function?
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Functions in the chloroplast as a unit, converting light energy to chemical energy
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There are two types of photo systems in the thylakoid membrane. What are they called?
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Photo system II (PS II) and photo system I (PS I)
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Photosystem II (PS II) and photosystem I (PS I) each have a characteristic reaction-center complex .....
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a particular kind of primary electron acceptor next to a pair of special chlorophyll a molecules associated with specific proteins.
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The two photosystems were named in order of their discovery, but they function sequentially, with photosystem II functioning first.
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Photo system II has a
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reaction-center chlorophyll a known as P680, with an absorption peak at 680 nm.
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Photo system I has a
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reaction-center chlorophyll a known as P700, with an absorption peak at 700 nm.
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During the light reactions, there are two routes for electron flow. What are they?
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Cyclic and linear
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______ _____ _____, the primary pathway, involves both photo systems and produces ATP and NADPH using light energy
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Linear electron flow
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A photon hits a pigment and its energy is passed among pigment molecules until ....
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It excites P680
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An excited electron from P680 is transferred to
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The primary electron acceptor (now called P680+)
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______ is a very strong oxidizing agent
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P680+
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H2O is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+ thus reducing it to
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P680
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O2 is released as a by product of this reaction
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Each electron falls down an electron transport chain from
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The primary electron acceptor of PS II to PS I
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Energy released by the fall drives...
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The creation of a proton gradient across the thylakoid membrane
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Diffusion of H+ protons across the membrane drives ...
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ATP synthesis
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What happens in PS I?
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Transferred light energy excites P700, which loses an electron to an electron acceptor
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What is the function of P700+?
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Accepts an electron passed down from PS II via the electron transport chain
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Each electron falls down an electron transport chain from the ...
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Primary electron acceptor of PS I to the protein ferredoxin (Fd)
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From the protein ferredoxin , the electrons are then transferred to...
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NADP+ and reduce it to NADPH
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The electrons of NADPH are available for the reactions of
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The Calvin cycle
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In P700, the process removes an H+ from the
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Stroma
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Under certain conditions, photo excited electrons from photo system I , but not photo system II, can take an alternative athwart, a short circuit called?
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Cyclic electron flow
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What is the process of cyclic electron flow?
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The electrons cycle back from ferredoxin (Fd) to the cytochrome complex and from there continue on to a P700 chlorophyll in the PS I reaction-center complex.
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Cyclic electron flow does generate ATP but ....
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There is no production of NADPH and no release of oxygen
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True or false: several living groups of photosynthetic bacteria have photo system I but not photo system II
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True
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Give an example of a species that only has photo system I
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Purple sulfur bacteria
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Cyclic electron flow is the sole means of generating ATP in photosynthesis
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Cyclic electron flow may be photo protective which is
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Protecting cells from light-induced damage
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True or false: Chloroplasts and mitochondria generate ATP by the same mechanism, chemiosmosis.
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True
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In both chloroplasts and mitochondria...
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an electron transport chain pumps protons across a membrane as electrons are passed along a series of increasingly electronegative carriers.
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• This process transforms redox energy to a proton-motive force in the form of an H+ gradient across the membrane.
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ATP synthase molecules harness the proton-motive force to generate ATP as ...
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H+ diffuses back across the membrane.
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There are differences between oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. List a few of them.
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○ In mitochondria, the high-energy electrons dropped down the transport chain are extracted from organic molecules (which are thus oxidized), whereas in chloroplasts, the source of electrons is water.
○ Mitochondria use chemiosmosis to transfer chemical energy from food molecules to ATP; chloroplasts transform light energy into the chemical energy of ATP. |
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The spatial organization of chemiosmosis differs slightly between chloroplasts and mitochondria, but similarities are also evident. List a few of them.
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The inner membrane of the mitochondrion pumps protons from the mitochondrial matrix out to the intermembrane space.In the mitochondrion, protons diffuse down their concentration gradient from the intermembrane space through ATP synthase to the matrix, driving ATP synthesis.
. The thylakoid membrane of the chloroplast pumps protons from the stroma into the thylakoid space inside the thylakoid. In the chloroplast, ATP is synthesized as the hydrogen ions diffuse from the thylakoid space back to the stroma through ATP synthase complexes, whose catalytic knobs are on the stroma side of the membrane.Thus, ATP forms in the stroma, where it is used to help drive sugar synthesis during the Calvin cycle. |
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summarize the light reactions
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○ The light-driven electron current also generates ATP.
○ Thus, the equipment of the thylakoid membrane converts light energy to chemical energy stored in ATP and NADPH. |
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True or false: • The Calvin cycle regenerates its starting material after molecules enter and leave the cycle.
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True
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The Calvin cycle is _______, using energy to build sugar from smaller molecules
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Anabolic
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Carbon enters the Calvin cycle as....
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CO2 and leaves as sugar
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The actual sugar product of the Calvin cycle is not glucose but...
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a three-carbon sugar, glyceraldehyde-3-phosphate (G3P).
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For the net synthesis of one G3P molecule, the cycle must ...
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take place three times, fixing three molecules of CO2.
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The Calvin cycle has three phases. What are they?
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carbon fixation, reduction, and regeneration of the CO2 acceptor.
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In the ______ ______ phase, each CO2 molecule is attached to a five carbon sugar, ribulose bisphosphate (RuBP).
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Carbon fixation
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This reaction is catalyzed by RuBP carboxylase, or rubisco.
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In carbon fixation phase, what happens to the six carbon intermediate
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• The six-carbon intermediate is unstable and splits in half to form two molecules of 3-phosphoglycerate for each CO2 fixed.
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During the ______ ______, each 3 phosphoglycerate receives another phosphate group from ATP to form ....
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Reduction phase; 1,3-bisphosphoglycerate.
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In the reduction phase, A pair of electrons from NADPH reduces each 1,3-bisphosphoglycerate to ...
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G3P
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In the reduction phase, For every three molecules of CO2 that enter the cycle, there are...
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six molecules of G3P formed.
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True or false: one G3P molecule exits the cycle to be used by the plant cell, while the other five molecules are recycled to regenerate the three molecules of RuBP.
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True
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In a complex series of reactions, the carbon skeletons of five molecules of G3P are ...
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rearranged by the last steps of the Calvin cycle to regenerate three molecules of RuBP.
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To accomplish this, the cycle spends three more molecules of ATP.
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The g3p from the Calvin cycle is ....
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the starting material for metabolic pathways that synthesize other organic compounds, including glucose and other carbohydrates.
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True or false: • Neither the light reactions nor the Calvin cycle alone can make sugar from CO2. Photosynthesis is an emergent property of the intact chloroplast that integrates the two stages of photosynthesis.
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True
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One of the major problems facing terrestrial plants is....
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Dehydration
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True or false : Metabolic adaptations to reduce dehydration often require trade-offs with other metabolic processes, especially photosynthesis.
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True
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The stomata are both the major route for gas exchange (CO2 in and O2 out) and ...
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the main site of the evaporative loss of water.
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On hot , dry days, plants ...
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Close their stromata to conserve water
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With stomata closed, CO2 concentrations in the air space within the leaf decrease and ....
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the concentration of O2 released from the light reactions increases.
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With conditions within the leaves as plant such as the closing of the stromata on hot days,favor an apparently wasteful process called
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Photorespiration
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True or false :Photorespiration may be an evolutionary relic.
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True
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In most plants (C3 plants), initial fixation of CO2 occurs via rubisco, forming ...
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a three-carbon compound, 3-phosphoglycerate.
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C3 plants include rice, wheat, and soybeans
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When the stomata of C3 plants partially close on a hot, dry day...
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CO2 levels drop as CO2 is consumed in the Calvin cycle.
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Although rubisco normally accepts CO2, as CO2 becomes scarce, rubisco can ...
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add O2 to RuBP.
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When rubisco adds O2 to RuBP, RuBP splits into a three-carbon compound and a two-carbon compound in a process called ....
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Photo respiration
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True or false : • Unlike normal respiration, this process produces no ATP. In fact, photorespiration consumes ATP.
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True
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How does photorespiration not produce sugar?
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photorespiration decreases photosynthetic output by siphoning organic material from the Calvin cycle and releasing CO2 that would otherwise be fixed.
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True or false: Plants that are genetically defective in their ability to carry out photorespiration are more susceptible to damage induced by excess light.
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True
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Photorespiration acts to ...
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neutralize otherwise damaging products of the light reactions, which build up when a low CO2 concentration limits the progress of the Calvin cycle.
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True or false: Certain plant species have evolved alternative modes of carbon fixation to minimize photorespiration.
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True
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_____ _____ minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds in mesophyll cells
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C4 plants
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______ _______ has a higher affinity for CO2 than rubisco does; it can fix CO2 even when CO2 concentrations are low
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Pep carboxylase
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The four carbon compounds are exported to _____-_____ ____, where they release CO2 that is then used in the Calvin Cycle
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Bundle-sheath cells
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Some plants, including succulents, use ____ ____ ____, to fix carbon
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Crassulacean acid metabolism (cam)
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_______ _____ open their stromata at night, incorporating CO2 into organic acids
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Cam plants
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True or false: in cam plants, the stromata closes at day time and co2 is released from organic acids and used in the Calvin cycle
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True
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