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Ch. 10 - Photosynthesis
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoFreeman 8th EditionCh. 10 - PhotosynthesisProblema 4
Capitolo 10, Problema 4

At what point in photosynthesis is the electromagnetic energy of light first converted into chemical energy?

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The electromagnetic energy of light is first converted into chemical energy during the 'Light-Dependent Reactions' stage of photosynthesis. This is the first stage of photosynthesis and occurs in the thylakoid membranes of the chloroplasts.
During this stage, chlorophyll and other pigments absorb light energy and convert it into chemical energy in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).
The process begins when photons from light hit the chlorophyll molecules, exciting their electrons and causing them to move to a higher energy state.
These high-energy electrons are then transferred through a series of proteins (known as the electron transport chain), which use the energy to pump protons across the thylakoid membrane, creating a proton gradient.
This proton gradient is then used to produce ATP through a process called chemiosmosis, while NADPH is produced by the reduction of NADP+ using the high-energy electrons. Both ATP and NADPH are then used in the second stage of photosynthesis, the 'Light-Independent Reactions' or 'Calvin Cycle', to produce glucose.

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Photosynthesis

Photosynthesis is the biological process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. This process primarily occurs in the chloroplasts of plant cells and involves two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle).
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Pigments of Photosynthesis

Light-dependent Reactions

The light-dependent reactions are the first stage of photosynthesis, occurring in the thylakoid membranes of chloroplasts. During this phase, chlorophyll absorbs sunlight, which excites electrons and initiates a series of reactions that convert light energy into chemical energy in the form of ATP and NADPH, while also producing oxygen as a byproduct.
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Light Reactions of Photosynthesis

Chemical Energy

Chemical energy refers to the energy stored in the bonds of chemical compounds, like glucose. In photosynthesis, the conversion of electromagnetic energy from sunlight into chemical energy occurs during the light-dependent reactions, where ATP and NADPH are generated, providing the energy needed for the subsequent light-independent reactions to synthesize glucose.
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Chemical Reactions
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Domanda del libro di testo

Why is chlorophyll green?

a. It absorbs all wavelengths in the visible spectrum.

b. It absorbs wavelengths only in the red portions of the spectrum (680–700 nm).

c. It absorbs wavelengths only in the blue part of the visible spectrum (450–480 nm).

d. It absorbs wavelengths in only the blue and red parts of the visible spectrum.

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Apply what you know of the relationship between the light-capturing reactions and the Calvin cycle to calculate the number of photons used to produce a new G3P and regenerate RuBP. (Assume 1 ATP is produced for each pair of electrons used to form NADPH.)

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What is the role of PEP carboxylase in C4 and CAM plants?

a. It fixes CO2 into an organic acid.

b. It produces ATP for the Calvin cycle.

c. It replaces rubicso in the Calvin cycle.

d. It releases CO2 from organic acids.

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How is energy transferred among antenna pigment molecules?

a. By heat

b. By redox reactions

c. By fluorescence

d. By resonance

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Why is the chlorophyll in chloroplasts less likely to produce fluorescence compared to extracted chlorophyll molecules?

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Describe the three phases of the Calvin cycle and how the products of the light-capturing reactions participate in this process.

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