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16 Cards in this Set
- Front
- Back
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Chlorophyll resides within the ______, which are stacked into columns called _______.
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thylakoid membranes; grana
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Chlorophyll is complexed with the metal __________
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magnesium
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the principle types of chlorophyll are:
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chlorophyll a and b; these are part of two photosystems
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a photosystem is:
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a light-capturing unit of the thylakoid membrane
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In photosystem I, the chlorophyll __ molecule is called ______
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chlorophyll a; P700
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In photosystem II, the chlorophyll mlc is called _____
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P680
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what are the two distinct reactions of photosynthesis and when do they take place?
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light reactions (light-dependent rxns) must take place in the light; dark reactions do not directly require light, but they will only occur during the day when the light rxns are replenishing the supply of ATP and NADPH
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The Light Reactions: high energy electrons can flow along two pathways:
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cycle electron flow or noncyclic electron flow (the key pathway of the light rxns & involves both photosystems)
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Describes what happens during cyclic electron flow of the light reactions.
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Light strikes chlorophyll a P700 in photosystem I and excites electrons to a higher energy state. These excited electrons move along a chain of e- carriers that ultimately return the electrons to P700. ATP produced by cyclic photophosphorylation
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Describe what happens during noncyclic electron flow of the light reactions.
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key pathway; involves both photsystems; excited electrons from P700 of photosystem I are transferred to NADP+ (instead of the carrier chain), which forms NADPH. P700 is left with "holes" and thus is a powerful oxidizing agent. When light strikes P680 of photosystem II, e- are excited then flow down the same electron carrier chain used in cyclic flow until they reach P700 and fill the "holes," producing ATP by noncyclic photophosphorylation. Now P680 has "holes" and oxidizes water to fill them. the H+ produced oxidizes P680 and the oxygen atoms combine to form O2. *The net result of noncyclic electron flow is the production of NADPH and ATP and the photolysis (breakdown) of water
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Describe the dark reactions (a.k.a. carbon-fixation or reduction synthesis reactions)
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Uses ATP and NADPH from light rxns to reduce CO2 to carbohydrates, primarily glucose. CO2 is the C source for carbohydrate production in the Calvin Cycle (similar to Krebs cycle but in reverse). The product of this cycle is PGAL (after 3X). Two mlcs of PGAL can be converted to glucose
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In six turns of the Calvin cycle:
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12 PGAL are formed from 6 CO2 and 6 RBP. the 12 PGAL recombine to form 6 RBP and 1 mlc of glucose, the net product
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During the day, stomata _____
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open due to the presence of high glucose content in the guard cells (swelling; turgor)
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During the night, stomata _______
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close to prevent water loss; photosynthesis will cease because of lack of CO2
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Veins containing _____ bring water to the leaf from the roots.
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xylem
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Veins containing _______ carry manufactured food out of the leaf
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phloem ("ph"="f"ood)
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