Review Cellular Respiration A57Brc&feature=relatedhttp:// A57Brc&feature=related - Cellular respiration and emphasis on the electron transport chain

Photosynthesis Why do we need to know this?

Photosynthesis Why do we need to know this? Renewable energy sources Global Warming Where our food comes from….. YOU need to make lifestyle CHOICES and VOTE in a democracy that is facing these DIFFICULT ISSUES

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.

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

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

The Overall Equation for Photosynthesis –The reactants and products of the reaction

–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.

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

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.

Figure 7.5

The Process of Science: What Colors of Light Drive Photosynthesis? –In 1883, German biologist Theodor Engelmann Performed an experiment using bacteria and algae and determined that certain types of light drive photosynthesis. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

Figure 7.6

–Chloroplasts absorb select wavelengths of light that drive photosynthesis. Light and Pigments

Figure 7.7

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

How Photosystems Harvest Light Energy –Light behaves as photons, discrete packets of energy. –Chlorophyll molecules absorb photons. Electrons in the pigment gain energy. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates ( and WH Freeman (

Figure 7.9 Check out:

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

How the Light Reactions Generate ATP and NADPH

–Two types of photosystems cooperate in the light reactions.

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

–The light reactions in the thylakoid membrane Light Reactions

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

Figure 7.14

Water-Saving Adaptations of C 4 and CAM Plants –C 3 plants Use CO 2 directly from the air. –Thus, C 3 plants depend on the constant opening of their stomata to produce sugar. Are very common and widely distributed. Examples: rice, wheat, soybeans

–C 4 plants (corn, sugarcane) Close their stomata to save water during hot and dry weather. Can still carry out photosynthesis. –CAM plants (pineapple, cactus) Open their stomata only at night to conserve water.

A review of photosynthesis

The Environmental Impact of Photosynthesis –Photosynthesis has an enormous impact on the atmosphere. It swaps O 2 for CO 2. It moderates global warming

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

–A similar process, the greenhouse effect, Warms the atmosphere. Is caused by atmospheric CO 2.

–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.