Chapter 7 Flashcards
(16 cards)
Which of the following is true?
a. Photosynthesis evolved in an atmosphere with little or no oxygen.
b. Photosynthesis occurs only in plants.
c. Oxygen is necessary for photosynthesis.
d. Carbon dioxide is necessary for photorespiration.
a
The Calvin cycle
a. can only occur when light is present.
b. is the part of photosynthesis where carbon is captured.
c. produces ATP and NADPH.
d. occurs in the thylakoids.
b
Which of the following is true?
a. Chloroplasts are found primarily in leaf mesophyll cells.
b. The region between the outer and inner membranes of chloroplasts is called the thylakoid space.
c. Mesophyll cells in the leaf’s center are packed tightly together.
d. Vascular bundles of the leaf circulate CO2 and O2.
a
Carotenoids
a. include chlorophylls a and b.
b. serve as accessory pigments.
c. are produced in the fall in temperate climates.
d. absorb mostly yellow and orange light.
b
Which of the following is false?
a. Photosystem II splits water.
b. Photosystem II captures energy directly from light.
c. Reaction centers contain chlorophyll a molecules.
d. Photosystem I generates O2.
d
Plant leaves contain pores called _________ that allow the plant to release _________ and take in _________. Photosynthesis occurs in organelles called ________ that are concentrated within the __________ cells of most plant leaves.
stomata, oxygen , carbon dioxide ; chloroplasts and mesophyll
Chlorophyll a captures wavelengths of light that correspond to the three colors _______, _______ , and _______. What color does chlorophyll reflect? ________ Accessory pigments that reflect yellow and orange are called _______. These pigments are located in clusters called _______ in the _______ membrane of the chloroplast.
red, blue, violet; green; carotenoids; photosystems and thylakoid
During the first stage of photosynthesis, light is captured and funneled into chlorophyll a molecules in the _________. The energized electron is then passed into a(n) _________. From here, it is transferred through a series of molecules called the _________. Energy lost during these transfers is used to create a gradient of ________. The process that uses this gradient to generate ATP is called _________.
reaction center; primary electron acceptor molecule; electron transport chain; hydrogen ions and chemiosmosis
The oxygen produced as a by-product of photosynthesis is derived from ________, and the carbons used to make glucose are derived from _________. The biochemical pathway that captures atmospheric carbon is called the _________. The process of capturing carbon is called _________.
water , carbon dioxide ; Calvin cycle and carbon fixation
Light reactions generate the energy-carrier molecules __________ and _________ , which are then used in the __________ cycle. Carbon fixation combines carbon dioxide with the five-carbon molecule __________. Two molecules of __________ can be combined to produce the six-carbon sugar _________.
ATP, NADPH, Calvin; RuBP (or ribulose bisphosphate); G3P (glyceraldehyde-3-phosphate) and glucose
Explain what would happen to life if photosynthesis ceased. Why would this occur?
Most forms of life would die soon after phosynthesis ceased. This is because maintaining life requires a constant expenditure of energy, and nearly all forms of life rely on solar energy trapped by photosynthesis.
Write and then explain the equation for photosynthesis.
The photosynthetic equation is 6CO2 +6H2O+Light –> C6H12O6+6O2. Light energy drives the use of carbon dioxide and water to produce sugar and oxygen.
Draw a simplified diagram of a leaf cross-section and label it. Explain how a leaf’s structure supports photosynthesis.
Refer to Figure 7-3 for a diagram of a typical leaf. The flattened shape allows maximum absorbance of light. Upper and lower leaf surfaces are protected by a layer of transparent cells of the epidermis, covered by the transparent, waxy, waterproof cuticle. A leaf obtains the CO2 necessary for photosynthesis from the air, through adjustable pores in the epidermis called stomata. Inside the leaf, mesophyll cells contain most of the leaf’s chloroplasts where photosynthesis occurs. Vascular bundles form veins that supply water and minerals to the cells and carry the sugars produced during photosynthesis to other parts of the plant.
Draw a simplified diagram of a chloroplast and label it. Explain how the individual parts of the chloroplast support photosynthesis.
Refer to Figures 7-3e and 7-8 for diagrams of a chloroplast. The thylakoid membranes create enclosed thylakoid spaces where H+ is concentrated. The membranes contain precise arrays of photosystems, energy-transfer molecules (electron transport chains), and H+ channels coupled to ATP-synthesizing enzymes. The membrane component molecules and the thylakoid spaces allow light capture and ATP synthesis by chemiosmosis. The stroma region inside the chloroplast but outside the thylakoids contains the enzymes that allow the reactions of the Calvin cycle to occur, producing the energy-storing sugar end products of photosynthesis.
Trace the flow of energy in chloroplasts from sunlight to ATP, including an explanation of chemiosmosis.
Light strikes the light-harvesting complex of photosystem II, and the energy is absorbed by chlorophyll or carotenoids. The energy is funneled to the reaction center chlorophylls, where it is used to energize electrons that are captured by the primary electron acceptor molecule. The electrons then travel through an electron transport chain (ETC) within the thylakoid membranes. Here, the energy is released in small stages. Some of this energy is used to produce ATP indirectly by chemiosmosis. During chemiosmosis, energy (released from the light-energized electron as it moves through the ETC) is used to pump H+ into the thylakoid space, creating an H+ gradient. These ions flow out of the space into the stroma through a protein channel linked to an ATP-synthesizing enzyme (ATP synthase), which harnesses the energy of the hydrogen ion flow to generate ATP.
Summarize the events of the Calvin cycle. Where does it occur? What molecule is fixed? What is the product of the cycle? Where does the energy come from to drive the cycle? What molecule is regenerated?
The reactions of the Calvin cycle occur in the stroma of the chloroplast, where overall, atmospheric CO2 is fixed to produce the simple sugar G3P. This is accomplished using chemical energy in ATP and NADPH harnessed during the light reactions. The molecule RuBP is regenerated.
