Photosynthesis: Using Light to Make Food CHAPTER 7 Photosynthesis: Using Light to Make Food

Biology and Society: Plant Power for Power Plants On a global scale the productivity of photosynthesis is astounding. All of the food consumed by humans can be traced back to photosynthetic plants. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

An “energy plantation” Is a renewable energy source.

Figure 7.1

The Basics of Photosynthesis Almost all plants are photosynthetic autotrophs, as are some bacteria and protists. They generate their own organic matter through photosynthesis. Cyanobacteria (Oscillatoria)

Figure 7.2

Chloroplasts: Sites of Photosynthesis Occurs in chloroplasts.

Chloroplasts Are found in the interior cells of leaves. Contain stroma, a thick fluid. Contain thylakoids, membranous sacs.

Figure 7.3

Unnumbered Figure 7.1

Sunlight is a type of energy called radiation The Nature of Sunlight Sunlight is a type of energy called radiation Or electromagnetic energy. The full range of radiation is called the electro-magnetic spectrum.

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Figure 7.6

In photosynthesis, Energized electrons are added to carbon dioxide to make sugar. Sunlight provides the energy.

A Photosynthesis Road Map Photosynthesis is composed of two processes: The light reactions convert solar energy to chemical energy. The Calvin cycle makes sugar from carbon dioxide.

Figure 7.4

The Light Reactions: Converting Solar Energy to Chemical Energy Chloroplasts are chemical factories powered by the sun That convert solar energy into chemical energy. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

Chloroplasts contain several pigments: Chloroplast Pigments Chloroplasts contain several pigments: Chlorophyll a Chlorophyll b Carotenoids

Figure 7.8

How Photosystems Harvest Light Energy Light behaves as photons, discrete packets of energy.

Chlorophyll molecules absorb photons. Electrons in the pigment gain energy. The energy is released and used.

Figure 7.9

A photosystem Is an organized group of chlorophyll and other molecules. Is a light-gathering antenna.

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Figure 7.11

Two types of photosystems cooperate in the light reactions.

Figure 7.12

An electron transport chain Connects the two photosystems. Releases energy that the chloroplast uses to make ATP.

Figure 7.13

The Calvin Cycle: Making Sugar from Carbon Dioxide Functions like a sugar factory within a chloroplast. Regenerates the starting material with each turn. Calvin Cycle Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

Figure 7.14

Water-Saving Adaptations of C4 and CAM Plants C3 plants Use CO2 directly from the air. Are very common and widely distributed.

C4 plants Close their stomata to save water during hot and dry weather. Can still carry out photosynthesis. CAM plants Open their stomata only at night to conserve water.

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Photosynthesis has an enormous impact on the atmosphere. It swaps O2 for CO2.

How Photosynthesis Moderates Global Warming Greenhouses used to grow plant indoors Trap sunlight that warms the air inside.

Figure 7.17

A similar process, the greenhouse effect, Warms the atmosphere. Is caused by atmospheric CO2.

Figure 7.18

Greenhouse gases are the most likely cause of global warming, a slow but steady rise in the Earth’s surface temperature. Destruction of forests may be increasing this effect.

Evolution Connection: The Oxygen Revolution The atmospheric oxygen we breathe is a by-product of photosynthesis. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

Cyanobacteria were the first organisms to carry out photosynthesis. The production of oxygen changed the Earth forever. The “oxygen revolution” was a major episode in the history of life on Earth.

Figure 7.19