Photosynthesis Quiz
Using energy from ATP, the remaining five G3P molecules are rearranged into three molecules of RuBP.
What is the fourth step of the Calvin Cycle (after G3P is rearranged)?
In C₄ plants, PEP carboxylase is partitioned in a specialized cell - the bundle sheath cell.
What is the main difference between the manner in which CAM plants avoid photorespiration, and C4 plants do so?
The purpose of photosynthesis is to make glucose.
What is the purpose of photosynthesis?
ATP is generated by the light reactions and is needed to power chemical reactions of the Calvin Cycle.
What is the role of ATP in photosynthesis?
Technically, the Calvin Cycle makes G3P and not glucose.
Does the Calvin Cycle technically make?
No!
Does the oxygen produced in photosynthesis come from carbon dioxide?
The stroma has a low concentration of H⁺ but a high pH.
Does the stroma have a high or low concentration of H⁺?
The thylakoid space has a high concentration of H⁺ but a low pH.
Does the thylakoid space have a high or low concentration of H⁺?
The Calvin Cycle is sometimes referred to as the dark reactions or light-independent reactions because none of the steps requires light directly.
Why is the Calvin Cycle sometimes referred to as the dark reactions or light-independent reactions?
Fossil fuels come from the remains of ancient organisms, and their burning releases CO₂ that had been removed from the atmosphere by photosynthesis over the course of hundreds of millions of years.
Why is the burning of fossil fuels so bad?
If one keeps Rubisco sequestered, one can manage the levels of CO₂ in the environment.
Why is the sequestering of PEP carboxylase in the mesophyll cell and the Calvin Cycle in the bundle sheath cell so important?
CO₂ is a heat-trapping gas.
Why is an excess of CO₂ bad for life?
Photosynthesis is a redox process because it depends on moving electrons from one reactant (H₂O) to another reactant (CO₂).
Why is photosynthesis a redox process?
Yes, they are misleading. The dark reactions mainly take place in the light. This is the case because they depend on the outputs of the light reactions. The dark reactions do not require darkness. Both dark and light reactions require light.
Are the terms "light reaction" and "dark reaction" misleading? Does the dark reaction only occur in the dark? Does it require darkness? Do light reactions happen only in light? Does it require light?
Unlike in cellular respiration, their potential energy increases during photosynthesis.
As electrons move from H₂O to CO₂, what happens?
Chloroplasts will quickly be depleted of NADP⁺ if it is not oxidized. When it is oxidized, electrons are donated to carbon compounds in the carbon cycle. So, it is more accurate to say that Calvin Cycle intermediates are, in a sense, the final electron acceptor. However, the part of the intermediates that need to be reduced are the ones that are the most oxidized, such as the carboxyl groups that trace their origin to the carboxylation step of the Calvin Cycle.
As you know, the final electron acceptor in cellular respiration's electron transport chain is oxygen, whereas NADP⁺ is the final electron acceptor in the photosynthetic electron transport chain. Yet, in a sense, one could think of carbon compounds, such as CO₂ as the ultimate electron acceptor in plants. Explain why.
The 9 ATP and 6 NADPH might seem like a high price to pay to generate one glucose molecule. However, the need for glucose cannot be overstated. Whatever the cost, photosynthetic organisms must make glucose in order to feed all anabolic pathways with the carbon compounds they use to build nearly every part of the organism.
As you know, the function of the Calvin Cycle is to convert the energy of sunlight (trapped in the high-energy molecules, ATP and NADPH) into high-energy carbohydrate molecules. However, the Calvin Cycle consumes 9 ATP molecules and 6 NADPH molecules for every three-carbon sugar (glyceraldehyde-3-phosaphate) generated. Because it costs so much in ATP and NADPH to make glyceraldehyde-3-phosphate, how is it that poants every story energy in the form of carbohydrates?
Both are interdependent. The light reactions require the NADP⁺ and ADP and P that are produced in the dark reactions. And, of course, the light reactions supply outputs for the dark reactions.
Can the dark reaction occur without the light reaction? Can the light reaction occur without the dark reaction?
C4 plants convert carbon dioxide and a 3-carbon molecule into a 4-carbon carboxylic acid. C₄ fixation is an addition to the ancestral and more common C₃ carbon fixation. The main carboxylating enzyme in C₃ is called Rubisco, and catalyses two distinct reactions, with CO₂ (carboxylation) and with oxygen (oxygenation), which gives rise to the wasteful process of photorespiration. C₄ photosynthesis reduces photorespiration by concentrating CO₂ around Rubisco. To ensure that Rubisco works in an environment where there is a lot of carbon dioxide and very little oxygen, C₄ leaves generally differentiate two partially isolated compartments called mesophyll cells and bundle-sheath cells. CO₂ is initially fixed in the mesophyll cells by the enzyme PEP carboxylase, which reacts the three carbon PEP with CO₂ to form the four-carbon oxaloacetic acid (OAA).
Explain how C4 plants have evolved to address photorespiration. Begin by explaining what photorespiration is.
Photosynthesis is often divided into two phases. The first phase is light-dependent reactions. We can begin to understand this process by focusing on photosystem II- a complex of proteins and pigment molecules embedded in the thylakoid membrane. The reaction center chlorophyll in PSII gets oxidized and loses an electron to the PSII electron transport chain. This results in the passage of electrons down the chain, which is accompanied by protons being pumped into the interior of the thylakoid. This results in a proton gradient which is utilized by ATP synthase to make ATP from ADP and P. The missing electrons from the PSII reaction centers attract electrons from water molecules. These water molecules give up electrons to the reaction center chlorophyll. The water-splitting enzyme helps to catalyze the transfer of electrons from water to PSII. The result of these redox reactions is that the water molecules are stripped of their hydrogen atoms, and the resulting O₂ is emitted as a byproduct. Finally, after PSI loses electrons, the electrons donated to the electron transport chain are donated to NADP⁺.
Explain the terms "light reaction" and "dark reaction."
These products of the light reactions are used in the dark reactions. ATP serves as an energy source, and NADPH is used to reduce the organic material intermediates of the Calvin Cycle.
How are the products of light reaction used in dark reactions?
The products of the light reaction (electrons and energy) are used to hydrogenate carbon.
How are the products of the light reaction used in the dark reaction (the Calvin Cycle)?
The light creates an "electron hole" in chlorophyll, and this hole calls to the electrons in H₂O, which usually would never split from H₂O, as oxygen is highly electronegative. In other words, it makes the water-splitting enzyme reaction favorable.
How do light and the "electron hole" affect water in photosynthesis?
While cellular respiration synthesizes ATP, photosynthesis requires energy.
How do the redox reactions of photosynthesis and cellular respiration differ on the most basic level?
The energy of the concentration gradient drives H⁺ back across the membrane through ATP synthase, which couples the flow of H⁺ to the phosphorylation of ADP.
How does the ATP synthase complex work in photosynthesis?
High in the atmosphere, high-energy solar radiation converts O₂ into ozone.
How is photosynthetic O₂ converted to O₃?
Two G3P molecules make one molecule of glucose.
How many G3P molecules make one molecule of glucose?
The Calvin Cycle begins with a five-carbon compound, RuBP, that reacts with CO₁ to form two G3P molecules.
How many carbons does the Calvin Cycle begin with?
It cost 9 ATP molecules and 6 NADPH molecules to make each G3P.
How much does it cost to make a three-carbon sugar (called glyceraldehyde-3-phosaphate) in the Calvin Cycle?
Rubisco has a higher affinity for CO₂ than O₂.
If oxygen is so much more atmospherically abundant than carbon dioxide, why does photorespiration not always overpower photosynthesis?
An enzyme in the mesophyll cells has a high affinity for CO₂ and can fix carbon even when the CO₂ concentration is low. The resulting four-carbon compound (OAA) then acts as a carbon shuttle; it moves into the bundle-sheath cells, which are packed around the veins of the leaf, and releases CO₂. Thus, the CO₂ concentration in these cells remains high enough for the Calvin Cycle to make sugars and avoid photorespiration.
In C₄ plants, what is special about the mesophyll cells?
In photophosphorylation, electrons end up in a high state of potential energy in NADPH.
In photophosphorylation, do electrons end up at a low energy level in H₂O or at a high state of potential energy in NADPH?
CO₂ becomes reduced to sugar as electrons, along with hydrogen ions (H⁺) from water, are added to it. Meanwhile, water molecules are oxidized; that is, they lose electrons, along with hydrogen ions.
In terms of reduction and oxidation, what happens in photosynthesis?
When chlorophyll is in an intact chloroplast, it transfers the energy to other pigment molecules and eventually to a special pair of chlorophyll a molecules. This pair passes off an excited electron to a neighboring molecule before it has a chance to drop back down to the ground state the way it does in isolation.
In what way does chlorophyll behave in an intact chloroplast that is very different to how it behaves in isolation?
Photosynthesis is endergonic.
Is photosynthesis endergonic or exergonic?
No, a cycle returns things to their original condition. Photosynthesis is the opposite of a cycle. It begins with low-potential-energy inorganic molecules (water and carbon dioxide), and it converts these into oxygen and to high-energy molecules of glucose.
Is the overall reaction of photosynthesis a cycle?
The carbon dioxide taken in during photosynthesis is used to manufacture carbon compounds. These carbon compounds would be isotopically labeled. The whole plant would become radioactive. The oxygen released from photosynthesis is derived from water, not carbon dioxide.
Suppose you provided plants in a greenhouse with an atmosphere containing radio-isotopically-labeled carbon dioxide, where the oxygen of the carbon dioxide is the radioactive isotope. Would the atmosphere in the greenhouse eventually contain radioactively labeled molecular oxygen?
The grana are stacks of membrane-bounded thylakoids in a chloroplast. Grana are the sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis.
What are the grana?
CAM plants are plants that use an adaption for photosynthesis in arid conditions in which carbon dioxide entering open stomata during the night is converted to organic acids, which releases CO₂ for the Calvin Cycle during the day, when the stomata are closed.
What are CAM plants?
C₃ plants are plants that use the Calvin Cycle for the initial steps that incorporate CO₂ into organic material, forming a three-carbon compound as the first stable intermediate.
What are C₃ plants?
C₄ plants are plants that preface the Calvin Cycle with reactions that incorporate CO₂ into four-carbon compounds, the end product of which supplies CO₂ for the Calvin Cycle.
What are C₄ plants?
They are pigments in the chloroplasts that are various shades of yellow and orange.
What are carotenoids?
Greenhouse gases are the gases in the atmosphere that absorb heat radiation like carbon dioxide.
What are greenhouse gases?
Heterotrophs are organisms that consume other plants or animals or decompose organic material.
What are heterotrophs?
Pigments are light-absorbing molecules.
What are pigments?
The reaction-center complexes are what contain the pair of special chlorophyll a molecules and a molecule called the primary electron acceptor, which is capable of accepting electrons and becoming reduced.
What are reaction-center complexes?
Soybeans, oats, wheat, and rice are all C₃ plants.
What are some examples of C₃ plants?
Corn and sugarcane are examples of C₄ plants.
What are some examples of C₄ plants?
1. Creates O₃ 2. Removes CO₂ (the first two roles work to create the second atmosphere) 3. Food for consumers 4. Growth 5. Everything human beings need come from plants/autotrophs and mines
What are the ecological roles of photosynthesis?
Photorespiration is an evolutionary relic from when the atmosphere had less O₂ than it does today, and the ability of Rubisco's active site to exclude O₂ would have made little difference. Also, photorespiration may play a protective role when the products of the light reactions build up in a cell (as occurs when the Calvin Cycle slows due to a lack of CO₂).
What are the hypotheses regarding the origin of photorespiration?
The inputs of the light reactions are light, water, ADP and P, and NADP⁺. The outputs are O₂, ATP, and NADPH.
What are the inputs and outputs of the light reactions?
The light reactions are the first of two stages in photosynthesis; they are the steps in which solar energy is absorbed and converted to chemical energy in the form of ATP and NADH. The light reactions power the sugar-producing Calvin Cycle but produce no sugar themselves.
What are the light reactions?
In oxidative phosphorylation, the electrons originally come from the oxidation of organic molecules. In photophosphorylation, the electrons originally come from water, and their movement is driven by light energy. Mitochondria transfer chemical energy from food to ATP; chloroplasts transform light energy into the chemical energy of ATP.
What are the main differences between oxidative phosphorylation and photophosphorylation?
Leaves are the major sites of photosynthesis.
What are the major sites of photosynthesis?
The stomata are pores in the epidermis of a leaf. When stomata are open, CO₂ enters a leaf, and water and O₂ exit. A plant conserves water when its stomata are closed.
What are the stomata?
The thylakoids are flattened membranous sacs inside a chloroplast. Thylakoid membranes contain chlorophyll and the molecular complexes of the light reactions of photosynthesis.
What are the thylakoids?
It can be used as fuel for cellular respiration, the starting material for making other organic molecules, and to make cellulose.
What can G3P be used for?
To ensure that Rubisco works in an environment where there is a lot of carbon dioxide and very little oxygen, C4 leaves generally differentiate two partially isolated compartments called mesophyll cells and bundle-sheath cells. CO2 is initially fixed in the mesophyll cells by the enzyme PEP carboxylase which reacts the three carbon phosphoenolpyruvate (PEP) with CO2 to form the four-carbon oxaloacetic acid (OAA).
What do C₄ plants do to ensure that rubisco works in an environment where there is a lot of carbon and very little oxygen?
They rearrange them into proteins (using nitrogen), lipids, carbs, and nucleic acids (using nitrogen and phosphorous)
What do plants do with the Calvin Cycle intermediates?
We see the green wavelengths that the pigments transmit and reflect.
What do we see when we look at a leaf?
Chlorophyll b broadens the range of light a plant can use by conveying absorbed energy to chlorophyll a, which then puts the energy to work in the light reactions. It absorbs mainly blue and orange light and reflects yellow-green.
What does chlorophyll b do?
The Calvin Cycle consumes nine ATP and six NADPH molecules in order to make one G3P molecule.
What does the Calvin Cycle consume to make one G3P molecule?
As the photoexcited electrons are passed down the electron transport chain connecting the two photosystems, hydrogen ions are pumped down the membrane from the stroma into the thylakoid space.
What happens as the photoexcited electrons are passed down the electron transport chain connecting the two photosystems?
In chemiosmosis, the potential energy of a concentration gradient of hydrogen ions across a membrane powers ATP synthesis. This gradient is created when an electron transport chain uses the energy released as it passes electrons down the chain to pump H⁺ across a membrane.
What happens in chemiosmosis?
The cooler the detector is, the higher the CO₂ concentration in the detector because that means that CO₂ is stopping the heat from the infrared lamp from reaching the detector.
What happens inside the carbon dioxide reader?
When Rubisco has oxygen in its active site, it causes the oxygen to react with G3P. This product cannot be converted to glucose, which results in a waster of G3P.
What happens when Rubisco has oxygen in its active site?
When a pigment molecule absorbs a photon of light, one of the pigment's electrons jumps to an energy level farther from the nucleus. In this location, the electron has more potential energy, and we say that the electron has been raised from a ground state to an excited state.
What happens when a pigment molecule absorbs a photon of light?
Cyanobacteria produce O₂ from H₂O in photosynthesis.
What how does cyanobacteria perform photosynthesis?
A light-harvesting complex contains various pigment molecules bound to proteins. Collectively, the light-harvesting complexes function as a light-gathering antenna.
What is a light-harvesting complex?
The input of light energy, represented by the large yellow mallets, boosts electrons in the reaction-center complexes of both photosystems up to the excited state. The electrons are caught by the primary electron acceptor on top of the platform in each photosystem. Photosystem II passes the electrons through an ATP mill. Photosystem II hands its electrons off to reduce NADP⁺ to NADPH.
What is a mechanical analogy of the light reactions?
A photon is a fixed quantitive of light energy. The shorter the wavelength of light, the greater the energy of a photon.
What is a photon?
A photosystem is a light-capturing unit of a chloroplast's thylakoid membrane, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes.
What is a photosystem?
An autotroph is an organism that makes its own food and sustains itself without consuming organic molecules derived from any other organism.
What is an autotroph?
Generally, the Calvin Cycle occurs during the daylight when there are light reaction to power the cycle's sugar assembly line by supplying it with NADPH and ATP.
Why does the Calvin Cycle occur during daylight in most plants?
Carbon fixation is the incorporation of carbon from atmospheric CO₂ into the carbon in organic molecules. During photosynthesis in a C₃ plant, carbon is fixed into a three-carbon sugar as it enters the Calvin Cycle. In C₄ and CAM plants, carbon is fizxd into a four-carbon cycle.
What is carbon fixation?
Chlorophyll a can participate directly in the light reactions, which converts solar energy to chemical energy.
What is chlorophyll a?
Chlorophyll is a light-absorbing pigment in the chloroplasts that plays a central role in converting solar energy to chemical energy.
What is chlorophyll?
Endosymbiosis is the theory that chloroplasts originated from a photosynthetic prokaryote that took up residence inside a eukaryotic cell.
What is endosymbiosis?
Global climate change is an increase in temperature and change in weather patterns all around the planet, due mostly to increasing atmospheric CO₂ levels from the burning of fossil fuels. The increase in temperature, called global warming, is a major aspect of global climate change.
What is global climate change?
Mesophyll is the green tissue in the interior of a leaf; it is a leaf's ground tissue system and the main site of photosynthesis.
What is mesophyll?
Photophosphorylation is the production of ATP by chemiosmosis during the light reaction of photosynthesis.
What is photophosphorylation?
Some carotenoids absorb and dissipate excessive light energy that would otherwise damage chlorophyll or interact with oxygen to form reactive oxidative molecules that can damage cell molecules.
What is photoprotection?
Photorespiration is a metabolic pathway that consumes oxygen, releases CO₂, and decreases photosynthetic output. Photorespiration generally occurs on hot, dry days, when stomata close, O₂ accumulates in the leaf, and rubisco fixes O₂ rather than CO₂. Photorespiration produces no sugar molecules or ATP.
What is photorespiration?
O₂ is released during the light reactions.
What is released during the light reactions?
Rubisco is the enzyme that performs carbon fixation and produces the first product of the Calvin Cycle (G3P).
What is rubisco?
Stroma is the dense fluid within the chloroplast that surrounds the thylakoid membrane and is involved in the synthesis of organic molecules from carbon dioxide and water. Sugars are made in the stroma by the enzymes of the Calvin Cycle
What is stroma?
The "electron hole" is a positive charge on a molecule of chlorophyll.
What is the "electron hole" in chlorophyll?
The Calvin Cycle is the second of two stages of photosynthesis; it is a cyclic series of chemical reactions that occur in the stroma of a chloroplast, using the carbon in CO₂ and the ATP and NADPH produced by the light reactions to make the energy-rich sugar molecule G3P.
What is the Calvin Cycle?
RuBP ⁺ O₂ → CO₂ + H₂O
What is the chemical equation for photorespiration?
6CO₂ + 6H₂O → C₆H₁₂O₆ ⁺ 6O₂
What is the chemical equation for photosynthesis?
The concentration of CO₂ is 0.04%.
What is the concentration of CO₂ in the atmosphere?
The concentration of O₂ is 22%.
What is the concentration of O₂ in the atmosphere?
CFCS, which were used in aerosol sprays, refrigerators, and Styrafoam products, get broken down by the intense solar radiation in the upper atmosphere into chlorine atoms. These chlorine atoms react with ozone, reducing it to O₂.
What is the danger of CFCs (chlorofluorocarbons)?
The electromagnetic spectrum is the entire spectrum of radiation ranging in wavelength from less than a nanometer to more than a kilometer.
What is the electromagnetic spectrum?
Meanwhile, light energy excites an electron of chlorophyll P700 in the reaction center of photosystem I. An adjacent primary electron acceptor captures the electron, and an electron that reaches the bottom of the electron transport chain from photosystem Ii replaces the lost electron in P700.
What is the fifth step of the light reaction (after the photoexcited electrons from water pass from photosystem II to photosystem I)?
In the carbon fixation step, the enzyme Rubisco attaches CO₂ to RuBP to make 3-PGA.
What is the first step of the Calvin Cycle?
A pigment molecule in a light-harvesting complex absorbs a photon of light. The energy is passed to other pigment molecules and finally to the reaction center of photosystem II, where it excites an electron of chlorophyll P680 to a higher energy state.
What is the first step of the light reaction?
It is the storable carbon-compound that is formed from carbon dioxide and another carbon compound through the PEP carboxylase enzyme.
What is the four-carbon compound, oxaloacetic acid (OAA)?
Each photoexcited electron passes from photosystem II to photosystem I via an electron transport chain. The exergonic fall of electrons provides energy for the synthesis of ATP⁺ by pumping H⁺ across the membrane.
What is the fourth step of the light reaction (after O₂ is formed)?
The function of the Calvin Cycle is to convert the energy of sunlight (trapped in the high-energy molecules, ATP and NADH) into high-energy carbohydrate molecules.
What is the function of the Calvin Cycle?
The greenhouse effect is the warming of Earth due to the atmospheric accumulation of CO₂ and certain other gases, which absorb infrared radiation and radiate some of it back toward Earth.
What is the greenhouse effect?
Ozone acts as sunscreen for the planet, as it shields Earth from ultraviolet radiation.
What is the importance of ozone?
Light energy absorbed by the chlorophyll molecule is used to drive the transfer of electrons and H⁺ from water to the electron acceptor NADP⁺, reducing it to NADPH.
What is the light energy absorbed by the chlorophyll molecule used for?
One problem that farmers face in growing C₃ plants is that hot, dry weather can decrease crop yield because in response to such conditions, plants close their stomata. This adaption reduces water loss and helps prevent dehydration, but it also prevents CO₂ from entering the leaf and O₂ from leaving. As a result, CO₂ levels get very low in the leaf, and photosynthesis slows. And the O₂ released from the light reactions begin to accumulated, and the rates of photorespiration sharply increase.
What is the problem with C₃ plants?
The proton gradient in chloroplasts is responsible for supplying proton flow to the ATP synthase in the thylakoid membrane.
What is the role of a proton gradient in photosynthesis?
Carbon dioxide provides all of the carbon atoms that are used in the Calvin Cycle.
What is the role of carbon dioxide in photosynthesis?
This is a pigment molecule that absorbs light energy.
What is the role of chlorophyll in photosynthesis?
Light is needed to excite the electrons in PSII.
What is the role of light in photosynthesis?
Oxygen is the byproduct of PSII and the water-splitting process.
What is the role of oxygen in photosynthesis?
PSI is a complex of proteins and pigment molecules that absorb light energy, which causes the reaction-center chlorophyll to lose an electron. This electron is replaced by electrons donated from PSII. The production of NADPH is the main function of PSI.
What is the role of photosystem I in photosynthesis?
Photosystem II is a complex of proteins and pigment molecules embedded in the thylakoid membrane. The reaction center chlorophyll in PSII gets oxidized and loses an electron to the PSII electron transport chain. This results in passage of electrons down the chain which is accompanied by protons being pumped into the interior of the thylakoid. This results in a protein gradient, which is utilized by ATP synthase to make ATP from ADP and P. The missing electrons from the PSII reaction centers attract electrons from water molecules. These water molecules give up electrons to the reaction center chlorophyll. The water-splitting enzyme helps to catalyze the transfer of electrons from water to PSII. The result of these redox reactions is that the water molecules are stripped of their hydrogen atoms, and the resulting O₂ is emitted as a byproduct.
What is the role of photosystem II in photosynthesis?
Rubisco is the first enzyme of the Calvin Cycle. It is responsible for combining CO₂ and ribulose 1,5-bisphosphate. The result is a 6-carbon product that rapidly rearranges itself into two 3-carbon molecules. Rubisco can also use oxygen as a substrate and this leads to wasteful photorespiration.
What is the role of rubisco in photosynthesis?
Water is the electron source that donates electrons to PSII?
What is the role of water in photosynthesis?
The final electron acceptor of an electron transport chain must b e a compound that can be constantly acquired and forms a harmless or temporary byproduct.
What is the rule regarding the final electron acceptor of an electron transport chain?
NADPH reduces the organic acid 3-PGA to G3P using the energy of ATP. To make a molecule of G3P, the cycle must incorporate the carbon atoms from three molecules of CO₂.
What is the second step of the Calvin Cycle (after the carbon fixation step)?
This electron is captured by the primary electron acceptor?
What is the second step of the light reaction (after an electron of chlorophyll P680 gets excited to a higher energy state)?
Photoexcited electrons of photosystem I are passed through a short electron transport chain to NADP⁺, reducing it to NADPH.
What is the sixth step of the light reaction (after a photoexcited electron in P700 gets replaced by another excited electron that has reached the bottom of the electron transport chain)?
The starting material of the Calvin Cycle is RuBP (ribulose biphosphate).
What is the starting material of the Calvin Cycle that we also end up with at the end?
NADP⁺
What is the textbook final electron acceptor of photosynthesis?
For every three CO₂ molecules fixed, one G3P molecule leaves the cycle as a product, and the remaining five G3P molecules are rearranged.
What is the third step of the Calvin Cycle (after G3P is produced)?
Water is split, and its electrons are supplied one by one to P680, each replacing an electron lost to the primary electron acceptor. The oxygen atom combines with a second oxygen from another split water molecule, forming O₂.
What is the third step of the light reaction (after an excited electron is captured by the primary electron acceptor)?
Plants are photoautotrophs.
What kind of autotrophs are plants?
Photosystem II absorbs red light best. Photosystem I absorbs far-red light best.
What kind of light do the photosystems absorb the best?
They do photosynthesis but do not produce oxygen.
What makes purple surface bacteria unique?
ATP from the light reactions provides chemical energy that powers several of the steps of the Calvin Cycle.
What powers the Calvin Cycle?
NADPH, produced by the light reactions, provides the electrons for reducing carbon in the Calvin Cycle.
What provides the electrons for reducing carbon in the Calvin Cycle?
A concentration gradient would be made, and ATP would be produced.
What would happen if you put chloroplasts in high pH after being put in low pH?
The chloroplasts would absorb loads of protons.
What would happen if you put chloroplasts in low pH?
Leaves close their stomata in an attempt to maintain water for reasons of heat or darkness.
When do leaves close their stomata?
Chloroplasts are high in concentration in the mesophyll cells, which are cells in the middle layer of the leaf.
Where are chloroplasts high in concetration?
The colors of fall foliage are due partly to the yellow-orange hues of longer-lasting carotenoids that show through one the green chlorophyll breaks down.
Where do the fall colors come from?
The hydrogens in photosynthetic glucose come from water.
Where do the hydrogens in photosynthetic glucose come from?
The light reactions of photosynthesis occur in the thylakoid membrane.
Where do the light reactions of photosynthesis occur?
The oxygen atoms in CO₂ and the hydrogen atoms in reactant H₂O end up in the sugar molecule and the water that is formed as a byproduct.
Where do the oxygen atoms in CO₂ and the hydrogen atoms in reactant H₂O end up?
The catalytic head of ATP synthase is in the stroma.
Where is the catalytic head of ATP synthase?
The electron transport chain is located in between the two photosystems.
Where is the electron transport chain located?
The thylakoid space is inside the thylakoid sacs.
Where is the thylakoid space?
There is more water in the southern hemisphere of the ocean than the northern hemisphere.
Where is there more water: the southern or the northern hemisphere of the ocean?
ATP synthase is facing the high pH side.
Which side of the membrane is ATP synthase in photosynthesis facing: the low pH side or the high pH side?
Melvin Calvin elucidated the Calvin Cycle
Who is the person that elucidated the Calvin Cycle?
In plants, photosynthesis takes place in the chloroplasts in leaves. Leaves are extremely thin, typically fewer than cell-layers in thickness. The reason leaves are so thin is that this enables a great deal of surface area to perform photosynthesis. Animals are often motile - they move. Carrying a sufficient amount of surface area to do photosynthesis at a meaningful rate is in conflict with movement.
Why are there no photosynthetic animals? Wouldn't it be nice to have the ability to make food with light, carbon dioxide, and water?
Plants that inhabit places that are constantly wet and cool have no need to adapt to photorespiration. These plants simply keep their stomata open and thus perform constant gas exchange. This would enable them to avoid photorespiration. In plants, such as this the energy and material used to produce PEP carboxylase would be wasted.
Why aren't all plants C4 or CAM plants?
