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51 Cards in this Set

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autotroph
organism that can capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer (pp. 67, 201)
heterotroph
organism that obtains energy from the foods it consumes; also called a consumer (pp. 68, 201)
adenosine triphosphate (ATP)
one of the principal chemical compounds that living things use to store energy (p. 202)
Van Helmont's Experiment
In the 1600s, the Belgian physician Jan van Helmont devised an experiment to find out if plants grew by taking material out of the soil. Van Helmont determined the mass of a pot of dry soil and a small seedling. Then, he planted the seedling in the pot of soil. He watered it regularly. At the end of five years, the seedling, which by then was a small tree, had gained about 75 kg. The mass of the soil, however, was almost unchanged. Van Helmont concluded that most of the mass the plant gained had come from water, because that was the only thing that he had added to the pot.

Van Helmont's experiment accounts for the "hydrate," or water, portion of the carbohydrate produced by photosynthesis. But where does the carbon of the "carbo-" portion come from? Although van Helmont did not realize it, carbon dioxide in the air made a major contribution to the mass of his tree. The carbon in carbon dioxide is used to make sugars and other carbohydrates in photosynthesis. Van Helmont had only part of the story, but he had made a major contribution to science.
Priestley's Experiment
More than 100 years after van Helmont's experiment, the English minister Joseph Priestley performed an experiment that would give another insight into the process of photosynthesis. Priestley took a candle, placed a glass jar over it, and watched as the flame gradually died out. Something in the air, Priestley reasoned, was necessary to keep a candle flame burning. When that substance was used up, the candle went out. That substance was oxygen.
Priestley's Experiment (II)
Priestley then found that if he placed a live sprig of mint under the jar and allowed a few days to pass, the candle could be relighted and would remain lighted for a while. The mint plant had produced the substance required for burning. In other words, it released oxygen.
Jan Ingenhousz
Later, the Dutch scientist Jan Ingenhousz showed that the effect observed by Priestley occurred only when the plant was exposed to light. The results of Priestley's and Ingenhousz's experiments showed that light is necessary for plants to produce oxygen. The experiments performed by van Helmont, Priestley, Ingenhousz, and other scientists reveal that in the presence of light, plants transform carbon dioxide and water into carbohydrates and release oxygen.
The Photosynthesis Equation
Because photosynthesis usually produces 6-carbon sugars (C6H12O6) as its final products, the overall equation for photosynthesis can be shown as follows:

carbondioxide(6CO2) + water (6H2O)
----light--->
sugar (C6H12O6) and oxygen (6O2)
Photosynthesis
Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy sugars. Plants then use the sugars to produce complex carbohydrates such as starches. Plants obtain carbon dioxide from the air or water in which they grow.
Photosynthesis (definition)
.....a series of reactions that uses energy from the sun to convert water and carbon dioxide into sugars and oxygen..
Where does photosynthesis take place?
Photosynthesis takes place in a plant organelle called the chloroplast
What else is needed for photosynthesis besides carbondioxide and water?
In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll, a molecule in chloroplasts.
What is sunlight?
Energy from the sun travels to Earth in the form of light. Sunlight, which your eyes perceive as "white" light, is actually a mixture of different wavelengths of light. Many of these wavelengths are visible to your eyes and make up what is known as the visible spectrum. Your eyes see the different wavelengths of the visible spectrum as different colors.
How do plants capture the energy of sunlight?
Plants gather the sun's energy with light-absorbing molecules called pigments. The plants' principal pigment is chlorophyll (KLAWR-uh-fil). There are two main types of chlorophyll: chlorophyll a and chlorophyll b.
What is chlorophyll?
One of the light-absorbing molecules called pigments.
Chlorophyll absorbs light very well in the blue and red regions of the visible spectrum. However, chlorophyll does not absorb light well in the green region of the spectrum, which is why plants are green. Plants also contain red and orange pigments such as carotene that absorb light in other regions of the spectrum.
What happens when Chloroform absorbs light?
Because light is a form of energy, any compound that absorbs light also absorbs the 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 make photosynthesis work.
What are the products of photosynthesis?
The products of photosynthesis are
sugars and oxygen.
Which organelle contains chlorophyll?
Chloroplast.
What takes place inside Chloroplasts?
In plants and other photosynthetic eukaryotes, photosynthesis takes place inside chloroplasts.
Chloroplasts
The chloroplasts, shown in the activity at right, contain saclike photosynthetic membranes called thylakoids (THY-luh-koydz).
Thylakoid
saclike body in chloroplasts made of photosynthetic membranes that contain photosystems (p. 208)
Thylakoid (II)
Thylakoids are arranged in stacks known as grana (singular: granum). Thylakoids contain clusters of chlorophyll and other pigments and protein known as photosystems that are able to capture the energy of sunlight.
What are the two stages of the photosynthesis reaction?
- the light-dependent reactions and
-the light-independent reactions, or Calvin cycle. The light-dependent reactions take place within the thylakoid membranes. The Calvin cycle takes place in the stroma, the region outside the thylakoid membranes.
The Reactions of Photosynthesis
1.Light-Dependent Reactions
The light-dependent reactions require light. That is why plants need light to grow. The light-dependent reactions use energy from light to produce ATP and NADPH. The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH.
Step 1 :Photosystem II
Photosynthesis begins when pigments in photosystem II absorb light. The first photosystem in the light-dependent reactions is called photosystem II because it was discovered after photosystem I. Energy from the light is absorbed by electrons, increasing their energy level. These high-energy electrons are passed on to the electron transport chain.
Does chlorophyll run out of electrons?
No, the thylakoid membrane contains a system that provides new electrons to chlorophyll to replace the ones it has lost. These new electrons come from water molecules (H2O). Enzymes on the inner surface of the thylakoid membrane break up each water molecule into 2 electrons, 2 H+ ions, and 1 oxygen atom. The 2 electrons replace the high-energy electrons that chlorophyll has lost to the electron transport chain. The oxygen is eventually released into the air as oxygen gas (O2). The 2 H+ ions are released inside the thyla
Step 2
High-energy electrons move through the electron transport chain from photosystem II to photosystem I. Energy from the electrons is used by the molecules in the electron transport chain to transport H+ ions from the stroma into the inner thylakoid.
Step 3
Pigments in photosystem I use energy from light to reenergize the electrons. NADP+ then picks up these high-energy electrons at the outer surface of the thylakoid membrane, plus a H+ ion, and becomes NADPH.
Step 4
As a result of the H+ ions released during water-splitting and electron transport, the inside of the thylakoid membrane becomes positively charged and the outside becomes negatively charged. The difference in charges across the membrane provides the energy to make ATP.
Step 5
H+ ions cannot cross the membrane directly. However, the membrane contains a protein called ATP synthase (SIN-thays) that allows H+ ions to pass through it. As H+ ions pass through this protein, the protein rotates like a turbine being spun by water in a hydroelectric power plant. As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP.
The Reactions of Photosynthesis
(continued)
II. The Calvin Cycle
The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars
Calvin cycle
reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugars (p. 212)
- does not require light, these reactions are also called the light-independent reactions.
Calvin cycle (step 1)
6 carbon dioxide (CO2)molecules enter the cycle from the atmosphere. The CO2 molecules combine with 6 5-carbon molecules. The result is 12 3-carbon molecules.
Calvin cycle (step 2)
The 12 3-carbon molecules are then converted into higher-energy forms. The energy for this conversion comes from ATP and high-energy electrons from NADPH.
Calvin cycle (step 3)
2 of the twelve 3-carbon molecules are converted into two similar 3-carbon molecules. These 3-carbon molecules are used to form various 6-carbon sugars and other compounds.
Calvin cycle (step 4)
The remaining ten 3-carbon molecules are converted back into six 5-carbon molecules. These molecules combine with six new carbon dioxide molecules to begin the next cycle.
Calvin cycle summary
The Calvin cycle uses six molecules of carbon dioxide to produce a single 6-carbon sugar molecule. As photosynthesis proceeds, the Calvin cycle works steadily, turning out energy-rich sugars and removing carbon dioxide from the atmosphere. The plant uses the sugars for energy and to build more complex carbohydrates such as starches and cellulose, which it needs for growth and development. When other organisms eat plants, they can also use the energy stored in carbohydrates.
How do heterotrophs and autotrophs differ?
Autotrophs use light energy from the sun to produce foodThese organisms, known as heterotrophs (HET-uh-roh-trohfs), obtain energy from the foods they consume. Impalas, for example, eat grasses, which are autotrophs. Other heterotrophs, such as leopards, obtain the energy stored in autotrophs indirectly by feeding on animals that eat autotrophs. Still other heterotrophs—mushrooms, for example—obtain food by decomposing other organisms
Describe the three parts of an ATP molecule
ATP and ADP The activities of the cell are powered by chemical fuels. One of the principal chemical compounds that living things use to store energy is adenosine triphosphate (uh-DEN-uh-seen try-FAHS-fayt), abbreviated ATP. As shown in the figure below, an ATP molecule consists of a nitrogen-containing compound called adenine, a 5-carbon sugar called ribose, and three phosphate groups.
Use the analogy of a battery to explain how energy is stored in and released from ATP
ATP can be compared to a fully charged battery because both contain stored energy, whereas ADP resembles a partially charged battery.
Compare the amounts of energy stored by ATP and glucose. Which compound is used by the cell as an immediate source of energy?
ATP and Glucose

Most cells have only a small amount of ATP, enough to last for only a few seconds of activity. Why is this? Even though ATP is very efficient at transferring energy, it is not very good for storing large amounts of energy over the long term. In fact, a single molecule of the sugar glucose stores more than 90 times the chemical energy of a molecule of ATP. Therefore, it is more efficient for cells to keep only a small supply of ATP on hand. Cells can regenerate ATP from ADP as needed by using the energy in carbohydrates like glucose.
How were Priestley's and Ingenhousz's discoveries about photosynthesis related?
The results of Priestley's and Ingenhousz's experiments showed that light is necessary for plants to produce oxygen
Write the basic equation for photosynthesis using the names of the starting and final substances of the process
The Photosynthesis Equation

Because photosynthesis usually produces 6-carbon sugars (C6H12O6) as its final products, the overall equation for photosynthesis can be shown as follows:



Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy sugars. Plants then use the sugars to produce complex carbohydrates such as starches. Plants obtain carbon dioxide from the air or water in which they grow. The overall process of photosynthesis is shown below.
What role do plant pigments play in the process of photosynthesis?
Plants gather the sun's energy with light-absorbing molecules called pigments. The plants' principal pigment is chlorophyll (KLAWR-uh-fil). There are two main types of chlorophyll: chlorophyll a and chlorophyll b.
Identify the structures labeled A, B, C, and D.

In which structure(s) do the light-dependent reactions occur? In which structure(s) does the Calvin cycle take place?
The light-dependent reactions take place within the thylakoid membranes. The Calvin cycle takes place in the stroma, the region outside the thylakoid membranes.
Explain the role of NADP+ as an energy carrier in photosynthesis
NADPH

When sunlight excites electrons in chlorophyll, the electrons gain a great deal of energy. These high-energy electrons require a special carrier. Think of a high-energy electron as being similar to a red-hot coal from a fireplace or campfire. If you wanted to move the coal from one place to another, you wouldn't pick it up in your hands. You would use a pan or bucket—a carrier—to transport it, as shown in the figure below. Cells treat high-energy electrons in the same way. Instead of a pan or a bucket, they use electron carriers to transfer high-energy electrons from chlorophyll to other molecules. A carrier molecule is a compound that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule.


Formation of NADPH When NADP+ accepts a pair of high-energy electrons, it becomes NADPH.



One of these carrier molecules is a compound known as NADP+ (nicotinamide adenine dinucleotide phosphate). The name is complicated, but the job that NADP+ has is simple. NADP+ accepts and holds 2 high-energy electrons along with a hydrogen ion (H+). This converts the NADP+ into NADPH. The conversion of NADP+ into NADPH is one way in which some of the energy of sunlight can be trapped in chemical form.

The NADPH can then carry high-energy electrons produced by light absorption in chlorophyll to chemical reactions elsewhere in the cell. These high-energy electrons are used to help build molecules like glucose.
What is the role of ATP synthase? How does it work?
H+ ions cannot cross the membrane directly. However, the membrane contains a protein called ATP synthase (SIN-thays) that allows H+ ions to pass through it. As H+ ions pass through this protein, the protein rotates like a turbine being spun by water in a hydroelectric power plant. As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP.
large protein that uses energy from H+ hydrogen ions to bind ADP and a phosphate group together to produce ATP (p. 210)
Summarize what happens during the Calvin cycle.
Calvin cycle
reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugars (p. 212)
How do the events in the Calvin cycle depend on the light-dependent reactions?
The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars.
Describe three factors that affect the rate at which photosynthesis occurs.
Many factors affect the rate at which photosynthesis occurs. Because water is one of the raw materials of photosynthesis, a shortage of water can slow or even stop photosynthesis. Plants that live in dry conditions, such as desert plants and conifers, have a waxy coating on their leaves that reduces water loss.

Temperature is also a factor. Photosynthesis depends on enzymes that function best between 0°C and 35°C. Temperatures above or below this range may damage the enzymes, slowing down the rate of photosynthesis. At very low temperatures, photosynthesis may stop entirely. The conifers shown below can carry out photosynthesis only on sunny days. The intensity of light also affects the rate at which photosynthesis occurs. As you might expect, increasing light intensity increases the rate of photosynthesis. After the light intensity reaches a certain level, however, the plant reaches its maximum rate of photosynthesis. The level at which light intensity no longer affects photosynthesis varies from plant type to plant type.
Using Analogies Develop an analogy to explain ATP and energy transfer to a classmate who does not understand the concept.
ATP can be compared to a fully charged battery because both contain stored energy, whereas ADP resembles a partially charged battery.