Light, Pigments, and Photosynthesis

Explain how wavelength of light factors limit the rate of photosynthesis.

1. Chlorophyll pigments absorb the most light energy within the blue-violet-indigo range. Lots of energy absorption → lots of photoactivation → lots of photosynthesis! 2. There is a trough within the green wavelengths because these wavelengths are not absorbed by the pigments. No absorption → no photoactivation → no photosynthesis! 3. Another peak (but lower) as chlorophyll absorbs light energy within the orange-red range. Lots of energy absorption → lots of photoactivation → lots of photosynthesis! Incorrect wavelength leads to no photoactivation. At the peak, chlorophyll absorbs blue, violet, and indigo. At the trough, green is not absorbed. At the lower peak, chlorophyll absorbs yellow, orange, and red.

Explain how water factors limit the rate of photosynthesis.

1. With abundant water, the stomata are open, allowing CO2 to enter the plant for the light independent reactions. 2. With decreased water availability, the stomata will close* to prevent water loss through the pores. CO2 can't enter the plant, which limits the light independent reactions. Not enough water causes the stomata to close to avoid plant dehydration which leads to no CO2 diffusion, leading to no carbon fixation and no calvin cycle. It is eventually limited by some other factor.

Explain how CO2 Concentration factors limit the rate of photosynthesis.

1. With low levels of CO2, there is no carbon fixation, so the light independent reaction stops. 2. With increasing CO2, the rate of photosynthesis will increase as the light independent reactions are triggered. 3. The rate will level off, because eventually there are not enough RuBP molecules or enzymes in the stroma that can be used. Just like you can only eat so fast no matter how hungry you are... a plant can only photosynthesize so fast, no matter how much CO2 there is! Not enough CO2 leads to no carbon fixation which leads to no NADP+ being reformed and eventually stopping light dependent reactions. It is eventually limited by not enough Rubisco enzyme.

Explain how light intensity factors limit the rate of photosynthesis.

1. With low levels of light, there is no photoactivation, so the light dependent reaction stops. 2. With increasing light, the rate of photosynthesis will increase as the light dependent reactions are triggered. 3. The rate will level off, because eventually there are not enough photosystems in the thylakoid that can be activated or maybe there isn't enough CO2 diffusing into the plant. Just like you can only eat so fast no matter how hungry you are... a plant can only photosynthesize so fast, no matter how much light there is! Not enough light leads to no photoactivation, therefore no electron transport chain, no NADPH, and no ATP. Without NADPH and ATP, there is no light independent reaction. It is eventually limited by not enough pigments for the photoactivation.

Explain how temperature factors limit the rate of photosynthesis.

1. With low temperature, there is little collision between enzymes and substrates involved in photosynthesis. 2. With increasing temperature, the rate of photosynthesis will increase as there are more collisions between the enzymes and substrates involved in the reactions. 3. Photosynthesis has an optimum temperature. Different plants have adapted to different environments, so different plant species will have different optimum temperatures. 4. Beyond the optimum, the enzymes involved in photosynthesis will denature and the rate of the reactions will plummet. An increase in temp increases molecular motion and collisions between enzyme and substrate. Then, it reaches an optimum temperature. Enzymes denature meaning the protein shape changes making the active site for the substance nonfunctional.

State the chemical equation of photosynthesis.

6CO2 + 6H2O -> C6H12O6 +6O2 It is an equilibrium equation (so use equilibrium arrows). The forward arrow is photosynthesis. The reverse arrow is cellular respiration. Solar energy also goes into photosynthesis. Chemical energy ATP and heat are also released in the reaction.

Distinguish between an action spectrum and an absorption spectrum.

Absorption Spectrum: a graph plotting a pigment's light absorption versus wavelength. Pattern of wavelengths that a pigment absorbs. Action Spectrum: A profile of the relative performance of the different wavelengths in photosynthesis. A graph of wavelength vs rate of photosynthesis. Profiles the relative effectiveness of different wavelengths of visible light for driving photosynthesis. Determined by illuminating chloroplasts with different wavelengths of light and measuring some indicator of photosynthesis rate: O2 released, CO2 consumed, Glucose made, Amount of plant growth (an indirect measure). Blue and red wavelengths are found to be most effective and green the least effective. It makes sense that the two graphs have the same basic shape... the wavelengths the pigments absorb are used for the action of photosynthesis.

Define Photosystem and Reaction Center

Absorption of light by photosystems generates excited electrons. Large complexes of 100s of proteins and pigments embedded within the thylakoid membrane. Photosystems contain many pigments that help collect light energy, as well as a special pair of chlorophyll molecules found at the core, reaction center, of the photosystem. At the reaction center, an electron in the chlorophyll molecule is energized and moves to a higher energy level. The high-energy electron is then passed to an acceptor molecule in the electron transport chain.

Carotenoids

Accessory pigments; yellow, orange

State evidence that suggests chloroplast were once free living prokaryotes.

As evidence of endosymbiosis, chloroplasts have: Two layers of phospholipid membranes, 70s ribosomes, and circular naked DNA

Protective Pigments

Attract pollinators and protect DNA from ultraviolet light.

State what is included in the light independent reactions of photosynthesis.

Carbon fixation, Carboxylation of RuBP, Production of triosphosphate, ATP and NADPH as energy sources, ATP used to regenerate RuBP, ATP used to produce carbohydrates

Define and state evidence for the "Great Oxidation Event."

Changes to Earth's atmosphere, including ocean and rock deposition, can occur due to photosynthesis. The rise in oxygen concentration to 2% about 2.4 billion years ago is known as the Great Oxidation Event. Banded ion formation in rocks dated between 2.4-2.2 BYO. Only when iron dissolved in ancient oceans where it was exposed to oxygen resulted in rusting.Due to no other significant sources of oxygen are known, scientists attribute the rise in atmosphere O2 to biological synthesis.

Describe the shape of curve for an absorption spectrum.

Chlorophyll a peaks at around 415 nm absorbed, then again at around 685 nm absorbed. Chlorophyll b peaks at around 480 nm absorbed, then again at around 655 nm absorbed. Carotenoids peaks at around 470 nm absorbed, then again at 500 nm absorbed.

State the primary and accessory pigments found in chloroplasts.

Chlorophyll a, Chlorophyll b, Carotenoids, Xanthophyll, and Anthocynanins are found in chloroplasts.

Explain why plants are green.

Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colors. - Chlorophyll-a doesn't absorb green light. So, plants with lots of chlorophyll-a look green to us because the green light is bounced back to our eyes. - Chlorophyll-b doesn't absorb green light. So, plants with lots of chlorophyll-b look green to us because the green light is bounced back to our eyes. - Caratenoids don't absorb yellow or red light. So, plants with lots of caratenoids look orange to us.

Anatomy of a Chloroplast Thylakoid

Contain flat, interconnected membranes called thylakoid membrane used during the light dependent reactions of photosynthesis

State the function ofthe thylakoids.

Contain flat, interconnected membranes called thylakoid membrane used during the light dependent reactions of photosynthesis

What is essential in photosynthesis experiments?

Controlling relevant variables in photosynthesis experiments is essential. Experimental design.

Turns of the Light Independent Reactions (Calvin Cycle)

Each turn of the cycle adds one carbon to the system. Three turns is enough to form one molecule of G3P. Two molecules of G3P are needed to make one glucose. So, six turns of the cycle are required to make one glucose molecule.

State the energy conversion that occurs during photosynthesis.

Energy is needed to produce carbohydrates and other carbon compounds from carbon dioxide. The chemicals go back and forth going from a low level of energy with Carbon Dioxide and Water to a high level of energy with Sugar and Oxygen. The sun gives the plant the necessary energy to transform lower levels of chemical energy into higher forms of chemical energy, energy that we animals can use. So photosynthesis is the process to convert light energy from the sun into chemical energy with sugar and oxygen, and respiration is the process of getting out the energy from the chemicals so that we can move and keep ourselves warm through mechanical process and heat energy.

Summarize the electron transport chain.

Excited e]\lectrons from Photosystem II are used to contribute to generate a proton gradient. Electrons pass from through a chain of electron carrier molecules. The energy released by the movement of electrons is used to pump protons across the thylakoid membrane, from the stroma into the thylakoid lumen. The result of the electron transport chain is a proton gradient, with a high concentration of protons in the thylakoid lumen.

Anatomy of a Chloroplast Stroma

Fluid interior called the stroma with many enzyme dissolved for light independent reactions of photosynthesis.

State the function of stroma.

Fluid interior called the stroma with many enzyme dissolved for light independent reactions of photosynthesis.

State the equation for photolysis

H2O->2H+ + 2e- + 1/2 O2 H+ is used to create a concentration gradient of hydrogen ions and NADPH; reduced to NADP e- goes to Photosystem II O2 is released by the plant. Oxygen produced in photolysis is a waste product of photosynthesis.

State what occurs in chemiosmosis.

In chemiosmosis, ATP is generated as protons move down their concentration gradient through ATP synthase. ATP synthase in thylakoids generates ATP using the proton gradient.

State the function of thylakoid lumen

In light-dependent reactions, chlorophyll and other molecules of the thylakoids capture sunlight energy. Sunlight energy is converted to the energy carrier molecules ATP and NADPH, which are electron carriers. Oxygen gas is released as a by-product of the breaking of water (hydrolysis). The compartment where molecular oxygen is produced from water during photosynthetic light-dependent reactions

Summarize Light Independent Reactions

In order for one G3P to exit the cycle and go towards glucose synthesis, three CO2 molecules must enter the cycle, providing three new atoms of fixed carbon. When three CO2 molecules enter the cycle, six G3P molecules are made. One exist the cycle and is used to make glucose, while the other five must be recycled to regenerate three molecules of the RuBP acceptor. 3CO2 + 9ATP + 6NADPH + 6H+ -> C3H6O3-phosphate + 9ADP + 8Pi + 6NADP+ + 3H2O NADPH and ATP from light-dependent reactions used to power glucose (C6H12O6) synthesis. Light not directly necessary for light-independent reactions if ATP and NADPH are available. Light-independent reactions are also called the Calvin Cycle.

State what occurs during carboxylation in the light-independent reaction.

In the light independent reaction, a carboxylase catalyses the carboxylation of ribulose-bisphosphate. The carbon fixation occurs in the chloroplast stroma. The 5-carbon molecule ribulose bisphosphate, RuBP, is carboxylated by CO2, forming 2 3-carbon molecules called Phosphoglycerate, PGA. The enzyme that catalyzes the carboxylation of RuBP is called ribulose bisphosphate carboxylase, rubisco.

Define Photolysis

In the thylakoid membranes of a chloroplast during light-dependant reactions, two molecules of water are split to form oxygen, hydrogen ions, and electrons. Oxygen is produced in photosynthesis from the photolysis of water.

Study anatomy of a chloroplast diagram (photo on this flashcard)

Label the inner membrane, the outer membrane, circular DNA, granum, lumen, 70s ribosomes, thylakoid membrane, and stroma.

State the location of the light independent reactions of photosynthesis.

Light independent reactions take place in the stroma.

State the function of pigment molecules.

Light-absorbing molecules. Photosynthetic pigments are the molecules responsible for absorbing electromagnetic radiation, transferring the energy of the absorbed photons to the reaction center, and for photochemical conversion in the photosynthetic systems of organisms capable of photosynthesis.

State the location of the light dependent reactions of photosynthesis.

Light-dependent reactions take place in the intermembrane space of thylakoids.

What does photosynthesis allow for?

Mechanical cellular work such as transport, movement, and building polymers.

Anatomy of a Chloroplast Lamella

Membranous channels, called lamella, connect the stacks.

Chlorophyll a Color

Most abundant pigment; darker, green/blue.

Summarize NADP to NADPH + H+

Occurs through a reduction reaction. Excited electrons from Photosystem I are used to reduce NADP. Photoactivation of the reaction center chlorophyll in photosystem I excites electrons which pass through a different electron transport chain. The electrons of Photosystem I are used to reduce NADP+ to form NADPH. NADPH is an electron carrier molecule. The electrons from the Photosystem II electron transport chain are used to replace the electrons lost during photoactivation of Photosystem I.

Oxidation vs. Reduction

Oxidation: adds oxygen, removes hydrogen, loses electrons, increases oxidation states, and has oxidizing agents. Ex: oxidation of glucose during respiration. Reduction: removes oxygen, adds hydrogen, gains electrons, decreases oxidation states, and has reducing agents In photosynthesis, H2O is oxidized and CO2 is reduced.

Describe the shape of the curve for an action spectrum.

Peaks higher than the absorption rates. Peaks at around 410 nm, then dips and peaks again at around 690 nm.

Phases of Light Independent Reactions

Phase 1: Fixation of carbon dioxide. Phase 2: Reduction of 3-phosphoglycerate to G3P. Phase 3: Regeneration of RuBP from G3P.

Reduction of Phosphoglycerate

Phosphoglycerate is reduced to triose phosphate using a reduced NADP and ATP. ATP from the light dependent reaction provides the energy for NADPH from the light dependent reaction to reduce PGA, forming a three-carbon carbohydrate, triose phosphate, G3P.

State that the light dependent reaction of photosynthesis includes:

Photoactivation, Photolysis, Electron Transport, Chemiosmosis, ATP synthesis, and Reducation of NADP to NADPH + H+

Where does photosynthesis take place in eukaryotes? How did this come about?

Photosynthesis in eukaryotes takes place in chloroplasts. Thought to have evolved from an ancient endosymbiotic bacterium. As evidence of ENDOSYMBIOSIS, chloroplasts have: Two layers of phospholipid membranes, 70s ribosomes, Circular, naked DNA.

Define photosynthesis

Photosynthesis is the production of carbon compounds in cells using light energy.

Define Pigment

Pigments are (usually protein) molecules embedded within the thylakoid membrane. Pigments are organized into clusters called "photosystems." Pigment absorb wavelengths of light; different pigments absorb different wavelengths of light.

Plant Pigments Flow Chart

Protective Pigments: Anthocyanins Photosynthetic Pigments: Chlorophylls and Carotenoids - Chlorophylls include: Chlorophyll a and Chlorophyll b - Carotenes include: Xanthophyll and Carotenes

Plant Pigments

Proteins that absorb wavelengths of visible light.

What energy conversion occurs during light dependent reactions?

Reduced NADP and ATP are produced in the light dependent reactions. The light dependent reactions convert light energy into chemical energy in the form of ATP and NADP.

Calculate the Rf value for pigments using pigment chromatography.

Rf = distance pigment traveled / distance solvent traveled The ratio of the distance moved by a pigment to the distance moved by the solvent is a constant, called the reaction front Rf. Each type of molecule has its own Rf value.

How is ribulose bisphosphate formed?

Ribulose bisphosphate is formed using ATP. ATP is used to regenerate RuBP from triose phosphate.

Outline the process of separating pigments using chromatography.

Separation of photosynthetic pigments can be down through chromatography. - Cut filter paper into a strip, and cut the tip to a point. - 2 cm from bottom (tip) of a strip of filter paper place a leaf and roll a coin over it so that you get a line of green pigment on the filter. Using a different part of the leaf, roll the penny again over the same line. Repeat this process until the line is fairly dark. - Put about a cm of ethanol acetone in the test tube. - Place your paper strip into the solvent. Make sure that the level of the solvent is below the pigment on the paper - you do not want to submerge the origin in the solvent. This can be done by taping your strip to a pencil to hold it up in the test tube. - As the solvent moves up the paper, the pigments move as well. - After about 20 minutes, take the filter paper out of the test tube and WITH PENCIL mark the distance the solvent travelled, any pigment bands and the location of the original pigment line.

What can carry out photosynthesis?

Some prokaryotes, algae, and plants carry out photosynthesis.

What are the possible limiting factors on the rate of photosynthesis.

Temperature, light intensity, and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.

Anatomy of a Chloroplast Lumen

The Lumen is the hollow interior of the thylakoid membrane

How does chromatography work?

The chromatography solvent is nonpolar. Nonpolar pigments dissolve well in nonpolar solutions, while polar pigments do not. Pigments that are more nonpolar will dissolve better in this solvent, traveling farther up the strip. More polar pigments will not interact much with the solvent, staying closer to the bottom of the strip. Pigments separate based on size and polarity. Move up the filter strip: smaller, more non-polar, hydrophobic pigments. Stay lower on the filter strip: larger, more polar, hydrophilic pigments.

What was Calvin's discovery and what did it allow?

The discovery of the radioactive 14C isotope allowed Calvin to determine the pathway of the light independent reactions of photosynthesis. Developments in scientific research follow improvements in apparatus...sources of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation.

Define Controlled Variable

The factor that is not changed in an experiment.

Define Carboxylation

The first step of the Calvin cycle, in which carbon dioxide absorbed from the air is added to a 5-carbon molecule.

Define Carbon Fixation

The incorporation of carbon from carbon dioxide into an organic compound by an autotrophic organism.

Define limiting factor

The law of limiting factors states that at any given moment, the rate of a physiological process is limited by the factor that is at its least favorable value. This factor is called a limiting factor because it limits the rate at which the process can take place. Changing the levels of other factors will not alter the rate of the process.

State where the light dependent reactions of photosynthesis begin

The light dependent reactions of photosynthesis begin at Photosystem II. It generates ATP via chemiosmosis.

Calvin's experiment to elucidate the carboxylation of RuBP

The light independent reactions are collectively known as the Calvin cycle • Calvin's elucidation (clarification) of photosynthetic carbon compounds is commonly classed the 'lollipop experiment' Lollipop Experiment • Radioactive carbon-14 is added to a 'lollipop' apparatus containing green algae • Light is shone on the apparatus to induce photosynthesis of the algae, which will incorporate carbon-14 into organic compounds through the Calvin cycle • After different periods of time, the algae is killed by running it into a solution of heated alcohol, stopping cell metabolism • Dead algal samples are analysed using 2D chromatography, which separates out the different carbon compounds • Any radioactive carbon compounds on the chromatogram were then identified using autoradiography • By comparing different periods of light exposure, the order by which carbon compounds are generated was determined • Calvin used this information to propose a sequence of events known as the Calvin cycle

Light Dependent Reactions

The light-dependent reactions take place on the thylakoid membranes. The inside of the thylakoid membrane is called the lumen, and outside the thylakoid membrane is the stroma. 2H2O + 2NADP+ + 3ADP + 3Pi + Light -> 2NADPH + 2H+ + 3ATP + O2 Light is captured by photosystems in the thylakoid membrane in chloroplast. Photosystem II Generates ATP via chemiosmosis. Photosystem I Generates NADPH. Splitting water maintains the flow of electrons through the photosystems.

Outline how chloroplast structure could evolve through natural selection.

The structure of the chloroplast is adapted to its function in photosynthesis. Chloroplasts are thought to have evolved from an ancient endosymbiotic bacterium. If the structure of chloroplasts varied, those organisms with the chloroplast that absorbed light and converted it into glucose most efficiently would have the advantage. They would have an increased chance of survival and would tend to produce more offspring. These offspring would inherit the type of chloroplast that produces glucose using light energy more efficiently. If this trend continued, the structure of the chloroplast would gradually evolve to become more and more efficient. (Chloroplasts are quite variable in structure but share certain features): A double membrane forming the outer chloroplast envelope. An extensive system of internal membranes called thylakoids, which are an intense green colour. Small fluid filled spaces inside the thylakoids. A colourless fluid around the thylakoids called stroma that contains many different enzymes. In most chloroplasts there are stacks of thylakoids, called grana. If a chloroplast has been photosynthesising rapidly then there may be starch grains or lipid droplets in the stroma.

Define Independent Variable

The variable that is changed in the experiment

State the function of the chloroplast double membrane.

They have an outer and inner membrane enveloping the intermembrane space. The inner membrane separates 'stroma' from the intermembrane space. The presence of a double-membrane helps in creating a concentration gradient and controls the flow of substances across it.

Photosynthetic Pigments

Thylakoid

State what occurs to replace the electrons lost during photoactivation.

To replace the electrons lost during photoactivation, the reaction center chlorophyll takes electrons by splitting water. Photolysis of water generates electrons for use in the light-independent reactions.

Regeneration of RuBP and Carbohydrate Production

Triose phosphate is used to regenerate RuBP and produce carbohydrates. In the Calvin Cycle, triose phosphate is used to regenerate RuBP and create glucose. Six turns of the Calvin Cycle are needed to produce on molecule of glucose.

Anatomy of a Chloroplast Membrane

Two outer membrane layers,

State the range of wavelengths that fall within the visible spectrum.

Visible light has a range of wavelengths with violet the shortest wavelength and red the longest. Wavelengths in the visible spectrum: 4x10^-7 meters to 7x10^-7 meters

State the relationship between wavelength and energy.

Wavelength and energy are inversely proportional. As wavelength increases, energy levels decrease. As energy levels increase, wavelength decreases.

Anatomy of a Chloroplast Granum

When the thylakoid is folded in a stack, it is called a granum (plural, grana).

Electron Transport Which reaction: What: Why: Where: How:

Which reaction: Light Dependent What: An electron transport chain (ETC) is a series of membrane bound molecules that transfer electrons via redox (both reduction and oxidation occurring simultaneously) reactions. The electron transfer fuels the pumping of protons (H+ ions) across a membrane Why: to create a proton gradient; a buildup of protons in the thvlakoid lumen (which is then used to make ATP during chemiosmosis). Where: in the thylakoid membrane. There are two electron transport chains, one for Photosystem I and another for Photosystem I. How: The high-energy electron (from photoactivation) travels between electron transport molecules embedded in the thylakoid membrane. The movement of the electrons from Photosystem I drives the pumping of H+ ions from the stroma into the thylakoid lumen, building a H+ gradient.

Photolysis Which reaction: What: Why: Where: How:

Which reaction: Light Dependent What: The breaking apart of a watermolecule, using light energy. H2O->2H+ + 2e- + 1/2 O2 H+ is used to create a concentration gradient of hydrogen ions and NADPH; reduced to NADP e- goes to Photosystem II O2 is released by the plant. Why: To generate electrons needed to replace the electrons that the reaction center chlorophyll lost during photoactivation of Photosystem II. Where: At Photosyste II in the thylakoid. How: Activated by light energy, water splits to form protons H+, electrons e-, and oxygen. The oxygen is a waste product of this process. 4e- is now added back to the pigment, which is usually chlorophyll.

Reduction of NADP to NADPH + H+ Which reaction: What: Why: Where: How:

Which reaction: Light Dependent What: The formation of an electron carrier molecule, NADPH, using the electrons from Photosystem I. Why: To make NADPH, which will be needed in the light independent reactions. Where: At the ned of the Photosyste I electron transport chain. How: The electrons that were excited out of the Photosystenm I reaction center chlorophyll are transported between electron carrier molecules and eventually given to the electron carrier molecule NADP. NADP gains electrons; so we say it is reduced to become NADPH. The NADPH will be used in the light independent reactions.

Chemiosmosis and ATP Synthesis Which reaction: What: Why: Where: How:

Which reaction: Light Dependent What: The movement of H+ ions down their concentration gradient is coupled with ATP synthesis. Why: To make ATP, which will be needed in the light independent reactions. Where: At ATP synthase, an enzyme embedded in the thylakoid membrane. How: H+ ions flow down their gradient, from the thylakoid lumen into the stroma through ATP synthase. ATP synthase creates ATP by combining ADP with an inorganic phosphate group, Pi. The making of ATP in photosynthesis is via Photophosphorylation. The phosphorylation of ADP to form ATP using the energy from sunlight.

Production of Triosphosphate Which reaction: What: Why: Where: How:

Which reaction: Light Independent What: Reduction of PGA to produce triosephosphate, G3P, using ATP and NADPH from the light dependent reaction as energy sources. ATP and NADPH are used to reduce phosphoglycerate, PGA, forming triosephosphate, G3P. Why: The electrons and hydrogens from the NADPH will become part of the carbohydrate that results from the light independent reactions. Where: In the stroma of the chloroplast. How: In two steps, ATP and NADPH are used to convert the PGA molecules, formed in carbon fixation, into molecules of a three-carbon sugar called glyceraldehyde-3-phosphate, G3P. This stage gets its name because NADPH donates electrons to, or reduces, the PGA to make G3P. G3P is a three-carbon sugar-phosphate that can be used to make a range of carbohydrates by other pathways. G3P is the carbohydrate product of the light independent reactions.

Regeneration f RuBP using ATP energy Which reaction: What: Why: Where: How:

Which reaction: Light Independent What: Using ATP, some of the G3P molecules are recycled to regenerate the RuBP molecule. Why: RuBP must be regenerated so that carbon fixation can occur again. Where: In the stroma of the chloroplast. How: Remaining G3P molecules remain in the cycle and are used to regenerate RuBP, which enables the system to prepare for more CO2 to be fixed. ATP is used in these regeneration reactions. G3P, with the help of ATP, makes ribulose biphosphate (RuBP) so the cycle can continue.

Carbon Fixation & Carboxylation of RuBP Which reaction: What: Why: Where: How:

Which reaction: Light Independent Reaction What: THe process of adding carbon from an inorganic molecule, CO2, to an organic compound. Why: The carbon from CO2 is eventually used to build carbohydrates (glucose), which fuels the entire food chain. Where: In the stroma of the chloroplast. How: CO2 enters plants from the air via stomata and diffuses (passive transport) into the chloroplast stroma. The CO2 attaches to ribuloase bisphosphate, RuBP. RuBP is a five-carbon molecule. Because a carbon is added to RuBP, we say it is carboxylated to become a six-carbon molecule. The enzyme that catalyzes the carboxylation of RuBP is called ribulose bisphosphate carboxylase (rubisco). The six-carbon molecule is immediately split into two, three-carbon molecules called phosphoglycerate, PGA.

Photoactivation Which reaction: What: Why: Where: How:

Which reaction: Light dependent What: Energy from light is used to excite electrons in a chlorophyll pigment (photosystems II and I). Why: So that the electrons can leave the pigment molecule (chlorophyll) and move through the electron transport chain. Where: In photosystems, which are large complexes of 100s of proteins and pigments embedded within the thylakoid membrane. i) There are two types of photosystems: photosystem I (PSI) and photosystem II (PSII). Caution: Photosystem II is used first and Photosystem I is used in the Light Dependent Reactions. ii) Photosystem II absorbs light at an average wavelength of 680 nm and Photosytem I absorbs light at an average wavelength of 700 nm. ii) Both photosystems contain many pigments that help collect light energy, as well as a special pair of chlorophyll molecules found at the core, reaction center, of the photosystem. How: When light is absorbed by one of the many pigments in the photosystem, energy is passed inward from pigment to pigment, via resonance, until it reaches the reaction center. At the reaction center, an electron in the chlorophyll molecule is energized and moves to a higher energy level. The high-energy electron is then passed to an acceptor molecule in the electron transport chain.

Define visible light

White light: Contains all the wavelengths of visible light. When it hits a pigment, the colors you can see are reflected and the colors you can't see are absorbed and therefore available to be used as energy for photosynthesis.

Chlorophyll b Color

lighter, olive green/yellow

Carotenes Color

orange

Anthocyanins Color

red/purple/blue

Define Responding Variable

the variable that changes in response to the manipulated variable; also known as the dependent variable.

Xanthophyll Color

yellow

List mechanism for measuring the rate of photosynthesis.

• Measuring CO2 uptake• H2O + CO2 -> H+ +HCO3-• Measuring O2 production:• Water displacement• # of bubbles• Measuring biomass: glucose production can be indirectly measure by a change in the plant's weight. After plant tissue has been dehydrated. Iodine staining will detect starch and can be qualified using a colorimeter.