Photosynthesis Ch. 8 Biology Ms. Haut

Copyright Pearson Prentice Hall 8-1 Energy and Life Photo Credit: ©Stone Copyright Pearson Prentice Hall

Basics of Photosynthesis All cells need energy to carry out their activities All energy ultimately comes from the sun Photosynthesis—process in which some of the solar energy is captured by plants (producers) and transformed into glucose molecules used by other organisms (consumers). 6CO2 + 6H2O C6H12O6 + 6O2 Light energy enzymes

Basics of Photosynthesis Glucose is the main source of energy for all life. The energy is stored in the chemical bonds. Cellular Respiration—process in which a cell breaks down the glucose so that energy can be released. This energy will enable a cell to carry out its activities. C6H12O6 + 6O2 6CO2 + 6H2O + energy enzymes

Autotrophs and Heterotrophs Autotroph—organisms that synthesize organic molecules from inorganic materials (a.k.a. producers) Photoautotrophs—use light as an energy source (plants, algae, some prokaryotes) Heterotroph—organisms that acquire organic molecules from compounds produced by other organisms (a.k.a. consumers) http://www.flatrock.org.nz/topics/animals/assets/conscious_animal.jpg

Chemical Energy and ATP Energy comes in many forms including light, heat, and electricity. Energy can be stored in chemical compounds, too. http://www.green-the-world.net/images/forms_of_energy.jpg Copyright Pearson Prentice Hall

Chemical Energy and ATP An important chemical compound that cells use to store and release energy is adenosine triphosphate, abbreviated ATP. ATP is used by all types of cells as their basic energy source. Copyright Pearson Prentice Hall http://www.accessexcellence.org/RC/VL/GG/ecb/ecb_images/03_32_ATP_and_ADP_cycle.jpg

Chemical Energy and ATP ATP consists of: adenine ribose (a 5-carbon sugar) 3 phosphate groups ATP is used by all types of cells as their basic energy source. http://dm.ncl.ac.uk/helencollard/blogger/wp-content/uploads/2009/04/atp.gif Copyright Pearson Prentice Hall

Chemical Energy and ATP The three phosphate groups are the key to ATP's ability to store and release energy. http://www.google.com/imgres?imgurl=http://student.ccbcmd.edu/biotutorials/energy/images/ Copyright Pearson Prentice Hall

Chemical Energy and ATP Storing Energy ADP has two phosphate groups instead of three. A cell can store small amounts of energy by adding a phosphate group to ADP. http://zymes.com/wordpress/wp-content/uploads/2007/04/atp_sr.jpg Copyright Pearson Prentice Hall

Chemical Energy and ATP Releasing Energy Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates. http://zymes.com/wordpress/wp-content/uploads/2007/04/atp_sr.jpg Copyright Pearson Prentice Hall

Chemical Energy and ATP The energy from ATP is needed for many cellular activities, including active transport across cell membranes, protein synthesis and muscle contraction. ATP’s characteristics make it exceptionally useful as the basic energy source of all cells. Copyright Pearson Prentice Hall

Using Biochemical Energy Most cells have only a small amount of ATP, because it is not a good way to store large amounts of energy. Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-1 Organisms that make their own food are called autotrophs. heterotrophs. decomposers. consumers. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-1 Most autotrophs obtain their energy from chemicals in the environment. sunlight. carbon dioxide in the air. other producers. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-1 How is energy released from ATP? A phosphate is added. An adenine is added. A phosphate is removed. A ribose is removed. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-1 How is it possible for most cells to function with only a small amount of ATP? Cells do not require ATP for energy. ATP can be quickly regenerated from ADP and P. Cells use very small amounts of energy. ATP stores large amounts of energy. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-1 Compared to the energy stored in a molecule of glucose, ATP stores much more energy. much less energy. about the same amount of energy. more energy sometimes and less at others. Copyright Pearson Prentice Hall

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8-2 Photosynthesis: An Overview Photo Credit: ©Stone Copyright Pearson Prentice Hall

Photosynthesis: An Overview The key cellular process identified with energy production is photosynthesis. Photosynthesis is the process in which green plants use the energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates and oxygen. Copyright Pearson Prentice Hall

The Photosynthesis Equation 6CO2 + 6H2O C6H12O6 + 6O2 Light energy enzymes Copyright Pearson Prentice Hall http://www.biologycorner.com/resources/photosynthesis.jpg

The Photosynthesis Equation Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen. Copyright Pearson Prentice Hall

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

Copyright Pearson Prentice Hall Light and Pigments In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll. Copyright Pearson Prentice Hall http://www.biologycorner.com/resources/photosynthesis.jpg

Copyright Pearson Prentice Hall Light and Pigments Plants gather the sun's energy with light-absorbing molecules called pigments. The main pigment in plants is chlorophyll. There are two main types of chlorophyll: chlorophyll a chlorophyll b Copyright Pearson Prentice Hall

Light and Pigments Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum. Chlorophyll does not absorb light well in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green. Photosynthesis requires light and chlorophyll. In the graph above, notice how chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum.

Copyright Pearson Prentice Hall Light and Pigments Light is a form of energy, so any compound that absorbs light also absorbs energy from that light. When chlorophyll absorbs light, much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons. These high-energy electrons are what make photosynthesis work. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-2 Plants use the sugars produced in photosynthesis to make oxygen. starches. carbon dioxide. protein. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-2 The raw materials required for plants to carry out photosynthesis are carbon dioxide and oxygen. oxygen and sugars. carbon dioxide and water. oxygen and water. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-2 The principal pigment in plants is chloroplast. chlorophyll. carotene. carbohydrate. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-2 The colors of light that are absorbed by chlorophylls are green and yellow. green, blue, and violet. blue, violet, and red. red and yellow. Copyright Pearson Prentice Hall

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8-3 The Reactions of Photosynthesis Photo Credit: ©Stone Copyright Pearson Prentice Hall

Photosynthesis: redox process Oxidation-reduction reaction: Oxidation-loss of electrons from one substance Reduction-addition of electrons to another substance

Copyright Pearson Prentice Hall Inside a Chloroplast In plants, photosynthesis takes place inside chloroplasts. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Inside a Chloroplast Chloroplasts contain thylakoids—saclike photosynthetic membranes. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Inside a Chloroplast Thylakoids are arranged in stacks known as grana. A singular stack is called a granum. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Inside a Chloroplast Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Inside a Chloroplast The light-dependent reactions take place within the thylakoid membranes. The Calvin cycle takes place in the stroma, which is the region outside the thylakoid membranes. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Electron Carriers Electron Carriers When electrons in chlorophyll absorb sunlight, the electrons gain a great deal of energy. Cells use electron carriers to transport these high-energy electrons from chlorophyll to other molecules. One carrier molecule is NADP+. Electron carriers, such as NADP+, transport electrons. NADP+ accepts and holds 2 high-energy electrons along with a hydrogen ion (H+). This converts the NADP+ into NADPH. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Electron Carriers The conversion of NADP+ into NADPH is one way some of the energy of sunlight can be trapped in chemical form. The NADPH carries high-energy electrons to chemical reactions elsewhere in the cell. These high-energy electrons are used to help build a variety of molecules the cell needs, including carbohydrates like glucose. Copyright Pearson Prentice Hall

Light-Dependent Reactions The light-dependent reactions require light. The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH. Copyright Pearson Prentice Hall

When photosystem II absorbs light an e- is excited in the reaction center chlorophyll (P680) and gets captured by the primary e- acceptor. This leaves a hole in the P680

To fill the hole left in P680, an enzyme extracts e- from water and supplies them to the reaction center A water molecule is split into 2 H+ ions and an oxygen atom, which immediately combines with another oxygen to form O2

Each photoexcited e- passes from primary e- acceptor to photosystem I via an electron transport chain. e- are transferred to e- carriers in the chain

As e- cascade down the e- transport chain, energy is released and harnessed by the thylakoid membrane to produce ATP This ATP is used to make glucose during Calvin cycle

When e- reach the bottom of e- transport chain, it fills the hole in the reaction center P700 of photosystem I. Pre-existing hole was left by former e- that was excited

When photosystem I absorbs light an e- is excited in the reaction center chlorophyll (P700) and gets captured by the primary e- acceptor. e- are transferred by e- carrier to NADP+ (reduction reaction) forming NADPH NADPH provides reducing power for making glucose in Calvin cycle

Chemiosmosis Energy released from ETC is used to pump H+ ions (from the split water) from the stroma across the thylakoid membrane to the interior of the thylakoid. Creates concentration gradient across thylakoid membrane Process provides energy for chemisomostic production of ATP

Light-Dependent Reactions The light-dependent reactions use water, ADP, and NADP+. The light-dependent reactions produce oxygen, ATP, and NADPH. These compounds provide the energy to build energy-containing sugars from low-energy compounds. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle The Calvin Cycle ATP and NADPH formed by the light-dependent reactions contain an abundance of chemical energy, but they are not stable enough to store that energy for more than a few minutes. During the Calvin cycle plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars. Because the Calvin cycle does not require light, these reactions are also called the light-independent reactions. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle Six carbon dioxide molecules enter the cycle from the atmosphere and combine with six 5-carbon molecules. The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle The result is twelve 3-carbon molecules, which are then converted into higher-energy forms. The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle The energy for this conversion comes from ATP and high-energy electrons from NADPH. The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle Two of twelve 3-carbon molecules are removed from the cycle. The Calvin cycle uses ATP and NADPH to produce high-energy sugars. Copyright Pearson Prentice Hall

The Calvin Cycle The molecules are used to produce sugars, lipids, amino acids and other compounds. The Calvin cycle uses ATP and NADPH to produce high-energy sugars.

The Calvin Cycle The 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to begin the next cycle. The Calvin cycle uses ATP and NADPH to produce high-energy sugars.

Copyright Pearson Prentice Hall The Calvin Cycle The two sets of photosynthetic reactions work together. The light-dependent reactions trap sunlight energy in chemical form. The light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and water. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Calvin Cycle Factors Affecting Photosynthesis Many factors affect the rate of photosynthesis, including: Water Temperature Intensity of light Copyright Pearson Prentice Hall

How Photosynthesis Moderates Global Warming Photosynthesis has an enormous impact on the atmosphere. It swaps O2 for CO2. http://www.destination360.com/asia/malaysia/images/s/borneo-rainforest.jpg

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 CO2.

Global Warming Greenhouse gases (CO2, CH4, CFC’s) 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. Combustion of fossil fuels

Global Warming Consequences Polar ice caps melting Rise in sea level and flooding of current coastline New York, Miami, Los Angeles underwater Change in types of plants—more adapted to warmer temps. and less water http://i.treehugger.com/images/2007/10/24/melting%20ice-jj-002.jpg

Copyright Pearson Prentice Hall 8-3 In plants, photosynthesis takes place inside the thylakoids. chloroplasts. photosystems. chlorophyll. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 Energy to make ATP in the chloroplast comes most directly from hydrogen ions flowing through an enzyme in the thylakoid membrane. transfer of a phosphate from ADP. electrons moving through the electron transport chain. electrons transferred directly from NADPH. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 NADPH is produced in light-dependent reactions and carries energy in the form of ATP. high-energy electrons. low-energy electrons. ADP. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 What is another name for the Calvin cycle? light-dependent reactions light-independent reactions electron transport chain photosynthesis Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 8-3 Which of the following factors does NOT directly affect photosynthesis? wind water supply temperature light intensity Copyright Pearson Prentice Hall

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