Biology Study Set 13

Biology

Quiz 7 :

Where It Startsphotosynthesis

Quiz 7 :

Where It Startsphotosynthesis

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Photosynthetic autotrophs use __________ from the air as a carbon source and __________ as their energy source.
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Autotrophs have the capacity to fix solar energy and are the first trophic level in an ecosystem. Autotrophs can utilize solar energy and synthesize energy-rich organic compounds that are utilized by the autotrophs and all the other trophic levels.
Photosynthetic autotrophs use carbon dioxide from the air as a carbon source and light as their energy source.

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In the light- dependent reactions, ________.
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The light-dependent reactions of photosynthesis occur in the thylakoid membranes of the chloroplasts. These reactions result in the formation of ATP and NADPH. Hence, the option (b) ATP and NADPH form is the correct answer.
img Thus, the correct answer is
The carbon dioxide is fixed during the light-independent and hence, the option (a) carbon dioxide is fixed is not the correct answer.
The light-dependent reactions of photosynthesis result in the formation of ATP and NADPH and there is no electron transfer to CO ₂. Hence, the option (c) CO ₂ accepts electrons is not the correct answer.
The sugars are formed during the light-independent step of photosynthesis. Hence, the option (d) sugars form is not the correct answer.

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Match each event with its most suitable description. img
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The given events are matched with its most apt description as follows:
a. Rubisco required : CO ₂ fixation
b. ATP, NADPH required : PGAL formation
c. Electrons cycled back to photosystem II : ATP formation only

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While gazing into an aquarium, you observe bubbling from an aquatic plant. What is happening
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When a photosystem absorbs light, _____________.
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What accumulates inside the thylakoid compartment during the light- dependent reactions
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Light- dependent reactions in plants occur at the ____________.
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Light-independent reactions proceed in the _________.
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Krishna exposes pea plants to a carbon radioisotope ( 14 CO ₂ ), which they absorb. In which compound will the labeled carbon appear first if the plants are C₃ C4
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A cat eats a bird, which earlier ate a caterpillar that chewed on a weed. Which organisms are autotrophs Which are the heterotrophs
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What substance is not part of the Calvin-Benson cycle
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Chlorophyll a absorbs violet and red light, and it reflects light of __________ and ___________ wavelengths. a. violet; red b. yellow; green c. green only d. white; orange
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The Calvin-Benson cycle starts when __________.
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About 200 years ago, Jan Baptista van Helmont did experiments on the nature of photosynthesis. He wanted to know where growing plants get the materials necessary for increases in size. He planted a tree seedling weighing 5 pounds in a barrel filled with 200 pounds of soil. He watered the tree regularly. Five years passed. Then van Helmont weighed the tree and the soil. The tree weighed 169 pounds, 3 ounces. The soil weighed 199 pounds, 14 ounces. Because the tree gained so much weight and the soil lost so little, he concluded the tree had gained all of its additional weight by absorbing water he had added to the barrel. Given what you know about biological molecules, why was he misguided Knowing what you do about photosynthesis, what really happened
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Most pigments respond to only part of the rainbow of visible light. If acquiring energy is so vital, then why doesnt each kind of photosynthetic pigment absorb the whole spectrum Why isnt each one black If early photoautotrophs evolved in the seas, then so did their pigments. Ultraviolet and red wavelengths do not penetrate water as deeply as green and blue wavelengths do. Possibly natural selection favored the evolution of different pigments at different depths. Many relatives of the red alga in Figure 7.16 a live deep in the sea. Some are nearly black. Green algae, such as the one in Figure 7.16 b , live in shallow water. Their chlorophylls absorb red wavelengths, and accessory pigments harvest others. Some accessory pigments also function as shields against ultraviolet radiation. Speculate on how natural selection may have favored the evolution of different pigments at different depths, starting at hydrothermal vents. You might start at Richard Monasterkys article in Science News (September 7, 1996) on Cindy Lee Dovers work at hydrothermal vents.
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Imagine walking through a garden of red, white, and blue petunias. Explain each of the colors in terms of which wavelengths of light the flower is absorbing.
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Only about eight classes of pigment molecules are known, but this limited group gets around in the world. For example, photoautotrophs make carotenoids, which move through food webs, as when tiny aquatic snails graze on green algae and then flamingos eat the snails. Flamingos modify the ingested carotenoids. Their cells split beta-carotene to form two molecules of vitamin A. This vitamin is the precursor of retinol, a visual pigment that transduces light into electric signals in eyes. Beta-carotene gets dissolved in fat reservoirs under the skin. Cells that give rise to bright pink feathers take it up. Select a similar organism and do some research to identify sources for pigments that color its surfaces.
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