Photosynthesis Quiz 3/Exam 3
difference in chlorophyll a and b?
1) Chlorophyll a appears blue-green in color because it absorbs best in the purple and red wavelengths. Chlorophyll b appears yellow-green because it absorbs best in the blue and orange wavelengths. 2)The molecular structures of these two chlorophylls are identical save for the aldehyde in chlorophyll b and the methyl group in chlorophyll a. Functional group affects their absorption properties.
How is action spectrum similar to the absorption spectra?
1)The graph of the absorption spectra of Chlorophyll a, Chlorophyll b, and the carotenoids look like the graph of the action spectra of a leaf because the chlorophylls and the carotenoids are the only photosynthetic pigments that are present in the leaf. 2)!!!!!Because the harvesting of light by plant pigments is central to the light reactions of photosynthesis, the rate of photosynthesis is highest at the same wavelengths that correspond to the highest light absorption by photosynthetic plant pigments. Conversely, the rate of photosynthesis is lowest at wavelengths that correspond with the lowest amount of light absorbed by these pigments.
photosynthesis formula
6CO2 + 12H2O + Light energy → C6H12O6+ 6O2 + 6H20 Need CO2 , H2O and light energy to produce glucose and excrete O2 and H2O.
Describe the function of a photosystem
A photosystem contains hundreds of pigment-protein complexes and is organized into two parts — a light-harvesting complex and a reaction-center complex. Pigments in the light-harvesting complex (Photosynthesis I ) gather light and funnel the energy from pigment to pigment to the reaction center complex. The energy passes from high energy to low-energy. The chlorophyll a in the reaction center has the lowest energy.
photosystem
A photosystem contains hundreds of pigment-protein complexes and is organized into two parts: a light-harvesting complex and a reaction-center complex.
What is a spectrophotometer and its necessity to absorption spectrum?
A spectrophotometer is an instrument designed to measure the amount of light absorbed by a particular material. Scientists construct absorption spectra using spectrophotometers. How does a spectrophotometer work (Figure 4)? A prism splits light into separate wavelengths so that it fans out/bends, or refracts, into different colors. Only one color of light with a specific wavelength passes through the pigment sample in the cuvette at a time. using a prism...A spectrophotometer shines incident light of a set wavelength onto a sample. The amount of light that is transmitted through the sample is recorded electronically on a photodetector and used to determine the amount of light the sample absorbed. Rotating the prism changes the wavelength that shines on the sample. A spectrophotometer will indicate how effectively individual plant pigments absorb different wavelengths of light. But spectrophotometer data cannot indicate the overall efficiency of photosynthesis
what are the shortcomings of using a spectrophotometer?
A spectrophotometer will indicate how effectively individual plant pigments absorb different wavelengths of light. But spectrophotometer data cannot indicate the overall efficiency of photosynthesis. Instead action spectrum is used.
after Photosynthesis I
After light is harvested by pigments and funneled to the reaction center complex by resonance energy transfer, the next act of photosynthesis is the conversion of light energy to chemical energy (photosynthesis II). Whereas the power supply involves only a few contributors — the sun, chlorophyll, other pigments — many contributors are needed for the reaction center to run. Water, carbon dioxide, transportation molecules are involved as well as the precursors of ATP and NADPH.
light harvesters?
All pigments absorb light. But most pigments do not participate in the actual photochemical reactions of photosynthesis. The accessory pigments, such as Chlorophyll b and carotenoids, do not transform light energy directly into chemical energy. So what do these pigments do? They are simply light harvesters. They absorb light and pass the energy to other pigments. Because accessory pigments absorb more light at different wavelengths than chlorophyll a, a broader range of light can be used for photosynthesis. All photosynthetic pigments are embedded in the thylakoid membranes of chloroplasts
What is an absorption spectrum?
An absorption spectrum is a graph of light absorbance versus wavelength. It shows what percentage of light a substance absorbs relative to wavelength. Scientists construct absorption spectra using spectrophotometers. A spectrophotometer is an instrument designed to measure the amount of light absorbed by a particular material.
Differentiate between linear and cyclic electron flow and explain how each process generates ATP and NADPH.
An electron transport chain transports high-energy electrons from chlorophyll pigment molecules in the reaction center of photosystem II through photosystem I. The stepwise reactions of the transport chain release some energy from the electrons. Some of that energy is used to pump H+ ions into the thylakoid space to form a proton gradient. ATP synthase converts energy from H+ ions diffusing across the membrane into chemical energy stored in ATP in the process of chemiosmosis. Electrons emerging from the transport chain PS I are taken up by NADP+ to form NADPH. Cyclic electron flow short-circuits PS II. Electrons emerging from PS I move back to the cytochrome complex between the photosystems and re-enter PS I. This process generates ATP but not NADPH.
How is electron transport different from resonant energy transfer that delivers energy to the Chl a pair?
As the name implies, electron transport chains literally move electrons from one compound to another by chemical reactions. Resonant energy transfer moves energy only — it does not involve any transfer of particles.
Autotrophs
Autotrophs, self-feeders, are able to produce food from inorganic compounds without having to consume other living organisms. Plants are autotrophs and are referred to as primary producers
Chlorophyll a is in the photosystem's reaction center. Would this Chlorophyll a absorb light energy at longer or shorter wavelengths?
Because light in the photosystem antenna complex funnels from pigments that absorb short wavelength (450nm high energy) light to pigments that absorb long wavelength (700nm, low energy) light, the pigment at the very center should absorb light close to the 700-nm limit. (Pigments in the light-harvesting complex gather light and funnel the energy from pigment to pigment to the reaction center complex. The energy passes from high energy to low-energy.The chlorophyll a in the reaction center has the lowest energy. ).
Are there non-photosynthetic plants?
Believe it or not, the Indian Pipe, or Corpse Plant (Monotropa hypopitys) does not perform photosynthesis (Figure 8). It absorbs nutrients from the ground, much like a fungus, but it is a plant nonetheless. Accordingly, it lacks photosynthetic pigments, which are necessary for photosynthesis to occur and which give plant parts their green, yellow, orange or brown colors.This plant lacks photosynthetic pigments, so it does not appear to have any color in its tissues. However, it is able to absorb energy from nutrients in the ground.
Which is most common chlorophyll a or b?
By far, the most abundant chlorophyll in green plants is Chlorophyll a. To us, Chlorophyll a appears blue-green in color because it absorbs best in the purple and red wavelengths. Chlorophyll b appears yellow-green because it absorbs best in the blue and orange wavelengths
Carbon fixation (calvin cycle) occurs in three stages
Carbon dioxide is fixed in three stages. First, it is added to a five-carbon acceptor molecule, ribulose-1,5-bisphosphate, by the enzyme Rubisco. The resulting six-carbon molecule spontaneously breaks into two copies of the three-carbon molecule glycerate-3-phosphate. Rubisco is the most abundant enzyme on earth. Next, glycerate-3-phosphate is converted to glyceraldehyde-3-phosphate in a two-step reaction, which is the reverse of the corresponding steps in glycolysis. In this stage, ATP is consumed and NADPH is oxidized. NADPH is closely related to NADH, the only difference being a phosphate group. Biosynthetic pathways such as carbon fixation generally use NADPH whereas catabolic pathways such as glycolysis use NADH. !!!!!In stage three, the original five-carbon substrate is regenerated, making carbon fixation a cyclic pathway. Carbohydrates are synthesized from glyceraldehyde-3-phosphate that exits the cycle. This process of carbon fixation is called the Calvin cycle. In the Calvin cycle, carbon in carbon dioxide is reduced while NADPH is oxidized. This process requires an input of energy and is driven by ATP hydrolysis. The Calvin cycle completes the process of photosynthesis. Light energy captured by the light-dependent reactions in the form of ATP and NADPH is subsequently used in the light-independent process to drive the synthesis of sugar from carbon dioxide and water. The energy from light is used to convert CO2 into sugar via the Calvin cycle. For every three molecules of CO2 that enter the cycle, the net output is one molecule of glyceraldehyde 3-phosphate (G3P).
Carbon fixation reactiond/calvin cycle
Carbon fixation reactions that has been commonly referred to as the Calvin cycle. In this process, the cell converts or "fixes" inorganic carbon from carbon dioxide into organic carbon in the form of a 3-carbon sugar molecule called glyceraldehyde-3-phosphate (G3P). Each cyclic step of carbon fixation is catalyzed by at least one enzyme. Constructing sugar from CO2 is an anabolic process that requires energy input. That's where the energy from ATP comes in (ATP hydrolisis). Each molecule of CO2 enters the cycle separately. It takes three CO2 molecules, or three "turns" !!!! of the cycle, to produce one molecule of G3P. (3 TURNS). A CO2 molecule enters the cycle by bonding to a 5-carbon sugar called ribulose biphosphate (RuBP). This reaction is catalyzed by ribulose-1,5-bisphosphate carboxylase oxygenase, most commonly known as RuBisCO, the most common enzyme in Earth's biosphere. The 6-carbon product of this reaction is unstable and immediately splits into two 3-carbon sugars (3-phosphoglycerate). The next stage in the process is to add a high-energy electron from the electron transport chain. This electron will ultimately be incorporated into G3P. This electron was excited to its high-energy state by the transfer of light energy. Transforming light energy to chemical energy is the essence of the energy storage mechanism that is photosynthesis!!!! The electron is carried from the electron transport chain by NADPH. The electron will travel with the H atom to join 3-phosphoglycerate. To provide the necessary free energy, the cell couples the reaction with ATP hydrolysis. An ATP donates its phosphate group to 3-phosphoglycerate to form 1,3-biphosphoglycerate. Some of the energy released in that reaction is used to drive the reduction of the carboxyl group on 1,3-biphosphoglycerate to an aldehyde group, thereby incorporating the high-energy electron and forming G3P.
caratenoids other function.
Carotenoid pigments protect plants from too much light. When a plant receives excessive light, carotenoids continue to absorb energy but, instead of funneling it to chlorophyll, they dissipate it harmlessly as heat. The dissipation of excess energy as heat is called quenching The continual bombardment of energy can overwhelm the reaction centers and cause damage to the photosynthetic machinery.
which pigment absorbs most energy?
Carotenoids (accessory pigments in photosynthesis) They absorb light in the blue wavelength of light. Blue wavelengths are not absorbed by chlorophyll a or chlorophyll b ( they absorb red and violet wavelength). So by absorbing blue light, more energy is absorbed by plants than by either pigment alone.
Where else are carotenoids found and why are they essential to organisms?
Carotenoids serve a protective function not only in plants. They also play an essential role in protecting skin and the retina of eyes in animals-including humans-from the damaging effects of light. How do we obtain carotenoids? They come from eating plants.
Chlorophyll a
Chlorophyll a (Chlorophyll a appears blue-green in color- absorbs purple and red ) is the most common and important pigment in the conversion of light into chemical energy. It is directly involved in converting light, carbon dioxide, and water to sugars (reaction center complex). Chlorophyll b does not play a central role in this process, and for this reason it is referred to as an accessory pigment. The carotenoids are also considered accessory pigments. Carotenoid pigments absorb best in the purple and blue wavelengths, and so appear orange or yellow
light dependent reactions
During photosynthesis, some of the absorbed light energy is stored as chemical energy in ATP as enzymes use the excited electrons to cleave water molecules into oxygen, protons, and electrons. Other enzymes extract additional energy from the excited electrons by delivering them to the coenzyme NADP+, reducing it to NADPH. During the light-dependent reactions, light energy is converted into chemical energy. Known as resonant energy transfer. Because they are directly coupled to the energy obtained from sunlight, the reactions that produce ATP and NADPH are referred to as the light-dependent reactions. Occurs in the thylakoid membrane called the lumen.
Why are there so many pigments in a light-harvesting complex?
Each pigment absorbs light only at particular wavelength range. Having different kinds of pigments ensures that the plant gathers light at as many wavelengths as possible. If a plant were suddenly cast in shade, where light quality differs slightly, the plant could continue to photosynthesize with minimum disruption
whats photosystem?
Each pigment is bound tightly to one or more proteins and grouped into large aggregates called photosystems. Between 200 and 300 pigment-protein complexes form a single photosystem.There are hundreds of photosystems in a chloroplast. Each contains a light-harvesting complex (antenna) and a reaction center complex (receiver) A photosystem contains hundreds of pigment-protein complexes and is organized into two parts: a light-harvesting complex and a reaction-center complex.
In cyclic electron flow, electrons exiting the transport chain recycle back to photosystem I. Why is this process less efficient than linear electron flow?
Electrons are unavailable for the carbon-fixation reactions. Correct This answer choice is correct because recycled electrons in cyclic electron flow cannot be used for carbon fixation because they are not transferred to NADPH.
Why is this energy-trapping system is ultraefficient?
Energy passes from shorter wavelengths (high energy) to longer wavelengths (low energy). Pigments in the light-harvesting complex gather light and funnel the energy from pigment to pigment to the reaction center complex. The energy passes from high energy to low-energy. Therefore, pigments on the outside of the light-harvesting complex absorb light at shorter wavelengths than those on the inside, closer to the reaction center. This energy-trapping system is ultraefficient. Scientists estimate that 95-99 percent of captured energy funnels to the reaction center.
early earth O2 was toxic. So they used what process to detoxify O2?
Fortunately for current life, a new type of respiration evolved that not only consumed the toxic oxygen, but produced 15-19 times more energy than glycolysis (glycolysis breaks down glucose and is first step of cellular respiration- process used to make ATP by taking O2 and breaking down glucose). Oxygen consuming, or "aerobic", respiration is essentially the exact reverse of photosynthesis; carbohydrate and oxygen react to form carbon dioxide and water.
organisms in early earth used what kind of process to use the energy stored in the bonds of the carb glucose?
Glycolysis was one of the earliest and most successful schemes to evolve that released energy from sugar. It is still found in most living systems today. Since it does not require oxygen (i.e., it is anaerobic), glycolysis was probably the method of choice to liberate energy for the earliest autotrophs.
Which of the following molecules is the ultimate source of electrons for the electron transport chain in the light-dependent reactions?
H2O This answer choice is correct because an enzyme splits water into hydrogen ions, and oxygen atoms, and the electrons that are ultimately transferred to the electron transport chain.
Heterotrophs
Heterotrophs, other-feeders, can't synthesize their food from inorganic materials and therefore must obtain their organic molecules by consuming other autotrophs or heterotrophs. They are the consumers and include all animals. Some heterotrophs consume organic wastes, like dead animals, feces and fallen leaves. These are the decomposers
light independent reaction
In a separate process, carbon dioxide is captured and incorporated, or "fixed," into carbohydrates such as glucose; this process begins in the stroma and continues in the cytosol. Because carbon fixation doesn't require sunlight, these reactions referred to as the light-independent reactions. Also called dark reactions/ calvin cycle. occurs in the fluid filled stroma
Importance of Rubisco in photosynthesis?
In the Calvin Cycle of photosynthesis, the enzyme rubisco grabs CO2 and incorporates it into RuBP (commonly called carbon fixation). The cycle continues until one G3P is made; a precursor to glucose.
The leaf and its function
Leaves are like food factories that manufacture glucose from water and carbon dioxide. Like any factory, it needs energy to function. The leaves gather light energy with pigments, molecules that upon absorbing a photon of visible light momentarily promote an electron to an excited high energy state. These light-harvesting pigments pass their energy between adjacent pigment molecules until the energy arrives at a "reaction center", where the work of capturing the energy begins in earnest. Ultimately photosynthetic organisms capture the energy in the form of ATP and NADPH, two high-energy compounds that are in turn harnessed to power the assembly of carbon dioxide and water into organic compounds such as glucose.
where does O2 comes from in photosynthesis?
Light energy/photons absorbed by photosystem II is used to split a molecule of water. Thats why oxygen can be released without the prescence of CO2.
light photons and wavelength
Light photons propagate in waves characterized by their wavelength, the distance between successive crests. (light can be waves or particles like photons) A wave's energy is inversely proportional to its wavelength. The shorter the wavelength, the greater the energy of the wave. Visible light is actually composed of a spectrum of colors, each with a different wavelength and energy
Several types of chlorophyll. Two most common ones are?
Most plants contain only Chlorophyll a (absorbes purple and red) and Chlorophyll b (absorbs blue and orange)
Do plants need animal for their CO2?
No but animals and plants are wholly dependent on one another (though plants dont need the CO2 from animals). Today, animals need oxygen to release the stored energy in the organic molecules they consume. Plants in turn consume the carbon dioxide byproduct of aerobic respiration to create the organic molecules in which they store the energy of sunlight. Of course, plants don't need animals to close this cycle. Plants use aerobic respiration themselves and can recycle their own carbon dioxide.
The source of the Oxygen released by plants come from CO2 or H2O?
O2 comes from water!
How arephotons and chlophyll related?
Photons of light at the shorter wavelength end of the spectrum have greater amounts of energy than photons at longer wavelengths. Chlorophyll absorbs photons in only some regions of the visible spectrum — at the lower end (red) and the upper end (blue and violet), but not in the middle (orange, yellow, green). Pigments take on the color of the light they reflect — not the color of the light they absorb.
Photosynthesis I
Photosynthesis I is the light-harvesting process, which supplies the energy that powers the chemical process in the reaction centers. Pigments gather photons, bundles of light energy, and transport them to the reaction centers by resonance energy transfer. Energy passes from short-wavelength, high-energy states to longer-wavelength, lower-energy states until it ultimately arrives at the chlorophyll a (Chl a) molecules in the reaction center.
Is the production of ATP in photosynthesis similar to the production of ATP in cellular respiration?
Photosynthesis is often described as the reverse of cellular respiration. Respiration breaks down complex molecules to release energy that is used to make ATP. Photosynthesis takes energy from photons and uses it to build complex molecules. However both systems use an electron transport chain and associated proton pump and ATP synthase as a key part of the process. In photosynthesis electrons enter the transport chain after receiving light energy - in respiration the electrons are provided by organic food molecules. In both cases the electron transport chain uses the energy to pump hydrogen ions across a membrane. The protons pass back through ATP synthase, driving the production of ATP. In photosynthesis this ATP is used to construct organic molecules from carbon dioxide and water.
What affects the rate of photosynthesis?
Photosynthesis occurs at different rates depending on the quality of light a plant receives. Differences in light quality reflect differences in spectral content. Plants photosynthesize faster and more efficiently when they are exposed to the wavelengths in which their pigments absorb most strongly. Scientists measure the rate of photosynthesis using a variety of methods. But most are based on the simple fact that photosynthesis uses carbon dioxide and releases oxygen — two measurable quantities. Therefore, an action spectrum could be produced by exposing a plant leaf to sunlight and measuring the amount of CO2 used or O2 produced under all wavelengths of light
extra notes on photosynthesis
Photosynthesis takes sunlight and carbon dioxide and produces sugar and oxygen in a chemical process that many of Earth's organisms, such as plants, bacteria and algae, use to generate food. Plants use some of that sugar to produce ATP for its own functions.
Plants contain two major classes of photosynthetic pigments
Plants contain two major classes of photosynthetic pigments: chlorophyll and the carotenoids.
ways a plant reduce impact of too much light energy.
Plants have devised many physical ways to reduce the impact of high light levels. The leaves of some plants turn on edge or fold up to avoid direct light. Some leaves can turn a reflective white. Chloroplasts themselves can migrate to parts of the plant where light is less direct. But these responses are relatively slow. When a plant receives excessive light, carotenoids continue to absorb energy but, instead of funneling it to chlorophyll, they dissipate it harmlessly as heat. The dissipation of excess energy as heat is called quenching.
cyclic electron flow
Produces ATP NOT NADPH!!! Sometimes the electron transport chain short-circuits, creating cyclic electron flow (Figure 5). Electrons emerging from PS I at the end of the chain cycle back to the cytochrome complex and re-enter PS I. Photosystem II is completely bypassed. Electrons emerging from PS I are not available to reduce NADP+, so no NADPH is produced during cyclic electron flow. However, H+ ions are still pumped in at the cytochrome complex, so cyclic flow does result in ATP production by chemiosmosis. Is there an advantage to cyclic electron flow? Most likely, this process is an evolutionary relic. However, evidence indicates that cyclic electron flow can be photoprotective for some types of plants in intense light conditions. The photoprotective role of cyclic electron flow is covered in more detail in the module on C4 photosynthesis. Click on the animation to see cyclic electron flow!!
photophosphorylation
Protons in the form of hydrogen ions (H+) build up inside the thylakoid space. Creates a concentration gradient where hydrogen ions diffuse from where they are at a higher concentration (thylakoid space) to where they are at a lower concentration (stroma). Proton pumps powered by the electron transport chain create the gradient. The resulting diffusion of hydrogen ions powers ATP synthase, which phosphorylates ADP into ATP. Photophosphorylation is the process of creating ATP using a Proton gradient created by the Energy gathered from sunlight. The process of creating the Proton gradient resembles that of the electron transport chain of Respiration. But since formation of this proton gradient is light-dependent, the process is called Photophosphorylation The electron transport system is found embedded within the thylakoid membrane and functions in the production of ATP. Protons in the form of hydrogen ions (H+) build up inside the thylakoid space. This creates a proton gradient — a difference in charge across the membrane separating the thylakoid space from the exterior stroma. As H+ ions diffuse across the concentration gradient from high concentration to low concentration, they pass through ATP synthase embedded in the membrane. This remarkable enzyme has a molecular rotor structure that spins as the H+ ions pass. Mechanical energy from the rotor transfers to the active site and facilitates the synthesis of ATP from adenosine diphosphate (or ADP) and a phosphate group. The use of proton diffusion to add a phosphate group to ADP is called chemiosmosis. End up in stroma. Cells use chemiosmosis in other applications besides photophosphorylation, including respiration.
How exactly is the released energy from the electron transport chain transferred to molecules of ATP?
Redox reactions release potential energy of electrons. The separation of electrostatic charges allows the cell to transfer energy to be temporarily stored in the form of a proton gradient and then transferred to mechanical energy in ATP synthase and finally to chemical energy in ATP. The function of the electron transport chain is to produce this gradient. The phosphorylation of ADP to form ATP using the energy of sunlight is called photophosphorylation. Photophosphorylation involves creating a concentration gradient where hydrogen ions diffuse from where they are at a higher concentration (thylakoid space) to where they are at a lower concentration (stroma). Proton pumps powered by the electron transport chain create the gradient. The resulting diffusion of hydrogen ions powers ATP synthase, which phosphorylates ADP into ATP.
Describe the source of the energy that is released in the redox reactions of an electron transport chain.
Redox reactions release potential energy of electrons. Electrons have potential energy due to their position compared to the nucleus (further away from the nuclues means more potential energy). The positively charged nucleus attracts negatively charged electrons. Therefore, energy is required to move electrons away from the nucleus. The farther an electron is from a nucleus, the more potential energy it has. Exergonic redox reactions release some of this potential energy by moving electrons to atoms in which they are positioned closer to the nuclei. the released energy formed is transferred to ATP molecule.
whats the most abundant enzyme on earth?
Rubisco is the most abundant enzyme on earth.
why do you see yellow/ orange leaves in fall?
Terrestrial plants contain many more chlorophyll pigments than carotenoids, so the carotenoids are hard to see. But in the fall, when many deciduous plants degrade their pigments, the chlorophylls disappear first,!!!!! leaving the orange and yellow carotenoids vividly apparent
Explain the role and function of carbon-fixation reactions.
The carbon-fixation reactions use carbon from three CO2 molecules to form a 3-carbon sugar called glyceraldehyde-3-phosphate. High-energy electrons carried from the electron transport chain by NADPH are incorporated into the sugar molecules for energy storage. ATP hydrolysis is coupled with endergonic reactions to provide the necessary energy to drive this anabolic process.
photosystem I (PS I) and photosystem II (PS II).
The center of each photosystem contains a pair of Chl a molecules embedded in a unique molecular structure. Energy originally from light transfers to the Chl a pair in each photosystem during the light harvesting process. The Chl a molecules are similar in the two photosystems, however, the surrounding structure!!! affects their electron distribution and results in a slight difference in the wavelength of maximally efficient absorption. The Chl a pair in photosystem II, called P680, absorbs 680 nm light waves most efficiently, while the absorption peak of the photosystem I pair, P700, is centered around 700 nm. the setting inside the reaction center is as important as the contributors, because structure enables function in cellular processes
chlorophyll structure similarity to hemogoblin and evolutionary relationship?
The circular structure of chlorophyll is called a porphyrin ring. Interestingly, hemoglobin, the bright red oxygen-carrying molecule in red blood cells, has a porphyrin structure nearly identical to that of chlorophyll. So does vitamin B12. The major differences are that chlorophyll is built around a magnesium atom; hemoglobin is built around iron; and vitamin B12 is built around cobalt. The similarity among these structures suggests an evolutionary relationship.
electromagnetic spectrum
The electromagnetic spectrum is the full range of electromagnetic wave energy. The distance between two successive crests (top of a wave) or troughs (bottom of a wave) is a wavelength. The electromagnetic spectrum ranges from short-wavelength gamma rays (less than a nanometer) to long-wavelength radio waves
light dependent reactions in depth.
The leaves gather light energy with chlorophyll, molecules that upon absorbing a photon of visible light momentarily promote an electron to an excited high energy state.These light-harvesting pigments (chlorophyll b and accessory pigments) pass their energy between adjacent pigment molecules until the energy arrives at the pair of chlorophyll a at reaction center complex. The pass energy not electron. also known as resonant energy transfer. the first stage of photosynthesis (light dependent reaction). Electrons are transported through a chain of complexes in the thylakoid membrane by electron carriers, including plastoquinone (PQ) and plastocyanin (PC) from reaction center PSII to PSI. This chain of events stores energy as a proton gradient, which is then transformed to mechanical energy by ATP synthase and finally converted to chemical energy in ATP. NADP+ accepts high-energy electrons from the electron transport chain. Specifically, ATP is generated by harnessing the proton gradient across the thylakoid membrane. NADPH is generated as part of the electron transport chain (reaction center PSII to PSI linear flow). Then NADPH and ATP (from light dependent reactions) provide electrons and energy for the carbon fixation phase of photosynthesis. (light independent reactions)
The light-dependent and light-independent reactions.
The light-dependent and light-independent reactions are so named because the light-dependent reaction requires light, whereas the light-independent reaction can occur either in the light or the dark.
whats light-harvesting complex?
The light-harvesting complex//Photosynthesis I (accesssory pigments) is the photosystem's light collector. It is sometimes called an antenna. It works somewhat like a satellite dish, collecting energy and concentrating it in a receiver. The receiver in this analogy is the reaction center complex
chlorophyll
The primary photosynthetic pigment in leaves is chlorophyll. Chlorophyll absorbs red and blue light reflecting the characteristic green light we associate with leaves. Found in thylakoid membrane of chloroplasts. Leaves also contain accessory pigments, such as carotenoids which are also involved in photosynthesis and absorb purple and blue spectrum and emit yellow and orange, and various anthocyanins which give fruits and flowers their characteristic red, purple, and blue colors. As days shorten and temperatures drop, chlorophyll production slows down, making the yellows and oranges of the carotenoids and the reds, purples, and blues of the anthocyanins more visible. Many of these pigments are produced primarily in the fall, when the levels of nutrients such as phosphorus drop.
what exactly happens in the reaction center complex?
The structural matrix holding the Chl a pairs enables the molecules to use light energy to boost an electron to a higher energy state and to pass that electron on to a molecule known as the primary electron acceptor. This begins a cascade of reactions known as an electron transport chain. The reactions pass the electron from higher to lower energy states in stepwise fashion. Redox reactions release potential energy of electrons. The separation of electrostatic charges allows the cell to transfer energy to be temporarily stored in the form of a proton gradient. Photophosphorylation begins with the separation of electrostatic charges. An enzyme-activated reaction splits a water molecule into two electrons, two protons in the form of H+ ions, and an oxygen atom. The splitting of charges provides electrons for the electron transport chain and H+ ions for chemiosmosis. Creating a concentration gradient where hydrogen ions diffuse from where they are at a higher concentration (thylakoid space) to where they are at a lower concentration (stroma). Proton pumps powered by the electron transport chain create the gradient. The resulting diffusion of hydrogen ions powers ATP synthase, which phosphorylates ADP into ATP. phosphorylates ADP into ATP.
The two types of chlorophyll
There are two different types of chlorophyll in plants: chlorophyll a and chlorophyll b
There are two major ways which organisms obtain energy
There are two major ways which organisms obtain energy, by either autotrophic nutrition or heterotrophic nutrition
Is light waves or particles?
Though the Sun emits light in all wavelengths, much of it is absorbed by particles in Earth's atmosphere. Most light that reaches Earth is in the visible range (graph inset).
How do pigments in the light-harvesting complex funnel energy to the reaction center?
When photons of just the "right" wavelength strike a pigment molecule, one of the molecule's electrons becomes excited as it absorbs the photon's energy. The incoming light energy boosts the electron into an outer orbital shell. The electron is unstable here. To return to its stable, resting state, it must rid itself of the energy. It passes it to another, neighboring pigment and then falls back — until another photon strikes it and the process starts all over again. Meanwhile, the pigment that received the energy passes it, in turn, to another pigment. The energy migrates until it reaches the reaction complex. The accessory pigments molecules do not transfer electrons. They transfer only energy!!!!!!!!.
short summary of process of photosynthesis.
When photopigments in plants absorb light, electrons in the pigment molecules are excited into higher energy states. The leaves gather light energy with chlorophyll, molecules that upon absorbing a photon of visible light momentarily promote an electron to an excited high energy state.These light-harvesting pigments (chlorophyll b and accessory pigments) pass their energy between adjacent pigment molecules until the energy arrives at the pair of clorophyll a at the reaction center complex. Note that the pigment molecules do not transfer electrons. They transfer only energy. This is the first step in a process that ultimately converts light energy into potential energy of the chemical bonds in carbohydrate molecules (occurs in the reaction center complex with chlorophyll a). In the light-dependent reactions, the excited electrons are used by various enzymes to create ATP from ADP and NADPH from NADP+. Specifically, ATP is generated by harnessing the proton gradient across the thylakoid membrane. NADPH is generated as part of the electron transport chain. ATP and NADPH are then used in the light-independent reaction to combine carbon dioxide and water into carbohydrates (carbon fixation). The energy ATP and NADPH is used to convert CO2 and H20 into sugar via the Calvin cycle. The oxygen from water is released into the air, as byproduct. 6CO2 + 12H2O + Light energy → C6H12O6+ 6O2 + 6H20
where chloroplasts and chlorophyll located?
When the edges of a cut leaf are magnified, (Figure 7), dozens of chloroplasts populate cells of the mesophyll (from Greek meso-, meaning "middle," and phyll, meaning "leaf"). Inside the chloroplasts are a series of discs called thylakoids. Thylakoids are stacked in layers called grana. Each granum looks like a stack of pancakes. Chlorophyll and carotenoid pigments are embedded in the thylakoid membranes.
carotenoids
absorb purple and blue spectrum (includes green) and emit yellow and orange. (think carotene carrot) Carotenoid pigments protect plants from too much light. As days shorten and temperatures drop, chlorophyll production slows down, making the yellows and oranges of the carotenoids and the reds, purples, and blues of the anthocyanins more visible. Many of these pigments are produced primarily in the fall, when the levels of nutrients such as phosphorus drop.
What is an action spectrum? /why is its used instead of spectrophotometer?
action spectrum measures the efficiency of photosynthesis across the visible light spectrum. Efficiency of photosynthesis is measured by comparing the oxygen output or carbon dioxide input of chloroplasts when they are exposed to the various wavelengths of visible light. Therefore, the action spectrum will indicate under which wavelengths photosynthesis occurs at the fastest or the slowest rate.
light independent in depth
after dependent light reaction.... light energy to chemical energy in the form of ATP and NADPH, photosynthetic organisms need the raw materials water and carbon dioxide to synthesize carbohydrates (carbon fixation)/ Calvin cycle. Water is absorbed by the plant's roots and moved to the chloroplast's stroma! Carbon dioxide is taken in through the stomata and diffuses into the stroma. (thats why it all takes place in stroma) Carbon fixation happens in the stroma.
Calvin Cycle
carbon fixation in light independent reactions. Light energy captured by the light-dependent reactions in the form of ATP and NADPH is subsequently used in the light-independent process to drive the synthesis of sugar (such as glucose which will later be used in cellular respiration) from carbon dioxide and water. Water is absorbed by the plant's roots and moved to the chloroplast's stroma! Carbon dioxide is taken in through the stomata and diffuses into the stroma. (thats why it all takes place in stroma) Carbon fixation happens in the stroma. The energy ATP and NADPH is used to convert CO2 and H20 into sugar via the Calvin cycle. It reduces O2 and oxidizes NADPH (uses H for the carbon??) . The oxygen from water is released into the air, as byproduct.
which has more energy in its bonds water or carb molecules? Why?
chemical bonds of a carbohydrate molecule to the energy in the bonds of the carbon dioxides and waters from which it was made, you would find that the carbohydrate has more energy. Matter does not usually spontaneously rearrange its atoms to produce higher energy configurations. The extra energy must come from somewhere. Photosynthesis uses energy from sunlight, thereby storing light energy in sugar.
chlorophyll structure
chemical structure that resembles the organic ring structure of the heme group in hemoglobin. One difference between chlorophyll and heme is that a magnesium ion, rather than an iron ion, occupies the central position of the chlorophyll molecule. Chlorophyll is located in the thylakoid membrane of chloroplasts. This pigment appears green to our eyes.Chlorophyll and accessory pigments absorb visible light. Chlorophyll absorbs light from the red and blue regions of the light spectrum, leaving primarily green visible light to be reflected back to the eye
difference between chlorophyll a and other accessory pigments?
chlorophyll a is directly involved in converting light, carbon dioxide, and water to sugars. All pigments absorb light. But most pigments do not participate in the actual photochemical reactions of photosynthesis. The accessory pigments, such as Chlorophyll b and carotenoids, do not transform light energy directly into chemical energy. So what do these pigments do? They are simply light harvesters
anthocyanins
give fruits and flowers their characteristic red, purple, and blue colors. As days shorten and temperatures drop, chlorophyll production slows down, making the yellows and oranges of the carotenoids and the reds, purples, and blues of the anthocyanins more visible. Many of these pigments are produced primarily in the fall, when the levels of nutrients such as phosphorus drop.
wavelength and visible light
he distance between two successive crests (top of a wave) or troughs (bottom of a wave) is a wavelength..The electromagnetic spectrum ranges from short-wavelength gamma rays (less than a nanometer) to long-wavelength radio waves. The part our eyes can perceive and that plants use occupies a very narrow part of the spectrum called visible light, which ranges from 400 nm (violet) to 700 nm (red) (think of red leaves and fire which we can see). Though the Sun emits light in all wavelengths, much of it is absorbed by particles in Earth's atmosphere. Most light that reaches Earth is in the visible range (graph inset).
where photosynthesis takes place?
in the chloroplasts. The chlorophyll captures the light energy (gives the green color) and then photosynthesis takes place in chloropasts. All of this happens in the leaf.
Linear electron flow
linear electron flow is the primary pathway; it invloves both photosystems II and I and produces ATP & NADPH using light energy; it also produces O2. Linear electron flow begins in the photosystem II complex with the separation of electrostatic charges and the transfer of light energy to an electron. An enzyme-activated reaction splits a water molecule into two electrons, two protons in the form of H+ ions, and an oxygen atom. This is, in fact, the only known biological water-splitting reaction. Electrons from this reaction pass one by one into P680 (PSII) at the center of the reaction complex. When light energy reaches P680 by resonant transfer, the electron excites to a higher energy state. The excited electron thepsn passes to the primary electron acceptor. The Chl a pair (from PSII) is left with a positive charge, denoted as P680+, and quickly scavenges the next electron.) From the primary electron acceptor, the high-energy electron passes through a series of redox reactions as it travels from PS II to PS I. How does the electron traverse the space between PS II and PS I? An electron carrier called plastoquinone (Pq) transports the electron from PS II to a cytochrome complex between the photosystems. A water-soluble protein called plastocyanin (Pc) receives the electron and carries it to PS I. Plastocyanin's solubility allows it to diffuse easily across the water-filled thylakoid space. When the electron reaches PS I, it fills a "hole" left by an excited electron leaving P700. An electron from P700 becomes excited and transfers to the primary electron acceptor, leaving a charged P700+. The acceptor passes it to NADP+, which becomes reduced to NADPH. The electron transported from PS II joins the Chl a pair, returning it to its neutral state for a brief moment until that electron becomes excited and moves on through the electron transport chain in PS I Electrons emerging from the transport chain PS I are taken up by NADP+ to form NADPH. The hydrogen ions that build up in the thylakoid space during this process come from two sources. The first is the water-splitting reaction that separates H+ ions from the electrons that feed into the reaction center of PS II. The second source is a pump that draws H+ ions into the thylakoid space as electrons pass through the cytochrome complex between photosystems . createsATP.
Chloroplasts contain two photosystems:
photosystem I (PS I) and photosystem II (PS II). The center of each photosystem contains a pair of Chl a molecules embedded in a unique molecular structure.the setting inside the reaction center is as important as the contributors, because structure enables function in cellular processes Energy originally from light transfers to the Chl a pair in each photosystem during the light harvesting process. The Chl a molecules are similar in the two photosystems, however, the surrounding structure affects their electron distribution and results in a slight difference in the wavelength of maximally efficient absorption. The Chl a pair in photosystem II, called P680, absorbs 680 nm light waves most efficiently, while the absorption peak of the photosystem I pair, P700, is centered around 700 nm
whats the reaction center complex?
reaction center complex is the actual site where the energy-conversion reactions of photosynthesis take place. The pigment in a reaction-center complex is a special form of Chlorophyll a.
Chloroplasts
where photosynthesis takes place. Chloroplasts have an outer membrane and an inner membrane, which encloses the fluid-filled stroma. Thylakoids look like disks which when stacked are called grana. The photosynthetic pigments, chlophyll, are embedded in the thylakoid membranes.
